old nitrocellulose finish on a guitar

[Rod 1944]

I have an old Maton slimline electric guitar in a black and green sunburst lacquer finish. It has a few chips and scratches and is bare to the wood in some spots, and also the lacquer is crazing slightly. I do not want to strip the instrument, just repair the damage as much as possible, and restore the finish as much as possible. I would be most grateful for any suggestions. I have had some self taught experience in repairing old violin finishes(spirit varnish, oil varnish, shelac etc ) but have never done any work on lacquer.
My sincere thanks, in advance, if anyone can advise me

[MacS]

Rod,

Lacquer is easier to repair then varnish, because lacquer dissolves and varnish will not. As lacquer ages, it may lose it plastercizing feature and may not reflow back, and could cause problems when you try to coat it.

I sugesst you buy an aerosol can of gloss lacquer, and spray a coat on a small area on the side, watch the lacquer closely to see if it opens up the lacquer on the side, and then closes up without any wrinkling or cracking. If it flows back your in business.

If not, then try padding it with shellac to see if it works and your getting adhesion.

Once you know, come back and let us know.

Good Luck

[Rod 1944]

Thank you for your help, I assume you are suggesting nitrocellulose lacquer, in an arosol can? This seems to be unavailable anywhere I have tried to buy it here in Australia, perhaps someone here can tell me where to try. Do you think the finish would be compatable with shellac? perhaps I could do a sort of french polish finish? that is something I am a bit more familiar with. I am also wondering about filling and colouring the damage (chips and scratches etc). Their is very little wood grain showing through the origional finish, so I am thinking maybe I can match the colour with acrilic model paint, ( including faking the grain of the wood)

[MacS]

Yes, I was referring to nitrocellulose lacquer.

Yes, it should be compatible, and you should be able to frennch polish on the nitrocellulose lacquer.

You first need to dewax and clean the finish, you can do this with white spirits and some clean cloth, keep wiping until the clothes are clean.

You could try increasing the alcohol (meths) in the french polish and work in circles this may remove the crazing in the coating, once the crazing is out, if it comes out, then pad in the conventional method. Do this on a small area to see it you can get it to work.

To try repaiiring the defects you might want to try filling the defects by using a small brush and dripping in the shellac and slightly over fill the defects, then allow the meths to evaporate and harden. Then with a sanding block and sandpaper level the dry shellac. You might want to do your coloring and graining before you do the filling. Then the French Polish can be used to pad over the defects and blend in the damages and the guitar.

Do some practicing in a small area until you get the feel.

Good Luck

[Rod 1944]

Mac, I appreciate your advice, I think I will try the french polish approach as I feel more confident using shellac.I will probably be some time before I get to it as I have several other repair jobs to get done done first, however, when I do it I will let you know the results.

Many thanks,

Rod

[durwood]

Stop!! don't try to mix shellac with nitro cellulose lacquer. You will end up in a terrible mess. Shellac is used as a finish by itself, it is dissolved in metho and is usually only used (other than a finish) to coat over other finishes to seal them off.

The N/C lacquer is originally a fairly clear coating the shellac is brown in comparison. Metho will slightly dissolve the N/C and you will be rubbing the two together and will probably get a mess.

There is a proper way to work N/C lacquer. Being a lacquer it will redissolve if its own correct thinner thinner is put on it and this feature lends its self to working the lacquer as you would shellac if you were french polishing.

The method is described here;

http://www.woodworkforums.ubeaut.com.au/showthread.php?t=19490&highlight=durwood&page=2


Read this carefully and try it first on an area which is not important until you get the feel of it.

You won't find N/C lacquer in pressure pack cans easily if a t all and don't use Acrylic lacquer its a different material especially under the N/C lacquer to colour it unless you apply very thin coats and leave it to dry for several days . N/C is still available along with its thinner but in a tin and it will have to be applied by a spray gun. You could brush or dab small chips with the N/C lacquer to build up the hollow and then fine sand and rub with the pad as described.

The crazing may repair itself if redisolved so try it also with the pad. I personally would spray a thin coat of N/C lacquer onto the crazing but I would not recommend you do so unless you are very at ease spraying thin lacquer or you may end up with runs and sags.

[astrid]

Stopp!!
I agree with durwood but will go one step further,
If this is a vintage guitar dont touch it without consulting an expert in old guitars.
Messing about with the original finish can reduce its value to almost zero.

Astrid:oo:

[Rod 1944]

The Guitar is not particularly valuable ( a few hundred dollars maybe). I am aware of the concerns about old instruments, so I will be proceeding with caution. Thanks for your comment.

