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Sealing Hump Molds


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I have a dozen hump molds I made and use on a regular wheel. I have a designated wheel and rack for this process and carefully clean the area up between uses to avoid any contamination.  

 

My problem is that as I move the molds around between the rack and wheel and throw on it, some small bits of plaster and plaster dust is around the area at the end of my session. Its not a lot but I would like to reduce or eliminate if possible. This weekend I was going to thoroughly clean the molds again to make sure all loose plaster from the making process is truly gone.

 

The side rim and bottom seem to generate the plaster debris I'm talking about and neither of these surfaces need to be particularly absorbent as the clay doesn't sit on the these surfaces. I figured after that cleaning I would lightly sand and then coat these surfaces with something to make them less prone to flaking.

 

Fist off does anyone see a problem with this plan and does anyone have a suggestion of what to use to coat the side rim and bottom. I may from time to time hit the rim with the tip of a throwing tool so I don't want to use anything that would cause too much havoc should a piece of it end up in clay and get fired.

 

I was thinking of brushing on something like diluted Elmer's wood glue. I like the glue idea because it is less likely to flake as a powder if its hit with a metal throwing tool and if a small piece did find its way in I assume it would burn out fine.

 

Any input would be appreciated. Just started working with molds and followed the best practices outlined here on a CAD posted article.         

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After a plaster mold had dried at room temperature and has been trimmed of rough areas with a knife and sandpaper, I dry it in an oven at 150 F for 24 hours at least.

 

Then I paint it with several coats of Murphy oil soap, diluted 1 to 1 with water. Makes for a durable mold from which clay releases easily.

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If you want to seal the surface-that is loose all the plaster asbsorption I would use PUP which is polyurethane Parting compound.

Its made to seal a master molds to cast your rubber off of. I have a gallon jug around just for this use.It seals plaster extremely well.

If you have a treal paint store you could ask them for some or order it from a full service ceramic supply house.This is what mold makers use to seal plaster.

Mark

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