Pottery Clays and Chemicals

Protect Your Health

Many materials used by ceramists are potentially hazardous to your health, some are immediately irritating: others accumulate in the body and become more toxic with continued exposure. Any of these ceramic materials in the dry powdered form can be inhaled and cause damage to the lungs. Free silica (sand, or flint) which is a component in all clay bodies, can lead to scarring of the lungs and is the well known cause of silicosis. Inhaling, ingesting or handling other chemicals can result in problems ranging from dermatitis and allergies, to nervous and muscular disorders, and even cancer. For additional material data safety information call (973) 340-3005

Safety Precautions:

• Do not eat, drink, or smoke in work area. Smoking… ohhh no• Do not brush or shake out your clothes, but, rather vacuum them and wash frequently.• Wear a respirator that meets NIOSH regulations (especially when mixing clay and glazes)• Wear gloves to prevent absorption through the skin.• Wear heat resistant gloves to protect against heat from the kiln.• Wear goggles against flying particles when grinding or chipping on ceramics.• Wear goggles against harmful rays when looking at such sources of them (the kiln).• Vent your kiln room and spray any area to be swept with a light mist of water to keep down dust when sweeping.• Do not sweep if possible, but rather sponge and wet mop surfaces to prevent raising dust. For large areas use a shop vacuum, or dust collection system - that exhausts outside.

Be sure all materials are kept out of the reach of children!

Potentially Hazardous Materials

Here is a partial list of the materials used by potters and ceramists which have been found to be potentially most toxic; Free silica from many clays, flint, feldspars, and talc: Metallic oxides, carbonates. etc. especially antimony, barium, beryllium, cadmium, cobalt, chromium, copper, Iead (in any form), Iithium, manganese, nickel, potassium bichromate, selenium, uranium, and vanadium.

Fumes from kiln firing (both electric and gas) that can be produced are fluorine, chlorine, sulfur dioxide, metallics, and in gas kilns, also Carbon monoxide.

About mixing your own glazes – something that calls for 3.5% had better be a real 3.50%, not a 3.4% or 3.6%. A good scale is a must.

Basic principal here: It’s precise, or it’s junk.

Toxicity Hotline

The Chemical Manufacturers Association has a hotline to answer questions about toxicity, disposal procedures and other problems related to chemicals in products. 1 (800) 262 - 8200.

Glossary of Slip/clay Chemicals and Raw Materials

This report is included as an attempt to answer some of the most often asked questions about chemicals as used in ceramics and pottery. It is by no means a complete definition of these materials. If you have any further questions - email, write, or call.

It’s recommended the producer of any for-sale dinnerware have their finished ware tested by an approved laboratory to determine whether or not it meets FDA guidelines in its own category BEFORE IT’S PUT ON THE MARKET.

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A

Alberta Slip Albany Slip substitute

Alumina Hydrate (Al203-3H20) – Usual source of alumina in glazes. Promotes stability and hardness in glazes. Used in kiln wash and as a wash to keep lids from sticking to pots, or pots sticking to shelves. The preferred source of alumina in glazes. A main kiln wash ingredient. Produces matt glazes.CAS#21645-51-2

Aluminum Oxide (Al2O3) - Calcinated alumina hydrate: in glazes will promote strength and matteness; usually added to a glaze through feldspar or clay. 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 appearanceCAS#1344-28-1

Albany Slip, Synthetic The physical and chemical properties of True Albany Slip duplicated in a more

stable and consistent form. So far it has been impossible to detect any differences from the results of True Albany Slip. Test before using.CAS#1332-587, CAS#14808-60-7,. CAS#65977-18-4

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. Use not suggested.

B

Ball Clay, OM#4 (Old Mine #4) The "universal" ball clay which can usually be substituted for most any ball clay in a formula, although some glazes might be sensitive to changes. Considered a plastic, light burning ingredient in clay formula.