Rod

[MacS]

Durowood,

Lacquer and Shellac are compatible coatings, in fact, the Lacquer Sanding Sealer which is used under the Lacquer is made up fron a Shellac mixing Lacquer.

When finishes are contaminated with silicones, Shellac is used as the "barrier coat" to seal in the silicones, and then Nitrocellulose Lacquer is used over the sealer.

Shellac, is used to "pop" the grains" of some woods, then Lacquer is used as the final clear coats.

I could go on and on about Shellac and Lacquer being compatible and used in combination.

Let him do it your way, your materials may not be the same as they are over here.

[durwood]

MacS
There is definately a big difference in sanding sealer in the USA and Australia. I don't think there are any N/C sealers with shellac in them here . In the industry here there has always been a distinct difference between using lacquer based products and shellac. Shellac is always the cheap, easy, least effective way to produce a durable lacquer finish. If you want to produce a first class finish you use lacquer sanding sealer and then the clear lacquer.

Your silicon must also be different but I don't see how it could be. Silicon is a natural repeller so painting over it produces the usually seen fish eyes. Paints don't stick to it so painting over it means the end result is a finish with poor adhesion to the surface. Sealing fish eyes with shellac comes under poor practice in my book if its a worthy restoration then only removal of the silicon is acceptable before proceeding.

[MacS]

Durowood,

The finest furniture made by our best woodworkers are not done in Lacquers, but are French Polished, or done with Wiping Varnishes.

French Polishing certainly is not considered a "cheaper" finish. It’s the Lacquer that is the cheap finish, Lacquer is the commercial coating used in production finishing.

Many restores over here, first use a chemical to wash down the surface to try removing the silicones, then they use the Shellac as a barrier coat, and then either French polish or apply a few coats with lacquer, they have been doing this for years. You know that you do not strip off the finish of antiques or other valuable pieces; this is one way of doing it.

Meths are one of the solvents that are used in nitrocellulose over here, I don’t know about your products. I will try to find some MSDS and see if I can find out what's in your lacquers that is not compatible with Shellacs.

[echnidna]

I've used shellac over and under lacquers with good success.

I suggest Durwood study Bob Flexner's ? works on finishing.
He's an industrial chemist as well as being a woodie

[jeffhigh]

If you just want to repair a few chips you can use nail polish which is nitrocellulose lacquer.
Just do a drop fill, leave it a few weeks then scrape sand and polish to blend with the old.
Calling shellac "Compatible" with NC lacquer is a bit misleading, sure you can use it under or over lacquer but you do not mix it.
Shellac is metho (alcohol) soluble
NC is acetone soluble

[durwood]

I'm not suggesting that you don't use shellac, as a finish its great in the right place such as on antique furniture but if you use it in conjunction with other finishes ( and you can use it with any type thats why its always suggested as a sealer) it weakens the finish,

If you wanted to use it on a surface thats OK but N/C lacquer is used when the limitations of shellac are a problem. French polish requires lots of hand finishing to produce its full gloss. N/C lacquer is a lot faster to do to get a gloss. You can easily compound and buff it using a machine something thats not an option with shellac you have to work it by hand. One of the reasons fine furniture has shellac as a finish it fits in with the hand craftmanship of the piece.

On modern furniture or guitars etc N/C is used to give a better more servicable finish than shellac does. For instance on a table where you don't want to have to put down coasters or table cloths to protect the surface from heat or sunlight.

If you introduce shellac into the process you degrade the performance of the final resulting finish. Thats why sanding sealer is used instead of the old system of sealing with shellac. Furniture which would fail the hot cup test with shellac as a sealer become a better finish.

Same would be the case if you used shellac as a sealer under polyurethane or any other clear you weaken the result because the shellac is so poor where the finishing process is designed to upgrade the end performance of the finishes

There have been several threads here on the forum recently where shellac has been the reason for the failures of finish. Sure its a good sealer but its not as good as the newer ones designed to go under the more modern tougher finishes.

I'm not a chemist but I have worked and had contact with many and have have over 40 years in the paint industry and on numerous occasions have come across failed finishes which have had shellac used in the process. It is never a good idea to substitute a better sealer by using shellac because of its poor heat and UV resistance. It will work great on a piece of furniture ( antique furniture is a good example of that) if it is kept inside out of the sunlight and away from heat but put it under any finish where that finish does get heat or UV exposure and it will degrade the possible life of the finish. Do a simple test put shellac under N/C lacquer on a piece of timber and then do another piece of timber using its correct sanding sealer and see how long they last outside in the sun, the shellac will always fail first.

