Official Luthiers Forum!

If you've been reading my posts, you know I'm a working repairman with 40 plus years at the bench who occasionally builds. I do not represent myself as a maker.



Yup. I do defend myself vigorously. Isn't that what you are supposed to do? I'm not always right, but I AM usually certain.



Sounds like maybe you are agreeing with me somewhat?

I'm a curmudgeon. I make no apologies. Like it, or lump it. No one is bound to take my posts as gospel. You don't, and that's fine. Have a great weekend anyway!

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"Act your age, not your shoe size" - Prince

I think all builders believe finished instruments sound different from unfinished (If not, then most builders I'm sure). There are several explanations why this is so - my favourite is that the finish makes the exposed surface less elastic and so damps chaotic overtones to some extent - but I don't think any theories have much evidence.

Most builders also agree that a well finished instrument sounds better than one in the white - but this might just mean it sounds more like other finished instruments.

Thick finish kills volume and probably reduces tone complexity. This is definitely because it increases the mass of the soundboard, maybe also it might change it's elasticity and thus modes of vibration.

Oil worries people because it soaks some way into the wood. It definitely adds mass, what else it does is speculative. I've read about soaked fingerboards becoming spongy, but that's mad owner maintenance, not a thin film as finish.

Tru Oil isn't an oil like salad oil - it dries in minutes and doesn't penetrate much. I think of it more as a wiping varnish.

Yeah it's amazing the difference a finish makes on tone. You don't even have to string one up in the white, then finished, to tell. I have done that and noted the difference but.. Even just handling the guitar, we all tap on them, whistle in them, blow in the sound holes etc... etc... in the white and then put a finish on it and do the same thing and you notice a big difference. In fact just picking up the finished body you hear the sound your fingers make touching it. It's almost like the finish is a 'presence' knob on an amplifier or something.

Then I wonder why do we even bother? If a finish changes it so much why don’t we just finish the neck and leave the body alone .... if tone and sound really are more important to people I’m surprised we don’t see folks who really value tone doing this. A FP or TO finish isn’t really a protection as much as a thicker lacquer is so it is indeed only cosmetic...
Now all this said... as a new builder I really don’t know how much a super thin finish protects things ... I can see how it would protect against discoloration or “spills” , but unless something gets soaked into the instrument .... well there we go valuing appearance over tone again..
I guess all that is crazy talk. I mean it m not sure I want an “unfinished” guitar ..


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The experience of centuries has taught us that finished is better than unfinished...

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"Act your age, not your shoe size" - Prince

I have a parlor I left in the white. There is a nasty grimy spot on the soundboard next to the bridge where my right wrist rests and there is a gross spot on the edge of the lower bout from my forearm. So agreed on the discoloration aspect.


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The smell of lacquer at the Martin factory yesterday was yummy.

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Hutch

Get the heck off the couch and go build a guitar!!!!

I'd say both. Soak your red spruce top in thin CYA and it stops sounding like red spruce and sounds like some CYA soaked thing. Too much finish and the tone begins to deaden. Harder finishes sound tinny. Violin oil/spirit varnish sounds VG and best when right on the surface of a mandolin or mandola, but does not sound as good on my guitars. My guitars, being much larger and basically flat-top sound better with an instrument lacquer.
Unfinished mandolins tend to have a more garbled sound in my opinion. They are more "uncontrolled", notes aren't quite clear and chords are jumbled.
As far as grain filler, who can say. I have never built a mandolin with open pore woods for back and sides. Sort of a moot point on guitars as open pore woods are all filled with something...
I have built enough "distressed" mandolins with thinner finishes than normal shiny mandolins to know that they tend to sound better. They are stronger sounding, more lively and break in quicker.
How do I know this? Build 50 F5 mandolins using the same wood & dimensions and you will be able to draw some conclusions.

Limiting my comments to French polish, since I have not applied an oil finish: I think the first half of that sentence is accurate (French polish is not as much protection as thicker lacquer) but the second half of the sentence is not accurate (so French polish is only cosmetic).

You might be surprised by how much protection a decent shellac finish provides. For many guitar owners, it meets or exceeds what they need from a guitar finish in terms of protecting the instrument. And that is not limited to classical guitar owners.

I think there can be a tendency to overstate the fragility of shellac.

Some time back Kevin Aram, a professional maker in the UK, wrote a detailed article in the GAL journal detailing his process for an oil finish.

It may not be quite the same product but the general principles are probably the same. Can't lay my hand on the journal just now so can't give you the number.

Dave

"Then I wonder why do we even bother? If a finish changes it so much why don’t we just finish the neck and leave the body alone .... if tone and sound really are more important to people I’m surprised we don’t see folks who really value tone doing this."

Many lutes and early guitars left the soundboard unfinished, some others only used an egg white coating. The lute boats and guitar backs and sides were often "varnished" with either spirit or oil and sometimes both, as Haans did with his mandolins.

