Many soap makers love plastic molds for their beautifully detailed designs and their economical price, but they can be tricky to use with cold process soap. Plastic molds come in a variety of designs that include molds for practically every holiday or event and molds that complement a wide variety of colors, fragrances and other soap making ingredients. Some of our favorite Milky Way® molds for this issue of Handmade include the Aloe Vera Soap Mold, Bee and Honeycomb Soap Mold, Lavender Guest Soap Mold and the Oatmeal Rounded Soap Mold. We have found three tricks that make for consistently molded soap bars in plastic molds.
Pictured: Cold process soap with Crafter's Choice® Energy Fragrance Oil and Safflower Powder. Molded with Milky Way™ Henna Teardrop Soap Mold (MW 258)
A water discount is simply using less water in a soap recipe than normal. The result is a harder bar of soap sooner. Let's take a minute to understand why. When using your normal recipe, after 4-6 weeks of curing water slowly evaporates from the soap to create your finished cured and hard soap bar. If less water is used, it means less water needs to evaporate to get to the same hardness in a shorter amount of time. Hard soap bars are much easier to unmold, as the hardness helps them come out in one piece. If your recipe is too soft, unmolding too early can result in pieces of your soap getting stuck into the nooks and crannies in the soap mold, and the finished bar lacking the detail of the mold. Please note that water discounting also quickens trace so you need to work faster.
Picture: We discounted our recipe using a "Water : Lye Ratio" in our lye calculator of 2:1. It is not recommended to discount any more than more than 1.5:1 as the concentration of lye to water can be too high and even leave undissolved lye.
Depending on your soap recipe, a water discount may not be enough for a hard bar of soap. Evaluate your soap recipe to decide how you can make it harder. First, look at your oils and butters; are you using enough hard oil such as 76º Coconut Oil or Palm Oil? Also, take a look at your superfat. A lower superfat equates to a harder bar. If you are uncomfortable changing these components of your recipe, you could alternatively add ingredients to harden your recipe. Our favorite is to add sodium lactate.
Picture: In our recipe we added approximately 1.5% Sodium Lactate.
Altering your recipe may not be an option for you, so our last tip is to freeze your molded soap. Once frozen, turn the mold over and carefully push the soap out. Freezing the soap temporarily hardens the soap, making it the right consistency to unmold while keeping all the detail of the soap intact.