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I recently began experimenting slip casting using commercial molds. One particular mold, the handle of the cup ,which is a neat little circle gets stuck everytime I take it out and then it breaks off. Is there a release agent I can use that will make the releasing process easier without hampering the osmosis between the clay and the plaster. Please advise ??

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No release agent for plaster moulds, that I know of.

Have you checked that the mould is clean?  Try vinegar and a sponge to clean it up.

Does your slip release easily from other moulds? 

Are you leaving it too long before un-moulding?  Too little time?  Casting too thick, too thin?

Small curved moulds are the devil to deal with.  I have had to enlarge the "funnel" on handle moulds as they never held enough "top-up" slip.

 

 

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Thanks for your reply . I did leave the mold overnight for the slip to harden properly maybe the slip shrank too much. I just have to keep on trying to get the timing right and will use some vinegar for cleaning

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That cup handle is often cast alone and added later.

The tricks are dry mold very well before use-after dumping it our pull it apart when cup is ready-time this on a timer. Do not leave overnight-take it apart when clay in handle has some give to it. The reason its cracking is is shrinking  onto the inside cast part of the handle.The idea is to get it out before it grabs the inner part.This type of cup with handle is a hard top deal with mold to get a handle cast to body in one pour.

many cup molds added the handle later as that is easier.

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Thanks Mark for your advice.I did attach the cracked off handles with some casting slip and I am surprised how well it binds after dipping the cup quickly in water.Just hope it will survive the firing. I also have another mold I want to use .It is a candle holder but it does not have a pouring cup .How do you cast that one?.Do you fill the one half with slip, put the other half on top and rotate it to get an even layer inside.?Please advise it is like casting blindfolded.

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