There have been several studies that actually measured the acoustic effects of different finishes applied to spruce. Here's one of the better studies: (It begins on page 27.)
https://stacks.stanford.edu/file/druid: ... kq5616.pdf

He uses the Liberon finishing oil, applied very frugally. It offers very little protection, after all there really is hardly anything on the wood. It's probably the equivalent of doing two wipe on coats of Tru oil, if that. The difference is that it's a non gloss finish so any marks and scratches don't show as much as the same with a gloss finish. It's very similar to the finish that some lute makers have been using on soundboards. I used it many years ago. It does show dirt in areas within a few years.

I don't know about "coats", meaning thick coats I guess, I've used it a lot and always rub in a very thin amount with a pad, nothing is there to build up or drip. 2 thin coats a day for a week, let it cure for 2-3 weeks, buff and it is beautiful. I use it on electrics, and acoustic necks in particular. I made a jumbo years ago that was 100% Tru Oil (no sealer on top first), and while it sounds good to me, I have wondered if the oil dampened the sound at all.

I tried Tru-Oil on my latest build.
I rubbed and wiped off three coats.
Wet sanded with 800 using the oil as lubricant.
Rubbed and wiped off four coats.
I ended up with a satin look.
The oil really made the Maple pop.
Too bad the picture is low quality.
It is now my favorite finish.

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wah
Wah-wah-wah-wah
Wah

Years ago I built a guitar for a guy who didn't want a finish on it. After a while it looked like crap. It was a filthy mess. So if anything a finish does it at least makes it easy to clean dirt off of it. I remember reading one study that showed that the required thickness for any finish to actually protect an instrument from humidity would be thicker than any able bodied luthier would ever put on their guitars. So really a finish is only there to make the thing look nice and easy to clean.

But it does affect the tone. I don't know how to describe it except it kind of reminds me of a 'presence' knob on an electric guitar amp. I like what the finish does to the tone but only up to a point.

As far as protecting it from humidity... I don’t see a finish doing that... the inside would also have to be sealed. I guess you COULD... but I haven’t personally seen it done


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Does anyone here here have experience of how Tru Oil compares with say, Minwax Wipe On Poly?

I have done several guitars with Tru-Oil. My results were really good, though my method was pretty basic. I started with the Birchwood Casey, Tru-Oil sealer. Dries faster than the TO itself, and has more solids. Probably reduces absorbancy, but my tests on scrap shows that TO doesn't really penetrate much, even on Cedar tops. A light scrape takes it right off.

My method, was to wipe on with paper rag material - comes in boxes at big box stores. I made little pads of folded paper, applied TO from a plastic bottle with Yorker cap, and wiped on lightly. Re-coated in 3 hours(40% shop), and after 2 coats, rubbed back with a gray abrasive pad. Continued to build the finish until it was fully level. Somewhere around 10 to 12 coats. Rubbed back with a white pad and put on a couple of more coats, very thin, rubbed back with white pad. Waited a few days and wet sanded through the Micro Mesh grits starting with the 3200.

Sycamore/Spruce guitar #10.


Walnut/Cedar #16

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Waddy

Photobucket Build Album Library

Sound Clips of most of my guitars

A friend of mine has a Daniel Fredrich classical guitar with a very light French Polish finish that is 40 plus years old.. H3e plays it regularly and the finish is still in great shape.
There are some (small) worn areas on the neck and body, but I bet it has another 40 years left if taken care of......

It is all relative to the care the guitar receives. A well taken care of FP guitar will do well, but if played with bare arm or sweaty shirt, the finish will pay. I have several guitars with students who play several hours a day, and the ones who take care of the guitar do quite well. Others, not so much. I have had to do some finish work on a couple of them.

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Waddy

Photobucket Build Album Library

Sound Clips of most of my guitars

I’m finishing my last build w TO, and I’m taken back at how red the wood has turned. I’m not exactly sure why. It is attractive I just wasn’t expecting it. Maybe it is a reaction w something in the fortification process? Here is the current build w only 6 coats or To, and then the same wood from the same supplier w lacquer




I feel it darkened considerably over night....
Anyone know if they use chemicals in the torification process?

The back isn’t darkening like the Spruce is. The back is sapelle



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Oil varnish/finish tends to darken wood more than shellac or nitro. . . . not sure to that extent though!

Apparently a good bit haha:)
I’m just going with it:) I’m also working in VERY thin coats of oil. So thin that if dust gets on it I can simply wipe it off wo it sticking. Similar to working FP very dry.
This... this will take a while but no hurry


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I have a friend that uses TO for his mandolins. I never seen any of his tops turn like that. Your top looks like mahogany now which is still a nice look. Too bad it was unexpected though.

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Hutch

Get the heck off the couch and go build a guitar!!!!