Ceramic Decorating Techniques

How to Make and Use a Plaster Press Mold to Make Ceramic Jewelry

Making Textured Ceramic Brooches with Plaster Press Molds

• July 20, 2020 • Read Comments (35)

Ceramic Jewelry

Plaster press molds are very useful when you are planning to make multiples of a particular form or an embellishment to a form. For Allistair and Sally MacDonell, press molds really came in handy for a series of ceramic jewelry that they wanted to make.

In this post, the MacDonells show us how easy it is to make plaster press molds. Plus they explain how they use stamps to texture each slab before molding it into the shape they want. – Jennifer Poellot Harnetty, editor.

Molds are very useful to speed up the process of repeating forms. Plaster is cheap and can be bought from specialist suppliers in a dry state. As shown in the illustrations, the MacDonells make plaster molds for their brooches.

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This article was excerpted from Ceramic Jewelry, which is available in the Ceramic Arts Network Shop.

Here the modeled face is attached to a slab of clay and surrounded by a cottle (clay wall). The plaster of Paris is then mixed as follows. Firstly, the volume of plaster needed is estimated by looking into the cavity created by the cottle (the surrounding clay wall) and estimating the amount of water needed to fill this space. Now half the estimated amount of water (the amount of water actually used is only half because the plaster expands in the water to fill the space within the cottle).

Pour the final amount of water into a large bowl or bucket. The plaster is then sieved over the surface of the water until an island of plaster appears, whereupon one more handful of plaster is sprinkled around the outer edge of the water in the bucket. Leave the plaster and water for a couple of minutes until all the plaster has been soaked through, then gently agitate the mixture from the bottom until it becomes thicker, being careful not to introduce air into the mix. When the mixture begins to thicken, it can be poured into the prepared cavity. It is then gently pushed down to ensure that the plaster has been forced into every detail of the model and that air bubbles have been encouraged to the surface. If the estimated amount of plaster is not enough, then the surface should be roughened by dragging a finger through it as it is becoming solid, so that another mix can be made and poured over it. If too much plaster has been mixed then the excess should be poured into a rubbish bag, NOT down the sink, where it will block the drain hole.

**First published in 2012.
Comments
  • Reader L.

    this may have been answered but i’m still not sure. For making brooches or for re-occuring embellishments, should I start the image using clay like porcelain or paper clay for firing high or low fire clay does it matter?? do I then make the mold while it’s still wet and somewhat soft from the unfired unfired clay? then pour the the plaster mixture over the image with the wall or cottle also made of wet clay in the form of a slab… how long before the plaster is ready and I will not need release agent for a wet clay, throw away model, correct? thank you -Michelle

  • Linda H.

    Do you make the mold when the modeled face and cottle are still damp or after they dry?

    • Jo A.

      Use the model when fresh as a sacrificial model. If allowed to dry it will shrink, but will also require generous soft soap to release the model cleanly.

  • hi, wouldn’t Super glue work for gluing brooch pins on the backs? Epoxy of course, too, but it’s more time consuming, thx.

  • Hi Alka, by not using any grease or soft soap the plaster has stuck. You will have to use a hammer and chisel to try and crack the plaster mold apart. If your model is made from plaster it will be ruined. sorry.

  • Alka G.

    Hi Kim, I am trying to make the 2 part ceramic mold from plaster of paris. I read one of the book article and tried it. i have not applied any separting agent. Now both the parts are joint. How should I separte the two part without danmaging the original piece? Anyone please give suggestion.

  • Here is the recipe for the mold grease.

    I bar of Velvet soap finely grated
    300mls vegetable oil
    500 mls boiling water

    Combine and continue to stir until soap is dissolved and mixture is smooth. That’s it!

    It sets when it gets cold

    cheers Kim

  • Hi Kim,if the model is made from clay it will release from the plaster mold easily by itself. If you use plaster as a model you need to coat it with soft soap so that it doesn’t stick.I have a recipe for mold grease somewhere I will look it up for you and post it back here. 🙂

    I love plaster molds and mold making. Thanks heaps for this article. I pressed some clay into some rocks and made molds of the rock faces, it was heaps of fun.

    http://frogpondsrock.com/2010/02/clay-impressions/

    cheers Kim

  • Kim B.

    hello. i’m new to mold-making but excited to give it a try. have a couple of questions though: what is the original model constructed of? clay or a non-drying modeling compound such as roma plastilina? also, is any kind of releasing agent necessary to help free the original model from the plaster? thanks…

  • Grit S.

    Bonjour, Good afternoon from south of France. I will use your ideas asap. Thanks for sharing.à bientôt.

  • BETH W.

    Ceramics Art Daily is the BEST! I learn as much here as going to over priced workshops and I can read all the infor in my “work clothes.” This mold idea will also work for details for architectural ceramics. Using clay to make the wall for the mold is just so simple and obvious but after years of making pottery, who knew?
    Thank You Ceramic Arts Daily!!!

  • Jonni W.

    Good morning from Mississippi! Love the mold instructions and plan to give it a try…thanks for sharing!

  • Vikki R.

    Just love getting new ideas and incentives from Ceramic Arts Daily.Got to try this one too at our Pottery shed.Dysart-Central Queensland Australia. It seems there are a few of us from many far off places. G’Day everyone!!

  • Brenda W.

    Best NOT to re-use the clay, as it picks up bits of plaster, and we all know what happens when plaster is fired in the kiln, don’t we? (KABOOM!)

  • Alka G.

    A small question:The clay used in making mould can be recycled with the normal clay and used?

  • Marilyn M.

    Nice, clear demo. I’m kind of timid about making plaster molds, but this is a size I can handle. And I do make ceramic coins and jewelry, so this is perfect.

  • Sue K.

    Nice Demo !! I’ve made a few molds myself but not from plaster. I think I’ll give this a try.

  • Donna R.

    Hi from Panama. Our whole line is press molded. We make plaques (most popular, everyone wants to hang everything on the wall), soap dishes, small pendants and tiles.
    Having moved from the USVI recently, we are in the process of setting up our shop again. I really enjoy reading ceramicartdaily. It keeps me thinking till I can get back into the clay again. Thanks!

    Donna & Ray

  • Jo M.

    Loved your mold making, people need to be aware that they can use the press molds for more than clay, Pmc, glass clay, polymer clay,Paper machaie and plaster .
    If you use a lead free, food safe glaze and clay then we can use them to make decorated food such as cookie dough, butter, chocolate, softened ice cream , rice mashed potatoes and the list goes on
    Looking forward to seeing more mold Ideas!

  • Kathleen R.

    I have been interested in the possibility of making plaster molds. This will be a good way to start, something small and interesting! Ann, how did your husband make sprigs?

  • Ann R.

    This is a well presented illustration. As a life long potter and teacher, I was successful in getting my husband interested in hand building. This is right up his street as he is exploring press mold possibilities and his own personal touch in the clay world. He went crazy making me sprigs and now press molds will keep him even more busy and out of my hair.

    Thanks!

  • Dorothy F.

    Peru! It’s going to be hard to invite you all over to my house. Just joking, but it would be nice.

  • Subscriber T.

    Thank you. I am very happy to find you at the Web. Greetings from Perú!!

  • Dorothy F.

    Thank you. I shouldn’t be allowed loose in the IT world. Pony Express is really more my speed.

  • Jim S.

    Just click on the image (Fig 10) and it will open inside your browser window in larger more detailed view.

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