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How In The World Do I Make This?

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#1 justin1287


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Posted 17 May 2014 - 06:17 PM

I 3d printed this object out, and am trying to make 2 a piece mold for it, but the plaster keeps sticking on the inside.  The inside angle is a little over 3 degrees.  I tried using oil to make it slippery, and even made a plaster mix with a higher water ratio than normal.  Thanks.

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#2 JBaymore



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Posted 17 May 2014 - 06:40 PM

As plaster cures, when it gets hot , it expands a tiny amount.  Are you letting it cool back off before trying to remove the core of that hollow piece?  3 degrees is not a lot of taper.... ..... also are you sure that the 3 d printer held that accuracy?





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Adjunct Professor of Ceramics; New Hampshire Insitute of Art

Former Guest Professor, Wuxi Institute of Arts and Science, Yixing, China

Former President and Past President; Potters Council



#3 jrgpots


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Posted 17 May 2014 - 07:58 PM

If you have an air compressor, you might be able to blow air into the crack between the plaster mold and the cup to break the suction.


#4 schmism


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Posted 17 May 2014 - 09:54 PM

can you use release agents with plaster?  (like pam non-stick spray)

#5 Pres


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Posted 18 May 2014 - 08:33 AM

Make it a 2 piece mold with the bottom separating from the wall. then you can work the piece out of the mold from top or bottom.

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#6 TJR


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Posted 18 May 2014 - 09:31 AM

can you use release agents with plaster?  (like pam non-stick spray)

You can use Murphy's Oil soap. Comes in a spray bottle. I think you can get it at Home Depot. I bought mine at Canadian Tire.


#7 Mart


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Posted 19 May 2014 - 03:27 AM

Are you sure you do not need a 3 piece mould? (I can not tell form the picture, how your piece looks like) - 2 for sides and one for the bottom.
If not, use 2 piece - one for the bottom.

I mix olive oil with "household soap" (old school stuff still used to hand wash clothes on washing board. I have no idea how it's called in US.) aka mould release etc.

The bottom part for your mould (blue).

Attached File  mould0.jpg   55.26KB   1 downloads

When the plaster gets hot and then starts to cool, it pushes lots of water out from the plaster. Sometimes (not always) this is the best time to open the mould. But it obviously depends what plaster mix is used, how big and what shape etc is the piece etc.
I have left stuff sitting overnight and never had problems. Start with that.

#8 justin1287


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Posted 19 May 2014 - 04:46 AM

Thanks for the ideas....will try some new ideas out when I have a chance to get back to that project!

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