The same as Martha Stewart uses to make her bath bombs on her show! The prefect round bath bomb mold, not too big and not too small! Makes 4.5 to 6 ounce bombs depending on the ingredients used. Tightly over pack your powder, push until both sides of the mold almost meet, then gently remove each side. Do not leave your bath bombs inside the mold, remove soon after they have been molded. TIP: Try using cocoa butter mixed half and half with your soft oil, cocoa butter is solid at room temperature and will make a harder bath bomb that will last longer in the tub!
Easy Bath Bomb Recipe
1/2 cup. baking soda
2 TB arrowroot powder
1/4 cup citric acid
1/4 cup Epsom salt
1 to 1 1/2 teaspoons water
1/4 teaspoon essential or fragrance oill
1 1/4 teaspoon oil (I like fractionated coconut)
Dash oxide coloring (optional) do not over colour your bath bombs, it is preferable to have a light shade
In a bowl combine the dry ingredients (the first four listed above). Whisk to remove any clumps, arrowroot tends to be clumpy. In a small bowl stir together the wet ingredients which includes the oxide color (the last four ingredients listed). Combine with the other ingredients. Slowly pour the liquid mixture in with the dry mixture, whisking as you go. If you see the mixture fizz or foam, you may be adding the liquid too quickly. Once all the wet ingredients are combined with the dry, take a small amount in your hand and squeeze it together. It should stick together fairly well in one or two big chunks. If it's still too powdery to hold together, just add a tiny bit more water and mix until it does hold together. It should feel like wet sand but on the dry side.
Then fill each half of your bath bomb mold with the mixture until it's just overflowing a little. Press together, then gently remove one side of the mold. Once you are ready to remove the other side, gently invert the bath bomb so the uncovered side is facing down, then gently remove the other half of the mold from the top. The key word, if you haven't noticed, is gently. These can fall apart on you very easily if you're not careful. If a bath bomb does crack in half while you're removing it, you can gently press it back on top of the other half, or remove all the mixture back to the mixing bowl and start the molding process again. I had this happen to a few, so don't fret, it's easy to fix.
Once they are completely out of the mold, allow them to dry out for 8 hours or overnight. Once very dry, you can wrap them in plastic wrap and store in a dry place until you're ready to use them, or you can gift them to friends.