[主页] [熔块系列] [熔化设备] [抗氧化涂料] [新特釉料] [技术陶瓷] [学术园地] [联系我们]

釉用氧化物

上一层

陶瓷釉及釉用原料中的氧化物

Al2O3 As2O3 B2O3 BaO BeO Bi2O3 C CaO CdO CeO2 CoO CO2 Cr2O3 Cu2O CuO

F Fe2O3 FeO Free SiO2 H2O InO3 K2O KNaO LOI Li2O MgO MnO MnO2 MoO2 Na2O NiO

P2O5 PO4 PbO PrO2 Sb2O3 Se SnO2 SrO TiO2 Trace U2O8 V2O5 Y2O3 ZnO ZrO ZrO2

分子式 分子量 膨胀因子 熔点 性质 在釉中的作用
B2B3 69.6 .031 577 Boric Oxide
(Sources: Borax Frits, Gerstley Borate/Colemanite, Boric Acid, Borax, Ulexite)
-Boric oxide has no melting point, but a progressive softening and melting range from 300-700C. The crystals begin to break down at 300C, and a series of suboxides are produced with partial melting until full fusion is reached at 700C. Boron glazes tend to have a fluid melt and lower surface tension.
Some other borate minerals are:
NaBO2: Sodium monoborate or sodium metaborate
BO2H: Metaboric acid
Na2B4O7.4H2O (Na2O.2B2O3.4H2O): Kernite, rasorite
Ca4B10O19.7H2O (4CaO.5B2O3.7H2O): Pandermite
Mg6Cl2B14O26 (5MgO.7B2O3.MgCl2): Boracite
-The way in which boric oxide combines with oxides like calcia and soda is not as well understood as other systems.
-Its low expansion makes it valuable in preventing crazing. However, each glaze recipe tends to have an optimum amount above which the effect is actually reversed and crazing can increase (10-14%). This effect is due to the loss of elasticity associated with excess B2O3. Predicting the expansion of high boron glazes can thus be misleading due to this factor.
-Boric oxide is a unique oxide often not fully appreciated for all its qualities. It reacts with whatever is available to behave as both the 'bones' and the 'blood' of glazes (acidic glass former and flux). In some ways, it can thus be considered a low temperature equivalent of silica. Because of its dual personality, technicians often are not sure where to place it in the unity formula. If placed with the amphoterics, where chemically it should go, it becomes difficult to relate the formula to others that have no boric oxide.
-Like silica it does not crystallize on cooling unless significant calcia is present to form calcium borate.
-Borax and Boracic Acid are both soluble and unsuitable sources for glazes, but fine for frits.
-Boron has many advantages as a glass-forming oxide (although Gerstley Borate, an important source, does have some consistency problems and can flocculate a suspension). Borosilicate glazes have been the major alternative to lead based formulations (melting as low as 750C), and thus boron is critical to the ceramic industry. 'Pyrex' ware, for example, is a low expansion high silica borosilicate glass. Boron glazes are less fluid and this has been the major challenge in switching from lead. While many users have increased firing temperatures to compensate, this has not fully solved the 'healing' and bubble clearance problems.
-In low temperature glazes, it both substitutes for fluxes of high-expansion, and for silica which cannot be present in large amounts.
-Boron's reactivity helps to form good clay-glaze interfacial zones that inhibit crazing.
-The action of B2O3 depends upon the ratio of bases to silica existing in the glaze before the addition. If the ratio is greater than 1:2, the glaze will tend toward opalescence and crazing; if less toward clear and transparent.
Toxicity of Boron:
The EPA Health Advisory Level for boron in drinking water is 0.6 ppm (set primarily for water taste). The level for chronic harm from regular exposure to boron is not well established.
Glaze Color Low fire transparent glazes employing boron frits, which have CaO and lack alumina, will have opalescent blue cloudy effects from the formation of calcium borate crystals. These 'boron blue' glazes work well visually on terra cotta bodies. These crystals do not form well if there is adequate alumina to stiffen the melt.
ZnO 81.4 .094 1800 Zinc Oxide
(Sources: Zinc Oxide)
-Together with PbO it is considered one of the metallic oxide fluxes.
-ZnO starts its fluxing action around 1000C (I.e. Bristol glazes) whereas by itself ZnO does not melt until 1975C. However, ZnO is easily changed to Zn metal by the action of CO and H2 in the reduction phase of a gas-fired kiln (and possibly poorly ventilated electric kilns). Pure Zn metal melts at 419C and then boils and vaporizes at 907C.
-It does take time for zinc to volatilize and meanwhile the it does encourage the melting process to begin earlier, making it more vigorous. However zinc metal in a more molten glaze is also more reduceable.
-ZnO is a low expansion secondary flux which is handy to prevent crazing if used for, or instead of, high expansion fluxes.
-It improves elasticity and extends firing range.
-In moderate to high amounts it acts to produce mattes and crystalline surfaces, especially if supersaturated (up to 0.8 molar) and cooled slowly. However, these surfaces can be rough enough to cause cutlery marking.
-Zinc can improve durability in some glazes.
-At low temperatures small amounts can have a marked effect on gloss and melting, although at temperatures below Orton cone 03-02 it is not normally an active flux.
-At middle temperatures, zinc can be used as a major flux in amounts to 5%.
-At higher oxidation temperatures it is valuable to provide a smooth transition from sintered to melted stage.
-In certain mixtures it is very powerful, even in small amounts. The melting power per unit added drops quickly as the amount used exceeds 5%.
-Zinc can have amphoteric qualities if it is used with boron.
-Zinc has a complicated color response. It can have harmful and helpful effects on blues, browns, greens, pinks and is not recommended with copper, iron, or chrome.
Glaze Opacifier In larger amounts ZnO can produce opacity or whiteness in glazes. It exhibits refractory properties and can contribute to the development of a crystal mesh surface.
Al2O3 102 .063 2040 Al2O3 - Aluminum Oxide, Alumina
(Sources: Kaolin, Clays, Feldspar, Calcined Alumina, AluminaHydrate)
-Alumina has a very high melting temperature and alumina ceramics can maintain up to 90% of their strength above 2000F. They are thus employed in many refractory materials (I.e. Calcium Aluminate Cements have PCE's above cone 35) and used to make parts that must withstand high temperature.
-Alumina controls the flow of the glaze melt, preventing it from running of the ware. It is thus called an intermediate oxide because it helps build strong chemical links between fluxes and silica.
-Fired alumina ceramic parts can be harder than tungsten carbide or zircon, two to four times as strong as electrical porcelain, and very resistant to abrasion. Alumina is thus used in grinding media, cutting tools, high temperature bearings, and a wide variety of mechanical parts.
-Alumina is second in importance to silica and combines with silica and basic fluxing oxides to prevent crystallization and give body and chemical stability to a glaze.
-It is the prime source of durability in glazes. It increases melting temperature, improves tensile strength, lowers expansion, and adds hardness and resistance to chemical attack.
-Increasing it stiffens the melt and gives it stability over a wider range of temperatures (although excessive amounts may tend to cause crawling, pinholes, rough surfaces). The addition of alumina prevents devitrification (crystallization) of glazes during cooling because the stiffer melt resists free movement of molecules to form crystalline structures. Thus crystalline glazes tend to have less than .1 molar equivalents of Al2O3. The addition
of small amounts of CaO will help reduce the viscosity of a melt and make it flow more freely.
-Calcined alumina does not work well in glazes or enamels as a source of Al2O3, however, the hydrated form can be effective to matte a glaze if it has a very fine particle size. If possible, kaolin or feldspar (and nepheline syenite) are the best sources. Kaolin especially is ideal because it is so important to other physical slurry properties (I.e. Suspension, adhesion, and shrinkage control). If glaze batches are being calculated from a source formula, it is normal to supply all possible alumina from feldspar and kaolin until the alkali targets are met, then furnish any additional alumina requirements with Bayer process alumina hydrate.
Sometimes Bayer alumina is added where exceptional freedom fromiron is needed.
-In most cases, the addition of alumina raises the melting temperature of a glaze or glass. However, in some soda lime formulations, a small alumina addition can decrease melting temperature.
-In glass, small amounts can reduce the coefficient of expansion, increase tensile strength and surface tension, improve lustre, lengthen working range, decrease devitrification, increase resistance to acid attack. When substituting for silica, alumina makes the glass more ductile and elastic.
-Alumina and boric acid are important constituents in all types of low expansion glasses for chemical ware, cooking, and thermometers.
-Alumina (preferably in the calcined form) can be used in clay bodies as an aggregate and filler in place of flint. This can increase the firing range, decrease quartz inversion firing problems, and increase hardness and whiteness in the fired body. However, alumina is much more expensive than flint.
-Alumina hydrate promotes opacity in enamels and glazes by generating gas bubbles in the glaze melt.
Surface Modifier: - MATTE
The ratio of alumina to silica is mainly responsible for the degree of matteness in glazes. In the absence of boron, ratios of less than 5:1 are generally quite matte; ratios of greater than 8:1 are usually glossy in the absenceof high titania, zinc, magnesia or calcia (which cause volatile melting or crystallization during freezing).Ratios of 1:18 are possible, but certainly not typical. If a glaze remains matte when fired higher, it is a true alumina matte.
Glaze Color: - COBALT BLUE Cobalt depends on presence of alumina or it will fire pinkish. Chrome reds like alumina also.
Glaze Color: - PINK
Alumina is used in combination with chrome, manganese and cobalt to achieve pink colors.
Surface Modifier: - CRYSTALLINE GLAZES
Since Alumina stiffens the glaze melt, it will prevent the growth of crystals during cooling. Thus most highly crystalline glazes have very little alumina.
As2O3 198 0 193 Arsenic Oxide
(Sources: Arsenic Oxide)
-Because of its oxidizing effect, it can be used as a fining agent to clarify iron containing glass. It will also fade the color of manganese and stabilize other colors (I.e. Light green).
-In pot glasses large quantities are used to reduce yellow coloration.
-Used in specialized enamels (I.e. Jewelry).
-Toxicity due to its vaporization on melting limits its use to tightly controlled environments (sublimes 193C)
Glaze Opacifier :Arsenic can be used as an opacifier in glazes, although not as effectively as tin.
BaO 153.3 .129 1923 Barium Oxide, Baria
(Sources: Barium Carbonate, Barium Sulfate, Baria)
-Baria is the heaviest of the divalent fluxing oxides and has some properties at high temperatures that make it similar to what lead does at low fire (I.e. Promotion of gloss).
-Together with CaO, SrO, and MgO it is considered one of the alkaline earth group of oxides.
-Barium is most popular for the production of classic barium mattes. These are dependent on adequate kiln temperatures and a slightly reducing atmosphere to decompose the material to yield BaO.
-Barium gives unique color responses with certain oxides (I.e. With copper it will give a marked blue compared with glazes fluxed with MgO, SrO).
-BaO often contributes a high index of refraction and this can enhance in-glaze colors.
-As a flux it can be very active in small amounts (not active at low temperature). For example, in small percentages it can improve gloss, mechanical strength, and acid resistance.
-Barium carbonate is very stable if not decomposed, and as such it will remain unreacted in the glaze melt. In the stable carbonate form, it can thus act as an opacifier and matting agent, especially in low temperature glazes. Such are not true barium crystal mattes and are not recommended because of the possibility of leaching and the ease with which other oxides will opacify or produce a low fire matte (I.e. CaO, MgO, Alumina, Zircon).
-Baria is more effective as a flux when associated with other fluxing oxides with which it can combine (e.g. If fused in certain frit formulations it can react readily in even low temperature glazes). It can also form a strong eutectic with B2O3 to produce a glossy and runny glaze.
-In larger amounts it becomes refractory and can produce dangerous leachable glazes, since it does not fully combine to form insoluble silicates. It is common to see glazes with more than 20% barium carbonate, and at times, a 40-50% recipes are traded in the pottery community. These are very likely not safe.
-Use with caution in functional ware! There is considerable controversy concerning the safety of barium in glazes (I.e. If you see larger amounts of barium in glazes labeled "Dry Matte" or "Stony Matt", be very cautious). Like lead, it can be leached from the surface (of improperly fired or formulated glazes) by acidic foods or liquids. Government agencies have the power to level fines if ware is found to be soluble.
-If possible, determine the reason for BaO in the recipe. The mechanism may well be better accomplished by another oxide. For example, SrO and CaO can both be employed to produce crystal mattes in saturation (although a calcium matte will likely be coarser). K2O may produce a better blue with copper or a brighter color.
-SrO has been promoted as a substitute for BaO and in some case this is true. It has a lower disassociation temperature and reacts earlier and is potentially able to produce a more perfect surface unmarred by the bubbles and pits associated with higher temperature decomposition. Still it is best to substitute BaO on a mechanism basis, choosing the best alternate oxide or formula adjustment in each case.
-CaO will also produce crystal mattes when dominant in the RO group, however, the texture will likely be coarser
Surface Modifier: Baria is well known for its tendency to cause the growth of a fine mesh of micro crystals to produce a silky matte texture.
Glaze Color Barium glazes are well known for their ability to produce matte turquoise colors with copper. While strontium is often used to duplicate the matte texture of barium it does not have the same color response.
BeO 25.011 0 2650 Beryllium Oxide
(Sources: Beryl)
-Beryllium is a specialty oxide available as a pure material in a wide variety of sizes and shapes.
-It is valuable for producing ceramics with high thermal conductivity, particularly in the lower temperature ranges. Its thermal conductivity is 400% more than that of dense alumina at high temperatures and even greater at lower temperatures. Its thermal conductivity is dependent on purity. For example 99.8% purity sees a 10-15% rise in conductivity.
-Has excellent dielectric properties.
-Has outstanding resistance to wetting and corrosion by many metals and non-metals.
-It's mechanical properties are only slightly less than that of 95% alumina ceramics.
-It has valuable nuclear properties including an exceptionally low thermal neutron absorption cross section.
-Like alumina, it is readily metallized by thick and thin film techniques

