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Issue 8
Good Clean Fun: Molded Soap
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Good Clean Fun: Molded Soap
Suds Up Your Own Soap
There are as many recipes for soap as there are for cake. This blend of olive oil, water, and lye is a cupboard classic. It’s also the variety most amenable to being cast. After a few days of slow cooling, the castile brick can be grated, melted down, and mixed with scents and grains, then poured into molds (a process called milling). The best place to try a first batch is in a utility sink or a bathtub. Here’s the dirt on how to make it.
Two-Piece Plaster Mold
Plaster molds are cheap and durable. But be warned: They don’t flex and certain shapes can’t be cast. Imagine that each half of the mold is an ice-cube tray. Would the cubes come out in one piece? If not, this is not the right mold for your shape.
If the objects you choose to cast are porous or soft, seal them with paint, varnish, dish soap, shortening, or Vaseline first. Plastic and rubber toys are good candidates. And remember to wear your protective gear-plaster of paris is serious stuff.
ingredients
- Wood glue
- Wood varnish
- 1 small bag plaster of paris
- Pottery clay
- Liquid dish soap
tools
- 4 5” x 10” x 3/4” scrap wood boards
- 4 1 1/2” x 5” x 3/4” wood pieces
- 12 1 1/4” long #8 flathead screws
- Pen
- Object to be cast
- 4 C-clamps
- Disposable flexible plastic containers
- Mixing stick
- Safety glasses or goggles
- Rubber or plastic household gloves
- Dust mask
- Vegetable shortening
- Rubber bands
- Heated milled soap (your own or store-bought)
- Butter knife
MAKE IT
Glue and screw the long wood pieces onto the edge of each board (see fig. c above). These are called cottles.
When the glue is dry, seal the board with a wood varnish of your choice.
Draw a line at the halfway point of the object to be cast. Place a strip of clay around the object just below this line (see fig. d, left).
Frame the object with the cottles, leaving about 1” between the object and the cottle. Clamp in place (see fig. e).
Extend the clay to the edge of the cottle, keeping it as flat as you can.
Lay a small amount of clay along the corners so no liquid plaster can escape.
Place a cone-shaped piece of clay on one end of the object. This will create a void in the mold to pour the soap into.
Mix the plaster in a flexible plastic bowl according to the instructions on the package (typically 11 ounces of plaster to 8 ounces of water).
Pour plaster onto the object being cast until it covers the object by at least 3/8” (see fig. f).
Allow it to cure for an hour. Then, wearing gloves, undo the clamps, remove the cottles, and flip the cast object over so the plaster is on the bottom.
Remove all clay and wipe the plaster clean. Clamp cottles around the plaster as closely as possible. Fill any openings with clay and lay the conical piece back in place.
Brush dish soap onto all exposed plaster to keep the next layer of plaster from sticking to it (see fig. g).
Clean the mixing bowl by flexing the container until the plaster pieces crumble off the sides and into the trash (never wash plaster down the drain).
Mix and pour the plaster as before.
After an hour or more, remove the cottles and gently pry apart the two halves, using a butter knife if necessary (see fig. h). Be careful: Plaster can be brittle at first.
Grind down the sharp edges of the mold with the edge of the knife. Set it aside for 24 hours before use.
Using the mold
1. Grease the inside of the mold with vegetable shortening. 2. Strap the two sides together with rubber bands. Stand the mold upright with the opening facing up. 3. Pour the heated soap into the mold almost to the top. Gently shake the mold to ensure even coverage. 4. Freeze the mold for a few hours, then thaw for 15 minutes and remove the object.
If your soap doesn’t liquefy when heated, it won’t distribute evenly inside the mold. Try laying the two greased halves of the mold on their backs and mashing the soap into place. Fill each half just above the edge. Then strap them together and proceed as above.
Additives: Add anything that won’t cause an allergic reaction, but don’t use too much of it or the bar won’t hold together. Add the powdered substances as late in the process as possible to ensure that they don’t all settle on the bottom.
Color: Try spices like cayenne, cinnamon, coffee, paprika, and cocoa. Or use crushed crayons for a subtler tone. Start out at around a tablespoon of pigment or one crayon per batch and add until desired hue is reached.
Scent: Add one drop of essential oil at a time, to your liking. Keep in mind that the scent will likely diminish somewhat once the soap sets.
Texture: Use a coffee grinder to pulverize oatmeal or wheat germ. Spices used for color may also have abrasive qualities, depending on how they are ground.
Moisturizing agents: Add milk, cream, or honey.
If your soap doesn’t liquefy when heated, it won’t distribute evenly inside the mold. Try laying the two greased halves of the mold on their backs and mashing the soap into place. Fill each half just above the edge. Then strap them together and proceed as above.
Additives: Add anything that won’t cause an allergic reaction, but don’t use too much of it or the bar won’t hold together. Add the powdered substances as late in the process as possible to ensure that they don’t all settle on the bottom.
Color: Try spices like cayenne, cinnamon, coffee, paprika, and cocoa. Or use crushed crayons for a subtler tone. Start out at around a tablespoon of pigment or one crayon per batch and add until desired hue is reached.
Scent: Add one drop of essential oil at a time, to your liking. Keep in mind that the scent will likely diminish somewhat once the soap sets.
Texture: Use a coffee grinder to pulverize oatmeal or wheat germ. Spices used for color may also have abrasive qualities, depending on how they are ground.
Moisturizing agents: Add milk, cream, or honey.