Having conducted paint technology classes for 33 years the easiest way to show students how good or bad finishes were was to do all manner of combinations on timber and metal and leave them on a test rack. Any finish that had shellac on or under it wasalways the first to fail. Ask a chemist to rank finishes and shellac would be on the bottom of the list. I don't know od a worse finish for performance.

As an example straight shellac lasts less than 3 months tops,(worse in summer better in winter) N/C about 6 months, Estapolmaybe 10 months acrylic lacquer 5 years, Urethane enamel 10-15 years depending on type.

Shellac under any of the others, less than the produce without it.

Echnidna, why would you put it over lacquer?

[echnidna]

To repair small defects instead of stripping the whole lot and starting from scratch.
Shellack also enables the use of oil based stains under lacquer which gives you a far wider choice of stains plus enabling making your own oil base stains from pigment powders, yet finishing with lacquer.

And buttonlac can also be a nice colour base at times.

I don't use indoor finishes on outdoor furniture.

[astrid]

I,m a bit confused here guys, I always thought that the finis in australia in the 20's thru 60's was a nitro cellulose, it certainly disolves with meths in a crusty sort of way. I strip it with meths alone, quite quickly and it give a musty sort of smell
Are we talking the same finish here?
old nc was sprayed on and was discontinued in general manufacturing here and in europe because of its highly flammable nature, (workers burned to a crisp) or so i have been told.
Best ask how old is the guitar and where was it made (guessing the US)
before we start giving advise on how to patch it up.
wasnt old film made from NC and dolls and records?

Astrid:)

[MacS]

Now, were going all over the place.

If you can use Shellac and Lacquer together, then they are COMPATIBLE.

Nail Poilish, is not made with Nitrocellulose, its made from Acrylics resins. Acetone, is the nail polish remover.

Nitrocellulose, will amber over time, whereas, Acrylics will stay water clear.

Bob Flexner, is not an industrial chemist, but he knows a lot about chemistry and wood finishing. he has a book worth reading on finishing.

Shellac, is a softer coating then Lacquer, because lacquer has been modified to be harder. Shellac takes too long to harden in comparision to lacquer, that's why lacquer is used in production finishing.

Custom woodworkers who use Shellac on their work, do not have to worry about their pieces being abused, these pieces are high end, and well taking care off, no lacquer off the gun can reproduce the look of french polishing, there is a place for both of these coatings in finishing.

[astrid]

My husband is a collector of vintage guitars and he this to say:

"If it's crazed then it's definitely nitro, modern laquers don't craze. If it's nitro it's probably 1960's, early '70's at the latest, nitro hasn't been used on guitars anywhere since around 1969 although Maton might have kept it for longer - I don't really know because I'm not a specialist in Maton.

Since it's 1960's, it's definitely valuable. I just checked and can see quite ordinary Maton's from that era going for around the $1300 mark and up - a price I can quite believe as Maton is a highly regarded brand and the price of even the junkiest 60's instruments have skyrocketed in the last 5 years. Maton is not junk.

Given that, any work on the finish will only devalue the instrument (and possibly the sound as well). Crazing doesn't affect value at all as most of these old instruments suffer from it. A few dings and scratches are immatterial. They just don't make guitars like they used to (I won't go into details, but the differences between old and new are real), and the demand for the old is very strong.

Secondly, in a past life I used to be a chemical engineer working with solvents. I can definitely confirm other comments here that shellac is incompatible with nitro. Application of shellac to nitro will mess it up. Further (guitar hat on again) the comment re. nitro being transparent finishes and shellac being opaque is dead on the money.

Speaking as a collector, I wouldn't touch it. I have quite a number of old guitars some of which have finishes in pretty ugly condition and it doesn't affect their value much at all. The only time finish is an issue is when you have a really top notch mint example. And mint means mint in this market - right down to every screw and wire being present, original and untouched. From the sounds of it he doesn't have one of them, and all that will be achieved by trying to tart it up is to reduce its value"

Credits to HWMNBO (except in this instance)

Astrid:)

[MacS]

I am no chemical engineer, but I was a field salesman for a company that sold finishing materials for over 30 years. I have serviced many thousands of finishing shops, and I have to disagree with you, Shellac and Lacquer do work together, I personally have been doing this for a long, long time, I mention this to customers all the time, if there is a problem it caused by the finishers and not the coatings.

If fact, I use this finish all the time same now, I write some finishing articles and do my own photos. I use the Shellac for the sealer coats, because shellac is an excellent sealer, but it has a high gloss sheen, so I have to use lacquer to reduce the sheen for the photos, so I do not get and flash back from the gloss.

