Polysorbate 80 is used in the bath and body industry as a surfactant. To keep it simple, this just means it allows the oils and colors in the bath bomb to be absorbed by the water. Without it, the oils would float on top of the water and the colors would stain the tubs. We personally recommend it because people do not like rings in their tubs from bath bombs, TRUST US!!
We won’t get in to much chemistry here, but the way it works is by lessening the surface tension between two items. Like with water and oil, you will never get those to ingredients to mix. The surface tension between the two does not allow them to be absorbed together. In terms of making a bath bomb, you can definitely leave out the Polysorbate 80. It will still fizz and release colors, but 2 things happen.
First, the colors, depending on which ones you use, will just float on the top of the water. They will not be absorbed into the water. They concentrate on top and eventually find the edges where the water meets the tub. Here, there is normally a ring of soap residue. The colors get immediately attracted to this residue and become absorbed. Hence the ring in the tub. Polysorbate 80 will allow the colors and water to be mixed and absorbed into the water. Thus, minimizing, if not eliminating, the staining of the tub.
Second, your fragrance oil and moisturizing oils will float on top of the water. It will not be evenly dispersed throughout the water. This can lead to oil eventually dripping from you onto the tub or floor surface and creating a slippery situation. Plus, people do not want just oil, in those concentrations, on their skin. If it is absorbed into the water, then your entire body is getting moisturized, even the parts UNDER the surface.
As you can see, Polysorbate 80 is a pretty important ingredient. We use it because it definitely works with the heavier oils used in bath bombs. The other cool thing it does is foam and bubble. So, not only is the color and oil being dispersed into the water, the bath bomb is fizzing and foaming at the same time. Just another good reason to be using Polysorbate 80.