Ball Clay - Fine grained (hence very plastlc) Iight-burning clays used in stoneware bodies to increase dry strength and virifcation upon firing. A source of Al203+Sl02 in glazes, used to raise firing temperature.CAS#1332-558-7

Barium Carbonate (BaC03) - May promote matteness in low fire glazes and hardness and brilliance in high-fire glazes. 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 scumming in clay bodies when added in small amounts. Suspected toxic leacher. Also known as witherite. Used to neutralize sulfate in clay bodies. TOXIC in raw slate; insolube in water. CAS#513-77-9

Barnard (Blackbird) - Iron saturated slip clay used as a glaze similar to Albany slip but contains more clay. Also used to darken clay bodies.CAS#1332-587

Bentonite (Al203-4S102-9H20) - Very plastic clay; contains colloidal mater, used as a plasticizer in clay: as a suspension agent in glazes 1-2% may be added to dry mix. A plastic montmorillonite clay containing colloidal matter which, in very small amounts, lends plasticity to a clay body. It is never used alone due to its high shrinkage rate and its tendency to cause swelling. Bentonite may also be used as a suspending agent in glazes.CAS#1302-79-9

Barnard Blackbird Slip A naturally occurring clay colorant or decorating slip. Similar in nature to Albany Slip.

Bismuth Subnitrate [4BiNO3-(OH )2-BiO(OH )] Used to produce iridescent luster colors (especially in raku).CAS#1304-85-4

Bone Ash [Ca3(P04)2] – AKA tri calcium phosphate. Important source of phosphate. Ground calcinated animal bones: used in porcelain bodies as a flux and to help promote translucence. Lowers maturing temperature. Used as a flux in high fired glazes; gives texture to low fired glazes.CAS#68439-84-1

BORAQ (plastic borate) blended mineral borate for use in glaze formulation replacing Gerstley Borate. A blend of Turkish Ulexite, Cadycal, Soda Feldspar and Hectorte. A compound of materials that’s very similar to Gerstley Borate

Borax (Na20-2B20-10H20) - Source of boron (see Boric Acid) Used in low-fire glazes as a flux in place of lead. Fritted form is more stable. Water soluble. A soluble, low temperature flux which lowers the fusion point of glazes and promotes a smooth melt. Gives bright colors with most oxides. A source of sodium and boric oxide in glazes.

CAS#1303-96-4

Boric Acid (B2O33H2O) - Source of boron, see Borax. A flux in low-fired glazes as a substitute for lead. 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.CAS#10043-35-3

C

Ceramic Stains Stains are coloring oxide combinations that have been pre-fired (fritted) for more stability. They may be used in glazes, slips, clay bodies and used as a wash to decorate with.

Zinc-bearing glazes seem to affect color results the most. A wide color range can be achieved by varying the percentage of stain, mixing opacifiers such as tin or zircopax and blending stains together.

Most colors are usually stable from cones 018-10. Different results can be expected from oxidation and reduction. Please experiment and test first.

*Be cautious with all stains. Do not eat, drink or smoke when handling stains. Use plastic gloves if you have an open cut. Wash hands, keep work area clean.

Cady Cal Calcium Borate or synthetic colemanite, an alternative natural colemanite with a high boron content and high calcium oxide content.

Calcium Carbonate CaCO3 Also known as whiting. This is the most common source of calcium oxide in glazes. High temperature flux.

Chrome Oxide (Green) Cr2O3 Used in glazes to produce various shades of green. The maximum percentage for use in glaze is 5%. Combined with cobalt it can give a peacock color. Mixed with tin oxide, pinks are possible. TOXIC IN RAW FORM.

‘Gum’ (CMC-Veegum T) Sodium CarboxyMethlCellulose. An organic vegetable gum that is used as a binder, thickener and suspending agent. Use .25 - 2%. If added dry to the glaze batch, sieve after wetting several times. Usually mixed with water, blended very well and then put into the wet glaze. This is a gelling substance.

Careful! Other things may be called ‘Gum’, too, but they are not real ‘Gum’.

Cobalt Carbonate (CoCO3) A pink/lavender powder, used as a glaze colorant and for brushed oxide decoration. 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. TOXIC IN RAW FORM.

