Stuarts Micrometer Engineers Marking Blue - 32g Tube (1 Tube, Blue)

I'd never used this before & used it to mark a small piece of hard-plastic before sanding to size.It spread either too thickly or too thinly. Where it was too thin, it was barely visible; where it was too thick it never really seemed to dry. Handling, when finally dry, rubbed it off. So no use at all; I just had to score the plastic & squint.I'd heard from some engineer friends that this is really hard to get off so I don't know if: 1. the formulation has changed? 2. I got a bad batch (some clear, oily stuff had separated out)? 3. It's just not suitable for the plastic that I was trying to mark?

This marking fluid was easy to apply and left really clear markings that were simple to follow when cutting out tool steel blanks.