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Silicone Block Mould – Pt.2

1-Piece Silicone Block Mould (Part 2)
By Paul Carnall
A M T Composites

This is a 2 part Project. In Part 1 we made a 1-Piece Silicone Block Mould of the “Artichoke Tea Light Candle Holder” using a 2 part room temperature cure silicone moulding rubber. Then, in Part 2, we cast into the silicone mould using “Metal Cold Casting Technique” with Bronze powder

Part 2: Metal Cold Casting Technique with Bronze Powder
In Part 2, we cast into the silicone mould we made in Part 1, using “Metal Cold Casting Technique” with Bronze powder that gives a very realistic effect similar to that of an actual Bronze Casting, weight & all!

Requirements for Casting into Silicone Mould

  • Smooth-Cast 300 casting resin
  • Black pigment
  • Bronze powder
  • 2 mixing containers (non-pourous)
  • Wooden spatula for mixing
  • Steel Wool

Instructions for Casting into Silicone Mould

Various casting materials can be poured into silicone moulds e.g. pewter, polyurethane and / or polyester plastics, epoxies, water (to be frozen), plaster of Paris, and more. For this project we used a fast cast 2 part polyurethane plastic and metal cold casting technique.

Step1: mixing the polyurethane casting resin and bronze metal powder The Smooth-Cast 300 has a 1:1 mix ratio by volume and has a very quick curing time, please refer to technical data sheet before use!

  1. Pour out equal quantities of Smooth-Cast 300 part A and part B into two separate mixing containers. (do not mix A & B together at this time).
  2. Add bronze metal powder to part A and then add bronze metal powder to part B.
    The trick here is to add as much metal powder as you can while bearing in mind that it still has to be poured into the mould. The more metal powder added, the more realistic the effect, but if too much is added, then the mix is difficult to pour and detail in the casting will be lost! While mixing the metal powder, lift mixing stick to check viscosity. The material must flow off the mixing stick and not create lumps.
  3. Once the metal powder has been mixed to part A & part B, add the 2 parts together and mix thoroughly for about 30 seconds then pour /cast into silicone mould.

Step 2: allow to cure & demould

  1. The Smooth-Cast 300 cures in about 10 minutes and is then ready to be demoulded.
  2. Carefully demould the bronze casting by pulling it out of the mould.
  3. Be careful not to damage the silicone mould, so that you can use it again and again.

Step 3: expose the bronze

  1. At this stage the casting will just look dark brown.
  2. Use steel wool to buff the surface to expose the bronze metal.
  3. This will give a brushed metal finish resembling a bronze casting.

You can make numerous castings into the same mould so that you have as many replicas as you need.