Cobalt Oxide (Black) Co3O4 A very stable oxide which is a black powder. In small amounts it produces very strong blues. Used as a glaze colorant, for glazes and for brushed decoration. 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 firing. TOXIC IN RAW FORM.

Colemanite See Gerstley Borate, or Boraq.

Copper Carbonate (CuCO3) A light green powder used as a glaze colorant. It may produce green, blue-green or copper red. To convert a copper oxide formula to copper carbonate, multiply the carbonate by 1.5. TOXIC IN RAW FORM.

Chromium Oxide (Green) (Cr20) Extremely potent. Usually produces greens in glazes, used with tin may produce pinks with zinc, and browns. TOXIC IN RAW FORM.CAS#1308-38-9

CLAY (Al2O3 -2SlO2)

SLIP CLAYS CAS#1332-558-7

Kentucky OM4 (“Old Mine #4”)Kentucky SpecialSPG#1Tennessee #5Tennessee XX Sagger XX Sagger is a ball clay used as fire to clay and used to make saggers (Saggers: a clay box into which delicate ceramic objects are placed to protect them in the kiln during firing.).

CHINA CLAY (KAOLIN) - Very fine clean, white or cream refractory clay which when fired to maturity wilI become vitreous and translucent. Used to make white-ware, china, and porcelain. Useful as a kiln wash ingredient.CAS#1332-558-7

English Grolleg - Very plastic white English clay: used to promote translucence in porcelain bodies

EPK - A plastic Florida clay also used in glazes

FIRE/BODY CLAYS - High refractory, more coarse than balI clay, may contain iron, calcium, manganese and other impurities

A.P.G. Missouri Fire Clay CAS#14808-60-7

Goldart Refractory clay of fair plasticity for bodies CAS#1332-558-7

Hawthorn Misssouri Fire ClayCAS#1332-558-7

Plastic Vitrox May be substituted for feldspar (half and half) to lower the firing temperature.CAS#14808-60-7

Redart - High iron content, plastic clay, usually used to produce earthenware bodies CAS#1332-558-7

Cobalt Carbonate (CoCO3) - WilI produce shades of blue, will speck if not sufficiently sieved: approximately 60% of the strength of the oxide form.CAS#7542-09-9 and 3333-67-3

Cobalt Oxide (Co3O4) - Small amounts usually less than 2%) will give strong blue color. In combination with other elements will produce pinks, purples, greens, or black.CAS#1308-06-1 and 1313-99-1

Cobalt Sulphate (CoSo4,5H20) See SULPHATES CAS#10026-24-1

Copper Carbonate (CuCo3) - May yield green and turquoise in oxidation or red in reduction with a slight fluxing reaction. Copper glazes may tend to volatize at higher temperatures and affect the color of the pieces around them. Carbonate form is more toxic than the oxide.CAS#12069-69, CAS#10214 -40-1, CAS#7440-50-8

Copper Oxide (Black cupric oxide - CuO) See COPPER CARBONATE Black cupric oxide can be soluble in fruit juices and should not used on ware intended for food or beverages. (Possible food use items should have a ‘Don’t use’ hole). The first (oldest) glaze colorant known. It is a strong flux and will produce fluid glazes. Can produce copper reds under reduction. Usually not preferred over copper carbonate. Use 2 - 5%. TOXIC IN RAW FORM, and it could be toxic in use. Use with care!CAS#7440-50-8

Copper Oxide (Red) Cu2O Will revert to CuO on firing and is interchangeable. Use a few drops of liquid soap detergent like "Ivory" to disperse the powder into the glaze batch. Can produce copper reds under reduction. Use 2 - 5%.

Copper Sulphate Crystals 21% 1 (Cupric) (FeSo4-7H2O) See SULPHATESCAS#779-99-8

Copperas (Iron Sulphate) (Ferrous) FeSo4-5H2O See SULPHATES May produce reds and violets at low temperatures.CAS#7782-63-0

Cornwall Stone (English Cornish or English Cornish Stone) A complex spar used in clay bodies to add strength while firing. Also used in engobe formulae because of its adhesive properties during and after firing. 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. Defluorinated.

