VC-17 easily dissolves in acetone.
Take a rag soaked in acetone and 'wipe' the paint. If it 'smears'
easily, possibly changing color back to brown/copper .... its probably
VC17.
You can also 'burnish' VC17 by taking 'stiff' newspaper .... (Sunday
magazine paper is usually stiff and is 'clay filled'), wad it into a
ball, then vigorously rub the surface of the paint .... this is how
one 'burnishes' VC17 to an ultra-smooth racing surface. When you do
this you sometimes convert whatever color the VC17 has become ... and
with the burnishing 'begins' to turn 'coppery' again.


In article , Ernest
Scribbler wrote:

"Rich Hampel" wrote
The green color is probably coming from 'verdigris' a copper acetate
compound which forms when copper or copper oxide is in contact with
Acetic Acid. ..... which depending on the acid content (pH) of the
water will turn greenish or brown/purplish.

Interesting. I suspected it might be sort of a patina or something. Main
reason I asked is I want to touch up some thin spots and, having no
experience with this stuff, was concerned I might be putting VC-17 over
something that might not be VC-17.