Official Luthiers Forum!

I may have missed it in the above postings, but do any of you guys mix other ingredients into your French polish? I've heard of luthiers who add alcohol-soluble resins resulting in a far more durable finish than straight flakes and alcohol. I can never remember what resins are used tho. I think one of them is the amber that Alexandru mentioned as being an ingredient in his varnish.

Jake.

French polish is a technique, not a finish. Shellac is the finish. Shellac, as a lot of other finishes, can be padded, brushed or sprayed.
Adding resins and gums to shellac transforms it into a spirit varnish, a very popular finish for violins in the 19th century. A spirit varnish, ideally, will be tougher, more resistant to solvents and sometimes more supple than pure shellac. It is also slower to cure. Behlen's "Violin varnish" is a ready-made spirit varnish, and makes a great sealer.

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

I've read this before about not using it on steel strings. What is the difference as far as finish durability between a steel string and a classical guitar?
Mike

When there are a vast number of solutions to one problem, it is usually either because *everything* works, or because *nothing* works. I have come to believe that the diversity in finishing techniques can be attributed to the latter: everything has its serious drawbacks. Every finish is a compromise, and each luthier must decide which attributes are most important and choose the finish that matches these attributes. That leads me to oil varnish: it gives the greatest depth of appearance, has great chemical resistance, it's durable enough, glossy enough, and it doesn't pose particularly major health risks. For that, I can deal with the skill and time it takes to get a good finish out of it. I do like shellac quite a bit too, whether French polished or brushed, but that gives up chemical resistance and some durability to gain ease of use. There are poisons less toxic than lacquer, and I don't have a spray booth, so I'm not touching that.

My varnish of choice for now is actually of the Ace Hardware variety, the can simply labelled "Varnish". It's probably either alkyd or phenolic resin based. It's cheap, and I find it gives the same results with fewer quirks than some of the more popular varnishes. The Ace Spar varnish was actually recommended to me by a violin maker, but it seemed a bit softer than the "regular" varnish, and I found the UV blockers made it look goofy under fluorescent lights. I currently use damar resin dissolved in toluene as a sealer, 2-hour epoxy from the hardware store as a filler, followed by another coat of the damar, and finally the varnish.

Water-borne finishes are an interesting matter. They are usually something along the lines of oil-in-water emulsions, with who-knows-what in the oil phase. Just about anything can be made into a water-borne emulsion finish, including oil varnish. Also, with emulsions you can take the same materials in the same quantities, mix them in two slightly different ways, and get two completely different results. Therefore, water-borne finishes simply cannot be categorized. However, there is one relevant characteristic of the entire format: it takes some real effort to get a water-borne emulsion to light up the grain of wood very well. It almost seems like it dries with some sort of roughness where it meets the wood. Al Carruth once showed me two pieces of mahogany from the same billet; one had sections finished in a variety of water-borne lacquers, the other had a coat of oil varnish on it. I literally laughed out loud: every one of the water-borne finishes made the wood look like laminate flooring next to the great depth of the varnished piece. For that reason, I would not dare to use a water-borne finish without a good sealer.

I've actually been experimenting with making an oil-in-water emulsion out of the Ace varnish. Not much luck so far, but that could change. Emulsion coatings do have some real benefits if used properly, not the least of which is that it can be cleaned up with water.

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Andrew Gamble
Sine Guitars
Custom Low-Impedance Pickups and Preamps
[url]sineguitars.webs.com[/url]

Amber doesn't really dissolve in alcohol. It just softens it a bit. If you spill alcohol on the finish it will become tacky and gummy, so as a result it can be french polished (as in the technique way, no shellac involved)
Next resin in hardness is copal, which can be even semi fossil (amber is fossil and millions of years old - it contains all sort of Jurassic Park bugs in it) Copal is easily softened by alcohol but I didn't manage to disolve it at room temp, not even after 3 weeks. The one I tried is an expensive variety from Madagascar. It seems you need to boil the solution a few times.
The resins that really work easily are sandarac, benzoin and mastic. I never used mastic, it is a soft one (and utterly expensive) used to add suppleness to the finish. Sandarac is hard and brittle so it should not be added too much. Benzoin has a wonderful smell and probably has a softening effect too - could not find much info in this yet. Most people do not add more than 10% resins to the shellac. I can't comment on them making it more resistant as I just finished the first guitar with resins 1 week ago. But the FP, the few leveling sessions and the rottenstone polishing (performed only after 3 days) went very well.

