Q: What colorants do you recommend for a solid bubble bath recipe using glycerin, baking soda, cream of tartar and SLS?

A: I’d probably recommend Labcolors, True Tones *or* you could do actual FD&C powders but they’re hard to control as they tend to be lighter than air. I’d start with a couple of the Labcolors and/or True Tones and then work with them from there. The bottom line is that you really want water soluble colorants Stay away from oil based colorants, such as oxides and ultramarines. These products are available at:

Brambleberry: Labcolors, or Brambleberry: Micas