Almost anything that will hold liquid can be used as a soap mold. Cardboard boxes lined with Wax paper, plastic tubs, heat-resistant glass containers, wood, stainless steel, and enamel pans, anything that is not aluminum. For simple square or rectangular bars of soap, you can use a brownie pan with square edges.
You can purchase soap molds from soap supply companies or craft stores, which are specifically made for molding soap. These come in a wide variety of shapes and sizes from bars to flowers and shells.
Molds that were meant for candies and candles can also be used. Just make sure they are not aluminum.
If you choose to make your own molds, here are some ideas.
Go to a home building supply store and purchase a short length of 2 inches and 3 inch PVC pipe, and a few caps for the ends of the pipe. A test cap is good for soapmaking since it fits inside the pipe and makes a flat bottom so the pipe stands up on its own. If you can not find a test cap, a regular cap will work, but you will have to stand the pipe up against something since the regular caps are rounded on the end. The PVC pipe should be cut into 2-foot lengths, and then washed and dried. One of the caps should be taped onto one end of the pipe so that no liquid can escape.
When your soap mixture is ready, pour it into the open end of the PVC pipe mold. Prop the pipe up in a place where it will not fall over, and leave it for at least 24 hours. After the soap has hardened, place the pipe in the freezer for an hour or two. Take the pipe out of the freezer, and remove the tape and cap from the end. Place the pipe under hot, running water for 30 seconds. Gently push the soap out of the pipe and let it harden for another day, before cutting it into round pieces.
You can also make soap molds out of scrap plywood or white/yellow pine.
Here are instructions for a 4 X 15-inch wooden soap mold.
1 base (5 X16 Â½ X Â¼ inch plywood)
2 sides (3/4 X 3 Â½ X 15) 2 ends (3/4 X 3 Â½ X 7)
4 end cleats (Â¾ X 3 Â¼ X 3 Â½) 4 hinges (2 inch utility) and nails, 4 – 3 penny nails and glue
1) Mark the base to locate the sides (2 inches) and ends (3/4 inches) 2) Attach the sides to the base using the hinges
3) Attach cleats to ends using nails and or glue
4) Position ends on sides to form box
5) Drill a small hole big enough for a 3-penny nail, through the cleat into the side of the box (on each side) and slip a nail into each hole
When your soap mixture is ready, use Wax paper, or Reynolds freezer paper (shiny side down), to line the mold. Pour the soap mixture into the mold. Cover it with an old towel and let it set for 24 hours. Test the soap with your fingertips. If it has not set-up, rewrap it and wait another 24 hours. When the soap is ready, unwrap the liner and unhinge the mold. Peel the liner away. The soap may be cut immediately, but must be allowed to cure for at least 3 weeks before using.