Fibre-Glass mould making and casting
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1.Using a pair of scissors cut some ‘tissue fibre-glass matting’ and some
‘course chop- strand fibre-glass matting’ into pieces around the size of
banknotes.
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2.Gel-coat is applied directly onto your master’s surface, which has
already been primed with a suitable release agent (PVA blue is a popular release agent for fibre-glass). We leave the gel-coat to cure for around 35 - 45 minutes.
If you are using a Silicone skin Gel-coat is not necessary.
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3.Apply a liberal coating of catalysed GP resin onto the gel-coat or
silicone surface.
Lay a piece of tissue fibre-glass matting over the wet resin surface and using the brush in a stippling action, press the matting into the resin until saturated. Working from the centre out, ensure all the air bubbles are removed from under the matting (Air bubbles are clearly visible through the wetted matting). The next piece goes on overlapping the first, wetted down with more resin on the brush, and matting.
You do NOT need to wait for each layer to set before starting the next.
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4.The next step is to de-laminate the course, chop strand matting we
cut earlier.
Although it can be used as it is, peeling the two layers of fibre-glass apart is helpful because it makes it easier to apply to a complex form, like a human face. Using the same technique of stippling, wet the matting down, again ensure all air bubbles are evacuated from beneath the surface. Usually two layer of this matting is enough for a mould the size of a face. Larger moulds will need more layers to add strength.
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5.This same process is repeated two or three times with a thin tissue-like
fibreglass matting and another two or three times with chopped strand matting. This laminating of layers of glass-fibre matting and polyester GP resin is what gives the finished product its strength.
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6.In order to avoid glass splinters from the finished piece it is
recommended that a layer of gel-coat is applied to the outside of the fibre-glass mould.
Smother the exterior completely with catalysed gel-coat, ensuring all the splintery textured glass fibre is covered.
7. Once all is fully cured the mould can be removed from the master. If it is a multi-part mould, it can be cracked apart along the shut lines using wedges and small pry bars. This can be tricky sometimes so ask a technician to help you.
Tip: At any stage though out the whole procedure, pigments may be added. Adding pigment when fibre-glassing is helpful to check you are getting an even coverage.
To CAST a fibre-glass object the same method must be used in the same order.