1 cup baking soda
1/2 cup citric acid*
1/2 cup corn starch
Sieve dry ingredients until you get a nice smooth blend. (Optional: add 1/3 cup epsom salts or coarse sea salt after sieving. This is recommended if making bombs in a more humid area.)
2 1/2 Tbsp sunflower or other light oil (I use sweet almond oil, available at drug or health food stores)
3/4 Tbsp water (can substitute flower water, such as rosewater, or a combination of rosewater and glycerin)
1/2 to 2 teaspoons essential oils or fragrance oils (depends on strength of the oils)
1/4 tsp Vitamin E oil (optional, but recommended - an antioxidant which preserves the oils somewhat)
1/4 teaspoon borax (an emulsifier)
vegetable or other natural colourant (optional - a few drops of food colouring works well)
Combine all the wet ingredients and borax in a jar. Cover tightly and shake vigorously. Drizzle slowly onto the dry ingredients and blend thoroughly. It should not fizz while you are drizzling and mixing. If it does, slow down!
Pack tightly into moulds and slide out. They should release easily. Allow to dry at least overnight.