Repairing Plaster Molds

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    I have purchased some plaster molds over the last few years and have lost

    glass pieces along with them as they cracked (Four to date). One, the first time I used

    it ($40 cost). Does anyone know how repair them?

    Stephen Richard

    Are you sure they are plaster.  Normally plaster would last only one firing before it cracks.

    If it is a ceramic mould, let us know how you are firing it (scheuldes, etc) and we may be able to help you stop breaking them.

    If they are plaster, there is no fix.

    If they are ceramic a material called “sairset” available from ceramics suppliers will work.



    One way to hold molds together during firing is to use stainless steel bands– the kind that is used for holding hoses onto washing machines. They come in different lengths and will hold a ceramic mold together or a “plaster mold.”

    But like the other person said, plaster molds are a one-shot mold for glass. Plaster molds can be “glued together” for the one-time firing by mixing a patch of wet plaster and properly drying the mold. I usually put a stainless steel band on that kind of mold if I think it might need more support.


    I’m suprised to hear that the stainless bands work — stainless expands a lot more than ceramic under heat so I would expect it to loosen.

    Helios Kiln Glass Studio



    Sorry, it does sound like “a bad mold will find new life with a hose clamp.” Not really the right message.

    I pour my own one-shot molds. The bands are meant to keep the mold together if I have to “glue” it because I drop or jostle the mold. For small, uncomplicated items, repouring the mold makes more sense than taking a chance. However, if I’ve invested a bit of time and materials and creative energies, I try to salvage the mold and use the hose clamps.

    Once it is in the kiln, I don’t mind if the band falls away because I’m a belt-and-suspenders kind of glass caster anyway. The bands “loosen” in the slow ramp up as the mold dries and the metal expands. The bands do their job which is to hold the thing together long enough to establish I’ve got a good repair, not much more.




    Ed Richburg

    I have used nichrome wire to sucessfully hold plaster molds together.

    Plaster is usually one use.

    I found that out the hard way.

    More permanent molds are made from clay.



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