Before you begin, gather the materials you are going to use together.
To produce a batch that will make 6 bombs use the following quantities. For more or larger bombs increase the quantities but keep the quantitative relationships to assure the best product.
Into your mixing bowl place 4 measures (8 oz.) of Sodium Bicarbonate, 1/2 measure (1oz.) bath salts, 1/2 measure (1oz.) Corn Starch Binder, 1 ml. body oil, and 1/4 to 1/2 ml. fragrance oil. Using a whisk thoroughly blend these ingredients and break up any clumps of material. Now mix 2 drops of Dye into 7 ml. (1/4 oz.) water and scatter this over the mixture. Your mixture should be just slightly damp and form a clump that falls apart in your hand. Now add 2 measures (4 oz.) Citric Acid and blend well. You will notice that your mixture becomes more cohesive at this point.
When you have thoroughly blended your batch, take a heaping tablespoon of the material and squeeze if firmly into a ball. If it forms a cohesive ball you are ready to form your bath balls. If the material does not form into a cohesive ball it will require a little more moisture be added. Add moisture sparingly by using a trigger sprayer set to very fine spray and lightly mist your moisture then immediately blend well with your whisk and test again. Repeat this procedure until your test produces a cohesive ball then proceed to form your bath bombs.
For small bombs press as much materical as possible into your Mold / Measure. Once packed, turn it upside down on a flat surface and press in on the base or tap it to release the bath bomb. For larger bombs, use a larger form or form then by hand. When all bombs have been formed, set them in a dry temerate area to age for 1 to 2 days. Then wrap them in tissue paper ready for use or gifting. Remember water sets off the reaction between the bicarbonate and the acid to release the CO2. You do not want this to happen until the bomb is used. So use the lease amount of moisture possible during your preparation of the bombs.
Tip: Remember that the less water you introduce to the mixture the better and that rapid and thorough drying of the finished bombs inproves both their performance and their shelf life. It is best to store the finished product in a cool dry place.
Moisture catalyzes the reaction of your ingredients to release the fizz creating Carbon Dioxide. So it is important not to introduce any more moisture to your mix than necessary to form your balls. This will assure you of the best possible performance from your finished product. Likewise storing the bombs in a cool dry place will extend their shelf life.
If you are having trouble getting your mix to form a cohesive ball you may need more moisture, or more corn starch binder, or less body oil, or adjustments to all three.
Try keeping bath bombs in molds overnight to keep bombs from falling.
CAUTION: Bath oils and soap can make your tube slippery. So be safe and use caution not to slip and fall.