Official Luthiers Forum!

Probably been covered before but - I have some nice reddish bearclaw spruce. I have stained bearclaw before with a light amber stain, and it brings out the patterns nicely, becoming almost 3D when the lacquer is applied. I don't want to stain this spruce as I really like the reddish color (I know it won't stay that way) but I would like to make the bearclaw pop a little. Any suggestions?

thanks,
Damon

_________________
Damon Wack
https://www.facebook.com/LindamonGuitars

Clear or Blonde De-Waxed shellac

_________________
Bill Hodge


One does not simply, own enough guitars!

In the French polishing parts of Ervin Somogyi's books, he mentions mixing some walnut oil in with the shellac when doing the initial spit coats if you want a wet, "deep" grained look. I haven't tried it myself yet, but I suspect it would work well on a bearclaw spruce top, although it will likely darken more than with pure shellac (which does pop figure pretty well by itself). Walnut oil will eventually dry, so it's ok to let some soak into the wood. Be sure and run tests on any method before putting it on the guitar though

Oil varnish. Or use Waterlox as a sealer, still an oil varnish.

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

I actually just used walnut instead of olive for a spitcoat yesterday and I don't see any difference. But it is just a few drops for the entire guitar. I wouldn't have the guts to use a larger quantity

_________________
Build log

What you want to do is use a finish with roughly the same refractive index as the wood itself, effectively allowing you to see into the wood a little bit. Wood is translucent, but it has a rough surface so the surface looks flat and opaque. Think frosted glass. When you apply a finish with the right refractive index, the wood and finish basically become one optically. The smooth surface of the finish does not scatter light the way the surface of the wood did, so it looks more clear and the figure becomes more noticeable. The layer of finish in direct contact with the wood is the most important in achieving this effect.

Things that are good for this include shellac, oil, most oil varnishes, and to a lesser extent laquer, epoxy and polyurethane. Things that are bad for this include vinyl sealer and most water-based finishes. Opaque pore filler, in my opinion, is the worst. Stain can make figured wood look good in pictures, but it loses some of the 3d effect where it looks like it's in motion when you look at it from different angles.

The best thing I have found for getting the grain to pop is damar varnish: just damar resin dissolved in turpentine. It gives a noticeable improvement to the apparent depth of the finish compared with shellac or oil. You can get damar for $10 a pound. I would recommend seeking out some real turpentine for this; hardware store turpentine often has other junk in it (even if it says it's pure), and I've had some problems with it. Art suppliers should have the good stuff. Damar should also be soluble in mineral spirits, toluene, xylene, etc., but I haven't tried any of that.

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

That is interesting Andy! I personally wouldn't use it on an acoustic guitar. This is an excerpt of an article written on another site a couple of years ago regarding damar.

"......in a nutshell: natural resins like damar, mastic, amber, and so on, are all vulnerable to environmental degradation as a result of exposure to ultraviolet light, heat, and moisture. They all eventually cross-link and become less soluble; they all yellow; they all become brittle and crack......."

No offense intended, but for the reasons mentioned above, I would personally choose to not use it on any of my guitars no matter how well it 'pops' the figure. Just my thoughts offered on the subject.

_________________
Bill Hodge


One does not simply, own enough guitars!

Bill, who wrote that article, and how did he come to that conclusion? Seems he's heaping the natural resins "and so on" into a pile and condemning them.
Shellac is a natural resin, Sandarac is a natural resin, Amber too. They are all unsuitable for varnishes and finishes? They become hard over time?
Sounds like a feature!
I have not used Damar, so maybe it is terrible, I don't know.

_________________
https://www.facebook.com/profile.php?id=100008907949110

Very hard varnishes can become brittle and chippy off violins but there's a long way from that to an extremely thin seal coat I guess.

_________________
Build log

It was written by AMIEN (The Art Materials Information and Education Network). The article is enough of a discomfort that I would personally not use it on an acoustic. Others can if they wish but I won't. I wouldn't use it on furniture either unless I was looking to achieve natural looking crackled antique finish over a shorter period of time. Just makes me feel better personally.

