What is Gerstley borate used for?

Gerstley Borate is a sodium-calcium-borate compound used in ceramics as a low and mid-range temperature flux. It is essentially a source of boron in glazes, and acts as a melting agent. It also can act somewhat as an opacifier and prevent crazing.

Is Gerstley borate the same as borax?

Gerstley borate is named after James Gerstley, former managing director of Borax Consolidated Ltd. It is manufactured by U.S. Borax and Chemical Corp.; the mine is located near Death Valley, CA. G.B. is an inexpensive source of B2O3 and CaO in glazes. It is often used in place of colemanite.

What can I use instead of Gerstley borate?

 Oxide Match -- Virtually identical to Gerstley Borate, this product requires no adjustment to formula and no extra additives are needed.  Mineral Match -- Gillespie Borate™ provides the same minerals to the glaze as Gerstley Borate, thus imparting the same glaze activity, texture and effects.

Is Gerstley borate a clay?

Thus it is common to find Gerstley-Borate-based recipes having no clay content. GB natural source of boron that was mined in southern California for many years. Mineralogically it is a combination of colemanite, ulexite and high plasticity clay (likely hectorite).

Is Gerstley borate toxic?

Gerstley Borate has a relatively low acute toxicity. Small amounts (e.g. a teaspoonful) swallowed accidentally are not likely to cause effects; swallowing amounts larger than that may cause gastrointestinal symp- toms.

Help for Long-time Gerstley Borate Sufferers!

What is Gerstley borate in glaze?

GERSTLEY BORATE (real) A sodium-calcium-borate compound used as a low and mid-range glaze flux. This is a conglomerate mineral made up primarily of Colemanite, Ulexite and Hectorite. Gerstley is a natural borate similar to but not interchangeable with Colemanite on a 1 to 1 basis.

Is Gerstley borate still mined?

It is a conglomerate mineral made up mainly of Colemanite, Ulexite and Hectorite. Gerstley borate is the substitute for Colemanite which has been gone for many years. US Borax Corp, the only source of Gerstley Borate in the world closed the mine in southern California in 2000.

What does Zircopax do in a glaze?

Zircopax affects glaze melt viscosity, surface smoothness, thermal expansion and color development and can be implicated in a range of glazes faults associated with these.

What is Laguna borate?

A specially formulated flux containing a high percentage of boron. This material mimics the fluxing characteristics of Gerstley Borate.

What is a frit in pottery?

A frit is a type of ceramic glass. It is a combination of materials that, when melted together, are rendered insoluble and resistant to acid attack. They are, therefore, a means of introducing certain materials into a glaze which would otherwise be toxic.

What is Custer Feldspar?

Custer Feldspar (NaKO. Al2O3. 6SiO2 ) is a one of the primary feldspars used in ceramics. It is used in both clay (up to 25%) and glaze (up to 100%) formulas and is made up of silica and alumina combined with sodium and potassium oxides. Feldspar custer is mined in Custer, South Dakota.

How do you make calcium borate?

It can be prepared by reacting calcium metal with boric acid. The resulting precipitate is calcium borate. A hydrated form occurs naturally as the minerals colemanite, nobleite and priceite. Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).

What can I use instead of calcium borate frit?

American substitute: Gerstley Borate.

What is EPK kaolin?

EPK (Kaolin)

Edgar Plastic Kaolin - is one of the most popular kaolins used in glazes for its suspening capability, EPK is a water washed kaolin mined in Edgar Florida. It is fairly plastic and very white firing compared with most other American kaolins.

What is Ferro frit?

Frits are glaze materials which have been melted, cooled, and ground into a powder which is then added to a glaze formula for the purpose of rendering insoluble any soluble materials. The use of frits also allows for the incorporation of certain raw materials in the creation of glazes.

What is the difference between Zircopax and Zircopax plus?

The designation 'Plus' refers to the particle size, it is a finer grained version zirconium silicate (also known as Superpax). This material is a more potent opacifier than Zircopax, testing will be required to determine how much less to use when substituting.

Is Zircopax a silica?

Notes. Zircopax is a brand name of zirconium silicate (or zircon). It is primarily used in ceramics to opacify glazes.

What does zinc oxide do in a glaze?

Zinc oxide is used in stoneware glazes in oxidation, usually as an auxiliary flux to start the melt. Larger amounts may promote opacity through growth of Willemite crystals (Zn2SiO4). Large, fan-shaped crystals can develop with a proper glaze formulation and firing schedule.

What is whiting in ceramic glaze?

Whiting- Calcium Carbonate – CaCO₃ (m.p. 4650^o F/2570^o C) is a finely ground powder composed essentially of pure Calcium Carbonate derived from Limestone, Chalk, or Marble. It is the most common source of Calcium in a glaze and clay body.

Where is Ulexite found?

It is found principally in California and Nevada, US; Tarapacá Region in Chile, and Kazakhstan. Ulexite is also found in a vein-like bedding habit composed of closely packed fibrous crystals. Ulexite is also known as TV rock due to its unusual optical characteristics.

What is Gillespie borate?

Gillespie Borate™ is a blended borate mineral for use in glaze formulas replacing Gerstley Borate on a pound for pound basis. Gillespie borate was developed through a careful formulation process that has resulted in a virtual chemical match to Gerstely borate. Gillespie Borate is a mixture of ulexite (Na2O. 2CaO.

Can you mix oxides with clay?

Generally, the stronger the oxide wash, the more it will bleed through the glaze. Mix ball clay with your oxide/water. This gives a better consistency and tones down the color. Brush a couple different oxides on, overlapping in areas.

What is oxide wash?

A WASH is a metallic oxide mixed with water. The metallic oxides we use for color in ceramics and their resultant colors are as follows: COBALT OXIDE - blue to blue-violet (quite strong, use diluted) IRON OXIDE - tan to rust-brown (quite weak, use less diluted)

Can you glaze over red iron oxide?

FeO (iron oxide) is a very powerful flux

In oxidation, iron is refractory and does not melt well (this glaze would be completely stable on the ware in an oxidation firing at the same temperature, and much lighter in color).