Crimson Stain - Produces pinks through crimson (See Index - Mason stains)

Crocus Martis, Red and Yellow (FeO2, + impurities) - Naturally occurring, contains iron and other impurities; will promote speckled effects, may give darker browns than red iron oxide.

CAS#1309-37-1

Cryolite (Na3AIF6) Used in small percentages as a flux: a source of insoluble soda; may promote crackle effects in glazes; the fluorine content when burned off may cause pinholes in gaze. Sodium aluminum fluoride. Source of sodium in glazes, some glazes will pit or pinhole because of the fluorine content. An active flux in most glazes that will produce crater effects.CAS#15096-52-3, CAS#10101-41-4 , CAS#1344-28-1 and CAS#497-19-8

Cornwall Stone (CalCO, NaK20-Al203-8Si02) May act as a flux in bodies: contributes sodium to glazes. Green dye has been added for identification purposes; it burns out when fired. Non-defluorinated.CAS#64876-25-5

Custer (typically K20-Al203-6SiO2) - High potash spar may be used in a glaze where a type of feldspar is not specifiedCAS#64876-25-5

Ceramic Frits (See also Frits) Frits are a kind of glass, chemical compounds that have been melted, rapidly cooled, then ground to a fine powder. Some can be used alone or as part of the flux in a glaze.

Frit F-75 (3110) (P311) (H90) A high soda-silica, low borate frit. Melts at 1400° F

Frit F-19 (3124) (P311) (H14) Soda-Calcium-Borate. Melts at 1600° F

Frit F-12 (3134) (P54) (H399) High calcium, low potash borate, low silica. Melts at 1450° F.

Frit FZ-25 (3819) (P25) (H259) Soda-Borate-Zinc with a little Flourine. Melts at 1320°-1420° F.

D

Dolomite [CaMg(CO3)2] - Will flux stoneware glazes; may produce buttery glaze finish. Insoluble source of magnesia; approximately 2% can be added to porcelain body. Dolomite is useful as a source of calcium and magnesium. It can be used as a high temperature flux and also to promote crystallizing. Produces "dolomite matts".CAS#16389-99-1

E

Epson Salts (MgSo4-7H2O) Magnesium Sulphate - May be used as a suspension agent in glaze. Make a solution of 3 parts water to 1 part salt. Use 2 teaspoons of this solution to each pint of glazeCAS#7487-88-9, CAS#7732-18-5

F

FELDSPARS A natural glaze at high temperatures. The primary source of alumina and silca for glazes. Usually classed as potash spars (those containing potassium as their characteristic component) or soda spars (those containing more sodium). Other oxides are often present.

Feldspar, Custer A standard potash spar used in clay and glaze formulas, mined in Custer, South Dakota

Feldspar, G-200 A potash spar, low in impurities, well suited for white glazed and porcelain clay bodies.

Feldspar, Soda F-4 A standard potash spar used in clay and glaze formulas.

F-4 Kona Kona A-3 substitute (typical Na20-Al203-6SiO2) A soda spar. Mix with equal portion of potash spar for Kona A-3 substitute.CAS#64876-25-5

G200 (typical K20-A1203 6SiO2) - A potash spar.CAS#64876-25-5

Flint (Silica) (SiO2) - Basic glass-former in both bodies and glazes, increases hardness and resistance to wear. Used to remedy crazing in glazes when added to either glaze or clay. In glazes it will reduce thermal expansion: In bodies it will promote thermal expansion.Warning: Contains Free Slllca. Do not beathe dust. Prolonged inhalation may cause delayed lung injury (silicosis). Follow OSHA safety standards for handling.CAS#744-44 2

Feldspar, NC4, Soda Na2O Al2O3 6Sio2 A soda spar used widely in both clays and glazes. More active than most potash spars.

Feldspar, G-200, Potash K2O Al2O3 6Sio2 This is a potash feldspar. It is a material that is extremely low in impurities which makes it highly suited to pure white glazes and as a flux in porcelain clay bodies.

Flint, SiO2 (silica) (quartz) Glass former in glaze and clay. Predominate ingredient in many glazes, this chemical will usually be the controlling factor for most glazes fitting properly.

