Use warm tap water and soap (if the molds have been used for soapmaking, simply soak in warm water for a half hour or so). Hot water, including dishwasher water, may warp the plastic.
The moulds can tolerate wax and transparent soap temperatures of 135-145ºF. If you're concerned about warping, set the molds in a shallow cold-water bath for hot-temperature pours.
Please don't manhandle the moulds when releasing contents! If you have any difficulties with soap or chocolate, place the moulds in your freezer. For chocolate, a few minutes of freezer time will allow for easy unmoulding. For soap, 1 hour should be sufficient.
Because opaque cold-process soap undergoes a chemical reaction in the moulds, there are a few extra considerations to keep in mind:
- Soap needs a certain amount of heat to saponify properly.
- Most cold-process soap books call for pour temperatures of 80-100ºF. These temperatures are fine if you're pouring several pounds into one large mold, but when soap is poured into individual 3 or 4 ounce moulds, heat is more easily lost regardless of how much insulation you use. If you've measured your ingredients correctly but your finished soap is soft and/or grainy, raise the soap's temperature to between 115-125ºF next time you pour.
Opaque Cold-Process Soap Considerations don't apply to transparent soap since it's neutral when poured. Transparents also lack "stickiness," so there shouldn't be any problem unmoulding them.
When filling many cavities, realistically consider just how much working time you have before your soap begins to thicken beyond the "easy-pour" state. Dividing soap up into smaller portions for different colors and fragrances will slow you down; some artificial fragrances will speed the thickening. If this is the case, think about making smaller batches. If your soap does thicken before all the cavities are filled, spoon the soap in and tap the moulds lightly on the counter top. The clear plastic will allow you to see if any air bubbles remain on the mould's detail surface.
Super fatted soap and/or soap high in soft oils such as canola, avocado, safflower, etc. are a bit sticky, and therefore may unmould with more difficulty than firmer soaps high in palm oil or tallow. These softer soaps will unmould if placed in the freezer for 1 hour.
For a firm, easy-release soap with a good lather try: 22 ounces palm oil or tallow 3 ounces coconut oil 2 ounces olive, canola or any other soft oil 4 ounces sodium hydroxide 8 ounces water Heat oils to 115-125ºF. then add 115-125 degree lye solution. Stir until traced.
If temperature has dropped much below 115-125 prior to pouring, reheat on stove top. Makes 2 pounds, or enough soap to fill approximately 9-10 cavities.
Mould designs show up clearer and "crisper" in hard soap than in soft soap.
If the soap is allowed to remain in the moulds for 12-24 hours after cooling down, it releases much more easily than unmoulding it immediately upon cooling. (During this extra time the soap is both shrinking and crystallizing.)
One final option:
If you'd like to experiment with a fairly effective mould release, melt one part paraffin wax then stir into 3 parts mineral or baby oil. Best used when it is hot and liquid, but if applied to the molds when cold (as a soft paste) use a stiff brush to insure thin and even application, otherwise inconsistencies can mar the smoothness of the finished soap. Plain mineral or baby oil can also be used to lightly coat the moulds (vegetable oils or PAM may possibly saponify if used as a mold release).