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Minnesota Clay Co. USA Technical Info - Glossary

Alberta SlipUsed 1 to 1 as a substitute for Albany Slip in recipes. Extremely craze resistant; applies well to green or bisqueware. Mixes and sprays very well. An iron saturate slip clay. It is fusible and when mixed only with water produces beautiful satin-gloss brown glazes at ^10. Depending on atmosphere and the underlying clay body it can range from a ""bean pot"" to Tenmoku glaze. Fires to a black brown color. 325 Mesh.
Ravenscrag Slip Ravenscrag slip was originally developed as an almost-complete base cone 10 glaze material with superior application and multi-layering properties. In educational and beginning pottery settings it is an ideal starting-point for material-blending style glaze development and experimentation with colors, opacifiers, variegators and matting agents.

A very plastic air-floated secondary clay used in clay bodies where ball clay or fireclay are called for. Suitable for light firing, high temp clays. Fires with approximately 7% shrinkage at cone 8. Fairly low sulphur content.

RedartA high iron, fine-particle, low fire, secondary clay used in glazes and clay bodies where a low temperature clay is required. Fires to a red-brown color with approximately 14% shrinkage at cone 1. Not very plastic on its own, but used frequently in terra cotta and smaller amounts for color in Stonewares. Will flux at high temps and can be used in or as a low-fire slip.
Kentucky StoneAir floated stoneware clay which may be used in clay bodies when Goldart or ball clay are called for. Fires to a light cream color with 11% shrinkage at cone 10.
Yellow Banks #401A very plastic air-floated stoneware clay with extremely low sulfur content. May be used as a Goldart substitute. Fires off-white with approximately 7% shrinkage at cone 8.
Kentucky Old Mine #4The "universal" ball clay which can usually be substituted for most any ball clay in a formula. A very plastic secondary clay used in glazes and clay bodies when ball clay is called for. Fires to a light gray-white with approximately 15% shrinkage at cone 10. (light-medium light gray powder)
Tennessee XX Saggar Ball Clay. A fine grained secondary clay with good plasticity and very low iron content. Fires to a light cream color. Approx 13% shrinkage at ^ 10.
Tennessee #1Ball Clay. A plastic secondary clay used in glazes and clay bodies. Fires white with approximately 14% shrinkage at cone 10.
Old HickoryBall Clay. A popular secondary clay used in both glaze and clay body formulas where a ball clay brand name is not specified. Fires to a light gray color with approximately 13% shrinkage at cone 10.
#1 Glaze ClayBall Clay. A high silica clay with excellent suspending qualities. May be substituted for ball clay in glaze recipes. (very pale gray powder)
English GrollegKaolin. A primary clay mined in England. Used for translucent porcelain clay bodies. Fires to a white color with approximately 14% shrinkage at cone 9. (white powder)
Florida EPKKaolin. A very plastic, fine particle, primary clay most often used in clay formulas and also glazes when kaolin is called for. Fires to a cream-white color with approximately 13% shrinkage at cone 9. Slightly more refractory than Domestic Kaolin. (cream colored powder form)
Georgia DomesticKaolin. Also know as Velvacast. A course particle primary clay used in both glazes and clay bodies wherever kaolin (china clay) is called for. Fires white with approximately 14% shrinkage at ^ 10. Used in casting slip to reduce warpage & improve mold release properties.
Domestic CalcinedKaolin. Also know as Glomax. Calcined to reduce shrinkage in glaze or clay formulas.
#6 Tile ClayKaolin. An air floated kaolin of high green strength, very clean, plastic & white used with Kaopaque#20 to produce a very translucent (when thin) workable porcelain. (creamy-white powder) (Virtually identical to Sapphire Clay.) 200 mesh
Hawthorne BondFire Clay. A Missouri fireclay of good plasticity and fine particle size. Light fired color with approximately 10% shrinkage at cone 10. 30 mesh
FritsFrits are combined raw materials that are mixed, fired, melted, crushed and ground into a powder. The reason for fritting is to render soluble materials insoluble; decrease toxicity of raw materials such as lead, barium and zinc; to reduce fusion point of glazes; and to avoid volatilization of unstable substances. Frits are often used in glazes as fluxing agents but can also be used in slips and clay bodies.
