1. Place dry ingredients into the gallon bag, seal and knead to combine ingredients.
2. Open the bag, spray two to three times with water, and reseal the bag. Knead the ingredients in the bag until all the moisture is absorbed.
3. Repeat Step 2 until you can squeeze ingredients in the bag, and the mixture stays clumped together when you let go. It should, roughly speaking, be the consistency of pie dough.
Note: If your bag expands and looks like it may burst, let the air out. This is natural, as the combined acid and alkali form carbon dioxide.
4. Add 25 drops of essential oil of your choice and mix again.
5. When it’s the right consistency, pack into your selected molds.
Tips: If you’re using a measuring cup, pack the mixture into the cup and turn the toilet bombs out onto a sheet of parchment paper to dry.
6. Leave the toilet bombs to dry for one to two days, and then unmold. The toilet bomb will be fragile at first but will continue to harden.
7. Store in a glass jar with a tight-fitting lid until ready to use.