I just thought I'd share this...
Whilst currently undergoing a refinish on my 2018 TLA-1, which I had originally applied a wipe-on poly finish to (longer story in another post) I was able to remove a "piece" poly by scraping it off with a razor blade.
Just out of curiosity, I measured it's thickness with my digital callipers. Now, these are not a highly calibrated instrument, but they are pretty close for 40 bucks (tested with feeler gauges).
Anyway, my point being that this flake of poly was the result of 28+ coats of homebrew wipe on poly (mixed 50/50 - poly/turps) then wet sanded and polished. as you can see the coating left on the timber is only 0.11 mm! (same as a single sheet of 80 GSM copy paper) That is sweet bugger-all!
I know it is difficult, if not impossible, to quantify what is "a coat" especially with a wipe-on finish, but I think this still illustrates what slim margins we're dealing with in our finishing pursuits.
So when we read about "sand-throughs" (we've all been there!) it's not hard to understand just how easily they can happen.
FWIW, I took samples from various areas of the body and they consistently measured between .009-.011mm.