Bi2O3 466 0 820 Bismuth Oxide
(Sources: Bismuth Nitrate)
-Melts at 820-860C
-Bismuth oxide is derived from the ignition of bismuth nitrate which in turn is obtained from the heavy metal bismuth, found in the US, Peru, and Mexico. Bismuth is very similar to lead, however there is no evidence that it is toxic. In fact, it is used in medicines taken orally for stomach complaints.
-It has been used instead of lead oxide in amounts up to 50% in optical glasses to improve durability and increase the specific gravitys and refractive indexes. Arsenic is often used with it to prevent a tendency toward grey coloration.
-Bismuth has also been used in low temperature frits and colors, as a flux in conductive glazes, and in metal enamels.
-During the 1990's, industry has been under much pressure to discontinue the use of lead compounds. Bismuth is a very effective substitute for lead, providing the same high gloss, flow, 'healing' and 'bubble clearance' characteristics, refractive index, surface tension, viscosity, and resistance to 'aggressive' dishwasher detergents. Bismuth melts lower than lead and thus glazes can be even more fluid.
-Bismuth is much more expensive than lead (glazes could be 3-4 times more) and it does not provide the same gloss and durability in some on-glaze cobalt blue and iron red colors.

C 0 0 0 Carbon
(Sources: ball clays)
-C can be entered into an analysis to signify that LOI in a material is carbonaceous matter that burns away during firing. Since it is lost during firing, a weight of zero should be used during calculations so there is no impact on the calculated formula or properties

CO2 0 0 0 Carbon Dioxide
-CO2 refers to the carbon in a material that burns away during firing. It can be used in an analysis to make clear the nature of LOI components. Since it is lost during firing, a weight of zero should be used in calculations so that there is no impact on the calculated formula or properties.
-CO2 is often produced when oxygen-hungry CO in the kiln chamber during reduction firing (or incomplete oxidation) encounters compounds from which it can rob an oxygen atom to form CO2

