I wasn't terribly precise. I filled a small glass jar 1/2 way with acetone
and then stuffed in whatever scrap plastic I had around, with the result
perhaps 2/3rds acetone, 1/3rd ABS. The texture is fairly thin - that lets
me quickly wipe a thin layer across the build plate while it's heating up,
with the layer being basically invisible. If the goop is too thick, it
leaves a much thicker layer, which doesn't look great if the colors don't
match. (And I'm not dedicate enough to keep separate jars of goop for every
color of plastic).

- LP