Replies to This Discussion

Permalink Reply by ThePracticalPeasant on April 17, 2017 at 6:04pm

Spontaneously catch fire?

I mostly try to keep them away from the welder and grinders and torch! ;)

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Permalink Reply by John Sawyer on April 21, 2017 at 4:14am

Linseed, danish and tung oils are well known for spontaneous combustion...

There are many documented cases of garage fires from a rag... a friend recently lost his garage, and nearly his house to a pile of oily rags. His garage door was open, the sun was shining on a small pile of rags which burst into flames... the garage heated up until other things started catching fire...

Google it.. linseed oil is very well known for this. Metal paint cans are cheap...

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Permalink Reply by Taffy Evans on April 18, 2017 at 12:47pm

Hi all, I am surprised that nobody has used Shellac. probably one of the oldest finishes.

Easy to mix as required

Easy to apply by brush or pad

Dries very quick

easily sandable

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.

Taff

 

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Permalink Reply by ThePracticalPeasant on April 18, 2017 at 12:49pm

Doesn't that [such a thick finish] have a pretty severe effect on resonance (tone)?

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Permalink Reply by Kigar on April 18, 2017 at 2:20pm

Ok, now you're just showing off! That is an awesome guitar! And does shellac need a top coat like wax or is it optional?

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Permalink Reply by Taffy Evans on April 18, 2017 at 1:25pm

Hi, I find the thickness of shellac coats is really governed by the ratio of shellac flakes to metholated spirits and the number of coats applied. I use a thickness that possibly could not be measured. And light sanding between coats gives a very thin final coat prior to applying wax or lacquer of your choice.
Taff

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Permalink Reply by ThePracticalPeasant on April 18, 2017 at 1:47pm

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.

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Permalink Reply by Hal Robertson on April 18, 2017 at 3:46pm

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.

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Permalink Reply by Taffy Evans on April 18, 2017 at 4:16pm

Hi, I gave a detailed reply but it's gone missing. Two points of note tho.

Many many Highly regarded luthiers use shellac "French Polish" on their very very expensive guitars.

There is a product called Hard Shellac, but it is made especially to be hard.

I use the wax to get the sheen I like.

Cheers Taff

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Permalink Reply by JL on April 19, 2017 at 2:37am

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

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Permalink Reply by Moritz Voegeli on April 19, 2017 at 3:39am

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.

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Permalink Reply by ThePracticalPeasant on April 19, 2017 at 3:53am

Very cool!

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