Gibson Finishes

[RobAlan]

Can anyone tell me please what finish was used on vintage Teens and 20's Gibson mandolins?

Thank you.

[sunburst]

In a word, "no".
In the teens, Gibson was using some sort of spirit varnish. Some think it was pure shellac, some think it had other "stuff" in it, nobody that I know of knows for sure.
In the early 20s, at least on the Loars, they apparently used a sealer of some sort ,followed by an oil varnish, followed by a french polish gloss coat of shellac or spirit varnish.
Sometime around late 1924 they started using nitrocellulose lacquer.

[man dough nollij]

Originally Posted by sunburst

In the early 20s, at least on the Loars, they apparently used a sealer of some sort ,followed by an oil varnish, followed by a french polish gloss coat of shellac or spirit varnish.

John, I'm one of many who gets lost in the definition of varnish and shellac. You say "shellac or spirit varnish". Isn't shellac normally applied via spirit varnish? I've seen threads here that explain that shellac is a resin made up of dried bug parts, which is usually applied by dissolving it in ethanol and applying with a dauber (and a little oil for smoothness), intermittently polishing it out with alcohol to make it shiny. Isn't that French polishing with shellac, or am I understanding it wrong?

Thanks,

Lee

[Jim Hilburn]

While shellac dissolved in alcohol can be considered a "spirit varnish", it is often simply called shellac.
When shellac is prepared with other additives like sanarac and gum mastic, it is more likely to be called a spirit varnish, although some still just call it shellac.
Remember the term varnish is pretty much like saying paint. It needs a lot more qualifications to know what your actually talking about.

[Martyweir]

"I'm one of many who gets lost in the definition of varnish and shellac."

X2 here! To quote wiki: "lacquer is a clear or coloured varnish" – boy, that makes it about as clear as mud...

No doubt someone will clarify, and correct me when I'm wrong here, but from the what I can gather in my limited research, shellac (yes it comes from bug secretions) is one type of "resin" or the build-up coating material in some varnish and lacquers. It's the shiny hard stuff. Depending on what type of solvents, hardeners, and other additives are mixed in with it to produce the can of liquid shiny hard stuff, determines whether it is a "lacquer" or "varnish". You can apply shellac pure - dissolved in alcohol to apply it as you described above, but a lot of guys on here say it’s pretty soft when done this way. In that case is it considered lacquer? Varnish? No Idea. From what I can tell, not all varnishes & lacquers use shellac as the primary resin - nitrocellulose lacquer uses (shockingly) nitrocellulose as the resin. Basically a plastic resin is produced by exposing cellulose (think wood pulp) to nitric acid, etc (common organic compound). The product is hard, water resistant, and has low solubility once it cures. Varnish is not as stable apparently, and if you spill your martini on your mando…

Another difference is possibly the inclusion of a “drying oil” (like, Tung oil, linseed oil, etc) in varnish. These oils can be used in pure form just like shellac - now the question is – pure Tung oil: is it considered a lacquer or varnish? SOOOOO CONFUSED!!!

[sunburst]

For a brief overview of what is varnish and what is lacquer, you go to the glossary, look up "varnish" and "lacquer", then click them and you will find it in as few words as possible. (credited to yours truly)
If you really want to learn about lacquer and varnish, read Understanding Wood Finishing by Bob Flexner. If you learn and understand everything in that book, you'll know all you need to know about wood finishing no matter who you are!

[Rick Turner]

Marty, if varnish is not as stable as lacquer, then why don't yacht owners lacquer there brightwork? I would say that "varnish" is more stable than lacquer as well as being tougher, especially high quality spar varnish. The reasons why car, furniture, and instrument manufacturers switched to lacquer are ease of application and fast cure time. Lacquer does not protect wood better than varnish.

If you spill your Martini on a spirit varnished mando, you've got problems. If you spill varnish on your oil varnished mando, you can wipe it right off.

Pure tung oil is NOT varnish because it does not have any dissolved resins in it. It's a drying oil.

Varnish is a compound starting with either shellac (which makes it a spirit based coating) or a drying oil, usually linseed or tung (there are other drying oils including "spike" which is lavender) to which is added resins like phenolic, urethane, alkyd, copal, etc. to add toughness, hardness, flexibility, etc.

Many "oil finishes" like TruOil, Waterlox, Zar tung oil, Formby's tung oil, etc. are, in fact, varnishes because they've had resins added.

How do you tell what's an oil, what's a spirit varnish, and what's an oil varnish? You read the ingredients, not the marketing hype.

[Rick Turner]

BTW, "spar varnish" has UV inhibitors added as well so the coating will hold up in sunlight.

[Martyweir]

Rick, Thanks for the clarification.

I don't know the answer to the yacht question, but I could guess that flexibility has a whole lot to do with it. A spar varnish is tung oil based and would be more flexible than a brittle lacquer finish, wouldn't it? I think by stable, I ment in terms of reactivity & solubility - another dangerous generalization... Oh well.

Boats... I can't wait until spring!

[Rick Turner]

Nitro lacquer is reactive and soluble. It outgasses nitric acid which is one of the reasons why gold and nickel plated hardware goes so bad when the instruments are locked up in cases. It breaks down as it loses plasticizers. It's very soluble in solvents like acetone, butyl acetate, acetal acetate, MEK, etc., though it hold up reasonably well to alcohol spills.

Oil varnishes polymerize which nitro lacquer does not, and that cross-linking makes the stuff pretty stable, hence we have violins that are 300 years old with original varnish which may be worn in places, but is pretty tough where not abraded by several centuries of handling.

I'm typing right now on a keyboard on a 250 year old table with it's original finish. I haven't tried alcohol on a hidden spot to see if it's spirit or oil varnish, but aside from normal wear and tear, the finish is in better shape than I see on instruments made in the late '20s that were lacquered with early nitro. Next to me is a 400 year old "Jacobean" blanket chest with what is probably a linseed oil finish. It looks pretty good, too! I might hit the top with a thin coat of Waterlox...