#1
Continuing with my attempts at guides, here's one on crack repair. Hope this helps someone! Please ask if you have questions.

The particular guitar I worked on had a few problems, among them a dry, cracked top. The first thing to do here is put to few dampits in the guitar and leave it in humidified storage until the crack swells shut.



Once the crack is swollen and tight, line it with tape. I used electrical tape. You want the tape to get pretty close to the crack itself (~1/32").



Spread thin wood super glue along the crack. You can press around the crack while you do this to work the glue deeper into the crack as well. Before the glue dries, remove the tape. If you wait for the glue to dry and then remove the tape, you might tear out some glue/wood. Here's my glue line after the tape was removed.



Once the glue is dry, it's time to remove the excess. Hand sanding with a block and 600 grit does a decent job, but be careful not to burn through the finish (if avoidable). A razor blade bent in a "V" shape is a great tool for carefully scraping the glue, but it is extremely important that you only scrape the glue.



After you've removed some of the excess glue, you can finish the job with 600 grit on the orbital.



As you can see, the crack is nice and tight, but the finish is a little dull.



For light touch-ups, spray can nitro is perfect.



Now I've got a decent amount of finish on, but it needs to be satin to match the guitar. (not to mention the fact that those ugly droplets from the can need to disappear)



Grab some 0000 steel wool and rub the whole area down.



That's it! You will probably still see where the crack was a little, but it is stable, closed, and under the finish.

#2
Thanks for the guide. So this happens when there's too little humidity yeah? Is there anything to do with the quality of the guitar, construction etc. that makes this more likely? I would have thought the bracing would stop anything like this happening. (btw PM Jim and see if you can get this and others added to the tutorials section of the links thread.)
#3
Quote by matt154
Thanks for the guide. So this happens when there's too little humidity yeah? Is there anything to do with the quality of the guitar, construction etc. that makes this more likely? I would have thought the bracing would stop anything like this happening. (btw PM Jim and see if you can get this and others added to the tutorials section of the links thread.)


You're welcome Matt! Yep, this happens when a guitar dries out. Acoustic instruments should be stored in 45-55% humidity ideally. Bracing can prevent cracking sometimes, but the only way to truly avoid it is through proper humidification. Pretty much all acoustics will be subject to cracking in poor storage. We see more Taylors, Martins, etc than we do cheap acoustics really.