Types of lacquer and the sound of the guitar.

[JohanAbrandt]

My finish of choice for woodworking these days is Danish oil, though I do use shellac sometimes as well. The former really brings out the wood grain, and the latter provides a nice warm vintage amber which can be adjusted depending on how it’s mixed.

Danish oil finish:

Attachment 91283

I did a bit of refinishing of vintage display cases recently and wanted that antique glow, so I went with amber shellac.

Attachment 91285

I wonder how Danish oil would affect the sound? It does take a long time to cure, and is still somewhat oily even days or weeks later, so probably not a great choice for instruments.

I have finished a few maple guitar necks with linseed oil and they feel really good and looks nice. I added some yellow and red pigments to make the grain pop a bit. They are still stable so no surprises yet.

[John A.]

I think after the type of the guitar, and the quality and condition of the woods involved, the finish is the most important thing, sound wise.

I've seen acoustic and classical guitars having just the top refinished, where you'd have a different instrument afterwards. Even in electrics refinishing changes the sound considerably.

Usually the best quality instruments have a very thin coating of whatever the builder chooses to use, to let the woods breathe and develop their acoustic sound. Especially in high end non-electric instruments that focus on this type of sound.

Of course there's also use for the dampening and compressing effect thicker coatings have, if that's what a builder is after (to battle feedback or to focus on distortion for example).

The wide use of poly over nitro has been a case of nitro being more difficult and time consuming to apply, less durable, and less environmentally friendly.

You can't refinish a guitar without also removing wood, and the new finish is rarely the same thickness as what was there before. So I don't think citing refinishing proves the case that finish material on its own makes a difference. I also think wood and/or finish "breathing" is a myth when it comes to finish comparisons. In acoustic guitars, only the outer surface of the instrument is finished. So if any gases or moisture are diffusing out from the wood, I can't see why the outer finish matters. I can imagine that finish thickness makes a difference in how an instrument resonates, though, and I can imagine that materials of difference stiffness/plasticity do as well, but I don't think I've ever seen a convincing, controlled demonstration of these hypotheses.

[Little Jay]

Yeah, 1 hour and then you are done =)

Only for the spraying itself of course ;-)

[Hammertone]

I have read shellac makes a good sealer coat. Also, it isn't clear, it seems amberish in colour and with age in examples I have seen. I really like a natural colour finish, so maybe not a good choice for that.

Shellac is a quick and safe sealer.
Nitrocellulose lacquer sticks to shellac.
Shellac is an excellent finish as well, IMO. It scratches easily, but is infinitely repairable.
Clear shellac is widely available.
Erich Solomon's archtops typically come with clear shellac finishes.

[Mark M.]

I have some really nice French polished classical & flamenco guitars and they sound amazing. However, I had one of the guitars built for me and I underestimated the time it takes for the shellac to cure and harden. As a result, the guitar i showing a lot of scratches and small nail marks o the top. It adds character and I’ll never part with the guitar so resale is not an issue. But, be careful with new shellac.

[EastwoodMike]

yep, maybe.

I have read shellac makes a good sealer coat. Also, it isn't clear, it seems amberish in colour and with age in examples I have seen. I really like a natural colour finish, so maybe not a good choice for that.

Never made a guitar but plenty of table tops. Thinned down Shellac makes great sanding sealer and a natural pore filler. Raises the grain nicely for fine finish sanding. But as others have noted it is fragile and easily damaged. It works great as a base coat under a more durable finish, and also acts to even out any stain you may apply to porous woods.

You can get amber or clear (blonde) shellac flakes. Not truly clear transparent but once watered down for sanding sealer purposes is effectively clear.

I don't know for sure but the short and long term flexibility of a dried finish probably needs to be considered as well as the thickness of the finish. Some more experienced on this forum may know of the flexibility of thin Poly vs Nitro and if it is linked to finish checking?

[kris]

You can't refinish a guitar without also removing wood, and the new finish is rarely the same thickness as what was there before. So I don't think citing refinishing proves the case that finish material on its own makes a difference. I also think wood and/or finish "breathing" is a myth when it comes to finish comparisons. In acoustic guitars, only the outer surface of the instrument is finished. So if any gases or moisture are diffusing out from the wood, I can't see why the outer finish matters. I can imagine that finish thickness makes a difference in how an instrument resonates, though, and I can imagine that materials of difference stiffness/plasticity do as well, but I don't think I've ever seen a convincing, controlled demonstration of these hypotheses.

Not long ago I gave Tele to refinish.
I don't know how the luthier did it but the wood wasn't moved.
The new laquier was put on the guitar perfectly.

