Plaster letter moulds are handy for making personalised craft items like address plates, nursery items and namesake crafts. Purchasing these moulds can be very expensive, especially if you are mail-ordering them, as packing and shipping on these items can be exorbitant. Making them yourself provides an easy and inexpensive solution to making personalised crafts. You also have the added benefit of making the entire alphabet, or only the letters you choose. These moulds are especially good for clay.
Take each letter and set it face up on a sheet of newspaper. Spray the letters liberally with a coating of cooking spray. This will help you to remove the letters from the plaster later on.
Mix the plaster of Paris with water, following the instructions on the back of the package. Do not try to stretch your plaster by adding more water, as this makes a thinner plaster that will chip when you remove your letters. You need enough plaster to fill the baking pans at least 2 inches.
Pour half of the plaster into each foil pan. Place your first letter into the plaster facedown, pressing it in until the plaster comes all the way up the sides, but doesn't overflow into the backs of them. Repeat this with the rest of the letters, putting half of them into one pan and half into the other. You must work very quickly at this point to get all the letters in before the plaster sets. It's easier if you have a friend to help you, but it can be done solo if you work fast.
Allow the plaster to set until it is completely hardened. Once the plaster is hardened, carefully remove each letter. Even though they are coated with oil, they may still be tricky to get out because plaster expands as it sets. Pull straight up rather than to the sides to avoid cracking the edges of your letter moulds.
Wash your letters in hot soapy water and stick them to your refrigerator. Your moulds are now ready to be used.