alanhoff Posted August 14, 2018 Report Share Posted August 14, 2018 Hello :-) Last week I started making plaster molds to help a relative. I'm already able to make single and double pieced molds but I'm having trouble with a relatively complex vessel. I attached a 2D representation of the sliced vessel. 1 - How can I mold that inner border at the top? 2 - Can someone recommend a tutorial/book/video on how to cast molds with more than two pieces? 3 - For how long should I keep the mold drying before trying to cast? 4 - I tried to use mineral oil to keep the plaster pieces from merging while making the double pieced mold, but sometimes they merge either way. Is that the correct oil to use? 5 - Do I need to apply mineral oil on the plaster before casting the slip? Thanks! Link to comment Share on other sites More sharing options...
preeta Posted August 14, 2018 Report Share Posted August 14, 2018 Saw this not too long ago https://ceramicartsnetwork.org/freebies/free-guides/ceramic-mold-making-techniques/ Clayflicks has a great video by Guy Michael Davis. Link to comment Share on other sites More sharing options...
Chilly Posted August 16, 2018 Report Share Posted August 16, 2018 On 8/14/2018 at 4:32 PM, alanhoff said: Hello :-) Last week I started making plaster molds to help a relative. I'm already able to make single and double pieced molds but I'm having trouble with a relatively complex vessel. I attached a 2D representation of the sliced vessel. 1 - How can I mold that inner border at the top? 2 - Can someone recommend a tutorial/book/video on how to cast molds with more than two pieces? 3 - For how long should I keep the mold drying before trying to cast? 4 - I tried to use mineral oil to keep the plaster pieces from merging while making the double pieced mold, but sometimes they merge either way. Is that the correct oil to use? 5 - Do I need to apply mineral oil on the plaster before casting the slip? Thanks! 1. I'll go dig out a mould I have for making a large bonsai pot, that has (I think) a level rim like that. Might be a while, it's torrential rain, and the studio is down the garden!! 2. Yes, Lark, Slip-casting and mould-making. https://blackwells.co.uk/bookshop/product/9781600590771?gC=5a105e8b&gclid=CjwKCAjwwdTbBRAIEiwAYQf_Ew9BbshqmHK9lWH57NeTQvPzoqCOxD_VUSwBhT42kSj2vLi0ouiPVRoCiZwQAvD_BwE 3. It depends, Time of year, humidity, heat. Could be 3-4 weeks, maybe more, maybe less. Feel it with your cheek to see how cold (damp) it is. If you cast when it is still damp, you will not get as thick a casting and it will take longer to set-up. 4. I use soapy release from Potterycrafts. (UK). Not sure what mineral oil translates to, but I don't think it's the right stuff to use. 5. NO. Definitely NOT. Don't use anything on your dry plaster. The clean, dry plaster will absorb the water in the slip, leaving a coat of clay. Link to comment Share on other sites More sharing options...
Chilly Posted August 16, 2018 Report Share Posted August 16, 2018 This is a two piece mould, bottom forms the base and the top forms the lip. (Please ignore the plywood, top half of mould broke in half, so used plywood to help glue it together.) The hole in the top half is 16mm smaller in both directions than the hole in the bottom half. This forms an 8mm lip all round. To get a bigger lip, make the hole in the top smaller. Link to comment Share on other sites More sharing options...
alanhoff Posted August 16, 2018 Author Report Share Posted August 16, 2018 4 hours ago, Chilly said: This is a two piece mould, bottom forms the base and the top forms the lip. Wow, very helpful! Thx a lot! Link to comment Share on other sites More sharing options...
Chilly Posted August 19, 2018 Report Share Posted August 19, 2018 On 8/16/2018 at 11:26 PM, alanhoff said: Wow, very helpful! Thx a lot! Don't forget to show us your finished mould andcastings. Link to comment Share on other sites More sharing options...
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