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rdhammah

bubbles in Plaster of Paris molds

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Tried searching this topic but could not find anything on it but I know this has come up before. When I make a POP mold, the bottom comes out perfect. No residual bubbles. after it dries for a day, I apply a small amount of Vaseline to aid in demolding. I Mix the POP/water  2:1 and slowly mix. Before I pour the mix into the mold to make the top half, I tap the cup to get rid of bubbles. I pour the mix and tap to make the bubbles rise. I demold after a day. there are a ton of fairly large bubbles. I have tried using a thinner mix with the same results. How do I get rid of these bubbles?  

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Paint a coat onto your master before you add the bulk of the plaster.   Should take care of any issues as seams you have addressed viscosity, removal of bubbles with agitation, etc....

Also make sure you master is seated well in the other  half.  Air can get trapped and work it way up as things heat up.  

Edited by Travis
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 I  typically  pour  the top portion along the outer areas and work the plaster in with a toothpick or cheap paint brush if needed and then typically just carefully rub some plaster of paris with my finger over the master carefully so not to disturb it.

Any tiny bubbles can be fixed later with a pop mixed with less water to make a  paste.  Pack it into the bubbles and blend out to the surface.  I have a set of small curved files, spatulas, and dental probes that are used to clean up molds add detail etc.. before I clear coat the mold.

 

 

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On ‎9‎/‎26‎/‎2018 at 6:41 PM, Travis said:

Paint a coat onto your master before you add the bulk of the plaster.   Should take care of any issues as seams you have addressed viscosity, removal of bubbles with agitation, etc....

Also make sure you master is seated well in the other  half.  Air can get trapped and work it way up as things heat up.  

it works! only had 3 minor bubbles that I filled all on the same bait. the other 2 were flawless (almost)

 

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