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Build log

Favourite finish? Has to be an oil varnish, largely because of the visual effect it has on wood. From a practical point of view, brushed (or perhaps sprayed) spirit seems a decent alternative. Takes about 30 minutes in total to get all the finish on. Any longer than that and your brush is sticking to the wood. Fumes are bearable (maybe desirable!), it's easy to make, brushes don't need to be cleaned and dust isn't really an issue. The only problem that I've found is that it's seriously difficult to execute. Makes French Polishing seem like a stroll in the park.

Oil varnish. No finish comes close in the way it refracts light on wood and how it warms things up. It's also relatively easy to achieve a thin, solid finish, although it is more time and labour intensive than any other finish. It is well adapted to the scale of my operation, a one man (small) shop, and compared to other finishes, pretty benign in terms of toxicity. Still, I can't stress enough the importance to use proper safety equipment (mask, gloves, fan etc.).
I've not tried the newest waterborne finishes, but they look better than ever for the small shop. I may try at some point in the future, the fast curing time is attractive.
Finish preference is mostly a technique preference, adapted to the scale of an operation. Most modern finishes require a serious investment in equipment, materials disposal etc. and thus are more adapted to production or factory settings. I would think the same of nitro-cellulose: I find it suicidal to use nitro without a properly ventilated spray booth and curing room. Modern catalysed and urethane finishes use solvents that are pretty lethal, even compared to lacquer thinner, but they outgas for a very short time and polymerise very quickly, becoming inert. Thus, in the long run, they're much less toxic than nitro that outgasses forever.

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

Laurent. I'm curious as to why you find it more labour intensive than something like FP. I actually find it takes me longer to clean the brush thoroughly than to apply a coat of oil varnish. To the point where I'm thinking of using throwaway foam brushes.
Of course you have to scuff sand between coats and there is the lengthy final flattening and buff. I still think I spend more time F.Polishing an instrument. Then again perhaps I make F.Polishing a far too long, drawn out process.

Three coats of shellac sanding with 320 in between. Rub out with fine steel wool and wax. To bad no one will buy that though so I keep on trying new stuff. I'm currently going back to oil varnish after waffling thru about everything else, including oil varnish. Wish me luck!

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Tickle your guitar daily, and it'll tickle you back.

John - I assume you mean three coats of brush-applied shellac. Will no one buy that because it is not "french polished"? In your opinion, is it as durable as a french polished finish? You've got me curious.

I don't know but I'm not being entirely serious either. I like rough looking finish's but it is personal taste (or lack of). I would only do this to a guitar that was not leaving. I would rub on something brownish and then brush on a few coats of shellac, then rub a dub dub and stringer up

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Tickle your guitar daily, and it'll tickle you back.

Gotcha, thanks John. As I get ready to finish my first build and consider the merits of the different finish options, I must admit the simplicity and relative inertness of a brushed shellac finish does sound very appealing.

This thread has been VERY informative! Thanks to everyone for the information. I love this forum!

But a brushed Shellac finish is NOT that easy to do well, unless you use retarders or you happen to be very good with a brush/technique. Try it! Start adding colour to the mix and things suddenly get even more difficult.
I've tried the 1704 recipe - the Benzoin makes it smell divine. If I could get my brush technique much better it would probably become my standard finish.

Michael, I do not use FP, as I do not think it suitable for a steel string. At least not one I wish to sell. I think some people can achieve a good FP finish in less than a day, or so they say.
Yes, oil varnish requires at least scuffing between the coats, and perfect levelling toward the last coats. Open coat 3M or Norton sandpaper really helps, but at between 6 and 12 coats (depending on the varnish and skill) it is still a lot of labour and time. One can't lay varnish too thick without catastrophic results. Some varnishes require 48h curing after each coat, it's a long time for the guitar to stay in the shop. I do spray the varnish BTW, although I brushed a dozen guitars with excellent results before deciding life was too short. I am not complaining: I love my finish and wouldn't do anything else at the moment, but I'll admit oil varnish finishing is not the easiest technique to master, nor the most economical way to finish a guitar.
Compare that with poly, urethane or catalysed finishes that cure almost instantly and can be sprayed thick. Depending on the equipment and skill, one can finish an instrument in one to three days. Even recent waterborne finishes cure much faster than varnish.