_________________
Bill Hodge


One does not simply, own enough guitars!

Thanks for writing that. Interesting stuff!

All of those concerns also apply to shellac, varnish, polyurethane, and especially lacquer. In fact, damar is a fairly soft resin, and it's pretty stable, so it's not going to become brittle and crack for a very long time. Damar is significantly softer, more flexible, and theoretically more UV stable than shellac (I forget where I read that last part, I could be wrong). If you don't have a problem with shellac, then you really shouldn't have a problem with damar.

Actually, of the three resins this author lists, only amber is going to become brittle and crack, but that's because the stuff is brittle to begin with. Mastic and damar are pretty close to the least likely to become brittle of any natural resins I'm aware of. The notion that the concerns listed rule out these resins is simply absurd.

The cross-linking mentioned is precisely what we want: the finish becomes more durable and less soluble as it ages. Almost all finishes yellow over time, and damar has a reputation for doing so relatively little. In fact, the conventional use for damar varnish is as a sealer over oil paintings. You can't have too much yellowing in that application. Also, that would be on canvas, where a brittle varnish would be useless.

In every area of concern mentioned damar varnish will fare much, much better than nitrocellulose.


Todd, are you saying that the index of refraction doesn't matter as long as the material is clear? Or a higher IR is better? Air is clear, and it has an IR of about 1.0003; obviously, it does not enhance the grain significantly. If I remember correctly, polyurethane's index of refraction is about 1.75 (pretty high), and that isn't very good for grain enhancement either. We're trying to see through the top layer of wood, and to do that we want the finish to be as close as possible to the refractive index of the wood itself (somewhere in the vicinity of 1.5). I think it certainly does matter what the material is. Try putting some water-based lacquer, vinyl sealer, oil varnish and shellac all next to each other on a piece of stripey mahogany. All of those materials are fairly clear, but I suspect you would vow never to use water-based lacquer or vinyl ever again.

I'll have to do some more experimentation with epoxy. I've only tested it as a sealer/filler once, and it did look pretty good, though not quite as chatoyant as damar. I expect different epoxies have different optical qualities as well.

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

OK Andy, I'll do some more detailed investigation of Damar Resin. I've been finishing wood for over 30 years, but with that said, I also have not tried or used everything there is available for wood finishing. The range of finishes that would benefit acoustic guitars is limited, but I'll never allow myself be too old to learn, or too proud to eat humble pie! Sometimes it just takes someone else convincing me to try something based upon their successful experiences. A little over a year ago I was completely against waterborne finishes. With some convincing from others in the forum based upon their experiences, I've been using Target EM6000 with great results, but only after "popping the grain" with shellac or true oil as a base. If I find enough information to satisfy me into trying it, I'll retract what I posted earlier. If not, I'll leave it be for those who are interested.

_________________
Bill Hodge


One does not simply, own enough guitars!

You have a darn good attitude Bill. I'm not surprised that water-based lacquer could work quite well over something with reasonable refractive properties as a sealer. Applied directly to wood though, it looks like a faux-wood laminate countertop . Recently I've been trying to concoct a natural resin oil varnish that will be suitable for guitars. It looks to me like that will be my primary finish when I get it figured out.

For the record, I have not tried using damar varnish as the finish on a guitar; I've only used it as a sealer in a very thin coat. It may or may not work as a finish by itself. I suspect it would be a bit softer than we want, and not terribly durable. I have attempted a cooked oil varnish with damar as the main resin, and it turned out much softer than I'd want on a guitar. Seems like it would be perfect for a violin, though.

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

As an artist (painter) I can tell you that Damar varnish is the finish of choice for oil painters. I would think that it does to wood exactly what it does to paint, make's it pops and unifies everything with a highly reflective sheen. As for yellowing (and I am only speaking for oil paint here) from my experience, the oil is far more likely to yellow than the damar, although the damar will crack as the paint expands and contracts (especially if the artist did not shellac/seal the material used, be it canvas, wood (my 1st choice) or masonite (my second choice). However, damar will last for years before it cracks on a painting, which is pretty much the worst of conditions....soft pliable film which reacts with temperature and humidity. Although wood shares these properties, it is far more rigid, which is why I always paint on wood, but never wood on paint . In any event, no finish will last forever and refinishing a guitar is far from impossible. If damar gives you the look you are looking for and will last 10 to 20 years, go for it. I believe that is what Somagyi is doing when he adds oil to a finish.

