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What kind of gloss finish on a newer Martin? Higher end

Finish repair question: it has about a 6-in scratch on the soundboard. However, it does not break through the finish. It looks more like a long dent from something blunt. Maybe only 1 or 2 thou deep. I was planning to fill with ca, but worried there will hardly be any left and maybe it will just come off?

Halfway thinking to just sand it level without putting any fill in. That would require sanding a larger area and possibly messing it up. Thoughts?

Pat

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Pat

It is lacquer that should be thick enough to sand out a dent that shallow. I would not use CA for this type of damage. Ever drop fill with lacquer? Given enough time, that is my preference.

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John

It looks like lacquer. It seems very thin though whatever it is. I can see the grain in it...

Pat

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Pat

It is without a doubt Nitro lacquer J Arnolds advice is sound no ca

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John Hall
blues creek guitars
Authorized CF Martin Repair
Co President of ASIA
You Don't know what you don't know until you know it

I’ve done several finish repairs on standard-series Martins using Gluboost Fill-n-finish. While this is a CA product, it is flexible and not designed to be used as a glue. Works fine on a nitro finish, while regular CA glues will be brittle and shatter with time. Yes, surface prep is important, i.e., degreasing with Naphtha. You can limit spread with tape to minimize cleanup with a safety edged razor blade. The fill is the easy part, it’s the care you take on the level and buff that defines the quality of the result.


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The problem with CA on a shallow, soft-edged dent in lacquer is that it will not feather out to blend with the lacquer. CA works better on deeper dents with more vertical edges, and on harder finishes like polyester.

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John

If it's lacquer I would do a drop fill and let it set for a few weeks before polishing it out.

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Jim Watts
http://jameswattsguitars.com

A costly guitar is no place to learn a nuanced skill. I suggest OP leave it alone and seek professional advice.

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Peter Havriluk

If it is that shallow you may be able to raise the dent back up with a damp rag and a soldering iron. Sometimes that can cloud the surface of the finish, which again you can - sometimes - buff out. Test on a small section before committing to the whole thing.

That's the beauty of Nitro and why I still like it as a finish. You can still melt in nitro on a guitar that built in 1930. It burns back into itself and becomes homogeneous.

As far as I can tell the wood is not really dented just the lacquer. Are you suggesting I could raise the finish with moisture and heat?


Pat

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Pat

As far as I can tell, Martin still uses nitro cellulose finish (yay for them). The only repair finish that you should use is nitro. You can test to see if it is nitro with a bit of acetone on the inside edge of the sound hole (and I mean a little bit!). If nitro, it should quickly become tacky. But all I could see on the Internet is that they use nitro. Leave some nitro out for a while to thicken up. Then fill.

Hi Pat,
Nitro finishes are usually pretty thin, and in your first post you mentioned it looked like a long dent from a blunt object. Finishes will scratch, but I haven't seen too many that will compress - usually it is the wood under them that compresses. If you think it is all in the finish and is only 1 or 2 thousandths deep then it might just buff out. Or you could do a light overspray of nitro, allow it to dry a week or two and rebuff the top. 1 or 2 thousandths is pretty miniscule. The average human hair is 2 to 4 times thicker than that.
Raising the dent with moisture and heat assumes the dent is in the wood, I doubt it would do much (good) for the finish.

Ever consider just leaving it? Honest wear gives character whether a face or a guitar.

I love seeing some dings on my guitars when I see them after a few years. At least they are being used for the purpose they were made.

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It's not what you don't know that hurts you, it's what you do know that's wrong.

DO NOT use a soldering iron on a finish that will cause a lot of problems on raw wood yes not on finish

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John Hall
blues creek guitars
Authorized CF Martin Repair
Co President of ASIA
You Don't know what you don't know until you know it

I’m with Terence here. The idea that you can somehow make repairs that are invisible just because it’s nitro is far-fetched. Yes, it can be done, but only by sanding down the entire surface, drop filling, waiting, levelling, more waiting, respraying the entire surface with several fresh coats, then more waiting before before levelling and buffing. The more waiting the better. And even then, that surface won’t look the same as the rest of the guitar, unless you’re prepared to treat them too. Most guitars, even standard Martins, don’t warrant that kind of restoration, so I have no qualms about using Fill n finish for cost effective repair that is no more visible than a repair with nitro, at a fraction of the cost. Often the purpose of finish repair is to seal the area exposed by a top crack or broken headstock and to make it smooth to the touch.
Yes, nitro burns into itself and so is repairable ... sort of. Realistically, any repair on nitro will remain visible, and attempts on older instruments will often devalue the guitar. I have a 1958 D-18 on my bench that has been treated well, but there’s no way I’m doing any finish repairs, not even with nitro. The dings and abrasions tell the story of the 84-year-old owner who bought the guitar new when he was 21. I’m only doing a partial refret and redoing a bridge repair that was done badly decades ago.


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Show of hands, please, by professional luthiers who'd take on this problem.

