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Forced-hot-air drying can extend the lifetime of plaster molds while saving users time and money.
Those in the ceramic industry often complain about the too-short life of plaster molds, along with their uneven absorption rates and long drying times at ambient temperatures. However, extensive testing* has shown that there's a fairly simple, long-term and economical solution to these problems: forced-hot-air drying of molds. Properly designed forced-hot-air dryers save time, extend the life of molds and reduce the cost of each mold and finished piece.
When forced-hot-air drying is done following the proper guidelines, users can achieve significant strength gains after the mold is 92% dry. In fact, these gains can be as high as 30% when the mold is 100% dry (see Figure 1). While the tests were conducted on several specific pottery plasters,** the advantages of forced-hot-air drying can be obtained with any plaster mold.
How a Plaster Mold Dries
To attain uniform results and achieve the maximum mold strength, plaster molds must be dried properly. But wherever a mold is being dried-in the workroom, outdoors or in a dryer-it will rarely become 100% dry without the use of forced-hot-air drying methods.
Drying involves transferring excess water from the mold to the surrounding air. Large amounts of water must be used to obtain a mixable slurry. After the plaster has been mixed, poured and has set, the excess, or "free," water must be removed. When evaporating this free water using forced-hot-air drying, the following process takes place. As the mold sets or hardens, a chemical reaction causes the piece to heat slightly. Because the...