CaO 56.1 .148 2750 Calcia, Calcium Oxide, Quicklime
(Sources: Whiting, Wollastonite, Feldspar, Colemanite, Dolomite)
-Together with SrO, BaO, and MgO it is considered one the Alkaline Earth group of oxides.
-Quicklime is pure calcia, but it reacts with water to produce calcium hydroxide or slaked lime. Calcium oxide, on the other hand, is an extremely stable compound.
-Calcium oxide is the principle flux in medium and high temperature glazes, beginning its action around 1100C. It lacks usefulness in high-fire bodies because its active fluxing action produces a body which is too volatile (melting if slightly overfired).
-Calcia usually hardens a glaze and makes it more scratch and acid resistant. This is especially so in alkaline and lead glazes. Its expansion is intermediate.
-Calcia and silica alone will not melt even at high pottery temperatures, but when soda and potash are added, calcia becomes very active in both oxidation and reduction. Hardness, stability, and expansion properties of silicates (of soda and potash) are almost always improved with the addition of CaO.
-It is not effective below cone 4 as a flux in glazes but in small amounts (less than 10%) it can dissolve in earthenware glaze melts especially with lead, soda, potash) to add hardness and resistance to leaching. In non-lead mixes it can also help reduce crazing. In larger amounts, it encourages the growth of crystals which can give decorative effects to glossy glazes and produce matteness (I.e. 30%).
-It reduces viscosity in glazes which have high silica, but if the melt is too fluid, devitrification may take place.
-Calcia is a moderate flux in the cone 5-6 range, but a very active one at cone 10.
-High calcia glazes tend to have good (although sometimes unexpected) color responses. For example, in oxidation iron glazes calcia likes to form yellow crystalline compounds with the Fe2O3 producing a 'lime matte'. Without the calcia, glossy brown glazes are the norm.
CaO is not found pure in nature but rather is contained in various abundant minerals (I.e. Calcite, aragonite, limestone, marble) but vary greatly in their purity (impurities usually include magnesia, iron, alumina, silica, sulfur). Of these iron and sulfur are most troublesome (I.e. Where clarity is important in glass). Lime minerals vary in the degree of crystallization and cohesion of the crystalline mass and the homogeneity of the matrix.
The term "lime" encompasses several different minerals and manufactured products.
-The term "Whiting" traditionally refers to calcium carbonate produced by the grinding of chalk from the cliffs of England, Belgium and France. However this title also refers to any ground calcium carbonate material (I.e. Those processed from marble and calcite ores).
-Ground limestone and calcined limestone (burned lime) are used in the glass industry.
-Dolomite (magnesium carbonate) is a mineral which supplies some magnesia in addition to its CaO complement. It is preferred in many situations because it more readily fluxes and the magnesia imparts desirable properties.
-Wollastonite is a calcium silicate which is more expensive than other sources of calcium, but is used bodies, glaze, porcelains, enamels and frits for its many superior properties.
See Calcium Carbonate, Whiting
Surface Modifier:High molar amounts of calcia combined with adequate silica and preferably lower alumina will form a calcium silicate crystal matte (lime matte). The presence of zinc will increase the size of crystals.
CdO 128.41 0 1426 Cadmium Oxide
(Sources: Cadmium Sulfide, Cadmium Silicate)
-Cadmium oxide is insoluble in water and alkalis, but soluble in acids and ammonium salts.
-Cadmium by itself does not produce color in a glaze, but when used in combination with selenium it gives red; and with sulfur produces yellow. Great care is required to maintain the correct slightly reducing atmosphere during firing for the latter.
Glaze Color Red enamels are made using cadmium-selenium-sulfur mixes because this combination goes into solution readily during the short firing period (copper compounds are too slow to dissolve).
Great care is required to maintain the correct slightly reducing atmosphere during firing.
Glaze Color Cadmium is blended with uranium to produce yellow optical glass and yellow enamels. For example, a yellow stain for enamels can be made with 12% selenium, 64.5% cadmium sulfide, and 23.5% cadmium oxide.
CeO2 172 0 2800 Cerium Oxide
(Sources: Salts, nitrates, carbonates)
-Used in glass and optics for UV protection properties
-It does react with other elements (I.e. Ti) to make colors (I.e. Ce-Ti yellow).
Glaze Color In combination with titanium, cerium produces a yellow glass.
Glaze Opacifier Used as an opacifier for special effects in the tile industry; as a replacement for tin opacifier in porcelain enamel.
CoO 74.92 0 2860 Cobalt Oxide
(Sources: Cobalt Oxide)
-Cobalt is a trace element in vegetables and an important vitamin (B12) in stock raising. Cobalt metal is used in steel and chrome alloys.
-Cobalt is a powerful and stable colorant used in glass, glaze, enamel, and even paint. As little as 2 PPM can produce a recognizable tint, thus cobalt is often cut in a medium to make it easier to weigh and distribute in a mix.
-It is not volatile even at 1400C.
-Various raw forms are available and all break down to cobaltous oxide (CoO), which is the stable form that combines with the glass melt to produce color. These include black stable cobalto-cobaltic oxide (cobaltosic oxide) Co3O4, which has a 93% conversion ratio and decomposes to liberate oxygen at 800C. Grey cobaltic oxide (Co2O3) is 90% CoO and mauve cobalt carbonate (CoCO3) has 63% effective stain content. Cobalt dioxide (CoO2) is not marketed for ceramics.
-Because cobalt is quite soluble in glaze melts, it has little or no opacifying effect.
-Although cobalt has a high melting point, it is a powerful glaze flux, dissolving readily in most glazes, especially alkaline and boron types. This active nature causes it to diffuse, making it difficult to maintain a clean edge on painted decoration, especially overglaze.
-It is very dependable under both oxidizing and reducing furnace conditions, fast and slow firing.
-Cobalt is used in a wide array of decal inks, underglaze colors, body stains, and colored glazes
Glaze Color Cobalt is often calcined with alumina and lime for soft underglaze colors. Stains often employ mixes of alumina, cobalt, and zinc for softer blue colors.
Glaze Color Cobalt is used in combination with manganese and selenium to mask excess yellow coloration (yellow plus blue gives green which is masked by the pink of selenium).
Glaze Color Combinations with iron and manganese can give a slate blue.
Glaze Color With barium shades of blue-green are possible.
With magnesia the color range is from violet to lilac.
Glaze Color With chrome and manganese blue-black and black are common.
Glaze Color With chrome and copper, cobalt can yield tints from pure cobalt blue, to greenish-blue, to the green of chromium. These effects work best when silica is not too high and there is adequate alumina.
Glaze Color With SiO2 and B2O3 and high MgO, red, voilet, lavender, and pinks can be made.
Glaze Color With SiO2 and B2O3 and high MgO, red, voilet, lavender, and pinks can be made.
Glaze Color Cobalt is a classic and reliable blue colorant at all temperatures and in most types of glazes. The shade of blue can, however, be affected in many ways by the presence of different oxides. Cobalt is powerful and often less than 1% will give strong color. If the color needs to be toned down, additions of iron, titanium, rutile, and nickel may work.
Glaze Color When cobalt occurs with manganese (I.e. 1-3% cobalt carb, 3-5% manganese carb), purples and violets can be made. Less cobalt will lighten the color. This effect works well in magnesia glazes. In high magnesia glazes, 1-2% cobalt alone will give purple. Add tin to move the color toward lavender.
Glaze Color With adequate SiO2 and high MgO (0.4 molar), purple, voilet, lavender, and pinks can be made using 1% or more CoO. Mimimizing boron, alumina, and KNaO will help prevent it from turning blue. Note that the high MgO will generally make the glaze matte and it could suffer some ill effects associated with excessive MgO.
Glaze Color With MgO, SiO2, and B2O3, red, voilet, lavender, and pinks can be made.
Glaze Color Cobalt is a classic and reliable blue colorant at all temperatures and in most types of glazes. The shade of blue can, however, be affected in many ways by the presence of different oxides. Cobalt is powerful and often less than 1% will give strong color. If the color needs to be toned down, additions of iron, titanium, rutile and nickel may work.
Cr2O3 152 0 2265 Chrome Oxide
(Sources: Chrome Oxide, Potassium Dichromate)
-Amphoteric chrome oxide is the only stable oxide of chromium metal and can be used at all temperatures to 1200C (after which it can volatilize somewhat).
-Chromium is a 'fast' color, meaning it produces its characteristic green in slow or fast and oxidizing or reducing firing. It is also used in paints and dyes.
-Chromium is used in the glass industry to make green glass (up to 1%). Antimony is sometimes used as a reducing agent to ensure an emerald green.
-Chromium is not very soluble in glass and does not form silicates or combine with fluxes readily unless compounds are finely ground and dispersed and amounts are not excessive (1% will dissolve in most glazes).
-Zircon opacifier 1-2% is often added to chrome glazes to stabilize them and prevent brown edges. Amounts up to 3% in a glaze recipe gives opacity and greyish green coloration.
-Chrome oxide can be used as a body stain in amounts to 5% to give grey-green.
-Drab chrome greens can be moved toward peacock green with the addition of cobalt oxide (1% each gives bright color). This works in boron and soda glazes.
-Chrome in zinc glazes tends to form brown zinc chromate.
-Because chrome reacts with normally inert tin to produce chrome-tin pink colors whiting and alumina are usually used instead of tin to lighten and clarify chrome green glazes.
-Chrome-tin pinks are much more consistent if the combination is premelted (I.e. Commercial stain) and if the glaze is high in calcium or strontium, and free of zinc. Strontium is most effective if a wide firing range is desired (0.1-0.5% chrome, 4-10% tin).
-Chromium oxide is added to enamels for green where borax and zinc are used to increase the brilliance of the color. However, chrome in ground coat enamels tends to react with the metal to cause blistering.
Properties
Glaze Color Drab chrome greens can be moved toward peacock green with the addition of cobalt oxide (1% each gives bright color, some MgO needed also). This works in zinc free boron and soda glazes.
Glaze Color Chrome in zinc glazes tends to form brown zinc chromate.
Glaze Color Chrome in high lead glazes forms yellow lead chromate. Zinc and chrome tend to produce orange.
Glaze Color Chrome is a constituent in almost all black oxidation colors. It is used up to 40% in Cr-Co-Fe blacks and as high as 65% in Cu-Cr blacks.
Glaze Color Chrome and tin are a widely used combination to produce pinks in zinc free glazes with at least 10% CaO and low MgO (alkaline glazes work well). Many stains are based on this system and typically have around 20-30 times as much tin oxide as chrome oxide. Tin would typically be around 4-5%.
Glaze Color Chrome in high lead glazes forms yellow lead chromate. Alkalies are recommended in the base glaze. Added zinc can extend the range to orange.
In other types of glazes, less than 0.5% chrome oxide will give yellowish or yellow green tints.
Glaze Color Chrome is a classic green colorant for recipes in oxidation and reduction at all temperatures. However, the shades it produces can be opaque, dull, and uninteresting. In the presence of CaO, the color moves toward grass green.
Glaze Color Below 950C in high lead, low alumina glazes, chrome will produce reds to oranges, often with a crystalline surface. The addition of soda will move the color toward yellow.
Glaze Color Chrome-tin pinks move toward purple in glazes with significant boron. One glaze with 3.3 SiO2, 0.27 Al2O3, 0.2 B2O3, 0.15 Li2O, 0.5 CaO, 0.1 MgO, 0.15 Na2O employed 5% tin oxide, 0.6% cobalt carbonate, 0.17% chrome oxide giving a good purple at cone 6.
Cu2O 143 0 1230 Cuprous Oxide
(Sources: Red Copper Oxide)
See Cupric Oxide
-Reduction firing reduces normal CuO copper oxide to Cu2O to produce bright red coloration in the reaction:
2CuO + CO -> Cu2O + CO2
-Bright red colors are usually achieved with very small amounts of copper (I.e. .5%).
-If larger amounts of copper are present, the reaction could precipitate very tiny copper metal particles (colloidal copper) in the glaze melt to yield a red color (I.e. Flamb?or sang-de-boeuf).
-Copper luster can be produced by oxidation firing at low temperature glaze (950C) with heavy reduction cooling to leave a metallic layer of copper on the surface. 2-8% copper is required and cooling should be done in 15 minute cycles of reduction, interspersed with intervals where the atmosphere is allowed to clear. This can be carried out in cooling electric kilns by creating reduction through the introduction of flammable materials.
Properties
Glaze Color Copper is well-known for it ability to produce blood-red and fire-red colors in steady reduction atmosphere firings where CuO is altered to Cu2O. See example copper red recipes in RECIPE area.
Bright red colors are usually achieved with very small amounts of copper (I.e. 0.2-0.5%) in a low alumina base with at least .4 molar equivalents of CaO and plenty of the alkalis. Tin oxide will enhance color. Use of silicon carbide in oxidation (2%) can produce red.
Glaze Color The use of boron in a copper red reduction glaze will give a purple hue.
The following formula produces good purple at cone 10: BaO 0.1, CaO 0.5, MgO 0.1, KNaO 0.2, ZnO 0.1, B2O3 0.15, Al2O3 0.2, SiO2 3.0.
Glaze Color In copper red glazes, barium additions in a high feldspar base will produce turquoise to deep blue depending on how much copper is added.
Glaze Color Large amounts of copper in a glaze give metallic and even graphite effects.
Glaze Color Fluoride, when used with copper, can produce blue green colors.
CuO 79.54 0 1148 Cupric Oxide
(Sources: Black Copper Oxide)
-Decomposes at 1026C
-Copper can be produced from many different raw materials, the main being black tenorite (CuO), deep red cuprite (Cu2O), bright green malachite (CuCO3.Cu(OH)2), and bright blue azurite (2CuCO3.Cu(OH)2).
-Under normal oxidizing conditions the CuO molecule remains unchanged and produces clear green colors in glazes.
-CaO is unlikely to affect the color of copper in a glaze.
-Copper is well-known for it ability to produce blood-red and fire-red colors in reduction atmosphere firings where it is altered to Cu2O (see Cu2O).
-Purple copper reduction glazes are the result of a mixture of copper in its green oxidized form and red reduced forms. This effect appears most frequently in high lime glazes or where early stages of firing are oxidizing or latter stages are light or neutral.
-The shade of copper greens can vary with firing rate and soaking changes. The best colors are generally obtained with fast firing and little soaking.
-Copper is an active flux and may increase melt fluidity and may increase crazing because of its high thermal expansion.
-Crystalline glazes can be attractive when done with copper.
-In the enameling industry, copper is used in combination with small quantities of cobalt, manganese, or nickel in making black where the black is produced in the smelter.
-Copper and titanium can produce beautiful blotching and specking effects. Pure copper metal filings can make an extremely potent specking material in reduction firing for both bodies and glazes.
-Generally additions of copper to a glaze will reduce crazing (if supplied in adequate amounts; beyond 1 or 2 percent).
Note: When added to low lead solubility glazes copper can cause the solubility of the lead to be greatly increased. Copper can have similar effects in other types of glazes at other temperatures also. If an overnight soak in vinegar or acid changes glaze appearance, be careful.
Properties
Glaze Color Under normal oxidizing conditions CuO produces clear green colors in most glazes. The shade of green depends not only on the amount but also on other oxides present (I.e. Lead in larger amounts will enhance and darken the green, the presence of alkalies or high boron will shift it toward blue).
Copper in calcium/magnesium glazes gives a green very different from that produced with lead.
Glaze Color Combinations of CuO with tin or zircon will give turquoise or blue-greens when the glaze is alkaline (high KNaO) and low alumina. Look for a frit with this profile for best results. Glazes of this type often craze.
Glaze Color Copper in a barium/zinc/sodium glaze gives a blue. Color can also be enhanced by lithia.
Tin and copper can produce turquoise to robin's egg blue.
Glaze Color 7% copper in glossy oxidation glazes can produce striking metallic green colors.
Glaze Color Combinations of CuO with tin or zircon will give turquoise or blue-greens when the glaze is alkaline (high KNaO) and low alumina. Look for a frit with this profile for best results. Glazes of this type often craze.
Glaze Color K2O can turn a copper glaze yellowish. If Na2O or PbO are present, K2O should not exceed 0.15 equivalent.
F 19 0 0 Fluorine
-Fluorine gas is given off during firing of some materials like Cornwall Stone and fluorspar. F is often listed separately in analyses from manufacturers (not included in general LOI) because of its hazardous nature during firing.

