Unlike practically any other compound, when plaster turns from liquid to solid it does not shrink, rather, it expands ever so slightly as it forms crystals.
Because it expands, plaster castings do not lose any detail, and a mold with a glass smooth surface will result in a glass smooth plaster casting.
How long does Plaster of Paris take to dry?
Plaster of Paris sets in a very short period of time depending on the temperature of the mix and the air temperature. Typically, it can be de-molded in about 30 to 45 minutes. If it is cool to the touch it has at least set.
How do you harden plaster of Paris?
How to Harden a Plaster of Paris Cast
- Pour prepared plaster of paris into mold.
- Touch the top of the cast gently with your fingertip when it looks like it could be dry.
- Remove the plaster cast from the mold carefully.
- Let the cast sit at room temperature in a location with good air circulation for a few days to harden completely.
Does plaster of Paris break easily?
Plaster of Paris is low cost, easy to use, and makes good castings. Plaster of Paris comes as an easy-to-mix formula that mixes with water and dries to a dense, durable, and smooth and bubble free finish.
Does plaster of Paris expire?
When stored under dry conditions, this product will have a shelf life of three months from the date of manufacture. Absorption of moisture can result in changes to physical properties including a reduction in the set strength of plasters and also a lengthening of setting time.