I am interested in writing and revealing a message in invisible ink for theatrical purposes. I found a list of potential compounds here but I am having a hard time prioritizing which to experiment/rehearse with.
The message will be written on a lab coat and revealed in the dim lighting of a night-time bonfire so the ink must be dark enough to see easily. Because I will be writing on cloth, I will need an ink that will not run, so that when the message is revealed, it will be legible and not distorted. Heat-activated inks are preferable because I will have the bonfire on hand for the reveal but there is the danger of revealing the writing too soon. Chemically-activated inks are less desirable because of the less-theatrical reveal and because many of the revealing-solutions look like they will stain the coat making the message difficult to read but I will keep them as candidates because I have not tested my staining hypothesis and because of the added control they offer. Blacklight-activated inks are not suitable.
I don't have enough lab coats to test all the compounds listed so my question(s) are:
- Which of the inks listed are least likely to run when applied to cloth?
- Of the remaining inks, which will appear darkest when revealed?
- Of the remaining heat-activated inks, which are easiest/hardest to reveal, in terms of temperature/time required?