CERAMIC
T-22 Earthernware slip casting powder a preferred clay for casting white earthernwares. Mix into a slurry with soda ash and sodium silicate with water. Stir well to deflocculate into a smooth slurry in water to powder ratio 2:1. Leave overnight or longer to age. During the aging process the clay particles swell and gel. To liquify stir in small amount of Reotan L until clay is liquid enough to cast. Do not add more water or sodium silicate as excess will slow down wall cast build up and over wetting the plaster mold. It also damages the mold with excess alkali clogging plaster pores and crystalline fuzzy growth on mold surface. In addition drying shrinkage will be high followed by higher firing shrinkages.
Guide mix : 10 litre water, 40 ml sodium silicate and 20ml soda ash dissolve well in water before sieving 25kg T-22 slip powder. Mix well with a stainless steel jiffy mixer attached to a power drill. For consistency mix use a hydrometer to determine the ideal specific gravity of the clay slurry. Note excessive water to clay ratio result in slower wall thickness build up and less productivity. Also excessive use of deflocculant sodium silicate and soda ash will curdle slip slurry rendering it useless in slip casting.
Sieve clay slurry with mesh 30 before casting. To enhance whiteness pass sieved slurry over magnetic funnel to remove any iron particles. Colored slip wares casting in layers by mixing body stains to slip clay. When carved with a curve tool reveals colored decorative and attractive stratas.
Recommended firing temperature is 1060°C or cone 03 to earthernware maturity. Fired color is white to foo white.
Slip casting earthernwares require use of Plaster of Paris mold for clay wall thickness build up with water absorption. Will not work with metal, silicon and other non porous molds.
Mesh finess: #200 0.5%, #325 1.5%
Fired shrinkage Cone 5 equivalent 1200°C : 9.5 %- 10 %
Aged semi dried moist T22 is very plastic suitable for hand building and sculpting. Handcraft beautiful clay flowers too.
BATIK
Interesting development by Kraftangan Malaysia Trengganu in the use of clay as a wax resist instead of paraffin wax and damar. Any misprint in stamping is easily corrected with no wastage of material unlike using wax damar as clay is water soluble. T22 slip clay with sodium silicate binder and possibly CMC thickner could be the solution and new development in century old batik stamping replacing wax damar.
