Things You'll Need
Casting sand, 25 lb. bag
Plastic dishpan tub, 2 1/2 gal.
Paper coffee cup
Plaster of Paris, 10 lb. bag
Plastic ice cream pail, 2 1/2 gal.
Plastic sherbet container, 1 qt. size
Assorted sizes rubber spatulas
Acrylic sealer, water base, 1 qt.
2 1/2 inch brush
Working with a plastic pail when mixing plaster is a good idea. Should the plaster completely harden before it's time to rinse out the pail, just apply pressure on the pail and the plaster will break away from the sides and the bottom.
Plaster gives off heat as it starts to set up or harden. The warmer the plaster feels the closer it is getting to hardening. This is how to judge how much time is left to work with it.
Hydrocal is another type of plaster that dries hard as stone. It is much more durable than Plaster of Paris and the flower pots will last longer if this is used instead.
Never pour wet plaster down the sink drain. It will harden in the plumbing pipes and a plumber will have to be called.
Wear a mask when mixing plaster. Plaster powder should not be inhaled.
Plaster of Paris is a material that can be used in many craft projects. When it comes to crafting, it's a jack-of-all-trades material. In the nineteenth century, craftsmen cast hands and feet using Plaster of Paris so fine artists could learn to draw the human form from them. Today Plaster of Paris can be used to make jewelry, bookends and even flower pots. Its an easy material to work with and a rewarding one because Plaster of Paris dries fast.
Creating the Mold Form for a Plaster of Paris Flower Pot
Fill the plastic tub with the sand. Take the spray bottle filled with water and start wetting the sand. Mix the sand around as it's being sprayed. Try to get an even consistency of dampness to the sand. Judge the dampness of the sand by picking up a handful and making a fist. If the sand sticks together it is wet enough.
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Scoop out some sand in the middle of the tub and set a perfectly smooth sided form down in the sand like a paper coffee cup from a fast food restaurant. Pack the sand tight against the cup. Make sure the sand is well packed 3 inches all the way around the cup.
Pull the paper cup out of the sand carefully. The mold in the sand is the outside shape of what will be a Plaster of Paris flower pot.
How to Mix Plaster of Paris
Take a clean 2 1/2 gal. plastic ice cream pail. Pour in a quart of cool water. Put on a dust mask and use the 1 qt. empty plastic sherbet container to scoop out some Plaster of Paris.
Start sprinkling dry plaster into the water. Add it slowly and steadily. Don't add the plaster all at once.
Keep adding plaster until the water won't absorb anymore of it. Dry plaster will start to sit at the top of the water. This is the signal that the right amount of plaster has been added to the water.
Take a rubber spatula and start stirring the water and plaster together. Do this gently so as not to get air in the mixture. Don't over stir or the plaster will start setting up too fast.
Coating the Inside of the Sand Mold With Plaster
Wait until the plaster is the consistency of a thick malt. When it reaches this point the plaster will be hardening faster and faster. There is not much time to work with it.
Take a straw that has been coated with Vaseline and stick it down into the sand right in the center of the mold so that the straw is standing straight up and down.
Dip the rubber spatula into the plaster and drop a blob of the plaster into the bottom of the mold. Quickly spread it around and try to sense how thick the plaster is on the floor of the mold.
Load the rubber spatula with more plaster and start buttering the inside wall of the mold being careful not to dent it. Keep moving the tub of sand around in a circle as the inside wall is being buttered so that the wall is evenly coated. Build it up so that it is at least 1/4 inch thick.
Let the plaster dry hard. Pull out the straw to reveal the drain hole at the bottom of the flower pot. Carefully pull the plaster flower pot out of the sand and brush off as much sand as desired.
Seal the plaster flower pot when it is bone dry with a clear acrylic sealer on the outside to help it last longer.