KB3d Posted October 1, 2023 Report Share Posted October 1, 2023 I have been doing slipcasting lately with some one-piece plaster moulds that I made. I would like to know if I can slip cast in a bisque ware bowl. I just threw the bowl in the picture to try this. Am i wasting my time? If you think it will work, I will also make a foot ring mould. Thank you. Quote Link to comment Share on other sites More sharing options...
Chilly Posted October 1, 2023 Report Share Posted October 1, 2023 Not tried it, but don't think the bisque bowl will absorb enough water to release the form. I have used bisque for press-moulding which does work, but half the water is not present to start. You can do a mini test, by pouring a spoonful of slip onto any plaster (outside face of a mould), and onto a bisque'd item. See what happens. Time how long it takes for the plaster one to dry out and release naturally with no intervention from you. Compare time with bisque one. etc......... Quote Link to comment Share on other sites More sharing options...
PeterH Posted October 2, 2023 Report Share Posted October 2, 2023 (edited) Off topic, but as you seem to be exploring the boundaries at the moment so you may be interested. Historically millions of bowls have been made in bisque moulds. Not by casting, but by a skilled-labour intensive slow-wheel process akin to manual "jiggering". Also see https://www.youtube.com/watch?v=2Nef_LuFDkc Note there is no attempt to mould-form the foot or the upper smooth-section-with-rim. But you get a lot of texture with little per-pot effort, and the use of stamps minimises per-mould effort. Edited October 2, 2023 by PeterH Hyn Patty and Chilly 2 Quote Link to comment Share on other sites More sharing options...
KB3d Posted October 2, 2023 Author Report Share Posted October 2, 2023 Thanks Peter. Quote Link to comment Share on other sites More sharing options...
Jeff Longtin Posted October 3, 2023 Report Share Posted October 3, 2023 Presumably it will work but the question is how long it will take to set up and how quickly do you want the pieces out of the mold? Without fail I cast for 30 minutes, and 60 minutes after that, I have a soft clay form out of the mold. (When using plaster.) You're looking for faster turn around? The one thing you could try, to speed the process, is heating the bisque bowl before using. (or during, or after?) Good luck! Quote Link to comment Share on other sites More sharing options...
Callie Beller Diesel Posted October 3, 2023 Report Share Posted October 3, 2023 Bisque makes great slump and hump moulds for handbuilding on, but I think plaster is a better tool for slipcasting. Magnolia Mud Research, Jeff Longtin and Chilly 3 Quote Link to comment Share on other sites More sharing options...
neilestrick Posted October 4, 2023 Report Share Posted October 4, 2023 It may be possible, but you'll need to make the piece very thick like a plaster mold would be. I don't think the bowl you show in the picture will be thick enough to absorb the amount of water needed for it to set up. Since you already have it thrown it would be worth a try, though. Might work for one casting, but you definitely won't get two out of it on the same day. I think you'll probably need to bisque fire it to very low temps to increase absorbency, like maybe just take it up to 1500F. It's not really important that all the organics burn out perfectly, you just need it to be set up and durable enough to do the job. Quote Link to comment Share on other sites More sharing options...
karend5 Posted March 23 Report Share Posted March 23 I have been using silicone molds for resin with clay. Press molds was fine but then I bought molds to make jars. I tried slip casting. It's been two days and they haven't dried much. Researched making plaster molds from silicone molds. Then today I thought of using clay and making bisqueware. The problem I'm having is the silicone is too soft to use for clay. I would need to make a jar and then use that to make the mold. How am I doing so far? Right now, either I'll need to wait till the slip casting dries or cut the silicone molds in half and use soft clay. Any suggestions? Quote Link to comment Share on other sites More sharing options...
