I'd like to see what it does to Hypalon, as the red or black could be very useful to add graphics, text etc, or even recolour faded tubes, but I'm not sure it would sink into the surface like it does on Vinyl.
I have some scrap Hypalon samples, but don't want to spend £14 plus postage to find out.
For small areas and lettering, Polymarine do a Hypalon and PVC specific products. See here
Looks like it's about same price for the smal tin and 2x for the larger.
