Disappearing Ink Refills, actually the indicator Thymolphthalein. You can use this with our chemistry bit disappering ink for a fun science project. Which will disappear quicker: (a) disappearing ink on a paper towel over a carbonated beverage or (b) disappearing ink on a paper towel over water? Disappearing Ink is really a thymolphthalein solution and is an acid-base indicator. It is a fun chemical toy and great for tricks, inquiry and many experiments. It is part of the Patriotic Colors Chemistry Experiment Kit and is also available as a Chemistry Bit.