Fire Clay High temperature (refractory) clay usually added to clays to raise their maturing temperature and give the body "tooth" (texture).

Fluorspar (CaF2) - Used as an opaclfier: may also be substituted for whiting to assist fusion. Over 5% may cause blistering. It’s use in a glaze changes colors one would normally expect from pigments. Flourspar has a lower fluxing temperature than other

calcia compounds. It can be used as a substitute for whiting to promote more fusible glazes. Can be destructive to kiln ‘furniture’ after long-term use because of fuming.CAS#14542-23-5

Foundry Hill Cream, New. A creamy colored ball clay.

FRITS Chemicals that have been combined, melted, cooled and ground to a fine powder. This procedure renders certaln soluble materials insoluble and in particular circumstances will render toxic materials less toxic. All frits are fused silicate glass substances. Manufactured for use as a reliable glaze and body fluxesCAS#65997-18 4

Ferro 3110 - A leadless hlgh soda, low-borate glaze and body fluxCone 3-5

Ferro 3124 - Soda-calcium-borosilicateCone 3-5

Ferro 3134 (Hommel 14, Pemco 54) - High soda-calcium, low potash-borosilicate, used in art glazes.Cone 06-04

Ferro 3195 - Calcium borate, low temperature alkalineCone 08-04

Ferro 3269 (Similar to Hommel 259, Pemco 25) - Soda-borate-zinc frit. Contains a small % of fluorine. Used for low temp glazes. Test as a substitute for 3819

Ferro 3824 - High soda, borate, zinc. A substitute for lead when fired to 150° F or higher

Frit F-280 (3110) (P311) (H90) (GF-134) A high soda-silica, low borate frit. Melts at 1400°

Frit F-19 (3124) (P311) (H14) Soda-Calcium-Borate. Melts at 1600° F

Frit F-12 (3134) (P54) (H399) High calcium, low potash borate, low silica. Melts at 1450° F.

Frit FZ-25 (3269) (3819) (P25) (H259) Soda-Borate-Zinc with a little Flourine. Melts at 1320°-1420° F.

G

Gerstley Borate - See Boraq, Gillespie Borate, or Plastic Borate. A sodium-calcium-borate compound used as a low temperature flux. Some action as an opacifier.

Gillespie Borate - A blended borate mineral for use in glaze formulas replacing Gerstey Borate calculated on a pound for pound basis. Mixture of ulexite bended wth various clay minerals and alkaline earth carbonates and silicates. 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. NOTE: The Gerstley Borate mine has been closed by US Borax and Gerstley Borate will no longer be available. If your glazes depend on this, see MURRAY’S BORATE.

Goldart Clay Light tan, air-floated stoneware clay suitable for light firing, high temp clays. Low sulfur.

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

Grog/Molochite - Pre-fired ground clay added to ‘open’ bodies to give texture and strength. Will assist drying by decreasing shrinkage and warping. Adds fired strength. Grog is typically added to buff and dark clay; Molochite is added to porcelain and other white clays. See Sand.CAS#1332-58-7

Gum Arabic A powdered natural gum material used as a binder and suspending agent in glazes. Many other non-pottery uses as well.

Gum: (CMC-Veegum T) - See CMC or CMC Powder. Organic cellulose substance used to promote glaze suspension and adhesion, hardness of glaze to ware before firing. Functions as a thickener, a binder and suspending agent in glazes. Mix with water and age before adding to a liquid glaze. See MacaloidCAS#12199-37-0

I

Iron Chromite (FeCrO3) - A colorant usually used to produce dark colors in engobes and underglazes. 2% will produce grays, browns with zinc, good in crystalline glazes.CAS#1308-38-9, CAS#7439-89-6, CAS#1344-28-1, CAS#1309-48-4

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.

Iron Oxide (Black Fe304) (Red Fe2O3) (Yellow Fe203-3H20) (Ferric oxide) - The varieties of irons mined - black, red, yellow - each give slightly different results. For consistent glaze effects it’s best to stick with one source of Iron. As a general rule, iron used in small amounts (under 10%) will produce browns, buff and rich reds in glazes. In larger quantities it may act as a flux. Synthetic irons are processed to meet specific standards and are more reliable. Ferrous Oxide. 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.