....on that note someone mentioned adding oil to a finish earlier. Personally I would not do that on a guitar unless it was sealed first, especially since I don't have the experience of Somagyi. Of course I apply much more oil onto a piece of wood for a painting than would be applied on a guitar, but the oil I use (linseed or poppy oil) quickly soaks into the wood and rapidly deteriorates it to the point that it is visually and physically noticeably weaker within a few hours. I don't believe that tongue oil "finish" is really an oil, as is "pure" tongue oil, but rather a heavier drying oil mixed with some other stuff, but I have never noticed the same affect using it to refinish any of my crappy factory made guitars. I do know other painters that use the pure tongue oil over linseed, because it does not yellow or deteriorate as readily as linseed, however, I've never had any of my paintings rot/mold, so I've never made the switch myself despite the yellowing properties of linseed.

I read quite a bit of the writings at that AMIEN site, and for woodworking use, I think their recommendations are pretty much not applicable. It is all about oil on canvas, art stuff.

_________________
https://www.facebook.com/profile.php?id=100008907949110

Several years ago I tried the side by side comparison (on Rosewood) between Shellac and Oil Varnish. The Oil certainly enhanced the colour variation of the grain for a more lively and dramatic effect. The Varnish was home made pine resin. I'm also currently trying a hybrid of seedlac, Benzoin and Sandarac with added Walnut oil. Early indications suggest that it's a little harder than straight processed Shellac but it's early days. Whether it gives problems later on with crazing/chipping is an unknown. That's something to monitor with any Spirit or Oil Varnish where the objective is to produce a harder surface finish.
I suppose the other alternative is to go for one of the wipe on finishes such as Danish Oil or Tru Oil. They may not stand up to rigorous use but it's pretty dang easy to maintain the finish every few years.

Visually, there is no comparison between shellac and varnishes (or oils) on wood. The more complex the structure of the wood, the more obvious. Try shellac and oil varnish on two similar pieces of ziricote for example, and it becomes obvious. Varnish will enhance the colour variegations, giving the whole a warm, brownish tint. Shellac will keep the greenish tint of the ziricote, lacking both depth and colour. The same is true on rosewoods, and even spruce. However oils and varnishes hardly cure on oily woods, and need to be considerably thinned to seal the oils. Burton suggested wiping a thin coat of Waterlox on and off, and I will try that. I remember Waterlox taking forever to cure on cocobolo, something like a week or so, although eventually it cured enough for subsequent coats of varnish to be sprayed.
One thing I do when I use shellac as a seal coat is to wipe on and off a thinned coat of linseed oil before spraying the shellac. It seems to enhance the grain much as varnish does. I suppose any oil would work, tung, linseed, whatever.

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

I do have a feeling that shellac may be one of the least grain-enhancing of natural resins, although I do not know why. It has exactly the refractive index I would be looking for, but you're right, it usually doesn't look great next to some other stuff. It's still very good compared to most synthetic finishes, but it's certainly not the best thing available.

Oil does do quite well at enhancing wood grain, but I don't really like the idea of having a bunch of oil in the wood. Oil dries to a somewhat rubbery mass that has very high damping, so I feel it would affect tone in a negative way if it is inside the wood. Also, if the top were to crack, you are now dealing with gluing to an oily surface to repair it. The same problems exist to a lesser extent with an oil varnish, which is why I like to use an oil-free sealer under it.

The reason that oil finishes do not dry on some woods is either that these woods contain antioxidants (which prevent the oil from oxidizing, which is how it dries), or that there are non-drying oils in the wood that adulterate the drying oil in the finish, effectively making it into a semi-drying oil. Cocobolo has a lot of both of these problems.

