* White take Add to low-fire clay to whiten or improve drying properties. Add if glazes are craving on a low-fire batch. * Redart (or other red burning clay): Add loredden a low-fire terra cotta batch (some plasticity will be lost, add | bentonite for each 20% redarnt added), Add less to red- den a medium-fire batch that is not vitre- ous enough. * FireclayAdd to non-white stonewares if they are too vitreous of need some earthy character, * [ron oxideAdd 1% amounts to darken fired colowr. Yellow iron is cleaner to work with thar rel, * Grog: To create a sculpture clay add as much as it will take and still be workable, Add extra ball clay to make room for even more grog. «“ Barium carbonate: Add 0.) to 0.5% if the body fires with soluble salts on the surface. * Paper: Add to make paper clay. Techno Tip: Recycling Clays by Tony Hansen For many of the above you could run a small test on S00) ¢ of the batch for extra insurance. [f you are a teacher you could have each student appraise the scrap batch und suggest what could he dome to condi- tion it inte something useful. What if the batch goes bad and appears unusable? This is highly unlikely; almost any clay can be used for something. In extreme cases consider compensating on the opposite properly extreme on the next batch and wedge them together. Dewatering the Batch This is net simple. There 1s no plaster table large enough to remove the amount of water typically required so one effective way is to mix it to the thickest possthle slurry soit does not setthe out and then pour small amounts on aplaster table io dewater as needed. Needless to say you need a plaster table or large portable plaster con- cave bats. In drer climates another method is to pour the slurry ontoa canvas stretched over a wooden or metal frame and cover it with another canvas. This will take some time to dewater by evaporation and you will have to fold the edges in as they dry faster, but this method can be effective. If you are suspicious that the batch is contaminated by chunks of plaster then pul the slurry through a 30 mesh screen as you pour it out onte the plaster table. Safety Dealing with scrup is generally a wet proc- ess, but if you need to deal with larger quantities of dry matenal and generate dust, then beware. Try searching the |i brary at www.ceramicmaterials.info for the words ‘safety’ or ‘dust’, There is a good article. Tony Hansen Digitalfire Corp. The Techne Tip column iy penereowsly spon- sored by Plainsewa Clay Lid in Medicine Har, Alberta, and irs RC affiliates, Greenbarn Poners Supply Lid. in Surrey and Vancouver Istand Porters Supply an Vancenver Island Good Service Competitive Prices Serving BC potters for 30 years 9548 192 Street, Surrey, B.C, VAN 3R9 Phone: 604-888-3411 Fox: 604-886-4247 Geen Darn POTTERS SUPPLY LTD. email. greeenbami@telus.net Monday -Friday 9-5 Saturday 9-1 Closed long weekends Potters Guild of British Columbia Newsbetter Novenber/December 2003