Iron Oxide (Red) Fe2O3 Ferric Oxide. Basically the same as black iron oxide except not quite as concentrated. 82-86% natural and synthetic iron oxides. Makes an excellent decorating wash.CAS#1309-32-1

Iron Sulphate (Ferrous) Copperas (FeSo47H20) See SULPHATESCAS#7782-63-0

K

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.

Kiln Wash A mixture of refractores used to coat kiln shelves to protect them from glaze. Typically 33% Alumina Hydrate (Al203-3H20), 33% EPK (China Clay), 33% Silica 200 meshCAS#7631-86-9, CAS#1332-8-7

Kyanite (AL2O3-BiO2) (Mullite) - Used as a grog for a very strong clay body with good resistance to thermal shock. Substance used as refractory filler that greatly increases thermal shock in clay bodies such as Raku clays.CAS#13002-76-7

L

Laguna Borate Low cost indirect Gerstley Borate alternative from Laguna Clay Company.

Lithium Carbonate (Li2C03) - Source of lithium: a flux in leadless glazes; may promote brightness and increase firing range of glaze. Used as a flux. It is a source of lithia which is a strong high temperature flux. Lithium carbonate improves the brightness of glazes and increases the firing range. Also reduces thermal expansion.CAS# 143077-3-8

M

Macaloid - See VEEGUM T CAS#12199-37-0

Magnesium Carbonate/Oxide (MgCO3) (MgO) - Insoluble source of magnesia; flux in high temperature glazes; may promote buttery surface, strength, and color in glazes. A very weak coloring agent. In an alkaline glaze, a blue-purple or plum color can be obtained. Manganese carbonate is more useful as a flux.CAS#546-93-0, CAS#1309-48-4

Manganese Dioxide / Carbonate (MnO2)/MnC03) - (Powder) Colorant: may produce purples, pinks, browns, and blacks - (Granular) Granular form will give speckled effect. 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.CAS#7439-96-5, CAS#598-62- 9

Molochite - White grog (See GROG) White firing porcelain grog suitable for use in any white clay body.

Mullite - See Kyanite

N

Nepheline Syenite (K3O-3Na20-4Al203-8SiO2) A soda spar May be used to introduce sodium: when used to replace other spars it will lower the melting point of the glaze. Will reduce crazing when added to a clay body.CAS#37244-96-5

Nickel Carbonate (Ni2CO3) (green) A colorant; may produce browns, grays, and muted greens. Usually added to influence and modify other colorants. 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.CAS#7420-02-0

Nickel Oxide (NI2O3) (black) - Similar but more concentrated than the carbonate form of Nickel. A black powder which produces browns, grays, blues and yellows in glazes. 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.CAS#1313-99-1

O

Ochre, Yellow (Yellow Fe203-3H20 ? ) Impure Iron oxide; used as a colorant source of iron. A natural iron-based colorant used in clays and glazes that produces tans and pale yellow tones. Can be calcined at 550 – 600 ° C.CAS#51274-00-1

Opax - (Zirox, Treopax) - A zlrconium oxlde. Commercially prepared opacifier; promotes color stabilltyCAS#1314-28-4

P

Paper Clay Pulp Cellulose (paper) fiber for Paper clay and paper slip.

Plastic Vitrox May be substituted for feldspar (half and half) to lower the firing temperature.CAS# 14808-60-7

Potassium Carbonate (K2CO3) Also known as Pearl Ash. It’s 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.

