Advantages:
Latex is a low cost mould rubber which usually does
not require a release, stretches easily, and cleans
up with soap and water
Molding Silicone is extremely versatile, no release
agent is required, many different varieties made.
Polyurethane is extremely durable, releases air bubble
easily and is made in many degrees of hardness.
Disadvantages:
Latex has very limited life,12 months usually, it
takes a long time to make a mould with half to one
hour between coats it can take several days to make
a mould and due to its flexibility it requires a mother
mould to hold the shape during casting.
Molding Silicone is more difficult to mix and usually
requires removal of air bubbles with a vacuum. It
is the most expensive rubber.
Polyurethane requires release agents, takes 24 hours
to cure and is limited in the number of mould types
it can be used for.
OUR PERSONAL FACTORY PREFERENCES
Wherever possible we use molding silicone. The extreme
ease and speed of use, reliability and easy release
qualities makes the price unimportant in our case.
The combination of a silicone mould and the use of
polyurethane resin as a casting medium opens the door
for the production of countless hard plastic items
from train and vintage car parts. 8 hours or less
for the molding silicone to cure and 10 minutes to
produce a white hard plastic figurine in resin.
WHEN DO WE USE THE OTHER RUBBERS
For hobby casting of plaster, latex is still our rubber
of choice and articles on how to make latex moulds
are available on our website.
We recommend that where you are just starting out
and the labour is your own, latex moulds can still
be used economically for casting concrete, replacing
the moulds on an annual basis. They are used as usual
with a fiberglass or plaster back up mould.
For concrete moulds of all types we prefer to use
polyurethane. It has outstanding long life characteristics
(up to 15 years) and does not need back up moulds.
