In a bowl, combine the dry ingredients (the first four listed above). Whisk to remove any clumps.
In a small glass jar, stir together the wet ingredients (the last four ingredients listed).
If you’re using coconut oil, give it a quick melt in the microwave or stovetop so it will easily 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 the wet and dry ingredients are combined, 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, add a tiny bit more water and mix until it holds together.
Fill half of your bath bomb mold with the mixture until it’s just slightly overflowing. Press together, and then gently remove one side of the mold.
Place the bath bomb on a tray and allow it to dry out before removing the other side.
Wait one hour before removing the bath bomb and then see if it removes from the mold without breaking.
If it breaks, just press into the mold again and let it dry out longer.
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.
If a bath bomb cracks 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.
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.