Pearl Ash - See Potassium Carbonate

Petalite (Li20-Al203-8SIO2) A lithium feldspar used in both clay bodies and glazes. A source of lithium and silica; a body flux that reduces thermal expansion and increases thermal shock resistance. Often used in flameware.CAS#68476-25-5

Plaster (GYPSUM) - aka Casting, #1 Potters, Potters, Ultracal, Hydrocal, Hydrostone, Ultrox, Tuf-cal

Plastic Borate See BORAQ

Plastic Vitrox See clayCAS#14808-60-7

Potassium Bichromate (Dichromate) (K2Cr207) Soluble in water. To introduce chromium oxide into low fire glazes CAS#7778-50-9

Potassium Nitrate (KNO3) Soluble in water. Source of potassium in glazes.CAS#7757-79-1

Pumice - See VOLCANIC ASH

Pyrophillite (Al203-4SiO2-H20) - May reduce thermal expanslon in bodies and crazing.CAS#12269-782

Pyrotrol Blend of milled pyrophylliter and andalusite ores to control shrinkage in white ware ceramic applications.

R

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 (TiO2) (LIGHT & DARK) Titanium oxide - (powdered ) - tan colorant containing small amounts of iron; may produce creams, oranges and tans in glazes; may also modify more potent colorants. A titanium dioxide colorant which contains a small amount of iron and vanadium. Will produce tans and mottle other colorants. Granular Rutile is often used as a speckling agent in clays.

S

Sand, Silica (Si02) Also known as flint or quartz. A smoother substitute for grog, with less tooth. 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. As (200 mesh) Silica it’s useful as a kiln wash ingredient. (Silica 200 mesh for clay 325 mesh for glazes)

CAS#7631-86-9

Silicon Carbide (SiC) - Use in glazes or placed near the ware as a local reducing agent. Often ground to 450-600 mesh. Coarser mesh for spot reduction. An artificial reduction agent used in oxidation which produces a localized reduction on the glaze. Add in 0.5 percent to alkaline glazes. Experiment!CAS#409-21-2, CAS#7631-86-9

Silver Carbonate Generally used as a glass colorant, gives large color range depending on the glass composition and firing atmosphere. Produces lusters.CAS#7761-88-8

Soda Ash (NaC03) AKA Soda Carbonate 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.

Hlghly soluble in water. Soda ash gazes should be used immediately or stored dry. Can turn into Sodium Bicarbonate (opposite action) if it’s not stored in a well ‘sealed container’ dry. Used as a deflocculant in slip casting clays.CAS#497-19-8

Sodium Bicarbonate (Na2C03-13H20) Soluble in water, used in Egyptian paste.CAS#144-55-8

Sodium Silicate (Na20-SiO2) Water glass - Used to deflocculate casting slip, and as a cement to secure insulation blankets to metal drums. Is used as a high temperature glue for motor gaskets. It’s clear and very sticky. I found it hard to paint in strokes, as it pulls the insulation, so I suggest you daub (?or use paint roller?). Brushes can be cleaned with soap and water. 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.

It’s available at drug stores (Spendy! $3.65 for 15 oz) for liquid bandage.CAS#10588-01-9

Spodumene (Li2O-Al2O3-4SiO2) Source of lithia, similar to petalite 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.

Valuable in flameware bodies due to its low thermal expansion. In glazes it promotes copper blue tones; may also correct crazing. Carries some impurities of iron. Chemical grade is available.CAS#1633-05-2

Stains - Prepared colorants for glaze underglaze sllp engobes and clay: see Mason Stains

Strontium Carbonate (SrCo2) - Similar to calcium. Used as a glaze flux. Slightly soluble and craze resistant. Source of strontium oxide in glaze formula.CAS#1633-05-2

Sulphates Cobalts, copper, and iron join with sulfur to form a salt. At low temperatures will give luster and other special effects to glaze and body. Effective in overglaze and raku.

CAS#7782-63 0

Superpax (ZrSi02) also known as Ultrox 5OOW. Zircon opacifier, used in a wide variety of applications. Effective in controlling texture, craze resistance and color stability. See Ultrox.CAS#14940-68-2, CAS#14808-60-7

T

Talc (3MgO-4Si02-H20) Source of insoluble magnesium. Used in earthenware bodies since it lowers the fusion point. In glazes it may promote opacity. A flux for low temperature, white clay bodies and low and high fire glazes. Gives a slight opacity to a glaze.

