I saw this idea a few times on the Martha Stewart site and I would really like to make these as stocking stuffers this Christmas. It seems like such an easy thing to do and would really take no longer than baking a cake. I have some lovely old jars that I could place these in too which would really make it a lovely gift for someone.
1. Sift 1 3/4 cup baking soda, 1 cup citric acid, and 2 cups cornstarch through a sieve to remove chunks. To make different tints, fill small spritzer bottles with water and add about 6 drops of food coloring to each.
2. Pour 1 cup of powdered mixture into a glass bowl. Lightly spritz, stirring after each spritz, until powder is desired color. Add water slowly, so mixture does not fizz. If mixing two tints, alternate colors as you spritz. Check the consistency of powder with your fingers; when it can be tightly packed or shaped, stop spritzing (this may take a little while).
3. Select an essential oil. Add 5 drops if it's one of the stronger scents (peppermint, lavender), 6 if it's a weaker one (lemon, grapefruit). Mix well. Firmly pack mixture into small baking molds. We used 1/4 cup for each fizzy, which is good for one bath. Allow mixture to set for 2 hours, then pop out carefully. Repeat with different tints for remaining powder.
If you wanted to have a different shape, you simply just need to use a different mold, like ice-cube molds.
This would give you a different way of being able to package them, like putting them in jars.