Ferro Frit 3110 1490° F melting point. High alkali, low alumina and boron leadless high expansion frit.
Ferro Frit 3124 1600° F melting point. Leadless high calcium borosilicate frit.
Ferro Frit 3134 1450° F melting point. Replaces Pemco P54. Leadless high calcia borosilicate frit.
Ferro Frit 3195 Leadless High Borax/calcia for glaze.
Ferro Frit 3269 1400° F melting point. Replaces Pemco P25. Leadless Sodium Boron Frit.
Fusion F-79 N/A ° Low expansion flux for high alumina bodies
Alumina hydrate The preferred source of alumina in glazes. Used in glazes to increase hardness, stability and aid in craze resistance and adhesion. Commonly used as a kiln wash in salt kilns as a kiln wash due to high refractory quality. Used in a glaze in excess, will tend to give a matt surface. Al2O3 3H2O
Barium carbonate
Main source of barium oxide in glazes. It is an active flux and will help in producing matt finishes. It may also be used to stop soluble salt scumming in clay bodies when added in small amounts(.05 - 2 %). Insoluble in water. Suspected toxic leacher, Poisonous.
A fine-grained plastic volcanic ash clay that is quite sticky with a high shrinkage. It is never used alone due to its high shrinkage rate and its tendency to cause swelling. Used in bodies in small percentages to aid in plasticity and Bentonite may also be used as a suspending agent in glazes (1 - 2%) suspension.
Bone ash
Ca3 (PO4)2
An important source of calcium phosphate. When added to a clay body such as bone china, it lowers the maturing temperature & adds translucency. Used to give texture in low fire glazes.
Brunt UmberA calcined hydrated iron oxide colorant with manganese dioxide and clay.It can be used as a slip or clay body colorant. Similar to ochre or sienna.
Calcium Carbonate Aerogem Used mainly as a calcia clay body whiting. (white powder)
Calcium Carbonate #10 Whiting
Previous referred to as #1 white. Source of calcia preferred for use in glazes. Whiting has traditionally been a source of CaO in raw glazes and glass (however whitings also typically contain some dolomite as a contaminant). Whiting is generally inexpensive and there is a large calcium carbonate industry worldwide for non-ceramic uses of this mineral.
Chromium Oxide Green
A refractory ceramic potent color used in clays or glazes for its strong green hues. Used with tin to produce pinks, or with zinc for browns. Volatile if fired over cone 07-may affect color of adjacent ware in the kiln. DUST IS TOXIC. Cr2 O
CMC GumAn organic cellulose binder/suspension/thickening agent-promotes hardness in dry glaze surface. Use 1/4% CMC to dry weight of glaze. Recommended use: mix 1 - 2 Tbsps. Per gallon of warm water and let stand for 24 hrs. Use approximately 1 part of the solution to 2 parts water when mixing a glaze to improve brushability. Use lesser amounts for dipping, pouring or spraying glazes. CMC will increase drying time which is not always beneficial to these application techniques. Avoid breathing dust.
Cobalt Carbonate
A pink powder, used as a glaze colorant and for brushed oxide decoration. A very potent colorany that produces various shades of blue and, where manganese is present can give a purple color. Better suited to oxidation. Use from 1 - 3%. May be doubled to equal the strength of cobalt oxide. Disperses easily in clay & glaze for uniform coloring.
Cobalt Oxide
A very stable oxide which is a blue-black powder. Fires to a strong blue with some dark blue speckling in glazes and clay bodies due to coarser mesh size than Cobalt Carbonate. In small amounts it produces very strong blues. Source of old time "flow-blue" decorations. Use .25 - 1%. This is the most powerful colorant and a very active flux. Well suited to reduction.
Copper Carbonate

A mint green dry color powder used as a colorant. Products a turquoise-green to red colorant in glazes and clays depending on firing atmosphere (reds require good reduction w/a soda base glaze.) The carbonate form will decompose in hot water and is more toxic than the oxide form. To convert a copper oxide formula to copper carbonate, multiply the carbonate by 1.5.

Copper Oxide-Black

The first glaze colorant known. Black dry color. Normally used wherever copper oxide is called for and red or black is not specified. It is a strong flux and will produce fluid glazes. Copper tends to volatilize somewhat at high temperatures (^ 8 reduction) affecting adjacent colors. Toxic in raw form and should not be used on dishes or drinking vessels. Not usually preferred over copper carbonate. Use 2 - 5%.

