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How To Use Stuart Bray Flat Moulds


 Working Smart

  • Moulds should be stored flat, taking care to not keep anything heavy on top which may damage or distort it.
  • Check the mould is clean and free of dust and dirt before use. Warm water and detergent can be used, or a solvent such as 99% alcohol for more stubborn dirt.
  • Ideally work on a flat, level surface such as on a non-porous board placed on a table.
  • Work in a well ventilated environment, taking all necessary precaustions to maintain sensible health and safety standards.
  • You are responsible for your health and safety, as well as those around you when working. Read all material and product information before using.


Once the mould has been released, you will need to apply cap plastic to the mould sur­face. I recommend using Super Baldies Cap Plastic by Mouldlife, as this is thinned with 99% alcohol. You can use standard acetone-based cap plastic instead if you prefer.

The cap plastic is supplied as a thick con­centrate, and needs thinning with solvent. As I will be brushing on my cap plastic, I mix in 2 parts alcohol to 1 part cap plastic.

If you intend to airbrush the cap plastic, you will need to thin it more, perhaps as much as 5 parts solvent to 1 part cap plas­tic. Do a test away from the mould to see how it is coming out of the airbrush. You may need to wash the nozzle should it be­come clogged.

Brush the mixture thinly all over, right up to the edge of the mould, taking care to not let it collect in pools in the deep areas of the mould. Work it into detail areas to ensure these are all covered.

This will need approximately three or four coats of cap plastic, allowing each layer to dry thoroughly before applying the next. You can use a blow drier to speed up the process.

If you want to airbrush the mixture on, then you may need to thin it further to maybe 4 parts solvent to 1 part cap plastic to get it to go through without cobwebbing.

When the cap plastic is dry, carefully pick at an edge of the mould with a pin to check the cap plastic is thick enough and doesn't have any obvious holes. If it does, then simply add a few more layers.

TIP: If you add more solvent to the mixture, remember to do extra layers as there is less cap plastic present in it by volume. The solvent evaporates - only the cap plastic remains.

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Once you are happy with the cap plastic, carefully measure out and mix the required amount of silicone for the moulds you are running. There is a guide for the amount required for each mould in this booklet.

I recommend using Platsil Gel 00, as this is a simple two part silicone mixed together in equal amounts, and does not require any softeners to be added.

Pour the silicone into the mould from high up, allowing to form into a thin stream as this will help to pop any larger air bubbles that may be present.

Smooth the silicone over the mould surface, and using a flat utensil as a scraper, carefully scrape the back of the mould. You want to press as firmly as you can without peeling the cap plastic layer up.

You may need to scape a couple of times to get the fine edges necessary. Ideally, you want to have a dry border around each piece where there is no silicone at all.

You can see this more easily is you use a lamp to create a reflection on the mould surface like this. Use a cotton swab if necessary to clean the edges.

For some moulds, you may wish to add a small amount of different coloured silicone to areas, such as a paler colour in the horns or sores. Once this has set, fill behind this with the required skin tone to create a superior appliance.

TIP: You can add Smith’s Prosthetic Deadener if you wish

to soften it further, but Plat Sil Gel 00 is fine for most


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As soon as the silicone has cured, apply a few thinned layers of cap plastic over the back of the piece, again going right up to the edge of the mould itself.

Silicone cure times vary depending on the ambient temperature you are in...the warmer it is the quicker it will set.

Once the cap plastic has completely dried (minimum of an hour), apply talc powder to the back. Carefully peel the appliance out of the mould, taking care to talc the inside as you go to stop it sticking to itself.

Once the piece is peeled out, you can trim off the excess cap plastic, leaving the thin border of silicone attached. This border will give you something to hold when applying the piece, and is dissolved off once it has been glued on.

Keep this piece somewhere flat, clean and safe until you are ready to apply it.