FD&C Red 40 DYE useful for bath bombs and other cosmetics. It is 89% pure dye and is water soluble. It's color is stable at a pH of 2-11 and over 11 it turns dull yellow.
It's batch certified so it's legal for use in appropriate for sale products in the USA. Because this dye is extremely concentrated, the dye in the bag will not be the same color as it is once it's dissolved. As with any colorant, lighter shades are achieved using less and darker shades achieved using more.
INSTRUCTIONS FOR USING DYE:
Dyes dissolve in water or glycerin and must be pre-dissolved before use in bath bombs. Add a very small amount of water to a condiment cup. Use a tiny spoon (like a 0.15cc mica spoon) to transfer dye to the condiment cup. Use the minimum amount needed to dissolve the dye. You cannot add dye dry to bath bomb mix or it will result in spotty weak color in the product. Run sample tests & keep notes to see how much to use for your recipe or product to get the shade you want. More will give a richer color, less will give a pastel color.
INSTRUCTIONS FOR USING LAKES:
Dyes are oil and water dispersible meaning you can add them directly to bath bomb mix without pre-dissolving. No need to "bloom" baking soda either. Just add, mix and go! They are the easiest to use bath bomb colorant and have about 1/2 the strength of dye, but are still very vibrant color.
Both dyes and lakes are u/v sensitive and can morph and/or fade in light or various pH. Some colors are more sensitive than others. Mica can be used in addition to anchor or alter visible color of products. Once dyes or lake colored products hit water, the colors will show true even if they have u/v faded or morphed. Dyes are more finicky than lakes. I personally prefer dyes for embeds and lakes for exterior product color. Dyes are finicky, but nothing is more vibrant in an embed as dye. Lakes are easy to use and easy to tweak color with and a bit more stable. Both are necessary in bath bomb making.