Copper Oxide-Red
A concentrated copper form. Reverts to CuO in oxidation. Use a few drops of liquid soap detergent like "Ivory" to dissperse the powder into the glaze batch. Can produce copper reds under reduction. Use 2 - 5%.
Copper SulfateA soluble blue powder used to obtain greens and reds depending on firing atmosphere and accompanying chemicals in glaze. Poisonous. CuSO4
Cornwall Stone

A complex spar used in clay bodies to add strength while firing. A feldspar of high calcium/silica content from the Cornwall district in England. Used as a flux in glazes and some clays and engobes. With the addition of a suitable flux, Cornwall Stone can be used as a glaze. Has a light green color in raw form and is almost iron-free. Potash/soda balance: 3.8% - 4%


Dolomite is useful as a source of calcium and magnesium used primarily in stoneware glazes as a flux and also to promote crystallizing. May be used to replace whiting for special glaze effects. Produces "dolomite matts".

Epsom SaltsA common suspension agent for glazes. (2 C. hot water + 2 Tbsp. Epsom salts in a vented blender. 1/4 tsp mixture to 1 gallon liquid glaze. Better to error on the side of too little. Can always add more if needed. If too much, then more liquid glaze must be added.)
Feldspar Custer (Potash)A potash feldspar used in glazes and clay bodies as a flux where low soda, high potash spars are called for. Commonly used where an undesignated feldspar is called for in a formula. Potash/soda balance: 40.4% - 3%. 200 mesh
G200 Feldspar (Potash)
K2O Al2O3 6Sio2

G-200 Feldspar is a high quality potassium / sodium / calcium aluminum silicate ground to 200 mesh for ceramic applications. It is a material that is extremely low in impurities (iron) which makes it highly suited to pure white glazes and as a flux in porcelain clay bodies.

Feldspar Kona F4(Soda)A soda feldspar used in glazes and clays where a soda flux is required. Often preferred where intense color is desired in a glaze or clay. Potash/soda balance: 4/8% - 6.9%. (white-very light gray powder)
Flint Flour
A slightly coarser mesh silica used primarily in clay bodies where a little openness is desired without the texture of silica sand. Toxic if inhaled. 200 mesh

Flint Powdered

A fine silica used in glazes and smooth clays. Glass former in glaze and clay. Predominate ingredient in many glazes, this chemical will usually be the controlling factor for most glazes fitting properly. Toxic if inhaled. 325 mesh


Flint Sand (75 mesh)
A very coarse mesh silica (sand grain) used in clay bodies. Adds Texture and strength. Softens at ^ 9.
Gillespie borate Chemically the same but physically different from "Gerstley Borate". Requires testing.
Gerstley Borate
2CaO3 B2O3 5H20

A sodium/calcium/borate compound used as a low temperature flux which helps to prevent crazing. Can act somewhat as an opacifier. Also can be used as a substitute for calcium in glazes where a pink or red is desired. In most cases can be substituted for Colemanite and is more stable. 200 mesh.

Grog-Medium (12 mesh)Prefired ground clay used primarily in sculpture clays for texture and a more open clay body. Strengthens and reduces shrinkage.
Grog-Fine (20 mesh)Finer mesh than above grog.
Grog-Extra Fine (30 mesh)Finer mesh than above grog.
Iron oxide - Black

Ferrous Oxide. Coloring oxide produces same range of colors as red iron depending on formulas and firing variations. Produces various shades of brown or green when used as a glaze colorant or decorative oxide. In high fire matt glazes, iron oxide and titanium can produce reddish glazes. Preferred by many potters when making Celadon glazes (blues or greens) in reduction. May act as a flux when used in excess.