Its structure is similar to asbestos (also sometimes may contain asbestos ) and it’s not known what its health hazards are. Therefore, handle with care in the powder form to avoid creating dust. Clear with a moist cloth rather than a broom. A flux for low temperature, white clay bodies and low and high fire glazes. Gives a slight opacity to a glaze.CAS#14807-96-6

Talc Nytal (New York) A hydrated magnesium silicate. The chief mineral of soapstone and steatite. Used as an insoluble form in magnesium glazes. This is a fibrous talc.

Talc (Texas) A platey form of talc.

Tin Chloride (SNCI) Crystals (See Stannous Chloride)CAS#7772-99-8

Tin Oxide (SnO) - Opacifier; renders a softness, depth and beauty as in Majolica ware. When used in excess (10%+) it will dull the surface of the glaze. 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.CAS#18282-10-5

Titanium Dioxide (TiO2) Important opacifier; may tend towards cream color. Rutile is a form of titanium that also contains iron. 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. Often used in glaze to affect acid resistance, color and textureCAS#7440-32-6

Treopax - (Zirox) Known as Opax. Opaclifer

U

Ultrox (ZrSiO2) also known as Zircopax A Ultox 500W known as Superpax. Opacifiers.

CAS#14940-68-2, CAS#14808-60-7

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.

V

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, Veegum T (Macaloid) – A gum, fires to a good white color. Can be used in glazes as a hardener, suspending agent and to increase drying rate of glazes: plasticising agent for non-plastic formulations such as high alumina or zirconia bodies: a binder in extruded bodies. Should be added as a water dispersion. Optimum results obtained with 1/2% to 2%, dry weight. 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.CAS#12199-37-0

Volcanic Ash (Pumice) (Formula varies. Usually contains MgO, CaO, NaO, K20, Al203, Fe2O3, SiO2, Cl3 + H2O) - Decomposed rock, may be used as flux in stoneware glazes. Frequently used as a feldspar substitute in glazes.(CAS# varies - see feldspar, clay, silica)

W

Wax Resist Used to coat the bottoms of pots so that glaze will not adhere and form a clean dry foot. Also used in brushing or decorating techniques. May be colored with food color to be more visible, color selected for that use will burn off.

Whiting (Calcium Carbonate) (CaCo3) A high temperature flux which promotes durability and hardness in glazes. At low temperatures in large quantities it will be refractory. This is the most common source of calcium oxide (calcia) in glazes. It is a major high temperature flux which gives durability and hardness to a glaze.CAS#1317-65-3

Wollastonite (CaSiO3) Natural calcium silica source. Reduces shrinkage and promotes resistance to thermal shock in body. 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.CAS#13983-17-0

Wood ash (Formula varies.) – Have a full knowledge of the contents, or you may never be able to make a particular shade again.

Z

Zinc Oxide Calcimined (Ceramic Grade) In small quantities (2%) acts as a flux and reduces crazing. In larger quantities it acts only as a flux. Prefer calcined zinc for better fit on pots in the raw state. Has a strong effect on colors. 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. CAS#1314-13-2

Zircopax, Zircopax A (ZrSiO2) known as Ultrox - Opacifier. Assures exceptional uniformity of opacity, texture and color over a wide firing range. Gives a hard, shinny scratch resistance surface; resists crazing. The original Zirconium opacifier. Used mostly where semi-opaqueness is desired.CAS#14940-68-2, CAS#14808-60-7

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NOTE: Science is notorious for telling us after the fact that something is toxic, poisonous or a carcinogen. Therefore, we recommend you treat all glaze chemicals and colorants with respect. Do not breathe dust - use a respirator. Do not eat, drink or smoke while using, mixing or spraying glazes. Use plastic gloves if you have an open cut. Wash hands, keep work area clean. Whenever possible use wet mop or micro vacuum cleaner such as Nilfisk.

Use a few drops of liquid soap detergent like "Ivory" to disperse a powder into the glaze batch

Vee-Gum T, Veegum T (Macaloid) - Fires to a good white color. Can be used in glazes as a hardener, suspending agent and to increase drying rate of glazes: plasticising agent for non-plastic formulations such as high alumina or zirconia bodies: a binder in extruded bodies. Should be added as a water dispersion.