I've found that damar does a better job of grain augmentation than oil does. It also has most of the attributes I want in a sealer (not brittle, very good adhesion, color retention, etc.), so that's what I'll use until I find something better (which I'm sure will happen soon). I sure wish the stuff was alcohol soluble though, turpentine takes a lot longer to really dry. Maybe I'll try using something nasty like toluene.

I have determined that really stripey quartersawn wood (like sapele) is the ultimate test of the refractive properties of a finish. There's really an amazingly obvious difference between good and bad in that application. I strongly encourage experimentation.

Micheal, if your spirit varnish turns out to be too brittle I would suggest adding a few drops of castor oil, an alcohol-soluble semi-drying oil, as a plasticizer. Benzoin and sandarac are both pretty hard resins. Good to see another guitar maker making varnish.

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

What exactly is damar? Is it a pre-existing product? How do you apply it?

Damar (also spelled dammar) is a tree resin from Asia available in solid chunks. Dissolve it in turpentine just as you would shellac in alcohol. About a 2-lb cut works fine, it doesn't really matter too much. I brush it on, you could also pad it on, or pretend it's shellac and French polish it. I don't see any reason why you shouldn't spray it. It won't fill the pores any more than shellac does, but that won't matter on spruce.

I buy it from http://www.woodfinishingenterprises.com/varnish.html, scroll down to Singapore Damar. It's less than half the price of shellac.

More information can be found here: http://en.wikipedia.org/wiki/Damar_resin

You can buy pre-mixed damar varnish from art suppliers, but I have heard stories of it not fully drying, much like pre-mixed shellac that has gone bad.

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

It sounds like an experiment is definitely in order. I have what I believe is an unusable quilted sapele back. I'm going to look at it again over the weekend, and if it truly is too thin for a back, I'm going to wipe a section with shellac, another with vinyl sealer, another with Rock Hard, one with Waterlox, and another with damar. I have a soundboard gone bad that I can use, too.

So just to confirm, you're using damar as your seal coat with nitro over it? What kind of filler do you use?

Laurent, are you referring to Waterlox Original or Waterlox High Gloss? From what I read on the website, it seems like Waterlox Original might be a semi-gloss.

Sweet. Please post the results of your experiment. I'd also request a section with nitro (straight onto the wood), and another with damar dissolved in toluene (or lacquer thinner), if it isn't any trouble. Epoxy would be cool too. Make sure you use enough of each that it just starts to build a film.

I do not use nitro, I think it's too darn toxic, doesn't age well, and doesn't look particularly good. I use mainly shellac and Rock Hard varnish, although I hope to be switching to a home-cooked natural oil varnish when I get it figured out. I use shellac and pumice for pore filling, although that is the part of my finishing process that I am least happy with. It's just the least bad thing I've gotten to work consistently so far. The normal opaque fillers will never touch one of my guitars. Damar and pumice does not work well, unfortunately. I've also tried adapting methods from violin makers, but those don't seem to translate well to real pores (as opposed to maple pores). I haven't tried epoxy, that would probably get acceptable results, but it's toxic and not natural. What I may end up doing is brush on a coat of thick damar, sand down to wood, and repeat until the pores are filled.

Good luck.

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

My method consists of wiping oil on and off before sealing, so there is certainly not a "bunch of oil" in the wood. Nor is there additional damping or oily surfaces to repair, just a very, very thin film sealed by a coat of shellac. As a matter of fact the guitars I've finished this way are the best sounding to date, and I do not attribute this to the finish.
OTOH this meme about oil varnishes being more penetrating than other finishes is simply not true. At least not with the hard varnishes suitable for guitars. Actually the main issue with most oil varnishes is poor adhesion: the film lifts easily from the wood, leaving a clean, raw surface. Hence the need of a sealer, whereas shellac or successive thinned coats of oil varnish.
Waterlox original, as recommended by Rick Turner. Of all the oil varnishes it has the best adhesion, actually it adheres much more than any sealer/finish I know, including shellac. It comes very thin in the can, and I've used it as a sealer only. Semi-gloss would mean it has flattening agents added to it, which seems unlikely. However it is so thin that it acts almost as an oil: to get a bit of body and gloss would require many coats. And no, it is not "penetrating" either.

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