Official Luthiers Forum!

Ok, I hear people talk about thier finish being .004 in.( or pick a number) thick. How are you measuring something so thin. Are you finishing a scrap and taking it to someone to measure with a some kind of high tech instrument to measure? I'm curious to see how thick of finish I'm using. Clinton

How about measuring with a micrometer, before and after? Pick a spot, say at the sound hole. I'm sure there are more scientific ways of doing it, with refraction of light or something like that.

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Waddy

Photobucket Build Album Library

Sound Clips of most of my guitars

I save a 'chip' when removing the finish at the bridge and/or the fretboard extension. I use a micrometer to measure the chip. This gives me an exact, after-buffing, thickness.

If you use plastic (fom old milk jug?) held in place by a balloon inside the soundhole during finishing, flexing the plastic will flake off chips so you can a)measure the thickness and b) keep on file for future (colour) reference.

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Dave
Milton, ON

I measure the finish I lifted at the FB extension and bridge locations with calipers. Usually between .003" and .006".

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Laurent Brondel
West Paris, Maine - USA
http://www.laurentbrondel.com/

Thanks. Looks like I have another tool on the wish list! Clinton

I do exactly what Mario described, chisel off under the bridge or fret board extension and mic it. If you are cutting a channel around the base of your bridges so they over lap the finish this is a key piece of info to know.

Once you're at or under about .006" to .008", you're in the ballpark. Getting all freaky about a .003" finish instead of a .005" finish is kind of like chasing your tail, and I don't think it makes all that much difference. There are other areas of guitar making that are far more important. This gets into the macho pissing contest area all too quickly. No, we don't like thick finishes. We also don't like burning through.

I like the idea of a cut off milk carton and balloon... wish I had thought of that!!!

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Joe Beaver
Maker of Sawdust

Rick, thanks for chiming in, actually I'm relieved to see that I have some wiggle room. I've been FP my guitars for a couple of years and I'm finally starting to get results that I'm happy with. I love the feel of this finish, but I think I'm going to learn to apply varnish,seems as though that it's more acceptable from most people, at least the ones I run into. I don't like nitro. Clinton

I totally agree with that. I have here a guitar where the finish at the bridge was .002" and another, of a similar build, at .008" (both varnish). Personally I do not hear a difference, or what the thinner finish does. To expand I do not hear the difference between FP, lacquer or varnish when the finish is well applied and thin enough (not to start a controversy…). Below .004" I apprehend going to the buffer, though…

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Laurent Brondel
West Paris, Maine - USA
http://www.laurentbrondel.com/

This is something that the fine furniture makers can help us with. For those that spray finish, scroll about a third of the way down the link:

http://www.furniturefinishwizard.com/viscosityandwetmils.htm

Its a good way to check out equipment and technique.

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Jim Howell
Charlotte, NC

I found Grumpy, or Sir Grumpy!

Gotta love that John Henry Banjo Mute!

Snowin' up there at the Falls Mario?

It's also possible that the mil thickness isnt the same in the bridge area that it is on the rest of the top. It's easy to take it thinner there while leaving the rest thicker.

Rick the only qualifier is that many of the modern finishes don't like being overly thick, particularly conversion varnishes that the manufacturers want a finished film thickness (this is after leveling and buffing of 3-4mils, and really on the thinner end of that.

I think that most of us can just look at a finish and know whether it's too thick or pretty OK. You can pick up on the refraction through a film and gauge pretty nicely whether it's right or not. I have the luxury of seeing my employees burn through my finishes on too regular a basis, so I know that the finishes are thin! I'm thinking my average polyester finish is about .006" to .008" at the thickest on solid bodies that get color. On acoustics it's probably .005" to .007". I do know this...after a few months as the tops go through humidity changes, I get that nice slight ridging effect with the spruce. I love that look, and it's a good indicator that the finish is not too thick.

I was under the impression that this ridging on the grain lines was a bad thing. I was upset when that ended up happening on one of my previous guitars. It showed up about 8 weeks after the final buffing.

-j.

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“If God dwells inside us like some people say, I sure hope He likes enchiladas, because that's what He's getting”
-jack handy

Nope, I like to see them too.

It would be kind of hard to do the ballon trick with french polishing I'd think.

I wouldn't be upset. If the top is smooth and flat without any telegraphing I think it looks unnatural.