Hand-rubbed nitro

Construction and repair of Classical Guitar and related instruments
tddarco
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Location: Vigo, Spain

Hand-rubbed nitro

Post by tddarco » Fri Jan 06, 2012 8:49 pm

Would someone be so kind as to enlighten me on this process? I just saw a 2010 Hauser an the GSI site with this finish. French polish I get. Just nitro is a synthetic spray, right? So, is it a combination of the two? Thanks. -Tony

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Anthony Campanella
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Re: Hand-rubbed nitro

Post by Anthony Campanella » Fri Jan 06, 2012 8:57 pm

Nitrocellulose Lacquer is made from wood fiber - its not synthetic
Sprayed - Hand-rubbed usually refers to the hand buffing and compounding for a very glossy finish

Robert Webster

Re: Hand-rubbed nitro

Post by Robert Webster » Fri Jan 06, 2012 9:59 pm

Alkyd resins that are in the varnish I use is made from the liquifided remains of dinosaurs and prehistoric plants. Does that make it nonsynthetic? I'd draw the line at a point where the raw material goes through some specific intentional modifications and subsequent purifications that renders the product chemically different from the starting material. The cellulose in nitrocellulose goes through some substantial processing before it's suitable for nitration and then is subjected to the nitration process. From a chemist's standpoint, I'd call that a synthetic product.

Bob

Brad Heinzen

Re: Hand-rubbed nitro

Post by Brad Heinzen » Sat Jan 07, 2012 5:06 am

I'm not entirely certain, but I think they mean that the nitrocellulose lacquer is rubbed out after being applied by spray equipment. You can buff out nitro for a higher gloss than you'd get from the spray gun.

Tongdee

Re: Hand-rubbed nitro

Post by Tongdee » Sat Jan 07, 2012 5:47 am

hand rubbed means just that the finish has been smoothed by hand after aplication. It can apply to nitro cellulose, French polish, even catilysed finishes (car clearcoat). It can be smoothed with fine sandpaper (1500,2000, 2500 for the fussey) pumice, rottenstone. Note that nitro can be brushed on as well as just sprayed. Went looking for my cans of brushable nitro cellulose laquer, gave up, I am rearranging. Watson or watkins as I recall. Even decades old finishes can be "hand rubbed" with wonderfull results....

Tongdee

Echi
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Re: Hand-rubbed nitro

Post by Echi » Sat Jan 07, 2012 10:46 am

At the beginning nitro finish, here in Europe was sometime given by hand through French polish system.
It was also common to mix both nitro and schellach ( I found the method in a n italian manual from the sixties).
For insatnce I know an Italian brand ( Sayerlack ) that is actually producing a very good nitro finish with the specific pourpose to be French polished. Actually the solvent is alcohol and not nitro thinner and it works great.
The procedure is the same used for the schellach.
Someone told me that in Spain this is a procedure well known.

David LaPlante
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Re: Hand-rubbed nitro

Post by David LaPlante » Sat Jan 07, 2012 4:45 pm

"Hand rubbed" is more of a marketing term than anything else I think.
High quality factory guitars (such as Martin) were given this type of finish (a few still are) since around 1930.
2-3 coats of Nitrocellulose lacquer is sprayed onto the sealed and pore filled guitar, level sanded with 320-400 coated paper and subsequent cycles of application/sanding are done till the guitar has around 7-9 coats of lacquer. Often the final coat was smooth enough to machine buff to a high gloss with no final fine sanding. Necks were done using a flatting agent to produce what was termed a "satin gloss" which required no work at all beyond the spray application.

Hand rubbed?, well maybe at the very end to do a final polish/clean up but this should not to be confused with a "padded" lacquer finish (akin to FP) or FP itself.