Iron oxide - Red
Ferric Oxide. Most commonly used as a colorant where iron oxide is called for in a clay or glaze formulas. Produces a broad color range from yellows, browns, red-browns, and blacks in oxidation; to grays, blues, greens, and blacks in reduction. Acts as a flux at mid-high temperatures lowering the firing range.
Iron oxide - SpanishAn iron variety; fires dark brown to black; used primarily for iron decoration under and on the pre-fired glaze surface; semi-refractory.
Iron sulfate (copperas)Ferrous Sulfate. Soluble colorant for reds and violets at low temperatures when the appropriate base glaze composition is used.
Kiln washA combination of refractory materials mixed with water and used to coat kiln shelves and posts to help protect them from glaze spatters and runs.
3Al2 O3 2SiO2

100 mesh Alumina-Silica ore. Highly refractory, expanding when fired at high temperatures. Used to reduce clay body shrinkage, to strengthen clay bodies, and helps with thermal shock in Raku bodies. (see mullite)

Lithium carbonate
Li2 CO3

Used as a flux. It is a source of slightly soluble lithia which is a strong high temperature flux. Lithium carbonate improves the brightness of glazes and increases the firing range. Also reduces thermal expansion. Poisonous

Magnesium carbonate

A very weak coloring agent. An insoluble source of magnesia that will act as a flux in high temperature glazes. Depending on the percentages and firing temperature, can give an opaque buttery surface or satin matt surface to a glaze. Adds strength, hardness and less shrinkage.

In an alkaline glaze, a blue-purple or plum color can be obtained. Manganese carbonate is more useful as a flux.