Fe2O3 160 .125 1565 Ferric Oxide, Ferrosic Oxide, Iron
(Sources: Iron Oxide, Stained Clays, many others)
-Iron compounds are the most common coloring agent in ceramics. On one hand, they are nuisance impurities where they stain an otherwise white clay or glaze or where they muddy an otherwise bright color. At the same time, iron exhibits so many personalities with different kiln atmospheres, temperatures, and firing cycles and with different glaze chemistries that it is among the most exciting of all materials.
-Chemically, iron is amphoteric like alumina. Fe2O3 generally behaves as a refractory antiflux material in a glaze melt, combining with alkalis. Oxidation iron-red glazes, for example, can have very low alumina contents yet do not run off ware because the iron acts like alumina to stabilize and stiffen the melt. However these glazes likely will have somewhat reduced durability.
-In glazes low in flux it can behave as an alkali, combining with silica.
-Fe2O3 is very affected by a reducing atmosphere where it can act as a flux in both bodies and glazes at high temperatures. Its fluxing action in reduction is quite remarkable and can be demonstrated using a line blend in a clear glaze. Higher amounts of iron exhibit dramatically increased fluidity (see FeO for more info).
-Fe2O3 is the most natural state of iron oxide where it is combined with the maximum amount of oxygen. In oxidation firing it remains in this form to typically produce amber to yellow up to 4% in glazes (especially with lead and calcia), tans around 6% and browns in greater amounts. In the 20% range, matteness is typical. However, once it reduces to FeO and immediately begins fluxing and forming a glass, it is difficult to reoxidize. Since the breakdown of carbon or sulfur compounds in body and glaze so easily reduces iron, a slow and very thoroughly oxidizing atmosphere is critical through the 700-900C range to assure that all the iron remains in its antiflux oxidized form.
-Most glazes will dissolve more iron in the melt than they can incorporate in the cooled glass. Thus extra iron precipitates out during cooling to form crystals. This behavior is true both in oxidation and reduction. For example, a typical mid-temperature fluid oxidation glaze of 8-10% iron will freeze black with fine yellow crystals. Lower temperature glaze with their high flux content can dissolve more iron (I.e. Aventurine).
-Zinc can produce unpleasant colors with iron.
-Titanium and rutile modify iron and can give some striking variegated effects. For example, a popular middle temperature pottery glaze employs 4% tin, iron, and rutile in a clear base to give a highly variegated gloss brown. Another popular cone 6 glaze uses 85% Albany slip, 11% lithium, and 4% tin to produce an attractive gloss brown with striations and flow lines similar to classic lead glaze effects.
-While many iron-stained clays are reddish in color, high iron clays can also be blackish, grey, brown and deep brown, pinkish, greenish and yellowish or maroon. Some can be quite light in color yet fire to a brown or red color. 6-7% iron is considered a high-iron clay, but some stained clay-like materials can have 20% or more iron. A typical ivory colored oxidation firing body has 1-2% iron oxide.
-Low temperature earthenwares can exhibit a wide range of iron red colors, depending on the firing temperature. Typically, low fired materials burn to a light orange. As temperature is increased this darkens to light red, then dark red, and finally to brown. The transition from red to brown is often very sudden, occurring across a narrow temperature range. Thus the working temperature should be sufficiently above or below this range to avoid radical color changes associated with kiln variations.
-Fe3O4 is an intermediate form of iron which is brown in color and exhibits intermediate properties. Fe3O4 can either be a mix of FeO and Fe2O3 resulting from an incomplete conversion from one type to the other, or it can be a completely different mineral form of iron known as magnetic iron oxide from the ore magnetite. The latter is a hard crystalline material of use in producing specking in bodies and glazes.
-Generally additions of iron oxide to a glaze will reduce crazing (if supplied in adequate amounts; beyond 1 or 2 percent).
Glaze Color In reduction glazes Fe2O3 tends to fire bluish or turquoise to apple green with high soda (boric oxide may enhance). 0.5% iron with K2O may give delicate blue to blue green.
Glaze Color
Glaze Color Fe2O3 tends to fire yellowish with calcia and in alkaline glazes straw yellow to yellow brown.
In reduction, 3-4% iron with 0.4 BaO, 0.15 KNaO, 0.25 CaO, 0.2 MgO, 0.3 Al2O3, 1.7 SiO2 and 15-20% zircon opacifier will produce a yellow opaque.
Glaze Color Low fire lead, potash and soda glazes encourage reddish colors with iron. Should be barium free.
FeO 81.8 0 1420 Ferrous Oxide
(Sources: Black Iron Oxide)
-Fe2O3 is easy to reduce to the FeO state with a light reduction firing as follows:
Fe2O3 + CO2 -> 2FeO + CO2
-Some suppliers quote iron in its reduced form as part of a materials formula.
-In clays and glazes, firing in reducing conditions, or with clays containing significant organic matter, the Fe2O3 converts to FeO as early as 900C. FeO is a very powerful flux. Once iron has been reduced and becomes active in glass forming, it is difficult to reoxidize it again. For this reason, reduction firings for iron effects should be light throughout to reduce the iron early before glaze melt and fired slowly through the 250-500C range to provide adequate time for organics to burn away. A period of clearing in oxidation at the end of a firing does not affect the color of iron in the molten glass.
-FeO is so active as a flux that it can often be introduced by substituting for other fluxes like lead and calcium oxide.
-Most glazes will dissolve more iron in the melt than they can incorporate in the cooled glass. Thus extra iron precipitates out during cooling to form crystals. This behavior is true of oxidation but doubly so of reduction. For example, a typical high-temperature fluid glaze with 15% iron will freeze to a sparkling rust colored mesh of crystals.
-Many popular iron glazes and slips for pottery are based on clays highly stained with iron. For example, Albany slip was used for many years to produce a wide variety of glazes which exploited its unique blend of high iron, low melting point, moderate plasticity, low thermal expansion, low cost and unique character. For example, using Alberta Slip (an Albany substitute) one can make a tenmoku glaze with 90% Alberta slip and a little added iron and feldspar.
-If clay is not allowed to oxidize thoroughly through the 700-900C range during firing, carbon present within will rob the Fe2O3 of its oxygen and escape as CO2 leaving the FeO as an active flux within the body to break it down from within. This is called black coring.
-Iron bearing clays fire much darker in reduction than oxidation. In addition, reduction fired iron bodies experience sudden color changes from red or tan to dark brown across a narrow temperature range characteristic to each formulation. Classic iron reduction mottled effects are created by firing to the transition point where color is just changing producing light and dark patching of color as the darker color invades the surface.
-In reduction firings it can produce greens and blues (I.e. Celadons), and yellows and maroons (I.e. Mustard, oatmeal glazes). In higher amounts it saturates to produce crystalline deep brown and black effects (I.e. Tenmoku 10-13% and kaki 13%+).
-Iron pyrite and similar minerals often contaminate stonewares and fireclays; and they are responsible for the popular speckling effects in reduction fired stonewares.
Glaze Color A typical high-temperature fluid reduction glaze with 15% iron will freeze to a sparkling rust colored mesh of crystals. Alkaline glazes work best. Barium can impede this effect.
Glaze Color Saturated reduction iron glazes normally firing to black in reduction will move toward brown if alumina is high, toward blue if alumina is low.
Glaze Color The presence of phosphorous pentoxide, lithia and soda also encourage blue in both normal and saturation conditions in reduction firing.
Iron glazes will move toward blue if alumina is low.