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Peter Havriluk

there is finish touch up that works and some that doesn't. I have been doing this 20 yrs and learned a few things. This is a simple repair in the hands of an accomplished finish repair person
if you never worked on this your repair may cost more to fix than the original repair and yes they can be done very well as long is it just the finish involved . Once you penetrate the wood you will not make it totally invisible.
This kind of repair is a process and it is a bit more involved that just drop fill . With Martins they often use toners and this can things more difficult but if it just the finish it can be done.

a quick and brief summary is that you must use solvent to help the burn in use the proper finish color and allow ample cure time. You can't drop in Monday and level fri .
a small ding is no big deal it is a guitar , it gets used , enjoy the mojo after all look at Willies Trigger that is one finish no one can ever fix and who would want to.
stay well my friends

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John Hall
blues creek guitars
Authorized CF Martin Repair
Co President of ASIA
You Don't know what you don't know until you know it

It’s like owning a brand new car. Unless you don’t drive it, you accept wear and tear. The shopping cart ping, the door ping, a rock chip. You cringe on the very first one, but you’re going to have to live with em.

My ability to do touch ups improved dramatically last year when I started to use Glue-Boost. I have even been brave enough to try it on a spruce top with fairly deep damage. I also give credit to the Kovax Tolecut sanding system which does a great job leveling drop fills and small repairs after scraping with a turned edge on a razor blade.

I've been using GluBoost since it came out and also really like the Kovax Tolecut sanding system. A good combo that has saved me a lot of time. Another thing that saves me a lot of time is not chasing minor dings and such; I tell my customers I don't fix those.

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Steve Smith
"Music is what feelings sound like"

Peter, hey man I'm trying! lol. I am the "pro" on this one. I have done many finish repairs that turned out well. This one is a bit different than what I have done b4. That is why I am asking the pros here and have gotten lots of valuable advice so far. Thanks everyone!


I am with you Terry. I love my guitars to look and feel well used. This one is for a client. In his defense, it is an otherwise pristine instrument with one long, more k9 than musician looking mark across the lower bout soundboard.

John, are you saying I must use an additional solvent than what is in my nitro? Like apply lacquer thinner (or?) (To soften it?) to the area first b4 i fill with thickened nitro? I was planning to clean the area with Natha first.


Same experience here Barry. Both those products have emboldened me to take on more finish repair jobs. Mostly modern, harder finishes though.

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Pat

you need to learn a lot more finish before trying this repair
yes lacquer thinner is in nitro laccquer acetone also may work this is the solvent that dissolves the solids of the finish.
It is what is used the thin the material for spraying , retarded will help slow down the drying for better flow but you don't need this

the point is that this is not something you want to try on an expensive guitar . Most of these finish touch up can be done at a reasonable cost and I have seen too often well meaning amateurs that cause serious damage to a guitar from not know the proper procedure.

There are many different techniques but here is the basic procedure
if there is toner of aged finish , I use a medium sized artist brush and cover the area with the thinner , and kind of scrub the area to get the finish to work into the thinner and allow that area to soften , then use finish to drop fill and level off.
This I let set for about 5 days to a week , then I may have to add more material till I can build up the area.

after that I will allow about 2 weeks for a good cure time. I then level sand. My preference is using micro mesh and work this till I am happy with the surface level , they let set a few days to see if this area sinks, If you don't the area will show up this sink. This is the time consuming part of finish touch up. Allowing proper cure time

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John Hall
blues creek guitars
Authorized CF Martin Repair
Co President of ASIA
You Don't know what you don't know until you know it

Just to add to John's excellent explanation. Lacquer solvents have vastly different drying times. Acetone is very fast, while retarder is the slowest. Lacquer thinner is in a range in between. I use the various solvents based on the desired result. To melt in on vintage lacquer, you typically need a slower solvent like retarder to melt it, simply for the added time needed for the solvent to do its job. The lacquer should be soft enough to mark it with a fingernail for a good melt in. Melting in is the key to avoid witness lines....something that is the hallmark of a good lacquer repair. Witness lines are expected with other finishes, including varnish, polyester, polyurethane, and on any repair using CA, since there is no burn-in.
Another point is that lacquer cures strictly by solvent evaporation, so ventilation will have a profound effect on the curing time. I always use a fan on my lacquer finishing and touchup, preferably in a well-ventilated space. Another factor in shrinkage is the percent solids of the particular lacquer that is used. Higher solids lacquers shrink less, and tend to harden quicker. There also is an art to using thickened lacquer for drop fills. There is a fine line between thick enough and too thick, which may leave bubbles in the drop fill.

Because the bulk of my repair work is on vintage instruments with potential collector value, I am often asked about removing old overspray. My response is that it is only possible if the overspray was incorrectly done. If you just spray new lacquer on vintage lacquer with no 'pretreatment' with a solvent, there is a possibility of visible witness lines when removing the overspray, due to the lack of burn-in. Witness lines are a valuable tool to gauge when you have removed the overspray. The problem is that factory oversprays (particularly those done by Martin) often do not exhibit witness lines. While some mechanical reduction in the finish thickness is still possible, it is much more risky.

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John

If there was a final test for luthiers before they could call themselves luthiers, doing an invisible repair on a spruce top would be it and there would be no luthiers. This is a very difficult repair. Good luck! -Bob/Pegasus Guitars

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“ The meaning of life is to find your gift and the purpose of life is to give it away” Pablo Picasso