Scratch repair

[Nige52]

Hi folks,
I just took delivery of a Tanglewood 12 string acoustic which has been damaged in the post. On the solid Spruce top is a scratch about 3" long and goes down to the wood underneath. I've been told that thin layers of super glue will bond it and bring the level up to where the lacquer is, then a polishing off.....?
I've never done this before so is the info correct or is there a better way? I am NOT a luthier




Cheers,
Nige

[Rodger Knox]

I suspect that is a poly finish, and filling with CA is the appropriate repair. Don't try to fill it all at once, that's a pretty deep gouge and will take 6 or 8 applications, at least 30 minutes apart. Let dry a couple of days (CA does shrink some as it hardens), and you can try scraping/sanding(starting at 600 grit), but you'll probably find you need a little more filling to bring everything up to level. Be careful, it's easy to make a mess by getting the CA somewhere you don't want it to be.
If it's a nitro finish, use thickened lacquer instead of CA.

[Frank Ford]

Looks like your guitar got a good hard bonk on the edge, and that's a compression fracture, namely a crack not a scratch. When the wood sprung back, the finish shot off and the result is a nice deep wound. The very best repair will always be visible, so the expectation should be to make it look "well attended-to."

Indeed, a fill with clear epoxy or cyanoacrylate may result in a build-up that can be leveled to the surrounding finish so it won't be too objectionable in reflected light, but the color will always be obvious, more or less.

[Halcyon/Tinker]

I'm not sure if it's approp to mention products by name, hopefully it's ok.

There is a new CA product called Fill'n'finish by GluBoost that would be ideal for that repair. Often applying thick coats of CA like is needed to fill that crack, some CA's will bubble, or turn white or yellow.

This product absolutely does not, and you can get an accompanying aerosol can of accelerant that cures it instantly, no bubbles, no yellow/white bits.

For this type of job, it's the bees knees.

[Nige52]

Thank you all for your advice
On a close inspection by a friend who knows a little more about guitars than me, he tells me its a satin finish all over, no gloss lacquer at all and he thinks that the very top veneer or the wood has sprung out after it received the knock. Now I'm wondering if superglue will still do the job?
Cheers
Nige

[LSemmens]

Just a thought, is it a brand new Instrument? Would the shipper not be responsible for the repair in any case? Insurance may well cover the cost of a professional repair, which is likely to be more invisible than one made by a person who is a hobbyist.

[Hot Vibrato]

Some good advice here. I agree that superglue is the way to go with this type of repair if it's a catalyzed finish and not lacquer (looks like a catalyzed finish). Don't touch it without washing your hands first. I don't know why, but the first thing people do when they see this kind of damage is they rub their greasy fingers all over it. Don't do that or it will permanently look dirty after it's been sealed in under coats of CA.

With this type of repair, you should protect the surrounding finish with tape at first. Scotch tape is good because it's thin. Sand or scrape it down to the thickness of the tape, and then wrap wet-or-dry sandpaper tightly around a hard block to further level the surface (plexiglass or acrylic is a good material). The trick is to get it perfectly level and polished without sanding or polishing through the finish. It's a good idea to start wet sanding with 320 or 400 while the tape is still attached, and you'll actually sand away some of the tape thickness. Eventually you sand the tape away and you have to level the fill with the surrounding finish. Proceed with 400 grit, or maybe switch to 600, and then don't switch grits until it's perfectly level, and then work your way up to 2000 grit and follow up with a good polishing compound. I like 3M Perfect-It. Good luck!