Glaze Color When 1-5% iron is used in a transparent reduction glaze which has some calcia and potash (barium also helps) celadon glazes are produced. 'Celadon' glazes are glossy shades of green which exhibit depth of color due to suspended micro-bubbles in the glass.
Glaze Color Classic reduction black-breaking-to-brown tenmoku glazes are made with 8-12% iron.
Glaze Color See Green Celadon.
Free SiO2 60.1 .035 1710 Free SiO2
(Sources: clays, feldspars)
-Some analyses quote two types of SiO2. This is a recognition that SiO2 in a material often exists by itself as particles of quartz or in combination with other oxides in minerals like NaAlSi3O8, KAlSi3O8, CaAl2Si2O8, CaHPO4, MgSiO3, FeSiO3, MnSiO3, etc.

H2O 0 0 0 Water
(Sources: clays, hydrated minerals)
-Some suppliers will quote moisture or water in a material's analysis. Many materials are hydrated. An example is calcium sulfate. When it is heated past a certain point, the chemically bound water is expelled, converting the material into one of different chemistry.
-Chemical water in materials burns away during firing and so it has no impact on the fired chemistry. Since it is lost during firing, a weight of zero should be used if included in calculations

InO3 277.64 0 0 Indium Oxide
-An n-type semiconductor used as a resistive element in integrated circuits.
-Used in certain stain formulations

K2O 94.2 .331 750 Potassium Oxide
(Sources: Potash Feldspar, Cornwall Stone, Nepheline Syenite, Frits in low fire glazes)
-Together with sodium and lithium oxides, it is classified as one of the Alkaline group. Colored glazes whose flux portion is alkaline-dominated tend to be visually intense, especially if the alumina is low.
-K2O is considered together with sodium, since it almost always occurs together with sodium and contributes very similar properties. When taken together the two are often labeled KNaO.
-It is an important auxiliary flux in high temperature glazes.
-It is a heavy oxide and in general hosts the brightest colors of all fluxes except for lead. It is usually preferred even to soda for a more brilliant glaze and longer firing range. The best colored glazes are thus made with K2O-PbO-SiO2 predominant formulas.
-Considered a very stable and predictable oxide.
-Relatively high expansion tends to contribute to crazing in higher amounts, but not quite as bad as sodium. Thus high alkali glazes almost always craze. If the color depends on this (I.e. Copper blue), then it may be necessary to adjust the body to eliminate crazing since a reduction of the alkalis to reduce crazing will mean a loss of color.
-The alkalis can increase lead solubility.
Glaze Color Reduction tenmoku black-rust glazes with 8-10% iron work well in high potash glazes.
KNaO 78.1 .359 0 Potassium/Sodium Oxides
(Sources: Feldspars)
This pseudo-oxide is provided for in cases where a manufacturers data sheet groups K2O and Na2O together. The weight and expansion are an average of the two.

