: Thanks everyone. The consensus is clear, once the pigments soak into the PVC
: they're not coming out.

: A friend at work gave me the answer: Lay masking tape where the line is going
: to go, make the mark on the masking tape, cut along the line, then peel
: off the tape.

: To quote T.H. Huxley's response to Darwin's first lecture on natural
: selection, "How extremely stupid of me not to have thought of
: that!"

I am going to try "whiteboard" marker pen. Will post results shortly.

Prasad