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I made the rookie mistake of using CA glue to stabilize a small crack in the soundboard.
It left a yellow stain that became evident after the first few coats of shellac.
Is there any way to remove it?
Expert opinions?
Thanks

I take it you tried a light scraping to see if this was surface only, so at this point, discussion of how a sunburst or other tinted/opaque finish (e.g., a black vintage Gibson-like finish) might hide the staining is worth having.

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What’s the brown rectangular piece on the picture? Is that where the crack started?
Trying to figure out how CA staining happened as it doesn’t seem you introduced the glue to end grain, unless that brown rectangular piece is inlaid?

I agree with woodie, try scraping it back, sharp single edge razor blade or chisel.


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The stain is typically a chemical reaction within the wood between the CA and the tannin. It will be as deep as the CA penetrated into the raw wood fibers. Being a crack, this will be the whole way trough and if you do scrape it out the crack will likely be unglued....

Options? Vintage amber tint works well in spray finishing. If you intend to FP buy a darker color shellac. Or paint it black....

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Brian

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Thanks. I will try that, although I have sanded quite a bit in the area already...
The brown rectangle is a piece of masking tape covering the majority of the bridge location.
And the customer wants a natural white top.

I'm also considering splicing in a thin wedge of spruce from an off-cut like this:
https://youtu.be/Oj8F-gA9HHQ?t=294
But I'm concerned it might stick out worse than the yellow if the figure doesn't match.

Under a clean clear finish, with that little wiggle in the grain..... my bet is on looking worse.

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Brian

You never know what you are capable of until you actually try.

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If a light scraping of the surface doesn't get it, I would move on to the staining (burst?) option. no sense digging a trough to add to your problems.

I agree with Brian.

If this is a customer guitar and is brand new, you need to replace the top. There's no short cuts for new guitars going to paying customers (even if they are only paying cost). 2 of the "customer guitars" I've done (they payed cost plus a bit.) I had to re-top due to my error. I could have repair each but it wouldn't be new then and it would be noticed.
This is part of the learning curve of this craft. It's a tough pill to swallow, but in the end you'll be happier that you did it right.

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I know s/he wants a natural white top but would some color be tolerable? That stain doesn't look too bad (at least on my monitor), I'm wondering if a darker than blonde shellac will hide it sufficiently. If natural is more a priority than white, this may be an option. Also keep in mind that it looks way worse to you than anyone else. Most probably wouldn't notice without it being pointed out. Is this between the bridge and soundhole or between the bridge and tail. If it is under the strings, I wouldn't worry about it. The strings will obscure that area and cast differing shadows, that stain will get lost in the shuffle.

Edit:

Rod posted while I was typing. If you do end up going with a re-top, I suggest trying to graft in new wood first. At worst you will lose some time and gt some experience, at best, it could work out. You really don't have anything to lose.

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Bryan Bear PMoMC

Take care of your feet, and your feet will take care of you.

Use hide glue for these kind of cracks. Warm up the wood, apply thin glue to both sides, and then press on it back and forth from both sides to work the glue into the crack. Then give it some thicker glue and work it some more. Wipe off the excess, clean up the residue with a wet rag (but not too wet or you'll wash the glue out of the crack as well), and it should be nearly undetectable even knowing where to look

i agree with Dennis about what you should do next time this happens. Re fixing the current situation: Bryan is very experienced and does lovely work. I think you should carefully consider his suggestion.

I have a different perspective. My experience is rich in terms of rookie mistakes, and mistakes in general. You can get lots of experience trying to repair errors, but you can also get experience from re-doing the whole operation with new material.

Beginners and semi-experienced builders like myself are frequently advised to try to splice in spruce to cover up mistakes. In my personal experience, and from what I have observed, making invisible repairs in spruce ranges from very difficult to impossible, depending on the situation. If you want to become an expert in challenging restorations, get started learning to splice spruce, but don't expect the first tries to be beautiful. Effectively covering up stains with colored finish is also difficult and requires an investment of time--worth learning to do if that's your goal, but this needs to be considered.

At a certain point repairing mistakes becomes an impractical time sink. Looking back on my learning process, my biggest regret is investing too much time trying to fix things. If I had just incorporated what the mistake taught me and moved ahead, I could have made more guitars and ended up with better products for the same amount of effort. My rule now is to only try one fix per cosmetic error; if it doesn't work, I move on. You've sanded quite a bit and it hasn't worked, unless you've sanded too much, in which case it's worked to make another mistake. If I were you, I'd take Bryan's first advice and live with the mark, or if I couldn't do that, I'd stain that top some more with salt tears, slam the door to the shop and stomp around the house yelling, and then go back and replace the top.

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I'm sorry this happened to you. Not likely to happen again I imagine. It happened to me once. Only solution I found was to amber tint (with some yellow added) to cover it up. Worked great.

If this happens to be a first I would just keep moving and not worry about it.


