such as StonePlast are not strictly speaking plasters but are gypsum
cements. Their main value as far as casting into latex rubber concrete molds is concerned is
that they are extremely hard in comparison with casting plasters.
This makes stone plasters very suitable for use in making chess pieces
or items that are handled great deal such as lamp bases. They are much
more expensive than Australian manufactured casting plasters being all
It is important to note that stone plasters require a great deal less
water to achieve a suitable smooth flowing mix. Accurate measuring is
extremely important to enable the stone plaster to achieve maximum
strength and give it the strong non-chipping characteristics that you
Measuring the StonePlast
Select a suitable plastic measure such as an aerosol cap or something
similar and fill the mould ¾ full of water counting the number of
capfuls required. Pour the water from the mould into a mixing bowl.
Dry the plastic measure and fill it with StonePlast leveling the top by
scrapping a knife blade across. You will now need 2 ½ times the number
of capfuls you required to ¾ fill the mould with water. So if 2 capfuls
were required you will need 5 capfuls of StonePlast. This may seem to
be a lot of the stone plaster but you will find that as you sprinkle it
across the water in the mixing bowl, it will absorb all the water.
Do not commence mixing as soon as you have sprinkled all the plaster
into the mixing bowl . Allow it stand untouched for 2 to
At the end of this period start stirring beginning at the outside of
the bowl and work inwards. It does not appear as smooth a mix as your
regular casting plaster but it will pour easily.
to Fill the Mould
Rinse the rubber concrete molds with CraftRinse solution and shake semi-dry, and then
fill the mould about half full.
the Mould of Air Bubbles
Work the StonePlast mix into all aspects of the latex rubber concrete molds by gently
squeezing. Pay particular attention to all areas where there is fine
detail and undercuts together with areas where air could be locked in,
such as hands and feet.
and Supporting the Mould
Fill the mould to the top with StonePlast mix and then place in the
support to set solid.
the latex rubber concrete molds
When the casting has set hard remove the mould from the support and
wipe the outside with either a soap solution or dishwashing liquid and
peel back the mould in a stripping action and remove the cast.
Store in a warm area to dry. If using artificial heat such as a forced
fan radiator.oil heater of oven do not allow the temperature to rise
above 40 degrees Celsius.