I have recently started working on slip casting. I couldn't find the plaster of paris molds in the market where I could search for laboratory scale slip casting. Plus I have read in papers they cannot be used again once a slurry is poured and dried in them. Should I make the molds myself every time I need to use one? Is it ok to use some other molds made of anything instead of plaster of paris if I don't need to make a hollow object?
Muhammad Waqas Khalid, It is difficult to find plaster of Paris (PoP) molds in the market for lab-scale experimentation. However, you can make PoP very easily using the dry PoP powders (~0.5-1 USD/kg) upon mixing with water properly & giving shape. Once it is dry, you can use it for casting your slurry. The pores in the PoP mold will draw out the water (or other liquid used for slurry making). So, after casting, you need to dry out the PoP completely before pouring slurry for another casting. You can use it many times (I used each mold at least 100 times, never counted though) until the integrity of the PoP remains ok. Hope this is helpful.
With best regards
MN
Hi Muhammad,
For making mechanical testing specimen we use simple flat plaster plates and flexible soft silicone molds as a lateral boundary.
Mithun is right. You can reuse the molds quite often.
How often depends on the amounts of additives you use. the more additives the faster the molds will deteriorate as the mold drains the slurry and the additves enter the capillaries. Upon drying the water is evaporated and the polymers stay in the porosity. In case of classical ceramics you need very little additives so that molds for sanitary porcelain or tableware may be used 500 times while molds for technical ceramics where you use ~1% of organics may be worn after 25 cycles. Any way do not dry above 40°C otherwise the plaster may decompose. In Germany there are some manufacturers of plaster molds left, you may also buy some molds for tableware in internet marketplaces providing equipment for hobby ceramists.
best regards
Frank
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