edan Posted January 3, 2016 Report Share Posted January 3, 2016 I'm interested in experimenting with alternative porous materials suitable for slip casting, with useful properties such as flexibility, faster drying, increased durability, machinable, etc. Can anyone suggest plastics (foamed PVC, polyurethane, etc.) or other plasters (eg: Hydrostone) worth looking into? Thanks! Link to comment Share on other sites More sharing options...
Mark C. Posted January 3, 2016 Report Share Posted January 3, 2016 Try USG.com Link to comment Share on other sites More sharing options...
BeckyH Posted January 3, 2016 Report Share Posted January 3, 2016 The big thing in molds is the ability of the material to pull water from the slip so the object wall builds up. Porosity and capillary action are essential. I can't see how plastics could manage this. Link to comment Share on other sites More sharing options...
Mark C. Posted January 3, 2016 Report Share Posted January 3, 2016 #1 pottery plaster is still one of the best matirials for this There are harder plasters for master work as well as plastics but for working molds plaster is still king. Link to comment Share on other sites More sharing options...
Chilly Posted January 3, 2016 Report Share Posted January 3, 2016 I'm interested in experimenting with alternative porous materials suitable for slip casting, with useful properties such as flexibility, faster drying, increased durability, machinable, etc. Can anyone suggest plastics (foamed PVC, polyurethane, etc.) or other plasters (eg: Hydrostone) worth looking into? Thanks! Good Luck with this. Plaster has been in use for many many years and nothing has taken it's place so far. I can't believe that plaster isn't machinable, although I do agree that durability is not one of it's features. Link to comment Share on other sites More sharing options...
edan Posted January 3, 2016 Author Report Share Posted January 3, 2016 The big thing in molds is the ability of the material to pull water from the slip so the object wall builds up. Porosity and capillary action are essential. I can't see how plastics could manage this. An example of plastic with high sorptivity and capillarity would be PVA sponges. Those sponges are smooth, rock solid when dry and flexible when wet. A sponge seems impractical for casting, but other plastics such as low density Ren Shape modelling boards might also work. I have found that non-porous surfaces can be incorporated into a plaster mold where precise machining and durability is required, as long as they are close to adjacent plaster surfaces with sufficient wall thickness, otherwise the slip doesn't seem to get sucked/pulled into the mold's internal corners. USG Hydrostone seems to stick to clay, and requires longer casting times with slower adsorption of slip. Good for small parts requiring very thin wall thicknesses, lasting minutes instead of a few critical seconds in plaster. Hyrdostone and plaster could also be combined in a single mold. Link to comment Share on other sites More sharing options...
oldlady Posted January 3, 2016 Report Share Posted January 3, 2016 Joan Gardiner, a tile maker in Unison, Va. makes and has many plaster plus hydrostone molds. you might want to contact her, she has been doing it for years. Link to comment Share on other sites More sharing options...
Chris Campbell Posted January 3, 2016 Report Share Posted January 3, 2016 You might also want to look into dental products ... They need accurate, flexible molds that must work well with porcelain. Link to comment Share on other sites More sharing options...
Mark C. Posted April 21, 2016 Report Share Posted April 21, 2016 Today I walking on lava near Kalaupapa leper colony and thought that lava would be a good clay absorber. When you see lava it has varying degrees of bubbles so a fine bubble stone may be perfect for your use. It's not plaster so that fits your non plaster clause. It's not plastic so maybe this does not fly for you. I suggest someplace other than Kalaupapa to gather lava from as its not accessible by car or boat. You hike in or ride a mule or take a small plane. You are not allowed to gather lava. You can take lava fron other islands but there may be a karma tax for doing so as pele is not happy with those that take here gifts away. Her gift is lava in Hawaii. Now there are many lava beds out west you could source from much closer to you. This material can be c&cd and the voids could be filled for smoothness and is highly absorbent. Link to comment Share on other sites More sharing options...
MatthewV Posted April 21, 2016 Report Share Posted April 21, 2016 Plaster: Pros-- cheap, right porosity, casts well, allows details, good surface finish, reasonably durable, able to make large molds Cons-- very few. Not highly machinable. I am not sure if it works with a vacuum forming process to pull water out. There will be other materials especially if cost is not the concern. I remember seeing some MDF-like semi-porous boards which were more machinable. The dental industry is the place to research on the latest casting technology. Link to comment Share on other sites More sharing options...
edan Posted April 22, 2016 Author Report Share Posted April 22, 2016 Today I walking on lava near Kalaupapa leper colony and thought that lava would be a good clay absorber. When you see lava it has varying degrees of bubbles so a fine bubble stone may be perfect for your use. It's not plaster so that fits your non plaster clause. It's not plastic so maybe this does not fly for you. I suggest someplace other than Kalaupapa to gather lava from as its not accessible by car or boat. You hike in or ride a mule or take a small plane. You are not allowed to gather lava. You can take lava fron other islands but there may be a karma tax for doing so as pele is not happy with those that take here gifts away. Her gift is lava in Hawaii. Now there are many lava beds out west you could source from much closer to you. This material can be c&cd and the voids could be filled for smoothness and is highly absorbent. Interesting idea, very curious to see if this works and what texture you get on the part. I will keep my mule well clear of Kalaupapa if ever I have the temptation to smuggle lava from the leper colony. I'm not sure how easily machined lava, or basalt rock would be. And how to fill it with porous resin? I did manage to find a supplier of high pressure slip casting resin: http://www.castimo.org/Porous-Resin.aspx Link to comment Share on other sites More sharing options...
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