[Elmoclayman]

I have recently started making molds of carved cylinders and cups. What is the recommended thickness of the plaster mold? (The thickness from the outer wall of the original to the outer edge of the plaster.)

Also what is the best cone 10 clay to use for slip, or does someone have a formula they wouldn't mind sharing, for casting? I am looking for something with very little sand, but is cost effective. I have been using Soldate 60 because I have a huge supply of it, but I am not really happy with the roughness of the soldate 60 slip.

Thanks in advance
Brian

[Lucille Oka]

Elmoclayman, on 07 October 2012 - 07:15 PM, said:

I have recently started making molds of carved cylinders and cups. What is the recommended thickness of the plaster mold? (The thickness from the outer wall of the original to the outer edge of the plaster.)

Brian

Figure on 1 1/2"- 2" thick all around,
-Not so thick that it takes a long time for the mold to dry after you release the casting.
-And not so thin that the mold will saturate with water.

[perkolator]

i always shoot for close to 2". gives nice thickness to absorb and not get saturated quick, and not so thick that it's overly heavy. as for casting slip, I cannot comment since I prefer to buy pre-made slip these days. there are plenty of recipes around, but sounds more like you're looking to modify a wet clay body vs start from scratch so I can't comment other than I know it's been done many times.

[Elmoclayman]

perkolator, on 09 October 2012 - 12:39 PM, said:

i always shoot for close to 2". gives nice thickness to absorb and not get saturated quick, and not so thick that it's overly heavy. as for casting slip, I cannot comment since I prefer to buy pre-made slip these days. there are plenty of recipes around, but sounds more like you're looking to modify a wet clay body vs start from scratch so I can't comment other than I know it's been done many times.

Thanks for the advice. I have made a total of 5 molds so far and have found that 2" seems to work the best.

[BeckyH]

If you plan to reuse the molds often and for a long time, a heavier mold will last longer. However, they do need more time to dry between pourings. If the mold is too light, it saturates, as already mentioned, and that leads to crumbling and leakage.
Good luck with your plaster work!