Plaster of Paris has been around for many centuries. It is so named from the vast deposits of gypsum found around Paris, France that are still mined to this day. Plaster of Paris is made from gypsum that is heated in large ovens and concentrated into a fine, moisture free powder. It is then packaged and sold all over the world under the name Plaster of Paris. While drywall compound is very similar to Plaster of Paris, the only difference is that drywall compound has some silica and fine sand added to make it easier to smooth out on a flat surface.
Plaster of Paris is used for a variety of craft purposes. These primarily include mold making but can be easily used to create a wide variety of projects from sculpting to bead making. Plaster of Paris is naturally white but accepts nearly any medium of paint with a little primer and latex based paints. Oils don’t work as well but can be used with enough lacquer thinner soaked into the Plaster of Paris.
My favorite use for Plaster of Paris is mold-making. Using pre-manufactured moulds are usually the best bet, but if you’re skilled at craft work you may be able to create your own mould using latex rubber. I won’t get into the details of making moulds in this article due to space constraints, but I will tell you its not very complicated.
Before you begin any mould pouring you need to set the mold. I use a bucket filled with sand to set the mold in place while it hardens. This way the sand takes the heat from the curing and doesn’t transfer any shock to the mold while transporting it from my work bench to the garage.
Once your molds are in place, its time to mix the Plaster of Paris. If you’re curious to see how much Plaster of Paris you will need, pour some water into one of your moulds until it is full. This is how much water you will need to mix with the dry Plaster of Paris powder.
Be careful when you mix Plaster of Paris. It should be down outside in a well ventilated area with lots of newspapers or a drop cloth under the work station. Try not to get any wet Plaster of Paris on your skin. As Plaster of Paris cures, it gets hot, real hot! So hot in fact it can cause blisters on the skin if you were to submerse your hand in it! Wash off any of the Plaster of Paris quickly in clean, cool water.
Mix the Plaster of Paris in a plastic bucket. Of course you should always mix it according to the manufacturer’s instructions but I like to mix my Plaster of Paris to the consistency of thinned sour cream. Use a plastic bucket and plastic spoon.
Now pour in the mixture of the Plaster of Paris into your mould. Pour it half way full then let it set for 30 seconds. This allows the bubbles to rise and come out from the mold. Fill the mould the rest of the way to the top. Add some pieces of medical gauze to thin moulds to help strengthen them.
Now set the moulds filled with Plaster of Paris aside and allow it to dry for approximately 30 minutes. Once they are dry, remove the moulds gently from the hardened plaster of Paris. Once the mould is completely removed set the hardening plaster aside for at least 24 hours to cure and dry properly. In 24 hours it’s ready to paint!
