Testing a finish schedule

[Steve Sawyer]

Appearance is easy to assess when testing a finishing schedule on scrap, but it seems that one of the issues to be tested is adhesion between coats, particularly dissimilar finishing products including grain fillers, sealers, stains, dyes, color coats and clearcoats.

Will an adhesion problem be immediately obvious, or is there something I should do to assess this?

[David King]

I'd suggest "sticking" with the tried and true unless you have a compelling reason to do otherwise. There must be an accumulated millennia of experience you can draw on here so just ask and someone will set you straight.

[Barry Daniels]

Strong masking tape is one way to test adhesion. But I agree with David. This is not a place to be mixing and matching different manufacturer's products unless you know they are compatible. Issues can turn up months later with incompatible materials.

[Steve Sawyer]

Thanks. I agree that there is merit in conservatsm, but new products do become available, and there are situations where there is value in experiment. I re-read the Big Thread on waterborne finishes which extensively covered Ennduro-Var, but I'm interested in exploring GF's High Performance waterborne product. However, re-reading that thread answered my question: cross-hatching the finish, then using Gorilla Tape to check for adhesion issues. You're correct, Barry, that passing this test is no guarantee that problems won't develop over time, but it will eliminate those schedules that are problematic right out of the gate.

[David King]

Most adhesion problems are due to not letting the underlying finish dry or cure completely before jumping to the next step. Most finishes would be compatible if folks were just patient enough and if they read the damn instructions on the can. When an overcoat suggests sanding to 220 with the grain they don't mean sanding to 1000 grit with an orbital sander -as fun as that can be. When they say that an oil based stain needs to dry for at least 48 hours or until all the smell has dissipated they don't mean 48 hours in your damp basement in 50 degree temps. That would take weeks if not months to dry in those conditions. Some oily woods like cocobolo present especially tricky problems for all finishes, the oil in cocobolo will mess with other oils and it will mess with epoxy cures, it will bleed out into shellac and lacquer, it totally messes with urethanes. I'll be mostly glad when cocobolo is simply off the table for instruments.

[Steve Sawyer]

David - your remarks point out that a finishing schedule isn't just the products used; it includes how they're applied.

[Craig Bumgarner]

The standard field test for paint and coating adhesion is the score the cured finish with a sharp knife in a 1" grid of lines, tape over with a strong adhesive tape and then rip it off. The results will be obvious.

[Gordon Bellerose]

It's really important to do a lot of research into the products you want to use.
I use strictly Water Based products. If I have to use a grain filler, then I use a water base compatible filler, or epoxy because water based lacquer will adhere to it.
I sometimes use shellac as a sealer, because water base lacquer will adhere to it also.
Every step along the way is directed toward the lacquer.
I used EM-6000 for a while, and now I use Brite-Tone. I don't know if it is available in the US. I buy it from Wood Essence, from Saskatoon Saskatchewan. (say that fast a few times)

I probably would be lost if I had to switch to oil base. Like starting all over again.

[Steve Sawyer]

Gordon - thanks. That's a very interesting set of observations.