Saturday, July 28, 2012

Some mold making techniques

Paul took us through a couple of traditional mold making techniques this week. The first was 'pressed clay'. This is what you do:

  • decide what you want to make - a plaque? a model of something? perhaps do a drawing to sketch out some ideas. We were encouraged to find a range of objects with different textures and use this workshop to experiment and play with the possibilities.
  • prepare the surface of the clay which is being used to press the objects into. 

  • Paul pressed a few objects into the clay...
  • then built a solid wall of clay around the area designated for the plaster.
  • Mix the plaster - water first! For the size of the clay moulds we were using about 5cms of water in a regular bucket was plenty;  sprinkle the dry plaster into the water quite quickly; when 'islands' of plaster start to form slow down the addition of the plaster; you want about 50% plaster and 50% water visible in the bucket; stir the plaster/water mix quickly with your hand to get the lumps out; when it is smooth and the consistency of cream (not whipped!) it is ready to pour into the clay mould

                                                       the clay mold with 'walls' around the imprint, filled with plaster
If you are making a plaque and want to hang it on a wall place a wire hanger; make loops on the wire to provide something for the plaster to 'grip' onto
  • leave the plaster to set for at least 40 minutes. If a fingernail scraped across the plaster leaves a deep indentation it is not ready to be released from the mold.
  • when the plaster is hard, peel the clay away from the plaster model.
  • wash the plaster model with water and brush to remove and clay left in deep indentations
  • leave the plaster model to dry - prop it up so that it dries underneath evenly
Here is my first effort. This technique provides a detailed casting and is easy and cheap, but one off. The clay is peeled away from the plaster when it has set so you lose the original mold.

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