You mentioned, that nitro being transparent finishes and shellac being opaque is dead on the money.

Were, you referring to both of them being in containers, where the clear shellac is milky white, and the lacquer is a clear amber, you do not mean when once they are applied as coatings?

Do they sell Shellac aerosol cans in OZ.?

[astrid]

What HWMNBO was refering to (I think) is that when shellac was used on a sunburst,
it was coloured so as to give a more solid colour finish,
not that the material itself is opaque. I think that, as in most cases, you can put shellac under NC, but not the other way round, i also think that 50's NC was made up different than it is today.
vintage guitar finishes are a trade in themself and not a generalist area.

astrid

[durwood]

Astrid,
You arn't confused pretty well spot on.

N/C lacquers are a product of the first world war. It appeared in the early 1920's and was a big break through as the old finshes were slow drying varnishes. Suddenly there was a finish that could be applied in a day and not weeks. It was a especially taken on by the automobile industry and is commonly refered to as "Duco" which is actually a brand name.

It was used up until 1960 on cars ( all Holdens were finished in it) when it was replaced by Acrylic lacquer. Duco was a so so product, some colours were good some were terrible. Black N/C was fantastic so much so it performed far better than acrylic lacquer blacks which only became reasonable 10 years later. White duco was hopeless ( it went yellow) and colours that were reasonable performers were pastel colours. It was rare to see a bright red car that didn't go pink quickly and maroon was even worse.

Acrylic Lacquer was far superior, it was not affected by the UV light and colours stayed the same, white stayed white and other colours stayed the same. The biggest breakthrough was with metallics which up until then were not possible. Now it was possible to have silvers and golds.

When A/L became the paint on Holdens and the baked enamel cars were repaired with A/L Duco was fazed out not because people were being burnt to death but because it was inferior. ( acrylic lacquer is even more inflammable)

It still was the base material in the primers and putties for A/L (still is) as it dries so fast compared to Acrylic materials and is the the easiest paint to use of any.

BUT the clear is lousy in sunlight as UV rays destroy it fast and its been reduced to the furniture/interior market and is still widely used for numerous products as its is easy to apply drys fast and requires not much in the way of equipment ( in its hay days it was sprayed in factories with little or no resourses such as booths just somewhere where it could be sprayed on and allowed to dry for a few minutes before being moved on.

Its also been relegated into obscurity by polyurethanes in the piano industry so its becoming less used all round but there still are a lot of users who use it as it fits their requirements. It has a place its just a smaller one these days.

[astrid]

Thanks durwood,
Re the guitar in question, would we be right in assuming that a 60's sunburst would be "decorated" in coloured shellac, ie the sunburst, and then finished in NC.
you can put shellac on under a lot of finishes but not over, as its too soft and will move the sub finish.?

Astrid:)

[MacS]

Shellac can be used over or under nitrocellulose, there are situations when it is used both ways.

Shellac, is also used under Varnish as the seal coat.

Shellac, is also used under water base coatings to seal the wood, other wise if the water base sealer or coating is used, they will raise the grains of the wood.

How "nitrocellulose" can about was after the war, there was millions of shells with gun cotton an actvator in the shell casings being stored, the goverment wanted to get rid of all these shells, it was Dupont that came up with the nitrocellulose lacquer by dissolving the gun cotton. Duco was a trade name for Dupont, and that was the beginning of the lacquers.

[Different]

Shellac can be used over or under nitrocellulose, there are situations when it is used both ways.

Shellac, is also used under Varnish as the seal coat.

Shellac, is also used under water base coatings to seal the wood, other wise if the water base sealer or coating is used, they will raise the grains of the wood.

How "nitrocellulose" can about was after the war, there was millions of shells with gun cotton an actvator in the shell casings being stored, the goverment wanted to get rid of all these shells, it was Dupont that came up with the nitrocellulose lacquer by dissolving the gun cotton. Duco was a trade name for Dupont, and that was the beginning of the lacquers.

Right on
Cotton (cellulose) reacted with Nitric Acid (Nitro) created as said Gun Cotton which when disolved with Ether and extruded in thin strips and dried forms Smokeless or Nitro Cellulose gun powder. Just happens to be my favorite invention too !!!

Rgds

Ross

[kiwigeo]

Best ask how old is the guitar and where was it made (guessing the US)
before we start giving advise on how to patch it up.
wasnt old film made from NC and dolls and records?

Astrid:)

Matons are made right here in Australia......

For good advice on finish repairs try here:

http://www.frets.com/FRETSPages/pagelist.html

Cheers Martin