Magnesium oxideFunctions much the same as magnesium carbonate with a larger particle size. Not a colorant.
Manganese dioxide-PowderA fine mesh colorant used to obtain purples, pinks, browns, and blacks. Resultant color depending on formula and firing variations. Toxic if inhaled or ingested.
Manganese dioxide-Granular60/80 mesh. Granular manganese colorant. Will give a speckled effect in glazes and clay bodies. Usually dark brown or black colored specks. Toxic if inhaled or ingested.
Mullite (100 mesh)Calcined Kyanite. A non-plastic, alumina silicate crystal (formed by calcination of kyanite to 3000° F). The needle-like crystal is stable to 3000°F and interlocks. Used in clay bodies, crucibles, kiln furniture to strengthen and improve thermal shock properties.
Nepheline syeniteA high alumina-soda flux. Usually used in formulas for medium to high range glazes ^ 4 - 8. (Alumina 24.05% Potash 5% Soda 10.2%)
Nickel oxideColoring oxide for browns, grays, blues, yellows and muted greens. Will yield colors similar to nickel carbonate. May be used to quiet other more intense and potent colorants. Maximum amount in glazes is about 3%. Toxic in raw form.
Petalite (200 mesh)Lithium feldspar used in medium to high temperature glazes and clay bodies. Has a high melting point and very low thermal expansion. Often added to flameproof clay bodies to help control thermal shock.
Pottery Plaster K60A plaster suitable for mold making, modeling, wedging tables or bats.
Densite Plaster K5
Pyrophylite (Pyrax)Similar to talc. A natural hydrated aluminum silicate. Used in some clay bodies as part of the refractory content because of its low shrinkage. Can use up to 20% in formula. (cream colored powder)
Rutile (ceramic grade)An impure iron-bearing ore of titanium. Often used as an ochre-cream colorant in oxidation. A variety of colors including blues, oranges, or pearls are possible in reduction. May also be used as a tone modifier for other more potent colorants such as cobalt or chrome.
Silicon Carbide ( 500 mesh)Used primarily as a local reducing agent placed near the ware in the kiln. Used in some glazes for locally reduced color. Used in glazes with copper carbonate & tin oxide to produce reds. Toxic if inhaled.
Soda ash (sodium carbonate)Anhydrous sodium carbonate. Deliquescent and soluble. Used as a deflocculant in slip casting.
Sodium bicarbonateA water soluble flux agent. Combined with soda ash, it is a good, non-toxic substitute for rock salt in salt firing. (M0st commonly used as part of the soda content in Egyptian Paste formulas.
Sodium silicate syrupA water-soluble solution of soda and silica. Used in conjunction with soda ash for the purpose of deflocculant in casting slips for both low and high fire. Care must be used because it will actually re-flocculate the slip if too much is added. It is also readily absorbed by plaster leading to deterioration and the eventual breakdown of slipcasting molds.
Spodumene LM (low melt)A source of lithia used in clay and glaze. This material is from a new source and is very low in iron. (similar to the grade available in the 1970's) Testing suggested.
Strontium carbonateSlightly soluble. Used as a glaze flux similar to calcium; improves hardness; lowers solubility in glazes; for less pin holing and less blistering and extends glaze firing range.
Talc Nytal (100 mesh)For clay bodies. Same characteristics as other talcs with a fibrous molecular structure. Used primarily in casting slips requiring less sodium silicate. (light gray colored powder)
Talc SteatiteFor glazes. Low temperature flux primarily used in glaze, but can be used wherever talc is called for in a formula. Lowers thermal expansion. May affect some colorants. A source of magnesia and silica in a glaze.
Talc WestexFor clay bodies. Low temperature flux used commercially in many whiteware bodies. As with all talcs, must be mixed well with other dry materials before adding water. Particle size larger than in the steatite talc. Platy, non fibrous talc.
Tin oxideOpacifier at all temperatures. Will not dissolve in the glaze, remains suspended as minute white particles. The best and most expensive. Produces even, opaque glazes. Normal usage is 2 - 10%. Stronger than Ultrox and twice the strength of Superpax and Zircopax. (white)
Titanium dioxideOpacifier. Promotes matte to semi-matte glazes. Also used as an agent in crystalline glazes at 6 - 15%. Impure forms of titanium are rutile and ilmenite.
Veegum TAn inorganic, processed, colloidal magnesium alumina silicate (iron free) used as a plasticizer-lubricant in white clay bodies. A good binder for extruder bodies. Can also be used as a suspending agent for glazes.Use 1/2% to 2% to dry weight of clay. Use 1/2% to 3/4% to dry weight of glazes.
WollastoniteA calcium metasilicate used in some commercial low temperature vitreous clay bodies as part of the feldspar content, and in some glaze as a source of calcium. Replaces silica and whiting.
Yellow OchreA colorant used in the same manner as the irons in glazes and clays to achieve different hues of yellows, browns, or brick-reds depending on firing atmosphere.
Zinc oxide (uncalcined)Used in small amounts as a flux in glaze, it often helps promote craze resistance. In larger percentages (3%+) may act as an opacifier and promotes matting. Zinc used at 18 - 28% produces crystals when cooled slowly. Zinc has a strong effect on many colorants-primarily in oxidation. Because of its high shrinkage ratio, calcining is often helpful when used in glazes formulated for bisqueware.
Zircopax plusOpacifier. 94 - 96% pure.Used much the same as Superpax now with a finer particle size. A little stronger & more economical to use than regular Zircopax.
Products no longer available or no longer carried
Albany SlipSee Alberta Slip.
AP Green / Missouri Fire claySedimentary clay with good vertical plasticity used mostly in ^ 10 bodies as a "refractory clay." Sometimes used as a mortar when mixed with water. Approx 11% shrinkage @ ^ 10. Fires light cream color.
Barnard / blackbirdAn iron-saturated, self-glazing slip clay. Used alone as a slip or stain or as a colorant in glaze & clay recipes, it fires brown/black depending on temp & atmosphere. Vitrifies ^ 4-10. Similar in nature to Albany Slip.
Bone Ash (calcium phosphate)Bone ash (crude and waterground) are ground calcined animal bone; used in bone china (up to 50%) to aid body translucency and strength. A flux and opacifier in glazes. May render surface texture in some low-fire glazes.
Na2O 2B2O3 10H20
Source of boric oxide and soda in glazes. A soluble, low temperature flux which in small amounts can increase fluidity of a glaze; larger amounts can lower the maturing temperature. Gives bright colors with most oxides.
Cedar Hts BondingStrong, fairly plastic fire clay. Low in sulphur, cleaner than AP green or Hawthorne.
ColemaniteSee Gerstley Borate.
A sodium-aluminum fluoride. Can be used as a source of insoluble soda flux but fluorine may bubble through glaze causing pinholes. Alumina content will tend to matt glaze surface. In small percentages, may be used as a flux in low temperature clay bodies.

Flourspar has a lower fluxing temperature than other calcia compounds. A whiting substitute for more fusible glazes. Can be used in porcelain for better translucency. Can be destructive to kiln furniture after long-term use because of fuming. Toxic in raw form.

