Can you please tell what releasing agent should i use for gypsum mold for slip casting, and how to use?
Usually slarry is poured into gypsum mold without a release agent. Sometimes gypsum mold is lubricated with graphite powder.
To enhance the capillary effectiveness of the gypsum or PoP mould, you do not want to use a "sizing agent" that will block the fine pores of the PoP mould. Your best option will therefore be a liquid soap base. In the alternative, you can use a thin film of nano particles clay slurry.
mold release agent is provided which is compatible for use with slip casting molds formed from alumina, which are more durable than conventional gypsum molds. The preferred mold release agent is a suspension whose suspended solid matter is water-insoluble, organic, and composed of fine natural or synthetic powders or fibers. The mold release agent forms a layer of particles and/or fibers on the mold cavity surface which promotes the ease by which the cast article can be removed from the alumina mold. The mold release agent is readily burned out during subsequent firing or sintering operations, so as not to leave an undesirable residue in the surface of the fired or sintered ceramic article. Furthermore, the mold release agent does not have an undesirable effect on the microstructure of the as-cast or sintered ceramic article, nor does its use result in any detectible surface or internal cracks in the as-cast or sintered ceramic article.
Thank you Mr. Vadim Verlotski , Mr. Felix Ugah Idu and Mr. D. S. Bhagat for your prompt replies.
Take a look at fibreglast.com. there is PVA release that may do the job. There is a video that shows the PVA film formation where sprayed in a mold surfaces
Slip casting generally doesn't need releasing agents, especially for alumina slurry, but you can add some talcum powder to the walls of the gypsum mold to add extra lubrication.
Thank you Mr. Habibi Mohamed and Ms. Ana Gabriela Storion for your kind replies.
Need help again, please... The pop mold I am using is cylindrical with 30 mm inner dia, 40 mm height.
If I use 0.7 um alumina particle in 80 wt% solid loading slurry, it takes around 8 hours for the slurry to dry in mold, and the cast is easily removable (hollow from up and a solid compact base). I grind the hollow part and use only the solid compact base for tests.
If I use 4 um alumina particle in 80 wt% solid loading slurry, the slurry gets dry within few seconds, similar hollow from top and solid compact base, and the sample is stuck inside the mold, not removable. I mixed soap and water but no lubrication possible as it is absorbed by the mold. Why the 4 um particle slurry is irremovable as you all suggested lubricant is not required generally?
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