GERSTLEY BORATE: Replacing it in your glazes Borax Frits All (nt manufacturers produce a wide va- nety of boron-containing [nts. A fnt is a ceramic glass that has been premixed from raw powdered minerals and then melted, cooled by quenching in water, and ground inte a fine powder, Huge quanuties and vaneves of fits are manufactured for the ceramic industry every year by dozens of different companies. Although the fntung process 18 eXpensive Ubere are many ad- vuntages to [nts in glaives, enamels, etc. To render soluble materials insoluble Often very useful oxides (Le. boron) are contained tn high proportions in raw mate- nals thatare either slightly or very soluble. These nermally cannot be used in glares because they have adverse effects on the slurry’s Muidity, viscosity, and thixotropy or make it difficult to achieve or maintain the desired specific gravity. [n addition suble compounds are absorbed into po- rous badies dunng gliing and this com- promises the body’s resistance to bloating and warping and the glaze’s homogeneous structure, Fnlted mixes contamning these matenals render them insoluble and inert. To improve process safety of toxic metals Some materials contain undesirable anal unsafe compounds, The fntuing process drives these off. Many other matertals are unsafe in the workplace and fritting de- creases their toxicity for ceramic produc- ton, Lead is a prime example, Lead {rts decreas: the process toxicity of raw lead compounds. Banum is another example, However the (ntling process has no effect on whether or not a fired glase will leach or not. This is a function of its chemistry: unbalanced and unstable glare formulas are just as likely with {nts as without. The pnmary safety benefit for fits is for work- ers who use frits in manufacturing. To reduce melting temperature and improve melt predictability Since frits have been premelted to form a glass, remelting them requires less energy and lower temperatures. Frits soften over a range of temperatures (in contrast to crystalline raw matenals that melt sud- denlv) and lend themselves very well to production situations where repeatability und case-ol-use are necessary. To avoid volatilization of unstable substances Most raw ceramic materials contain sulfur or carbon compounds as well as H20. These vaporize at various temperatures as matenals decompose and are dnven off as gases during lining. This volatilization maetivity has a detnimental effect on the glaze surface and matnx. The fritung proc- est dinves off these compounds and glazes are much more defect free. To achieve homogeneity Osher than dissolution and very localized migration, fired raw glaze melts do not mix well to create an evenly dispersed oxide structure. The Intting process em- ploys mechanical mixing to assure acom- pletely homogenous glass that will exhibtr the intended properties. To achieve oxide blends difficult or impossible with raw materials Many glaze formulations cannot be achieved with insoluble raw materials (i.e. high borax, high sodium), Pots employ soluble materials to make almost any com- bination possible. VN FOTCTERS. JEPPLT LT0 Serving Western Canadian Potters for the past 30 years On Vancouver Island see our new dealer The Pottery Warehouse in Nanaimo 250-716-9966 ° Clays « Materials e Underglazes ¢ Stains « Glazes * Tools + Equipment * Wheels « Kilns ° Books « Videos « Magazines 9548 - 192 Street, Surrey, B.C. V4N 3R9 Phone: 604-889-3411 Fax: 604-888-4247 E-mail: greanbam@be.sympatico.ca Intemet: www.greenbarn.com Monday-Friday 9-5 Saturdays 9-1 8 Potters Guild of Bnitish Columbia April 2000