LOI 0 0 0 Loss on Ignition
-The LOI summarizes the components within a raw material that burn away or products of decomposition that are lost as gases during firing. Some companies separate the different components of weight lost during firing as C, H2O, SO3, etc. A formula weight of zero should be used in each oxide of this type so there is no impact on fired formula calculations.
-Note that if a material contains a volatile in its analysis that you would like to enter into the analysis and have it treated like an LOI, and if that item is not contained in the OXIDES database, you can manually key an "L" in the status column of the analysis to force FORESIGHT to accept it as an LOI type material.
-A material's formula weight is equal to the sum of the weight of the oxides in its formula divided by 100-LOI divided by 100

Li2O 29.8 .068 1000 Lithium Oxide, Lithia
(Sources: Lithium Carbonate, Lithium Feldspar I.e. Spodumene)
-Lithium is the lightest, smallest, and most reactive flux. Adding small amounts by weight introduces disproportionately large amounts to the glaze formula.
-Together with boron and sodium, it acts as a melter at lower temperatures. Together with sodium and potassium oxides, it is classified as one of the Alkaline group.
-Lithium Carbonate, its main source, has a very low melting point and is a very active and powerful flux. It is typically used in smaller amounts to improve fluidity, uniformity, and reduce maturing times.
-High cost limits its use in larger amounts, but in small amounts it acts as a powerful auxiliary alkaline flux with welcome thermal expansion lowering effects.
-1% additions can increase glaze gloss to a marked degree and slightly greater amounts (3%) can reduce melting temperature by several cones and affect surface tension of the melt.
-Calculated expansion projections tend to break down with all but low additions of lithium to glazes (less than 5%). Its contribution in nonlinear, especially in high sodium and potassium glazes. Often high lithium glazes appear to shiver whereas the calculated expansion does not indicate a sufficiently low expansion. It is known that molten lithia is mobile (diffuses into the surrounding matrix because of its small ionic radius and low charge). It can also diffuse into the body and create a low expansion glaze interface. One theory proposes that glazes with more than about 5 mol% Li2O could develop a lithium-rich interface (this could be coupled with a lithium-deficient upper glaze layer). The result could be crystallization of a spodumene layer thereby introducing its inversion and associated sudden expansion at 1082 C during cooling.
-Lithia gives the most intense colors in low alumina in high alkali glazes.
-The alkalis can increase lead solubility.
-Its expansion is much lower than soda or potash, and it is used to produce special low-expansion bodies and glazes which are resistant to heat-shock. When used as a substitute for sodium and potassium oxides, it produces glazes of lower expansion.
-It can promote textural effects in the glaze surface.
-In some systems small additions of lithium will react with quartz during firing and can eliminate the alpha-beta quartz transition in the cooling cycle.
-Lithia promotes devitrifaction in glass systems
Glaze Color Lithia can produce blue effects with copper.
Glaze Color Lithia can produce pinks and warm blues with cobalt.
Surface Modifier Lithia contributes to mottled and flow effects when used in small amounts (-1%).
MgO 40.3 .026 2800 Magnesium Oxide, Magnesia
(Sources: Talc, Dolomite, Magnesium Carbonate)
-Together with SrO, BaO and CaO it is considered one the Alkaline Earth group of oxides.
-Like CaO, MgO is refractory at lower temperatures, so much so that it can be used to increase opacity, as a matting agent (I.e. Magnesium carbonate), and as a check to glaze fluidity in a manner similar to alumina (I.e. To prevent devitrification, that is, the tendency to produce crystalline surfaces). When mixed with CaO, it is not as refractory.
-It can act as a catalyst in low temperature bodies assisting in the conversion of quartz to higher expansion cristobalite which reduces crazing.
-In high temperature glazes it acts as a flux (beginning action about 1170C) producing viscous melts of high surface tension and opaque and matte glazes. Like CaO, its melting action drastically accelerates at high temperatures.
-The surface tension of MgO-containing melts is less of a problem in reduction.
-Zircon and Magnesia melt at 2800C making them the highest melting oxides. Remarkably, MgO readily forms eutectics with other oxides to melt at surprisingly low temperatures.
-It is valuable for its lower expansion and crazing resistance. When introduced into a glaze it should preferentially replace calcia, baria, and zinc before the alkalis to maintain surface character. Adding too much will generally move the surface texture toward matte or dry.
-MgO is a light oxide and generally is a poor choice for glazes to host bright colors. However, it does work well in earthtone and pastel glazes, especially in high temperature reduction firing. Likewise, it may be harmful to some under-glaze colors.
-Does not volatilize.
Surface Modifier Magnesia is well known for the pleasant vellum 'fatty matte' and 'hares fur' tactile and visual effects that it produces around 1200C, especially in reduction firing (dolomite matte). However, it can produce matte effects at all temperatures.
MnO 70.9 .05 1650 Manganous Oxide
(Sources: Manganese Dioxide)
-Manganese monoxide exists only above 1080C where the dioxide form disassociates to release its oxygen.
-Manganese is a colorant using in bodies and glazes, producing blacks, browns, and purples.
-Manganese is a constituent in many igneous rocks, and thus occurs in many clays weathered from these parent rocks. In most cases it is a very minor oxide, but does occur in much greater amounts in some slip and highly stained materials. It is thus a color contributor in many traditional and historic slip glazes.
-Smaller amounts are easily dissolved in most glaze melts; however, around the 5% threshold, the manganese will precipitate and crystallize. In large amounts in a glaze (I.e. 20%), metallic surfaces are likely.
-Above 1080C, half of the oxygen disassociates to produce MnO, a flux which immediately reacts with silica to produce violet colors in the absence of alumina, browns in its presence. Manganese browns have a different, often more pleasant character than iron browns.
-High temperature glazes well above 1080C can use large amounts of manganese to produce very metallic bronze-like surfaces. Manganese dioxide by itself can be used and will fuse well, even running down the ware.
-Manganous oxide is unaffected by reduction, but is normally considered, at its best, in oxidation slips and glazes above 1200C.
-Manganese fuses and dissolves very well above 1200C in oxidation. Like iron, it will dissolve to a greater extent in a hotter melt. This means that if more than about 4% MnO is used, the oversupply will precipitate on cooling leaving a network of crystals in a manner similar to iron in high fire reduction. Speed of cooling, glaze fluidity, and amount of manganese will all affect the results.
Glaze Color In glazes below 1080C, it can give coffee color browns when used with tin and dull browns in lead and low alkaline glazes.
Glaze Color Very pleasing tan-brown reduction fired glazes can be achieved with 5% manganese dioxide in reduction.
MnO2 86.9 .05 1080 Manganese Dioxide
(Sources: Manganese Dioxide)
-Manganese dioxide exists only below 1080C, above which the dioxide form disassociates to release its oxygen (see MnO for more information).
-Manganese is a colorant using in bodies and glazes, producing blacks, browns, and purples.
-Manganese is a constituent in many igneous rocks, and thus occurs in many clays weathered from these parent rocks. In most cases it is a very minor oxide, but does occur in much greater amounts in some slip and highly stained materials. It is thus a color contributor in many traditional and historic slip glazes.
-Smaller amounts are easily dissolved in most glaze melts, however, around the 5% threshold, the manganese will precipitate and crystallize. In large amounts in a glaze (I.e. 20%), metallic surfaces are likely.
-In glazes below 1080C, it can give coffee color browns when used with tin.
Glaze Color Purple colors can be produced in glazes of high alkali (KNaO) and low alumina, especially in combinations with cobalt (look for a frit with this profile for best results).
Glaze Color Manganese and cobalt mixture produce black. Iron can also be used. For example, a mix of 8 iron, 4 manganese, and 0.5 cobalt make a raw black stain.
MoO2 143.94 .094 780 Molybdic Oxide, Disulfide, Trioxide
-In glazes, glasses, and bodies, small amounts (-0.2%) act as a wetting agent during the melt phase. It lowers surface tension dramatically. This can encourage the development of crystals in crystalline glazes. Moly can give an iridescent quality to crystals and lustres.
-Also used in enamels as an adherence promoter and in some stains.
-It oxidizes quickly above 800F