Georgia DiamondReplacement for Georgia Pioneer Kaolin which is no longer mined. Clean firing with high green strength @ ^ 10. Fires white.
Gerstley - Calbo (ulexite)200 mesh and finer. The material is more finely ground than Gerstley Borate. It is also cleaner, has a slightly lower melting point, and will help eliminate dark specks in glaze.
IlmeniteAn ore of titanium and iron. Granular ilmenite is used to produce a speckled effect in clay bodies and glazes. In small amounts in can promote or ""seed"" the growth of crystals in glazes-especially those containing rutile.
Iron ChromateForm of iron usually used when darker browns and red-browns are desired.
Iron Oxide - yellowFe2 O3 .H 2O Hydrated ferric oxide. A coloring oxide much the same as red, tends to produce creams and buffs.
Minspar 4Interchangeable feldspar with Kona F-4. Both are mined in NC
Mississippi M&DVery fine-particle ball clay used to improve plasticity and strength in clay bodies; no more that 10% - large quantities may increase warpage and shrinkage.
MolochiteA fine textured (22 - 80 mesh) porcelain grog. Used to maintain the white color in porcelains where more tooth is required.
Nickel Carbonate-GreenColoring oxide for browns, grays and muted greens. Used primarily in oxidation atmosphers in glazes and clays. Refractory nature may tend to cause glaze matting.
North AmericanA non-plastic refractory clay. Fires light tan.
SuperpaxZirconium silicate opacifier 92 - 94.5%. Used in slips and glazes as an opacifier much the same as zircopax, ultrox or tin oxide. Has a relatively small particle size for better dispersion. NLA use Zircopax.
Tennessee #5Plastic ball clay used both in clay and glaze formulas. Approx 15% shrinkage @ ^ 10. Fires grey-white.
Ultrox A very stable, reliable opacifier widely used in large commercial potteries. Not as potent as Tin Oxide but stronger than Superpax. NLA use Tin Oxide.
Volcanic Ash (pumice)Used as a flux in glazes and added to earthenware clay bodies for aiding in thermal shock resistance during pit and raku firings.
  • Alumina Oxide Al2O3 Responsible for the mattness or brilliance of glazes. Prevents devitrification and adds strength. Insoluble in water and melts at 3550° F. Addition of too much alumina can cause dry, under-fired appearance

  • Antimony Oxide Sb2O3 This is sometimes used as an opacifier in older glaze formulations. It was primarily used to produce Naples Yellow when combined with lead oxide. Toxic.

  • Boric Acid, Granular B2O3 2H20 Used as a flux to increase gloss and elasticity of glazes. Acts as both a glass former and a flux. Improves the fit between the glaze and clay body. Tends to be soluble in water.

  • Grolleg Clay Kaolin mined in England. The main ingredient in "True English" style porcelains.

  • Grog Refractory brick which is crushed to various mesh size and added to throwing and sculpture bodies to increase working strength and to reduce the amount of shrinkage. Also aids in drying for large pieces of unusual thickness.

  • Gum (CMC) See CMC.

  • Iron Chromate FeCrO4 Produces dark colors in engobes and underglazes. Can also be added with manganese stains to clay bodies as a colorant. Fugitive above cone 04.

  • Kaolin, EPK. Al2O3.2SiO2.2H2O. A plastic kaolin mined in Edgar, Florida. Suitable for both glaze and clay formula. May be substituted for any china clay.

  • Kyanite, .

  • Lithium Carbonate

  • Manganese Carbonate MnCO3

  • Manganese Dioxide MnO2 A black powder which will produce brown, purple or black tones to clay bodies and glazes, depending on composition. Manganese carbonate may be substituted by using 1.5 times the carbonate.

  • Manganese Dioxide (Granular) A colorant to give specks to clay bodies and low fire glazes. It tends to over flux after cone 8.

  • Molochite. White firing porcelain grog suitable for use in any white clay body.

  • Nepheline Syenite K2O.3Na2O.4Al2O3.9SiO2 A very active soda spar. Helpfull in reducing crazing when added to clay bodies. This substance usually settles into a hard mass in the bottom of the glaze bucket, use any suspender to help lift it.

  • Nickel Carbonate (Green) NiCO3 Produces nickel oxide which is a colorant that yields a variety of browns, blues, grays and yellows depending on the presence of various other materials. Nickel Oxide is stronger.

  • Nickel Oxide (Black) NiO A black powder which produces browns, grays, blues and yellows. Can also tone down more intense colorants such as copper and cobalt. Its limit as a colorant is 3%. Black and green nickel are interchangeable.