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I would not try to patch it.... human eye is designed to pick up high frequencies. You will never hide it. As I recall, I used a water white finish. For the top, I tinted the finish with transtint yellow. Maybe some amber. I experimented until the color matched the stain. came out great. Lesson learned. Never let CA come into contact with raw spruce. This poses issues with "flood fill" rosette. Just seal before using.

No expert here but depending on how much you're into the build you could stain the top of this one and build a whole new one. That's what I'd do anyway, but each one of my builds has something I should re do and I end up living with it because I'm desperate to hear how it sounds and hopefully I don't make that mistake again!

If it is Sitka Spruce, it will turn that pumpkin orangy color in a couple of years. Martin used to pre-pumpkin some of their guitars with a tint in the finish. Just a touch of color might solve the problem

Ed

This is what I was thinking too. I remember once a friend lamenting the contrast between my brand new Larrivee, and his 20 year old version. He really envied how white my top was in comparison...

Haha, I was in a repair course last summer and the instructor was telling a story about a classical guitar he had built. He told us how he had already done two or three major repairs to the top of the otherwise brand new guitar when yet another problem arose. In a totally straight faced, dead pan manner he told us how he walked over to the guitar which was hanging from the wall, picked up a chisel and calmly forced it through the top. I guess sometimes it is better to just stop...

Thanks for all the input. My plan of attack is as follows:

1. Talk to the client (my brother-in-law who knows this is just my hobby, and who I forewarned before starting the project that I'm no professional, and that I can't give any guarantee of quality or workmanship).
a. If he doesn't care about the blemish, I will leave it.
b. If he suddenly wants an amber tinted top, I will tint with amber shellac.
c. If he wants me to try to fix the color and accept the risk of me making things worse, then I will try one or more of the methods below.
d. If he has any concerns about the structure of the top due to the crack fix, then I will replace the top. (Again, I have a feelings I could make things worse in this scenario)

2. If he wants me to try to fix the color and accept the risk of me making things worse, then I will try one or more of the methods below after practicing and testing on off-cuts from the top.
a. Sand back to bare wood, and treat the blemish with oxalix acid to hopefully bleach it
b. Glue in a tiny sliver of a graft. (mostly just to practice that technique, it will probably look worse)
c. Replace the top (Again, I have a feelings I could make things worse in this scenario).

3. If a top replacement is in order. I like the following method.
a. http://www.grevenguitars.com/retopping-demo.html
b. Any recommendations for other methods or modifications? My fear is the new top bracing won't fit nicely into the kerfed lining notches.
c. This method will help keep the body shape, since the new top is cut using the actual guitar as a template. Then when the old top is removed, and the body inevitably splays out due to the tension in the back, it can be forced back into place when gluing the new top.
d. If I have to replace the binding after that, so be it. I will also need to adjust the neck angle a bit.

I would suggest that you try to make a sample with a piece of spruce and super glue with a similar blemish (or maybe a few of them).
Then I would color match the yellow of the blemish over the entire sample. Once you have the color of the top blending with the discoloration you can add other stains to bring the top to amber, or what other shade you can manage. Making the top blend into the discoloration would be my first step toward making the blemish disappear.

Since you are a bit concerned about over sanding, remember you can strip that shellac with alcohol and save yourself one sanding operation should you go with 2a.

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Bryan Bear PMoMC

Take care of your feet, and your feet will take care of you.

I like the part where you discuss this with the client before doing something silly and higher risk than attempting a little shading of the top. I also like the part where you provide a few shots of amber-burst/tea-burst guitars to the customer to prime the pump for the discussion to be had.

As support for this course of action, I'll quote from a recent John Arnold post on the topic from Mandolin Cafe, Subject: Super Glue Stained Spruce:



https://www.mandolincafe.com/forum/threads/140390-super-glue-stained-spruce

_________________
We have become a civilization that elevates idiots, prostitutes, and clowns. Am I still to defend it? Yes, for its principles. Yes, for what it was. Yes, for what it still may be.

-Mark Helprin, The Oceans and the Stars: A Sea Story, A War Story, A Love Story (A Novel)

I think the very best option is to leave it ... But given that you mentioned grevens guitar method and I have done two top replacements where I kept the binding I thought I would answer.

You can fill the kerfed linings and recut them tight to the new top. Given that your new braces can be very close, you will cut 90% or more of the plug you glued into the linings.

The shape of the body does change when the top is removed but because you cutting the exact size replacement top, fitting the new top into the body helps push it to the correct size. If the body still fits in a mold (I am assuming you can remove the neck if it is on) you can put some spreaders in through the sound hole and dial in the size for the top. Either way fitting the top is not a huge deal.

I have kept both the linings and the purfling using this method. Given that the router cutting out the new top is using the same index (the rims) as when you originally cut the binding channel the top fits remarkably well. I did this on a new 8 string nylon guitar as I built it too light, when finished it look like a new guitar.

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