Acoustic guitar finish

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Matthew Atkinson
Posts: 28
Joined: Wed Feb 01, 2012 1:19 pm
Location: MA

Re: Acoustic guitar finish

Post by Matthew Atkinson »

Not oil. I mean to put behlen's over it.
-Matt

Rodger Knox
Posts: 497
Joined: Mon Jan 09, 2012 2:02 pm
Location: Baltimore, Maryland

Re: Acoustic guitar finish

Post by Rodger Knox »

Behlens Rockhard varnish is a drying oil, similiar to TruOil. They are both oil varnishes, one is a "long oil" and the other is a "short oil", but I don't remember which is which. There are four basic types of varnish, composed of one of two types of oil and one of two types of resin, and I don't remember off the top of my head what the two types of resin are.
Anyway, they go on fine over shellac. You may get better results sanding back to wood , leaving the shellac in the pores, but only for a high gloss finish. As Alan said, it has the same refractive index as the wood, so you get some nice light effects when it goes on bare wood, but they probably wouldn't show much without a high gloss.
This is a definite test on scrap to get the look you want, and you can probably get it with any of the products discussed.
A man hears what he wants to hear, and disreguards the rest. Paul Simon

Christ Kacoyannakis
Posts: 228
Joined: Sat Jan 07, 2012 8:58 pm

Re: Acoustic guitar finish

Post by Christ Kacoyannakis »

You can also brush the Target Coatings EM6000 water based lacquer. Use a very fine brush designed for water based finishes (or a very soft artists brush). As with the nitro, get the retarder. Very little smell. You can buy matte, or just buy the gloss and finish up to whatever level of matte you want. I find that if I use up to a 2000 Abralon pad in a random orbit sander, it is a very nice soft sheen. If you go to 4000, it is just shy of shiny, and only needs a bit of buffing to get to full gloss.

Alan Carruth
Posts: 987
Joined: Sun Jan 15, 2012 1:11 pm

Re: Acoustic guitar finish

Post by Alan Carruth »

Roger Knox wrote:
"Behlens Rockhard varnish is a drying oil, similiar to TruOil. They are both oil varnishes, one is a "long oil" and the other is a "short oil", but I don't remember which is which. There are four basic types of varnish, composed of one of two types of oil and one of two types of resin, and I don't remember off the top of my head what the two types of resin are."

First; there's a big difference between a 'drying oil' and an 'oil varnish'. I know what you probably meant to say, but it didn't come out like that. Oil/resin varnishes do dry the way they do because of the drying oil, but the resin brings a lot to the party, too, to quote a TV chef...

Mayer, in 'The Artist's Handbook', which is a pretty standard reference, lists a dozen natural drying oils that you might run into, and says there are another fifty or so that are not commonly used. As far as I know, any of them can be used to make a varnish, although many of them probably aren't. The major ones are linseed, poppy, walnut, safflower, sunflower, soya, tung, perilla,oiticica, lumbang, stillingia, and tobacco seed. There's an even wider variety of resins. Again, so far as I know, any resin can be cooked with any drying oil to form a varnish of sorts, and it's possible to use more than one oil or resin too. All of these varnishes harden by oxidation and polymerization, and that might be what you mean by a 'basic type' of varnish: the point is that there's a lot of variety within that basic type.

'Rockhard' varnish is a 'short oil' or 'rubbing' varnish; it has a relatively small proportion of oil, and the high rsin content means that it dries hard, and can be polished up nicely. 'Long oil' or 'spar' varnishes have a lot more oil, are more flexible when cured, and the softer surface might be hard to polish out. I've only used a little bit of Tru-oil, and never tried to build up a real film with it, so I can't say where it falls in the 'long-short' spectrum. I do know they thin it out a lot.

Drying oils don't really form a protective film by themselves very well. Some of the polymerized linseed oils do, to some extent, and they don't saok in the way the usual boiled linseed oil does because they don't have any low molecular weight components left. One of my students used an oil like that on a solid body bass many years ago: it looked OK new, but I can't say how well in might have aged. Anyway, the whole point of putting in the resin is to get it to form a nice film on the surface to protect the wood.

Alan Carruth / Luthier

Rodger Knox
Posts: 497
Joined: Mon Jan 09, 2012 2:02 pm
Location: Baltimore, Maryland

Re: Acoustic guitar finish

Post by Rodger Knox »

Thanks for the clarification, that's mush closer to what I meant than what I said. :D
A man hears what he wants to hear, and disreguards the rest. Paul Simon

Matthew Atkinson
Posts: 28
Joined: Wed Feb 01, 2012 1:19 pm
Location: MA

Re: Acoustic guitar finish

Post by Matthew Atkinson »

Well I have applied a brushing laquer instead of the Behlen's and I am wishing I was more patient and ordered up some Varnish. I couldn't find the Behlen's in the store so I used laquer because I didn't want to wait. Looks ok but having a very tough time getting a smooth coat on the top. The back and sides went fine, 2 coats but the top is harder to get an even stroke because I am worried about drips on the edges and at the SH. I have 3 coats on the top but will have to sand it flat again and try once more. Tough with a brush!
-Matt

Bill Snyder
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Joined: Sat Jan 07, 2012 2:18 am
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Re: Acoustic guitar finish

Post by Bill Snyder »

I would think that if it is lacquer that once you have enough of a build coat on it you can level sand it, go through several grits of Micromesh (or equivalent) then polish.

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