[j4zz]

Not long ago I gave Tele to refinish.
I don't know how the luthier did it but the wood wasn't moved.
The new laquier was put on the guitar perfectly.

I was thinking you have to sand it back, no matter what. Now you could put a new finish over the top of the old one by just sanding it back a little, but to be able to say whether it makes a difference to the sound, you'd need to remove all the old finish. This might include an underlying first coat or sealer of something different, but when you get back to that first coat, that is soaked into the top layer of wood, to remove it, you'd need to take off some wood - just a little maybe.

[JohanAbrandt]

Depends on what you refin from, a nitro is easy to remove, a thick poly with plastic dip under you cant refin without sanding unless you just spray an opaque on top of whats already there

[kris]

I bought a small bottle of shellac and am trying to put it on part of the top plate of my old classical guitar.I like working with shellac - little shellac layers and you can see the effect.

[JohanAbrandt]

When working with shellac I have found that being able to vary the ratio shellac to alcohol is a big advantage. If you get a too thick layer then do the next 2 with a more diluted mix. The finish layers are mostly alcohol to smooth out. Also some drops of mineral oil on the sponge can help to get smoother movement

[kris]

When working with shellac I have found that being able to vary the ratio shellac to alcohol is a big advantage. If you get a too thick layer then do the next 2 with a more diluted mix. The finish layers are mostly alcohol to smooth out. Also some drops of mineral oil on the sponge can help to get smoother movement

Very good advice. I'm working on it right now.Thanks...:-)

[alltunes]

I just picked up an Eastman SB55 V which surprisingly comes with a varnish finish. The guitar is very resonant unplugged. A versatile guitar and well worth $1,400. High end mandolins are almost always varnish.

SB55/v - Eastman Guitars

[JohanAbrandt]

Wonder what they mean with varnish though, its a very generic term

[Mark M.]

I just picked up an Eastman SB55 V which surprisingly comes with a varnish finish. The guitar is very resonant unplugged. A versatile guitar and well worth $1,400. High end mandolins are almost always varnish.

SB55/v - Eastman Guitars

I had an Eastman T64 with a varnish finish and it was very resonant. More builders should use varnish.

[Cunamara]

I have a Telecaster, mahogany back with a flame maple top, that I finished in boiled linseed oil. It was very easy to apply (this was my first time finishing a guitar) and the final product is remarkably hard and durable, not to mention attractive. I get a lot of compliments on the looks of that guitar. It seems to be ambering slightly as it ages. The look of a finish that penetrates into the wood versus sitting on top of it is different. I really like it. If I was ever to finish an archtop, I would be very tempted to use BLO with that.

I did not use it on the neck; the neck is a Warmoth neck which they finished in nitro.

Varnish is the traditional finish for violins, including the great Cremona violins, and it's pretty hard to get a greater vote of confidence than that. I think it is probably less suitable as a product for use in assembly line manufacturing and that nitro was easier to apply, easier to get a good finish and probably cheaper in the long run than using varnish. A lot of these decisions by Gibson, Fender, Epiphone, etc., were not made on the basis of "tone" but on the basis of cost and the eye candy appearance of the final product for the purpose of driving sales. Also the much larger surface area of a guitar versus a violin would much more easily reveal anything irregular or uneven in the finish.

[JohanAbrandt]

Well, there is material to study impact on tone on a solidbody. Just get 2 1950’s strats, one in lake placid blue (acrylic), and one in sonic blue (nitro) and compare.

I am convinced that I would not hear a difference, but who knows

[Marinero]

"I've seen acoustic and classical guitars having just the top refinished, where you'd have a different instrument afterwards. Even in electrics refinishing changes the sound considerably." Alter

I've posed this question to two luthiers over the years: A. LoPrinzi and R.Brune. Neither advocate refinishing a CG top for the above reason. My two "Artist Model" CG's are both over 30 years old and show significant play wear above/below the strings and in friction areas under the right arm and on the lower bout from playing in the upper register. And, then throw in unavoidable dings/dents, and string slaps(early in their life) and you have the quintessential player's guitar. Both instruments have very unique voices and refinishing the soundboard is not an option for me.
Marinero

[kris]

Shellac is great stuff!
I've been working with shellac for several days and I really like the effect of the work.

[Greywolf]

Polyurethane by nature due to it's molecular structure is sound deadening , it has been used it for that purpose for years. Now the thin coat UV cured poly these days is not much of a hindrance to tone. That being said, I prefer a Nitro finish despite they are more time consuming and fragile. I've done french polish , and tonally I'd say it is a winner . That's why so many Violin family instruments use it. It is an art to get it right to be sure.