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

Hey, Just yesterday I sanded out 2 brushed coats of varnish.
I really like this stuff!
I am using Old Masters brand.
Really levels out nice!
I think 2 more coats sprayed will do it.
Weather ain't permitting now.
The varnish really brings out the gold color in the koa.
This may be my new default finish!
Thanks for the tips on sealing the coco, Laurent!
Alan

The main hesitation I have had about oil varnish is the amber color it seems to impart on a spruce top...I do prefer a very light colored top. Are there any good oil varnishes that have no (or minimal) amber tint?

Since my concern is primarily with the top, and the warmth and grain enhancement offered by oil varnish on the B&S is actually appealing to me, is it possible to use the varnish on the B&S and another finish on the top? My concern there is compatibility issues where the two finishes meet at the edges.

BTW - I do not have any spray equipment so brushing is my only option at this point. It sounds as a nice finish can be achieved with brushed varnish.

For me a complete (sprayed) oil varnish finish takes ~4 hours actual working time. The curing time is much longer but I have areas where guitars can hang while curing without getting in my way. The total calender time is usually 2 weeks, but can take longer. Nitrocellouse lacquer, catalyzed urethane, or catalyzed polyester takes me an hour less or so. Nitro has to cure a LONG time to get what I consider a good finish. The calender time is usually ~6 weeks with nitro. Catalyzed urethane is usually around 2 to 3 weeks. It hardens quickly, but shrinks for a while so you have to wait before buffing. Calender time for a polyester finish can be a week or even less since it cures quickly, and doesn't shrink much at all.

The catch is, 2 oil varnish guitars, finished at the same time would take pretty much twice as much time as finishing one. Catalyzed finishes, and even Nitro to some extent don't require as much attention between coats so finishing 10 guitars at once may not even take twice as long as finishing 1.
I'm not claiming to be a finish expert, but I'm not some self proclaimed know it all who's just posting stuff I've read somewhere. (I'm not saying anyone in this thread is just posting stuff they've read, but it happens online all the time) I've used all of the finishes I've mentioned. I'll post some pictures later if anyone wants to see them, but this isn't really a picture thread. I done a little French Polishing years ago, but pretty much all I remember is it made my arm tired. LOL

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I didn't mean to say it, but I meant what I said.
http://www.brackettinstruments.com/

Woody - I, for one, would love to see some photos!

You're welcome, glad it worked out.
Ace Hardware interior varnish, Behlen's water white restoration varnish and Pratt&Lambert #38 are pale varnishes. Unless your finish is .010" thick, they all will be pretty light in colour. Epifanes is a tad more amber than those, and the darkest amber is Behlen's Rockhard, by a long stretch.

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

C'mon Woody!
I've been sick for a week now,
it's rainin' out,
all I can do is play my geetars,
and poke around the forums.

Thanks for that, Laurent!

Sorry, long time before I got back to this. My main concern is over what picks could do to the finish. I usually play fingerstyle on steel-string guitars, and my own SS I built for myself is French Polished.

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Jim Kirby
kirby@udel.edu

While I have never finished a guitar with it, I don't see why a brush grade lacquer wouldn't work. I have fished more than a few pieces of furniture over the years with Watco's brushing lacquer. It can be sanded and buffed and in fact even continues to self level over the course of 2-3 weeks as it completely cures. There is a technique to applying it, and I recommend a quality badger brush for best results. This may be a good alternative for those of you who would like to use lacquer but can not spray it for whatever reason. While the air does not hang heavy with standoff, fumes are still present and a respirator should be worn. Just a thought.
Brian

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Brian

You never know what you are capable of until you actually try.

https://www.howardguitarsdelaware.com/

Although I can't comment on the specific product you mentioned, furniture lacquer is usually too hard for musical instrument use. Instrument lacquer has stuff added to it to make it more flexible, and less prone to checking. It's my belief that harder finishes are also bad for tone. You can brush instrument lacquer (like Mohawk, Behlens, Seagrave ect) by adding a little retarder. The retarder is needed so it doesn't dry before the brush marks flow out.

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I didn't mean to say it, but I meant what I said.
http://www.brackettinstruments.com/

Be careful what you ask for............, and Laurent, I love looking at your guitars, how 'bout some pics of them.


This is a nitro finish, on a manufacturered guitar I re finished last year. (Mohawk)



This is a (catalyzed) Polyester finish. (Mcfaddens)



This is a catalyzed Urethane finish. (ML Campbell)



This is Epifanes Oil Varnish


This is Sherwin Williams Oil Varnish. It's my current varnish choice. It cures a little quicker than Epifanes. You can recoat in ~4 hours, instead of waiting overnight or longer.

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I didn't mean to say it, but I meant what I said.
http://www.brackettinstruments.com/