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Probably one of the easiest moulds to manufacture
with RTV silicone is the single piece mould.
Made easily by preparing a former and fence
and then mixing the two parts, silicone base
and catalyst together and pouring.
The are two types of RTV Silicone:
Condensation Cure, also known as Tin Cure
and Addition Cure, also known as Platinum
Cure. The first variety (assuming you use
a quality silicone) has low linear shrinkage
of 0.4% or less. Platinum cures are superior
and offer only 0.1% linear shrinkage.
Tin cure silicones should NEVER be used for
lifecasting (body moulding) since Tin is an
accumulative poison like lead and very bad
for you. Platinum cure do not pose this hazard.
Drawbacks include bubbles on the mould surface
by encapsulating air in silicone when mixing
and not having expensive vacuum or degassing
chambers for removal of this air. If you have
no such equipment use a slow catalyst with
long potlife and allow the mixture to self
de-gass Mix using a folding motion!
For directions on the manufacture of a mould
using this product follow this link:
RTV
Silicone Single Piece Mould
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Vinamold, commonly misspelt
Vinamould in the UK, is a very versatile product
that allows reuse of the moulding compound.
It is manufactured from PVC.
It is more difficult to use
than a pouring silicone since it must be heated
to around 150-170 degrees Celsius to achieve
a pouring state. For larger moulds melting
pots are needed, thermostatically controlled
with oil filled jackets.
Small quantities can be melted
in double walled vessels or very heavy gauge
saucepans, though this can be dangerous and
can burn the Vinamold releasing noxious fumes
similar to burning plastic and reduce the
number of re-melts.
Other dangers with the use of
Vinamold include serious burns due to its
melting point of 15-170 Celsius. Spillage
of this material on the skin will cause burns
more serious than boiling water.
Drawbacks of the system include
bubbles that are created at the mould surface
during pouring made by the presence of water
turning to steam on contact. This can be avoided
to a degree by ensuring a completely dry former
(particularly with plasters) and preheating
of the former.
To see our section on making
a Vinamold Mould click the link below:
Vinamold
Single Piece & Sectional Moulds
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