Before reaching for the MEK, many sprayers press a fingernail into an inconspicuous spot on a cooled part. A soft, marking film suggests undercure; a hard one that resists suggests cure is close. It is fast and catches gross problems, but it cannot confirm full cure, and a warm part always feels softer than a cold one.
Did the fingernail test on the bracket edge and it dug right in, these never got to temperature.
Also heard as
- thumbnail test
- nail test
Related terms
MEK rub test
A cure check that rubs the film with a cloth soaked in methyl ethyl ketone and rates how much softens or rubs off.
Undercure
A film that did not get enough time at temperature to crosslink fully, so it looks fine but performs poorly.
Pencil hardness
A scratch test that rates film hardness by the hardest pencil lead that will not gouge it.
PMT
Part metal temperature, the temperature of the substrate itself, which is what actually drives the cure.