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Alternatives To Plaster For Slip Casting.


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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!

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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.

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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.

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  • 3 months later...

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.

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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.

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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

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