Plaster Molds are so much fun the ways you can use the pieces are innumerable.
Casting plaster is so easy!
You will need:
Plaster of Paris
Plastic container to mix plaster in. Do not use glass or metal as plaster will stick and not come out.
Cup or container to scoop out plaster of paris from bag.
Wire wisk (find one cheap at the dollar store).
Mold spray release or cooking oil spray.
Paper towels to clean the mixing container.
To begin, place the mold on a protected level surface. I like to lay a garbage bag under my mold to protect the surface.
Spray the mold with either mold release or cooking spray. Do this lightly as you don’t want it to puddle in the recesses of the mold. If it does, simply wipe it lightly with a paper towel to distribute the spray.
Read the directions on the container of Plaster of Paris. The mixing instructions will say that the mixing proportions will be one part water to two parts plaster of paris.
To find the amount of mixed plaster of paris you will need for your specific mold, simply pour your mold 1/2 full with water. Dump it in to a measuring cup. Now, multiply that number times two and that will be how much plaster of paris you will need to add to create enough mixed plaster to perfectly fill your mold (with just a little left over).
Pour the water in to a mixing container.
Measure and add the plaster of paris.
Mix with the wire wisk until it becomes the consistency of cake batter.
Fill the mold with the mixed plaster of paris. Avoid over filling. Once filled, lift the mold slightly and tap it up and down on to the surface to allow the plaster to settle in to all the detail of the mold design and release any air bubbles. (You will see them rise to the surface. This is good.
A squeegee comes in handy if you have over filled your mold. Use it to level the surface and scrape away excess plaster.
Make sure your mold is level. With some designs, I prop up the edges with old towels, newspaper ect.
Allow the plaster to set up hard. Feel the back of the plaster. If it’s warm to the touch, it’s not ready. When it is completely cold, you can now remove the piece from the mold. Most designs take around an hour to set up.
To remove the plaster piece from the mold, turn it design side to face you and press very lightly on the face of the mold to release the piece. Be very gentle. Do not allow the piece to come out so quickly that it falls on to the surface and breaks. Sometimes I un-mold certain, thinner pieces over an old towel for cushion.
When your piece comes out, often times you will find rough edges that slightly overlap the mold design. Simply take the paring knife and just like you’re peeling an apple, peel them away with the paring knife.
All pieces must dry completely before applying them to any surface. For small designs, this could take a day or two. For large designs, a week or more. But we have a trick to dry them quicker below!
To mount the piece to a wall, ceiling, piece of furniture or craft item, simply use pre-mixed joint compound right out of the bucket. Spread a 1/4″ layer over the entire back of the plaster piece.
Hold the piece to the intended area for 60 seconds.
Once the plaster piece is up on the wall, use your finger to spread joint compound in the space between the wall and the piece. Filling this area with joint compound will give your design a more professional look. (Ignore the bandage, I cut my finger that day.)
The mounting is now finished. Let the compound dry and then paint as you desire. Pieces can also be pre-painted before applying to walls or ceilings. Just leave the back un-painted so that the joint compound has that porous surface to stick to.
NEVER RINSE EXTRA PLASTER OF PARIS DOWN YOUR SINK OR TOILET! Plaster of paris can actually harden in the water in your drains.
To clean up, first, pour extra plaster in to the garbage can, then wipe the excess with paper towels to remove all residual plaster. If you’ve gotten it all, it’s safe to rinse the container or utensil in the sink. I often rinse my tools and containers in a bucket of water then dump it outside.
Breakage: If your piece breaks easily, mix your plaster of paris a little thicker. You can also add toothpicks or even cut up pieces of cloth and insert in to the wet plaster after you have filled the mold, for very thin molds to make them stronger. If they break, the material holds the piece together and once you have it applied to the wall or ceiling, simply smooth joint compound over the break and it will disappear!
If the plaster seems to be setting up before you can get your mold poured, you mixed it too thick.
You want your pieces to dry faster
Cast all the pieces you need for your project then place on the racks in your home oven on 300 degrees for one hour. Make sure pieces do not touch one another on the rack. Allow them to cool completely in the oven. They will all be ready to mount to your project once cool.
Now that you know how easy it is to cast and mount plaster pieces, start designing! Try combining plaster mold designs to create ceiling frames,
Beautiful ceiling medallions or
Unique projects of your own.