Aldax Moulds and Mouldmaking Supplies

How To Cast Stone Plasters Into Latex Rubber Concrete Molds

Stone plasters 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 imported products.
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 require.


Measuring the StonePlast
Select a suitable plastic measure such as an aerosol cap or something similar and fill the mould 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 times the number of capfuls you required to 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.

Mixing the StonePlast
Do not commence mixing as soon as you have sprinkled all the plaster into the mixing bowl . Allow it stand untouched for 2 to 3 minutes.
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.

Starting to Fill the Mould
Rinse the rubber concrete molds with CraftRinse solution and shake semi-dry, and then fill the mould about half full.

Ridding 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.

Filling and Supporting the Mould
Fill the mould to the top with StonePlast mix and then place in the support to set solid.

Removing 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.

Drying the Casting
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.

 

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