1 ½ cups baking soda (sodium bicarbonate)
 ¾ cup citric acid
 ½ tsp. Water based food colouring (or less for softer colour)
 ½ tsp. Fragrance oil or blend of Essential oils
 Spray mister filled with water

Mixing
Place your fragrance and dye in your bowl first.
Add the baking soda and mix lightly
Add your citric acid last. (if the citric acid is added to the liquids it will cause the acid to react)
Stir all the mixture together with a spoon to disperse the fragrance and dyes.
Blend the entire mixture with your hands until the color and dye are evenly dispersed and the mixture begins to hold its shape in your hand when you press it together. If you find your mixture is too dry and not holding it's shape, spray one or two mists of  water. You may need to repeat this step a couple of times to get the consistency you need to mold your bath bomb.
 

Molding
Take a handful of your bath bomb mixture and pack it tightly into your mold. Level off the back of the bomb, trim off any other excess mixture and flip out onto a waxed lined cookie sheet or other flat surface that is lined with wax paper.  Allow your bath bomb to set up for one day.

If you find your bath bombs are sticking in the mold, chances are you may have too much water in them. Lightly dust the inside of the mold with baking soda and pack a new bomb in again.

If you find your bombs are crumbling, you probably need to add one or two mists of water and mix well again. Be careful not to over mist.
 

Making Multi-Colored Bath Bombs
To make multi-colored bath bombs, make two or three of the recipes as above, but use water in one, one color of dye in another and another color of dye in the third. Place a bit of the mixture from each recipe in your mold next to each other. Press mixture firmly in the mold, remove excess and level off the back before releasing onto your drying surface.