Using an emulsifier in Bath Bombs...
A great moisturizing Bath Bomb will have just enough oil and or butter to soften your water and leave you feeling silky, soft, and moisturized.
Last time we talked about how to determine just how much oil and or butter is needed per bath bomb and how to apply that measurement to your recipe. So now that you have your recipe adjusted to have just the right amount of the oil and butter combination, we will need to add some type of emulsifier to disburse them throughout the water.
Our choices are a bit limited and each of the two suggested additives bring a different attribute to the finished product. Let's begin by discussing each one and the affect it will have on the Bath Bomb.
SLSASLSA or sodium lauryl sulfoacetate and also known as Lathanol - According to Brambleberry the description of SLSA is: A fine white powder is excellent for blending into "bath bombs," bath fizzies, powdered bubble baths, bath salts for super foam, scrubs and more. Makes a blanket of bubbles that last! Long lasting SLSA powder provides excellent foam and viscosity response.
When used as an emulsifier in Bath Bombs only a tiny amount is needed. We recommend 1/4 to 1/2 teaspoon per 5 pounds of Baking Soda. This amount perfectly emulsifies the butters and oils with the tub water. Using a tiny amount will usually not affect the bath bomb mixture and rock hard bath bombs can still be produced with ease.
In the water the Bath Bombs will release a small amount of foam that usually will disapate fairly quickly after the Bath Bomb has finished it's fizzing. A small amount of SLSA will also not interfere with the fizzing action of the bath bomb.
So in conclusion, when using SLSA in small amounts you can acheive hard bath bombs that will emulsify your oils and butters into the water and create a small amount of foam. Using large amounts of SLSA in your bath bombs will give you a bubbly bath bomb and less fizzing action. Usually the mixture will be hard to mold or release from the mold, and when dry your bath bombs will likely be soft and easily dented.
Polysorbates according to Wiki: Polysorbates are a class of emulsifiers used in some pharmaceuticals and food preparation. They are often used in cosmetics to solubilize essential oils into water-based products. Polysorbates are oily liquids derived from ethoxylated sorbitan (a derivative of sorbitol) esterified with fatty acids.
When using polysorbates in bath bombs the usual ratio is 1 part polysorbate to 1 part oil or butter. It is not necessary to include the fragrance oil in your calculations or you will end up using way too much and your results will show it. Since you are trying to emulsify a carrier oil or butter into water, you want to use polysorbate 80.
Polysorbates are often used in bath bombs to disperse micas, glitter, and luster dust to keep them from gathering, pooling in the water, or sticking to the sides of the tub. When using polysorbates for this purpose you will want to still use the 1:1 ratio of poly to oil or butter. Using too much poly in your bath bomb mix will lead to a soft bath bomb that will crumble and dent easily.
Polysorbates are liquid and adding extra liquid to your bath bomb mix creates it's own set of issues. When using polysorbates in your recipe, you should adjust the amount of liquid by decreasing it or leaving it out altogether, whether it be water, witch hazel, or alcohol to avoid over wetting your mixture.
Polysorbates create a foaming action and it does interfere with the fizzing action of the bath bomb once it hits the water. There is nothing wrong with that, and that is a different conversation we will have another time. But for the purpose of emlusifying the oil and water, lots of makers reach for polysorbates.