PeterH Posted March 24 Report Share Posted March 24 15 hours ago, karend5 said: I have been using silicone molds for resin with clay. Press molds was fine but then I bought molds to make jars. I tried slip casting. It's been two days and they haven't dried much. Researched making plaster molds from silicone molds. Then today I thought of using clay and making bisqueware. The problem I'm having is the silicone is too soft to use for clay. I would need to make a jar and then use that to make the mold. How am I doing so far? Right now, either I'll need to wait till the slip casting dries or cut the silicone molds in half and use soft clay. Any suggestions? People have used bisque moulds to slip cast in, although you may need to pick a bisque-firing temperature to maximise absorbancy. Note the contributions by @Tyler Miller and @Viking Potter in: Have you considered casting a plaster master in your silicone mould? If necessary immersing the mould in sand to minimise distortion. I assume/hope the silicone could be stretched to release the plaster master. PS I'll walk through the slip-casting process in order to make a few points about slip-casting. 1) Assemble mould The mould needs to be made of a very absorbent material (plaster is the almost universal choice). And you need enough plaster (or whatever) to absorb sufficient water from the slip to form the walls before you drain the mould. A slip-casting mould cannot have any undercuts, so the casting can be removed without damage. This form seems to require a 3-part mould: one for each "side" and another to handle the foot-ring. 2) Pour slip into mould. Casting slip needs to be suitably deflocculated and it contains a lot less water that watered down clay of the same viscosity. https://digitalfire.com/article/understanding+the+deflocculation+process+in+slip+casting Optimal casting requires that the slurry have minimal water content (e.g. 30% instead of 60%), good flow and draining properties and that it not settle out or gel too quickly. When the slurry is right the casting process works amazingly well. The slip is left for a while so that a thickened lay of semi-dry slip forms on the inside of the mould. The water removed from this layer has been absorbed by the mould. 3) Drain mould. The liquid slip is poured out of the mould, leaning the semi-dry layer layer on the mould walls. 4) Trim After waiting a while for the clay to firm-up a bit the casting can be trimmed. Small details of the mould are often designed to make this trimming fairly fool-proof. 5) Remove the mould. Wait until the casting is ready to remove from the mould. Too early release may result in slumping. Too late release can cause shrinking-on issues. ... then let the pot dry fully. Hulk 1 Quote Link to comment Share on other sites More sharing options...
Jeff Longtin Posted March 24 Report Share Posted March 24 Hello Karen, Can you post pictures? From my experience only plaster molds can be used with slip casting. I do know folks who have used rubber molds for pressing wet clay but that has its own challenges. I would recommend you make plaster molds, from your silicone molds, and then use the plaster molds to slip cast. PeterH 1 Quote Link to comment Share on other sites More sharing options...
karend5 Posted March 24 Report Share Posted March 24 Hi Jeff I have the molds filled with slip right now. I'm waiting for them to firm up. I poured them three days ago and they still haven't dried. I'm going to try silicone press molds and see if that works. It doesn't look like making boxes is going to work. They aren't getting any air. I would like know how to make bisque molds for them. Quote Link to comment Share on other sites More sharing options...
karend5 Posted March 25 Report Share Posted March 25 How? Quote Link to comment Share on other sites More sharing options...
karend5 Posted March 25 Report Share Posted March 25 The way it looks to me is in order to make a plaster mold I would need about end product of silicone mold and then use that to make the plaster mold. An I close? Quote Link to comment Share on other sites More sharing options...
PeterH Posted March 25 Report Share Posted March 25 12 hours ago, karend5 said: The way it looks to me is in order to make a plaster mold I would need about end product of silicone mold and then use that to make the plaster mold. An I close? You would need to - cast a "master" in the silicone mould, plaster would be a natural choice (and doesn't shrink) - remove the master from the silicone mould (hopefully the mould will flex/stretch enough to allow this) - make a plaster mould from the plaster master - remembering to give the mould time to dry out before you cast in it (it has to absorb water from the slip) Note that the plaster mould may need to be multi-part (so you can get the slip-cast object out) ... as illustrated in these two videos. How to Make a Two Part Plaster Mold at Home! Ceramic Orange Juice Jug! - YouTube https://www.youtube.com/watch?v=wcSytuNXKfQ Quote Link to comment Share on other sites More sharing options...
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