Na2O 62 .387 800 Sodium Oxide, Soda
(Sources: Feldspar, Nepheline Syenite, Sodium Frits in low fire glazes)
-Soda is a slightly more powerful flux than potassium. Together with potassium and lithium oxides, it is classified as one of the Alkaline group.
-It has high expansion and will promote crazing in glazes lacking silica or alumina.
-Sodium can begin to volatilize at high temperatures.
-It decreases tensile strength and elasticity compared to other common bases.
-Gives strong color responses to copper, cobalt, and iron, but the color can come at the expense of glaze fit and excessive fluidity because high soda is required. High alkali glazes definitely tend to craze. If the color depends on this (I.e. Copper blue) then it may be necessary to adjust the body to eliminate crazing since a reduction of the alkalis to reduce crazing will mean a loss of color.
-Soda works well with boric oxide (and also lithia and potassium) in low temperature lead-free glazes.
-Low alumina in high alkali glazes give the most intense colors.
-The alkalis can increase lead solubility.
Glaze Color Copper red reduction glazes are best in formulations with high alkali. The presence of boron can give a more pleasant red.
Glaze Color Oxidation copper blues work best in high alkaline, low alumina glazes. Increasing copper to 4-6% will move color toward turquoise.
NiO 74.7 0 1453 Nickel Oxide
(Sources: Nickel Oxide)
Most often used to modify and soften the color of other metallic oxides and thus small amounts are normally employed.
It is not normally used in low fire glazes due to the refractory nature of nickel oxide powder. Glazes that are already matte or immature will thus be made more dry by the addition of nickel.
Since nickel is used in smaller amounts, flashing from other glazed ware and the chemistry of the glaze can have an effect on ware color.
Glaze Color Nickel with zinc oxide can produce steel blues. With larger amounts of zinc, lavender blue can be made.
Glaze Color Nickel with calcium can produce tan.
Glaze Color Nickel with barium can produce brown. In high sodium glazes it can fire brown also.
Glaze Color Nickel in lead glazes tends to produce grey colors.
Glaze Color Nickel can produce pinks in high potash or lead glazes.
Glaze Color In lithium glazes nickel can produce yellow.
Glaze Color In the presence of high MgO, nickel can produce greens. Zinc is also helpful to develop color.
P2O5 141.9 0 580 Phosphorus Pentoxide
(Sources: Bone Ash, Wood and Plant Ash)
-Phosphorus along with calcium is an essential element in plant and animal growth, thus its principal source is organic ash (I.e. Calcined cattle bones).
-Phosphoric oxide is normally present in only trace amounts in ceramic materials.
-It can act as a melter in middle to high fire, but its power per unit added drops drastically beyond 5% additions.
-Small amounts can produce colloidal opacity as in Chinese chun glazes. The depth of Sung glazes is attributed to phosphorus.
-P2O5 is a glass network former like boric oxide and silicon dioxide. Phosphoric glass tends to show as a bluish flush in glazes. It is not in any way a substitute for silica and does not enter the silica chain, but remains as a separate colloidal presence in the silicate matrix.
-Phosphorus can vitrify porcelains without softening and is the key to translucency in bone china.
-Phosphate ions are added to glaze frits as a color control agent during the melting of titania opacified frits.
-P2O5 is known to influence the rate of nucleation and/or crystallization in Li2O and MgO low expansion glaze systems.
-P2O5 combined with certain oxides of iron forms colorless compounds. This suggests that P2O5 could be used to allow the use of less pure materials in glazes and glass.
-Phosphorite mineral Ca3(PO4)2 and Apatite 3Ca3(PO4)2 Ca(Cl,F)2 are the parent rocks of phosphate fertilizers. The latter can thus be used to introduce phosphorus into glazes and frits.
Surface Modifier Phosphorus can produce variegated and mottling effects in glazes (especially low fire) when used in small amounts (e.g. Up to 2%). Bone ash is a source.
PO4 94.969 0 0 Phosphorus Oxide
(Sources: Bone Ash)
Phosphates in this form are contained in bone ash and tricalcium phosphate type materials

PbO 223.2 .053 888 Lead Oxide
(Sources: Lead Frits, Litharge)
-Together with ZnO, PbO is considered one of the Metallic oxide fluxes.
-Reacts easily with silica to form low melting lead silicates of high gloss and deep character. Lead is very easy to use. It is the heaviest oxide and produces incredible colors and surface characteristics. Lead also has 'blemish healing' and flow characteristics that are unmatched. Lead glazes tend to have high resistance to chipping. In addition, lead is a 'forgiving material' that tends to hide imperfections on the finished fired surface. Lead glazes have been demanded for fine China for many years, although substitutes have been developed.
-Lead carbonate, a favorite source is highly pure and has a very fine particle size. It also promotes good suspension in raw glazes as well as rapid fusion.
-Lead promotes low expansion, a long firing range, and it decreases viscosity and tendency to devitrify.
-Lead is often used in combination with boric oxide which improves crazing problems and resistance to chemical attack.
-Problems include toxic nature of many forms, volatilization, and loss of gloss during higher firing; dimming of brilliance after long use, and less abrasion resistance. Note that even leaded frits can produce glazes which are soluble if the formulation is faulty or firing is wrong.
Lead Safety:
Public and industry attitudes toward lead have shifted in the past few years, and finally most potters and companies are realizing that the narrow parameters within which lead can be used safely (or perceived to be used safely) are just too difficult to work within. Public paranoia is common even though, for example, there are no known cases of lead related illness in the US for domestic manufactured ware.
Inhalation exposure to lead is considered to be significant if the amount of lead in the air is more than half the lead-in-air standard I.e.. >0.075 mg/m3 over an 8 hour working day. Concentration in the human body is significant if it exceeds 40 micrograms/100ml of blood.
The US FDA (Food and Drug Administration) has been a driving force in the move to eliminate lead worldwide. European standards (I.e. (European Community Directive 1984) are less stringent and will be modified to allow export to the US. The Compliance Policy Guide adopted by the FDA in 1992 reduces allowable limits dramatically. It is based on the standard 4% acetic acid text as follows:
Category, Samples, Lead Release (micrograms/ml), Pre 92, Current
--------------------------------------------------
        Flatware, 6, 7.0, 3.0
Small Hollowware, 1, 5.0, 2.0
  *Cups and Mugs, 1, 5.0, 0.5
Large Hollowware, 1, 2.5, 1.0
       *Pitchers, 1, 2.5, 0.5
     *New category
The US Consumer Product Safety Commission and the Environmental Protection Agency has also issued voluntary standards.
In the early 90's, industry has been in a compliance mode, adopting quality assurance standards and formulation expertise (I.e. BS 5270, ISO 9000) to meet the challenge and increase credibility. However, environmental concerns and political pressure are forcing the industry to eliminate lead completely or face a total ban. The sectors which most depend on lead are bone china, vitrified hotelware, feldspathic porcelains, and earthenware.
International industry leaders (Corning, Lennox, Mikasa, Noritake, Pfaltzgraff, Royal Doulton, Villeryoy & Boch, Wedgewood) have formed the Coalition for Safe Ceramic Ware to represent the interests of the industry. Only companies with good reputations for producing quality ware are eligible for membership. The CSC called for the reduction of lead limits and was instrumental in the FDA's revisions in Apr 1992. The CSC has continued to develop and apply quality and design control standards which individual members must document and validate with sampling programs. In addition, the CSC has published material to help consumers assure that tableware products are safe to use.
CSC has also taken on the challenge of educating the public as to what it sees as inappropriate. Examples are California's Proposition 65 which requires that consumers be warned if lead levels are more than one-one thousandth of the level at which there is observable effect on human health. For example, a restaurant must warn its patrons with signage. Lead levels of this nature are difficult to measure with test equipment

PrO2 172.9 0 0 Praseodymium Oxide
(Sources: Stains)
-Used for lemon yellow stains in combination with zircon. These stains are not as powerful as antimony or vanadium but are flexible.
-PrO2 can be used in reduction firing, even at high temperatures.
-While it is toxic, it is not as dangerous to use as either vanadium or antimony.
-Different glaze chemistries can produce brighter yellow coloration.
-PrO2 glazes do not tolerate contamination of other coloring oxides well.

