Mix together the 2 cups of epsom salt and the bubble bath in a mixing bowl.
Then stir in the essential oil and the food coloring. The mixture will be quite soupy.
Spread the mixture out on a baking sheet that's been lined with a couple layers of wax paper. Let the mixture set for 24 hours to dry.
After the 24 hours, stir the mixture which should now be more crystallized. The mixture can then be stored in a jar. This recipe fits nicely in a pint mason jar.
To use, add 1/2 cup to 3/4 cup of your bath salts to a tub of warm water.
The Mr. Bubble Extra Gentle is an unscented clear liquid which allows to you tint and scent the mixture as you wish. If you use a different bubble bath that is already tinted or has fragrance, you will probably want to omit the essential oil and food coloring.You can also try different essential oils and different food coloring combinations with the unscented Extra Gentle Mr. Bubble, or you can leave them out for a scent-free and color-free version.