Robert Webster

Re: Hand-rubbed nitro

Post by Robert Webster » Sat Jan 07, 2012 6:12 pm

Echi wrote:At the beginning nitro finish, here in Europe was sometime given by hand through French polish system.
It was also common to mix both nitro and schellach ( I found the method in a n italian manual from the sixties).
For insatnce I know an Italian brand ( Sayerlack ) that is actually producing a very good nitro finish with the specific pourpose to be French polished. Actually the solvent is alcohol and not nitro thinner and it works great.
The procedure is the same used for the schellach.
Someone told me that in Spain this is a procedure well known.
I'd be interested in knowing more about the Italian method that you cite. I'd be a bit suspicious, however, that the Sayerlack is actually nitrocellulose because nitro is not ordinarily soluble in alcohol. I just tried a little piece of nitro binding and it was not affected at all by alcohol. That said, I've had a very well known luthier recommend that I try a mix of nitrocellulose lacquer and shellac in French polishing cedar tops, the objective of course being to lay down a tougher finish via a padding method. My attempts were not particularly successful because I had trouble keeping both the shellac and the nitrocellulose in solution. It seems to me to be quite a juggling act to get the mix of solvents right so that both solids stay in solution. If you have any insights on this I'd really like to hear them.

Bob

Echi
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Re: Hand-rubbed nitro

Post by Echi » Sat Jan 07, 2012 7:05 pm

Hi,
the procedure was used in the past, whereas nitro varnish was used to be handled by artisans quite skilled in french polishing. It is described in a very well done italian book (650pages); the author is Antonio Turco (page 238 and followings).
That's the link if you are interested:
http://books.google.ie/books/about/Colo ... redir_esc=
Sayerlack (I use their product being an amateur luthier,not out of commercial interest) produces different products for the mentioned purpose : SAYERLACK SU 236 is the name of the pore filler; SAYERLACK SA 1000 is the proper nitro varnish to be hand rubbed, while SAYERLACK SA 40 is the name of a varnish made mixing shellach and nitro in an alcohol basis, aimed for the last hands.
Here is the link.
http://www.sayerlack.it/scripts/default ... on=seconda

Robert Webster

Re: Hand-rubbed nitro

Post by Robert Webster » Sat Jan 07, 2012 7:23 pm

Echi, what an incredible book. Thanks for the link. It's going to challenge my working knowlege of Italian but it certainly looks to be worth the effort. Hopefully, Sayerlack will approve my application for registering on their site so that I can look at the MSDSs for some of these products. The info on included solvents will be enlightening.

Bob

tddarco
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Location: Vigo, Spain

Re: Hand-rubbed nitro

Post by tddarco » Sat Jan 07, 2012 8:16 pm

I wonder why Hauser III would choose to use this method over FP. Seems a shame to spray over those aged woods he's constructing with just to save some time, doesn't it? -Tony

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Alexandru Marian
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Re: Hand-rubbed nitro

Post by Alexandru Marian » Sat Jan 07, 2012 8:36 pm

I doubt it is to save time. He probably considers it not to be detrimental to the sound, not to mention much more resistant than FP. Plus, that's what his father used too!

tddarco
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Re: Hand-rubbed nitro

Post by tddarco » Sat Jan 07, 2012 8:41 pm

Alexandru Marian wrote:I doubt it is to save time. He probably considers it not to be detrimental to the sound, not to mention much more resistant than FP. Plus, that's what his father used too!
Oh, ok. It's just that those lacquer finishes always bother me. Literally cold to the touch in winter and a real plastic feel to it.

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Alexandru Marian
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Re: Hand-rubbed nitro

Post by Alexandru Marian » Sat Jan 07, 2012 8:52 pm

To each his own. My best friend and customer is bugging me for years to use nitro on his guitars and I refuse. :P

Jabberwocky
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Re: Hand-rubbed nitro

Post by Jabberwocky » Sat Feb 11, 2012 3:27 pm

Funny how different things are in the classical guitar world. Over in the archtop, hollow, semi-hollow and electric guitar world, the worry is about nitrocellulose versus polyester. Nitro is considered the quality finish option and polyester is frowned upon. Gotta have nitro because "nitro allows wood to breathe" or else...

In classical guitars, nitro is considered the "cheap" finish. It is kind of ironic.

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