  • Ochre A natural iron-based colorant used in clays and glazes that produces tans and pale yellow tones.

  • Plastic Vitrox. 1RO.1.69Al2O3.14.64Sio2. A complex type of material similar to potash feldspar and Cornwall stone.

  • Potassium Carbonate K2CO3 Also known as Pearl Ash. It is a strong flux and can be used as a color modifier in glazes. Can change copper greens into yellow-greens or bright blue.

  • Pumice Also known as Volcanic Ash. Frequently used as a feldspar substitute in glazes.

  • Redart Clay, A low temperature, air-floated clay that produces red to brown clays. May be used as a colorant in high temp clays.

  • Rutile (Ceramic Grade) TiO2 A titanium dioxide colorant which contains a small amount of iron and vanadium. Will produce tans and mottle other colorants..

  • Silica Sio2, Also known as flint or quartz. Glass former. In a glaze it will raise the maturing temperature and increase the hardness of the glaze. It will lower a glaze thermal expansion, but will increase it in a clay body.

  • Silicon Carbide SiC,(FFF) An artificial reduction agent used in oxidation which produces a localized reduction on the glaze. Add in 0.5 percent to alkaline glazes.

  • Soda Carbonate Na2CO3 Soda Ash. This is an active flux which also serves an important function as a deflocculant for slip casting bodies. Increases strength and workability, reduces shrinkage. As a glaze deflocculant, you should add 3 gm for every 100 gm dry ingredient.

  • Sodium Silicate (Wet) Sodium Silicate is a major deflocculant in slip casting and in glazes that settle. NOTE: Read directions carefully. Adding too much can cause the opposite effect. Can sometimes be combined with Soda Ash.

  • Spodumene. Li2O.Al2O3.4Sio2 An important source of Lithia and an active flux. This ingredient helps promote unusual copper blues. Can be added as a replacement for feldspar in some clay bodies to reduce shrinkage and maturing temps.

  • Strontium Carbonate SrCo3. Source of strontium oxide in glaze formula.

  • Superpax ZrSiO4 Zircon opacifier, used in a wide variety of applications. Effective in controlling texture, craze resistance and color stability.

  • Talc 3MgO 4SiO2 H20 A flux for low temperature, white clay bodies and low and high fire glazes. Gives a slight opacity to a glaze.

  • Tin Oxide SnO2 The most effective opacifier to produce even, opaque, glossy glazes. The normal content of tin oxide in a glaze is between 5 and 10%. The results obtained are consistent. A dull matt glaze can result when used in excess. Excess may also result in crawling glaze. Will pick up pink flashes if chromium oxide is present in other glazed items in the same kiln. *

  • Titanium Dioxide TiO2 The best opacifier for white matt glazes, usually will cause the most effect on other colorants. 10% is the maximum content limit. Useful in forming crystalline glazes. *

  • Umber (Burnt) A hydrated ferric oxide with manganese dioxide. It is used as a decorative element to produce a reddish-brown color. Also can be added to clay bodies to make the color darker.

  • Vanadium V2O5 A weak yellow colorant that is usually combined with tin oxide to give a yellow color capable of firing to higher temps. Use up to 10%.

  • Vee-Gum T A macaloid-type gum suspension for glazes. Also used as a surface hardener. It is an extremely plastic, hydrous magnesium silicate used to give plasticity to non-plastic white-ware and refractories.

  • Volcanic Ash Also known as Pumice. Frequently used as a feldspar substitute in glazes.

  • Whiting (Calcium Carbonate) CaCO3 This is the most common source of calcium oxide in glazes. It is a major high temperature flux which gives durability and hardness to a glaze.

  • Wollastonite CaSio3 A natural calcium silicate used to reduce shrinkage in clay bodies and glazes during firing. Can replace silica and whiting. It will reduce firing shrinkage and also improve heat shock in clays and glazes.

  • Zinc Oxide ZnO, Calcined (Ceramic Grade) A high temperature flux. It increases the maturing range of glazes and produces bright colors and promotes a high gloss finish with reduced expansion. Also may be used to give opacity to glazes.

  • Zircopax ZrO2 SiO4 The original Zirconium opacifier. Used mostly where semi-opaqueness is desired.