Varnish

Construction and repair of Classical Guitar and related instruments

Varnish

Postby Anthony Campanella » Sun Apr 08, 2007 3:56 am

In the past I’ve seen varnish recipes which included “copal amber”
I didn’t have any reason to investigate this but I was somewhat skeptical because I knew amber to be fossilized tree resin, some millions of years old, which can be as valuable and as hard as some gemstones. On a recent trip to a museum though, I was able to purchase this nugget of copal amber for under a dollar. I found out that copal amber is immature amber, hundreds to thousands of years old. It’s not easy to describe the hardness. It reminds me of a hard plastic, which, for a natural material seems ideal for a finishing product.
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Postby Michael.N. » Sun Apr 08, 2007 1:13 pm

I don't think 'copal amber' as such exists. It's probably just be termed wrongly. You've either got Amber or Copal. Both will make a fine varnish and the Copal in oil is like the old fashioned coach varnish that is still sold by specialist suppliers. Trying to incorporate it into oil isn't easy and involves pretty high temperatures, it's dangerous and the fumes are something to be avoided. I tried once and gave up because of the fumes even though the process was carried out of doors. Spirit is much easier.
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Postby Anthony Campanella » Mon Apr 09, 2007 12:43 am

I wouldn't' suggest making it. I think its available from some of the violin suppliers

From or friends at Wiki- ""Copal is a type of resin produced by plant or tree secretions, particularly identified with the forms of aromatic tree resins used by the cultures of pre-Columbian Mesoamerica as a ceremonially burned incense, as well as for a number of other purposes.[1] More generically, the term copal is now also used to describe resinous substances in an intermediate stage of polymerization and hardening between more viscous and 'gummy' resins and amber.[2]
The word copal is derived from the Nahuatl language word copalli, meaning "incense". "" Apparently the Mayans were fond of the fumes !

As indicated above [2} One of the terminology usages of "copal" is the intermediate stage of hardness, between its gummy tree resin origins (which is more easily used for spirit varnish) to its ultimate fossilization

Whats most interesting and appropriate about it is that it's a product made from trees to (finish) protect and beautify - wood
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Postby Michael.N. » Mon Apr 09, 2007 7:40 am

The terminology used for much of the gums and resins is confusing. True Amber is a fossilised resin, Copal is a more recent resin and can vary depending on it's age but can be found in a semi fossilised state. You also have to be careful when following some of the ancient Lute and Violin varnish recipes largely because the use and meaning of some of the terms has changed over time. The pegbox forum at Maestronet has lots of information on the use and application of the types of varnishes made from the various gums and resins, fiddle makers take this sort of thing very seriously.
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Postby Anthony Campanella » Mon Apr 09, 2007 11:24 am

Thanks for that link http://www.maestronet.com/index.cfm. There are some stunning photos of some of the finest bowed instruments ever made(?)
Very active forum for builders - are you involved in violin making?
You're right - I would'nt dare make any statements concerning varnish there
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Postby Michael.N. » Mon Apr 09, 2007 12:15 pm

I don't make violins although I share a workshop with a someone who does. My main interest is in Lutes and guitars. Although I do make a small modern instrument I prefer making earlier types such as the Romantic guitar and the
cute smaller Torres. That explains my interest in oil varnishes and why I take an interest in violin making. There is an oil mastic recipe that doesn't need to be cooked and is very easy to produce, on the Maestronet forum they refer to it as the Michael Darnton recipe. It's a little too easily worn for guitars and I use a cooked pine resin varnish courtesy of my violin making friend.
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Postby Anthony Campanella » Mon Apr 09, 2007 12:23 pm

These resin varnishes - are they more durable than shellac? lacquer?
Do you hand polish to a gloss finish - pumice/rottenstone?

Have you seen much in the way of wire strung romantic guitars?

Thanks for your time
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Postby Michael.N. » Mon Apr 09, 2007 2:41 pm

Big can of worms regarding durability and what some people term 'toughness'. If by laquer you mean the modern nitro-cellulose then I doubt that any of the natural resins are as durable. Violin makers refer to Shellac as being 'bombproof' but some classical guitar players think it wears too readily. It all depends on what you are trying to achieve as to which one you use. Shellac using the technique of French Polishing should result in a very high gloss finish and great depth with a minimal amount of the said polish on the actual instrument. The actual shellac layer is very thin which is why it can rub off over a few years with the constant friction. Some makers add a small amount of a resin like Benzoin to 'toughen it up', too much of this resin can make it brittle and chippy.
Typical oil varnish is applied with a brush and usually results in a thicker layer but you wouldn't really call them tough, not in the sense of modern chemical finishes. They can be polished to a high gloss but not to the depth of a French polished finish, their beauty lies in the fact that the oil and resin content really helps to 'pop the grain'. Many of the high end fiddle makers simply don't like the look of a flat over polished surface, the so called Ferrari look, for them it lacks visual interest. It's a bit like looking at a Steinway grand piano finish, impressive at first sight but becomes boring after only a few seconds. With Lutes and Violins you can finish the wood with a scraper and start applying a finish. The resultant textured surface is probably historically correct. If you used this technique on modern guitars you would fast become known as a shoddy maker, no matter how competent the woodwork. Sad but true.