Sb2O3 291.6 0 630 Antimony Oxide
(Sources: Antimony Oxide, Antimony Sulfide)
-Antimony oxide is used as an opacifier in low fire glazes and porcelain enamel (mainly leadless but it has been replaced to an extent by titania). Antimony is easily reducible; thus an oxidizing agent like potassium nitrate may be required to prevent it from going into solution and losing its opacifying power and affecting color.
-It is not useful in glazes over cone 1 due to volatilization.
-Antimony can be used as a yellow body stain in combination with rutile or titanium.
-Antimony will bleach the surface of low fire red-burning clay to a buff color to produce variegated coloration.
-The glass industry uses antimony as a decolorizing and fining agent to clarify glasses and as a stabilizing agent in the production of emerald green glass.
Glaze Opacifier Antimony works to a limited extent as an opacifier to cone 1.
Glaze Color It can give a yellowish color if the glaze contains lead, this is a result of the precipitation of yellow lead antimonate (known as Naples yellow).
Se 111.2 0 217 Selenium
(Sources: Element itself, sodium selenite, barium selenite)
-Semi-metallic element of the sulfur group. Its main value as a colorant depends on a reduction or mildly oxidizing atmosphere to maintain its metallic state.
-With cobalt it is a good decolorizer for glass because it produces a pink which is close to complementary of iron green thus canceling it out.
-Used as a colorant in making rose and ruby glass.
-Used in some special purpose stains.
Glaze Color Used in making red glazes with cadmium for low fire. Lead enhances the coloration.
SnO2 150.7 .02 1127 Tin Oxide, Stannic Oxide
(Sources: Tin Oxide powder)
-The fully oxidized state of tin metal. It is a very white powder of low density. Although tin metal melts at a very low temperature, the oxide form is stable to cone 1150.
-Tin oxide is used primarily as an opacifier in amounts of 5-15% in all types of glazes for many centuries. The amount required varies according to the glaze composition and temperature. The mechanism of the opacity depends on the white tin particles being in suspension in the molten glass. At higher temperatures, these particles will start to dissolve and opacity will begin to be compromised.
-Like zirconium oxide, larger amounts of tin in lower temperature glazes have a refractory effect, stiffening the melt and increasing the incidence of pinholing and crawling.
-Tin white is considered a softer white than that produced by the very popular and much cheaper zirconium opacifiers.
-One peril with tin is that it reacts very strongly with minute amounts of chrome to produce pink colors. If volatile chromium is flashing in the kiln atmosphere from other glazes, the white color will be lost.
-Other opacifiers include zirconium oxide (gives a harsher glassy white), calcium phosphate (problems with off-coloring to greys), cerium oxide (restricted to low temperatures), antimony (dissolves in some glazes and gives yellows with lead), and titanium dioxide (discolors if any iron oxide is present).
Glaze Opacifier Tin is an effective opacifier to transform transparent glazes to white. The quality of color tends to be a 'soft-bluish white' compared to harsher effects with other oxides.
SrO 103.6 .13 2430 Strontium Oxide, Strontia
(Sources: Strontium Carbonate)
-Together with CaO, BaO, and MgO it is considered one the Alkaline Earth group of oxides.
-Does not break down till 1090C (cone 02) so it is not useful as a glaze flux below this temperature. SrO must thus be employed in frit form below 1090C to be effective.
-It has an expansion akin to CaO and a similar decomposition behavior.
-Strontium compounds have not been widely used because of their more limited availability, although the value of this oxide has long been known.
-It is very useful at lower temperatures (I.e. Cone 1) for high gloss, craze resistant glazes which develop a good interface with the clay body. The interface development is thought to occur due to the mixed-oxide effect (bodies do not normally contain SrO).
-Strontium is important because of its non-hazardous, non-poisonous nature. With it, glazes of all temperatures can be made free of lead and barium (in spite of its different expansion, it can be a viable substitute for small proportions of lead).
-Even though it has a very high melting temperature, SrO is an effective flux above 650C when interacting with other oxides (provided it is added in fritted form).
-Like CaO and ZnO, it forms a crystal matte surface on cooling if dominant in the RO group. Conversely, a diversity of fluxing oxides associated with SrO will reduce crystallization.
-SrO has been used with success as a substitute for lead oxide in glazes using smaller amounts. Glossy glazes melting as low as cone 01 without any zinc are possible (long soaking periods may be necessary). Like lead, strontium develops vivid colors.
-Small additions of SrO can improve the surface of viscous high fire zirconium glazes.
-If BaO is replaced in whole or in part with SrO, glazes can develop better interface and have a lower expansion. However, they may also be less elastic than those formed by Ba and this could lead to fit problems where body and glaze are not closely compatible. SrO has a different color response to copper and cobalt; it has a lower expansion, and is a little more powerful at fluxing.
-The lower temperature decomposition of SrCO3 potentially produces an earlier reaction of SrO giving the melt more time to clear of bubbles and pits.
Surface Modifier Like calcia and baria, it will produce a fine crystalline mesh to give attractive satin matte surfaces.
TiO2 79.9 .144 1830 Titanium Dioxide, Titania
(Sources: Titanium Dioxide, Rutile)
-Titania is a complex material because it opacifies, variegates, and crystallizes glazes. It also modifies existing colors from metals like Cr, Mn, Fe, Co, Ni, Cu.
-In amounts below 1% titania can dissolve completely in a glaze melt. In slightly greater amounts it can give a bluish-white flush to transparent glazes (depending on their amount of alumina).
-Above 2% it begins to significantly alter the glaze surface and light reflectance properties through the creation of minute crystals. This crystal mechanism gives soft colors and pleasant opacity, and breaks up and mottles the surface. In the 2-6% range, it increasingly variegates the glaze surface. Many potters add titania to their glazes or paint on overglaze titania washes for this purpose.
-Large amounts (10-15%) will tend to produce an opaque and matte surface if the glaze is not overfired. They will also subdue color and can add sparkle to the surface. As much as 25% can be absorbed by some lead glazes. Up to 0.8 molar can be used to effect crystal melts in glossy glazes.
-Although titania will form a glass by itself, it is not highly soluble in silica melts. However, it is considered by some as a glass former in certain circumstances since it can stiffen the melt and stabilize the fired glass against leaching (I.e. It is used in lead frits to lessen the solubility of the lead).
-Titania can act as a modifier and within a narrow range it will combine with fluxes to make a glass. It can also act in a flux-like way in very high silica melts.
-Minute amounts (I.e. 0.1%) can be used to intensify and stabilize colors (I.e. Iron can be altered to produce yellow and orange). It can alter and intensify existing color and opacity in a glaze. Titania can be reduced to produce colors in keeping with the elements present. If highly reduced it can yield a red, with iron the color could be yellow, brown or green. Other combinations can yield blues, greens, yellows. Titania is oxygen-hungry and will quickly oxidize from its reduced state if given the chance.
-Glazes containing titania are phototropic and can change color slightly by the action of light. They can also be thermotropic in that they can change color (I.e. Toward yellow) when heated.
-Some have chosen to treat TiO2 as an 'inert' with respect to the chemistry of the glaze. However, a phase diagram of Al2O3 and TiO2 shows a eutectic at 80% Al2O3 at 1705C demonstrating that TiO2 does 'react' with the second most important ceramic oxide.
-TiO2 is considered an impurity in ball clays and kaolins used to make porcelain because it can react with any iron present to form rutile crystals which detrimentally affect body color and tranlucency.
Glaze Opacifier Titanium can be used as an opacifier.
Trace 0 0 0 Trace Elements
Use this item to group trace elements together in an analysis. It should be defined with a weight of zero to ignore them in any formula calculations.

U2O8 842 0 2176 Uranium Oxide
(Sources: Uranium Oxide)
A colorant which can be used in amounts to 15% to achieve or modify yellows, reds, and oranges. Although this form of uranium is said to be less radioactive, the use of any form of uranium is considered dangerous by most authorities.
Other oxides of uranium are also available.
Glaze Color It is possible to achieve reds in lead silicate glazes low in alumina and having no boric oxide. Zinc is also helpful to develop the color.
Glaze Color Yellow is the usual oxidation color for uranium modified glazes. The presence of CaO and ZnO are beneficial.
V2O5 181.9 0 690 Vanadium Pentoxide
(Sources: Vanadium Oxide)
An acidic metallic oxide which produces yellow coloration in amounts to 10%. Its color in generally weak, but can be strengthened when fritted with tin and zirconia. Although yellows can be prepared with antimony, vanadium is stable at higher temperatures.
The most vibrant color is obtained in leaded glazes.
Also a strong flux.
Another form, Vanadium Trioxide (V2O3) also exists and is alkaline in nature.
Glaze Color A classic yellow colorant.
Y2O3 225.81 0 2585 Yttrium Oxide
-Used in electrical conducting ceramics, refractories, insulators, glass, and stains.
-Used with Sc, La, Cs oxides in TiO2 bodies for better control of properties than possible with alkaline earths.
-With ZrO2 it make good high temperature refractories.

ZrO 107.2 .02 0 Zirconium Oxide, Zirconia
(Sources: Zircon opacifiers, Zirconium silicate)
See ZrO2
Zirconia has an inversion with an associated 3% expansion/contraction.
Surface Modifier ZrO can produce patterns of minute darker and lighter areas in an otherwise drab glaze surface. Significant amounts are needed (e.g. Up to 15%).
Glaze Color Zircon is used in stains to stabilize colors.
ZrO2 123.2 .02 2700 Zirconium Dioxide
(Sources: Zircon opacifiers, Zirconium silicate)
-Zirconium oxide is an extremely refractory material and its metallic form likewise melts very high, the highest of all oxides except MgO.
-It is primarily used as an opacifier in glazes with properties similar to tin oxide. Tin is about twice as effective in producing opacity. The opacifying effects of zirconium are a product of its ability to form a second crystal phase.
Glaze Opacifier Zirconium is an effective opacifier, especially in the Zirconium Silicate form. Parent materials of finer particle size are more effective.
In lead glazes a cream tint is likely. Glazes high in boron or alkalis, or low in alumina and silica may not opacify well.

By copied http://www.crramic.com

返回页首

• 上一页 • 主页 • 上一层 •


如有关于本站点的问题或建议,请向站点管理员发邮件。对本站点内容,我们谢绝任何形式的复制、拷贝,违者本站点保留一切法律诉讼的权利!
版权所有(C) 淄博张店鹤鸣色釉料厂 2000年9月建立;鲁ICP备05027285号