Spontaneously catch fire?
I mostly try to keep them away from the welder and grinders and torch! ;)
Easy to mix as required
Easy to apply by brush or pad
Dries very quick
great for pore /grain filling
Ok under most finishes I've used
I use 3-4 coats and then a wax rubbed to a soft gloss.
Just a thought see photo.
Doesn't that [such a thick finish] have a pretty severe effect on resonance (tone)?
Pardon me for sounding argumentative, I don't intend my response as such...
Shellac, like some other finishes, does cure very hard. I'm not an expert builder of instruments (including acoustic stringed instruments), but I would expect that such a hard coating/finish would impede the soundboard from vibrating as much as it might with a different finish.
"Thickness" wasn't really the direct point....
And with that, I repeat my previous comment/question.
I think what Taffy is demonstrating is micro thin coats - several of them, sanded in between. It's gotta be fairly thin 'cause I can still see shadows from the wood grain (beautiful stuff, btw). Even the nitrocellulose they use on "fancy" guitars is basically a form of plastic.
I'm guessing most finishes alter the sound of the instrument in some way. I've shot spray poly on 4 of the CB Ukes I've built and they still sound fantastic. 3 coats each, as I recall. Super thin and sanded between applications. Did it mostly to protect the fancy paper and stickers.
My latest go-to has been a rattle-can of spray shellac quick and easy and dries fast.
and yes the finish does impart character to the tone and timber, the search is still on for the secret formula that Stradivarius used
There's no more a mistery behind Stradivarius' lacquers, check «Secret behind the composition of the varnish on Stradivari violins revealed», https://phys.org/news/2009-12-secret-composition-varnish-stradivari..., with the original study published in Angewandte Chemie, International Edition, Volume 49, Issue 1, pages 197–201, January 4, 2010, http://onlinelibrary.wiley.com/doi/10.1002/anie.200905131/abstract, where we have to pay to read the whole research.
These old instruments were played for centuries, maybe that's one reason they sound extraordinarily well.