Guitar finishes and Tone?

[Armitage]

Here's what Terry McInturff had to say about it here before the pinheads here annoyed him enough to leave...

 

There are, basically two types of finishes used on guitars.

 

1) OIL FINISHES

 

These are not really "oil" at all, but rather a resin that is dissolved in a solvent. The solution soaks into the wood, the solvent evaporates, leaving the resin behind. Examples are "danish oil" (unknown in Denmark! ), tung oil, "gunstock oil" ( actually a wipe-on polyurethane) and others.

 

A finish that deeply penetrates the wood will generally lower the primary resonant frequency of that wood. The resins inside the wood have an acoustical "loading" effect. I do not recommend these finishes for acoustic guitars, where this lowering of the resonance can have a pronounced and unpredictable effect....the once lively and resonant plates will now sound dull.

 

The effect upon an electric solidbody is less pronounced, although still there. A great finish for a maple neck...feels really fast and broken-in! Not much tonal effect when used for this purpose.

 

2) HARD SURFACE FINISHES

 

These finishes do not penetrate the wood to an appreciable degree; rather, they sit on top of the wood and harden either by evaporation of solvents, a catylitic chemical reaction (similiar to that of epoxy glue), or a combination of the two.

 

These include, but are not limited to, nitrocellulose lacquer, acrylic lacquer, the various urethanes, and the various polyesters.

 

In general, it can be said that a hard surface finish stiffens the wood and hense raises the predominate resonant frequency.

 

Much attention has been paid to the "differences in tone" of nitrocellulose lacquer vs. polyester. I have extensive experience with both. I have come to the conclusion that there is no INHERENT audible difference between the two. This flies in the face of popular opinion. Permit me to explain further.

 

A surface finish affects the resonant frequency of a given piece of wood IN DIRECT PROPORTION TO THE FINISH'S FILM THICKNESS.

 

There is no inherent difference in tone between cellulose resin and polyester resin. Yet, we can often hear a difference between the two. Why?

 

Answer: Because a polyester finish is almost always considerably thicker than a nitro lacquer finish. When mixed for spraying, polyester ranges from 50% to 95% solids content. Nitro lacquer ranges from 10% to 25% solids content. .

 

A production spray schedule requires a certain number of coating steps in order to complete the finish. First are the "sealer" coats. The sealer is sanded flat. Next comes the "color" coats, and a number of clearcoats on top of the color. These clearcoats are then sanded flat. Finally come the last clear coats, called the "top coats". These are sanded flat, then buffed to a high gloss (except of course in the case of a satin finish).

 

Due to the dramatically higher solids content, polyester finishes can be mighty thick by finishing standards. A .030" film thickness is common. This has an effect upon tone that even a non-player can hear. The lows are attenuated and the highs are boosted, because the stiff, thick finish has raised the resonant frequencies considerably. It is very difficult for the builder to accurately predict, or to control this effect upon the finished product.

 

Nitro cellulose lacquer has far less solids content, and hense (properly applied) a nitro film thickness can be very thin. The average film thickness on a TCM finished with nitro averages out at aprox .008 when fresh. The finish will continue to shrink over the years, and will lose about another .002" in two years. A thin film such as this has FAR less influence upon the resonant frequencies of the raw wood. Hense, it is more controllable. One can design a guitar that sounds as intended in the raw wood form, and the finish will not shift that tone hardly at all.

 

Now, if a polyester finish had the same film thickness as did nitro, the finishes would sound IDENTICAL. This is very, very difficult for most mfg's to achieve in a production environment, however.

 

 

[iluvnoise]

Here's what Terry McInturff had to say about it here before the pinheads here annoyed him enough to leave...

 

Wow. Nice to hear an expert's take rather than just a "lay" opinion like mine.

 

Thanks for posting that, Armitage.

[walt0915]

The vibration response of a material varies dramatically with frequency. Take any block of wood, and it may resonate nicely at some frequency, but will also fail to respond at all at others. Even a hard block of rubber will vibrate at certain frequencies, though it certainly dampens many others.

 

The tone of all instruments is defined by the dampening of frequencies. Every instrument produces a set of harmonics, and then proceeds to dampen specific harmonics leaving the characteristic tone of the instrument. Guitars are the same - harmonics are produced on the string, some are conducted well by the bridge and neck, others aren't. Some of picked up well by the pickups and others aren't. Changing key variables can gratly affect tone - positions 2 and 4 on a Strat are highly prized because they dampen out certain frequencies to create the "quack" tone.

 

Its really hard to predict how all of the variables in a complex system like a guitar will interact to produce a final tone. Certainly if we vulcanize a 1/4 inch of rubber to the body that will probably deaden the tone a lot, but small differences can be hard to detect, and even if detected, deciding which is "better" is nearly impossible. In fact, you may wish you could have both!

 

The finish argument is one that has played out here many times. I, personally, don't feel the need to worry too much about it. I've been happy with all of my guitars regardless of finish. On the other hand, when *I* do the finishing, I might as well put some thought into the choice, and for me laquer works well on many levels, but tone has never been a major consideration. There are others here who feel strongly the other way, and I respect their opinions as well.

[No Soul]

 

I think he was referring to the OP's original link. Lots of wrong stuff there.

 

 

yep.

 

And thing with french polish is it actually gets absorbed into the wood, which does change the tone. Even a light coat of poly will not do that.

[TimmyII]

 

Here's what Terry McInturff had to say about it here before the pinheads here annoyed him enough to leave... There are, basically two types of finishes used on guitars.

 

 

thanks for the read.

 

i think my philosophy is to keep things simple. i don't think you need to consider diffrent materials and tech this and tech that. what it's really about is vibration. let it vibrate as much as you can and keep it simple.

 

i think the article i first posted made a lot of sense in that regard. the more solid your piece of wood is and the less there's hassle between the parts the better it will sound.

[OrvilleGibson]

My $0.02...

 

French Polish is indeed used on violins, but only on the neck. The rest of it is covered (traditionally) with a wide variety of varnishes. If you think the flame wars regarding finishes on guitars are bad, take a gander at what's been said regarding violin finishes over the last few hundred years. Another thing about violin varnishes is that they are purposely used to alter the tone of the instrument, to keep them from being too harsh/brash/bold/insert your favorite responsive tone description here.

 

As for French Polish soaking into the wood, I'd have to disagree (at least based on my experiences). I've used your basic combination of walnut oil and flake shellac as both finish and sealer, and I've been able to easily remove it when necessary. Of course, it doesn't come off as easily as water-based finishes, which can be simply peeled off.

 

Keep in mind, the only reason "nitro" was originally used on guitars was because it was faster, simpler, and cheaper than French Polishing in a production environment.