I can't say I've come across wire strung Romantic guitars although I certainly wouldn't consider myself an expert on them.
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Postby Alexandru Marian » Tue Apr 10, 2007 1:54 pm

This is interesting. I am currently building my first guitar and between stages of the work on the top, I am looking on how the wood looks after various operations such as scraping or sanding. I have to say that fine scraping with a shaving blade gives the nicest look, polished being one important aspect when compared to sanded.
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Postby Anthony Campanella » Tue Apr 10, 2007 10:13 pm

What will you finish your guitar with AlexM ?
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Postby Alexandru Marian » Wed Apr 11, 2007 6:15 am

I will try shellac. This is a great chance to learn how to do it - I wouldn't want to be in the dark with it when I'll start the second guitar. :roll:
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Postby EJplaystheCG » Thu Apr 12, 2007 1:27 pm

If you are FPing it, try sizing the spruce top with egg white (after mixing it well and letting it stand overnight). 1-2 coats, sand lightly with 400-600 grit 3M sandpaper, then FP it. It should give the top a nice 'old' look by raising the grain of the wider grain lines.

You could also add coffee or cocoa powder to the egg white to darken it, but I think that might be abit risky unless you try it on some scrap spruce first and let it sit around for awhile to see how it 'ages'. :)

I haven't tried the coffee/cocoa method but the first method works pretty much as it should.
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Postby Marcus Dominelli » Fri Apr 13, 2007 2:02 am

Oh yes, Varnish - the endless topic....I'll keep it short, even though the subject fascinates me....
I use several different spirit varnish recipes depending on the goal at hand. Copal does toughen the finish up a bit, but how much? I cannot really say. It is way harder to dissolve in alcohol, so I know the guitar will suffer less if the finished guitar gets wine spilled on it at a juerga or something....
A pretty good finish for toughness is two-thirds seedlac, one-third copal. Throw in a little mastic too, especially if you live in a place that gets really dry, and you're bad at humidifying the guitar. The mastic helps keep spider-web cracks at bay.
One of the others on the forum mentioned using egg-whites with coffee or something added to age the look. I have tried this but found it does'nt work too well. Try using seedlac as the first coat. Once the darkness you want is achieved, do the remainder of the finish with super-blonde shellac, adding copal to the super-blonde if you want.

Don't get oil in the wood!! especially a non-drying oil like olive or mineral oil. It will show up in the wood, and possibly soften the finish.

Build a U.V. booth and use this to darken the wood if you want a reliable method for aging - and it is consistent. Careful though with cedar tops; they darken very quickly.
Non of the shellac finishes are super-tough. But they are the most beautiful finishes, are very easy to repair, and virtually non-toxic. They are certainly the best finishes for musical reason's too.
Have fun learning how to french polish. It is well worth the effort!!

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Postby Michael.N. » Fri Apr 13, 2007 1:36 pm

Be very careful when building UV cabinets, not only because of the dangers of specific types of UV but for humidity reasons as well. If anyone is really interested in cabinets then read the threads over at Maestronet.
A safer way is to expose the sounboard of the instrument to natural light, commonly takes me 6 to 8 weeks to obtain the colour I desire -afraid that's the UK for you.
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Postby Anthony Campanella » Sat Apr 14, 2007 4:41 am

Great information - thanks to all!

At the risk of someone's displeasure -
I would like to ask how you think nitrocellulose lacquer compares to varnish and shellac. I think it has an undeserved bad reputation.
It's made from cellulose - wood fiber - ok, under the influence of nitric acid.
It's attractive and has outstanding clarity - self sealed, it pops grain like all get out.
Can be applied very thinly - 4 mils are typically recommended - 4/1000"
Thats about the thickness of a hair (Blonde 1⁄1500th to 1⁄500th inch -Black 1⁄400th to 1⁄250th inch - wiki)
So I'm not sure that film thickness needs to be an issue.

Anyway, I wouldn't classify it with the (popular) wholesale chemical finishes - conversion varnish and catalyzed lacquer.
I think its a lot finer than them.
I have a Ramirez that is suffering from a conversion varnish finish
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