I current an working on a commercial sports product that involves the use of about 3.5 oz of a 50/50 solution of propylene gylcol / distilled water. The liquid is in motion in the product and moves about,. when we attempt to dye the liquid red, it begins to foam slightly as it moves about. How can I dye the liquid, or another liquid safe and similar in viscosity that will not foam.
Thank you for any help anyone can offer, I am in desperate need!!
Andy

Do you have to mix the propylene glycol with water? They are semi- miscible, you are pretty much asking for foamyness. What is the dye soluble in - the water or the propylene glycol? If you need to dilute the propylene glycol try in a hydrophobic (oily) solution and you should have more luck. If it's in the water thicken it up with something else that is water soluble.

Don't fully understand what you are trying to do but I hope this helps a bit - or at least gives you something else to try.