I had a guitar I built come back with a couple of top cracks that the owner said occurred when the bridge came loose, although looking at the abused case, I have to wonder what caused the bridge to come loose. One long crack runs toward the butt of the guitar from the 6th string bridge pin hole for about 7 inches (see pictures). The other crack is in the center seam and runs about 2 inches across the bridge area (can't really see this one, but it is there!).  Since the owner (a relative) was going to leave it with me for several months, I opted to remove the bridge, remove the finish from the top (kind of regret this step now), humidify the guitar to get the cracks to close up, fix the cracks, and then refinish the top.  I used thinned yellow glue, pressed on the inside of the guitar near the cracks, as I attempted to work the glue into the cracks with my fingers (at least I thought I worked the glue into the cracks). Actually, I think it was yellow glue and not hide glue. Unfortunately, I didn't write it down and it has been too long for me to remember!  I then clamped it up and let it dry. The next day I made some small cleats that I glued (with hide glue) across the cracks in a couple of locations on the inside.  I then hung it up in my humidified shop where it stayed for a few months until I could get back to it to reapply the finish.  When I came back to it last week, the cracks had opened up again!  I am guessing that I didn't get glue into the cracks like I thought.  I humidified the guitar and am able to get the crack to close up. I removed the cleats on the inside and am now wondering what to do to really fix the cracks!  I would like to use hide glue, but I fear that I won't have enough working time to get the glue into the cracks before it sets up. I probably worried about that last time and is why I think I may have used thinned yellow glue the first go around.  Any suggestions on how to make sure the cracks are really fixed this time?

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It is a very narrow crack.  It is just too big to close well, so do I need to cut a "V shape" in the crack and fit it with a V-shaped spline? I am concerned about widening the crack too much and making the repair really conspicuous, or could I just fit in a spruce shaving?
I can't tell from the pictures but you're going to be finishing over it so it should be pretty hard to see (if at all) when you're done.
If you take a bit of time trying to get a fairly close match to the original wood and grain, it will be pretty hard to see after a refinish. At any rate, it should be harder to see than a reoccurring crack. If I can't get a really close match on the color, I like to use something a bit lighter so I can touch it up with stain.
Here are some pictures of the splint I put in to repair the crack. I tried to match the color as best I could with what I had, but it is still a little light. There is no finish on the top. Any tips or techniques I can use to blend it in with the rest of the top either before I apply the finish, or after, or both?
Ned, would it work for Philip if  he masked off the entire top, except for the splint, and put it in the direct sunlight for a few days? I know that even a single day of direct sunlight will yellow a top. I had a guitar retopped about 20 years ago, and had to put the pickguard on after it came home. That whole 1st day, I was out in the sunshine and at the end of the day the pickguard fell off! (vera old two way tape)  There was a totally distinguishable line exactly were the pickguard had been, and the rest of the top was yellowed...


I think it may be possible but I usually just use a very fine brush and touch it with stain. I keep some alcohol based stains that I mix very thin for this sort of touch up. I've never thought about what you suggested. I don't know how much of the yellowing is actually the wood and how much is the finish. The wood will oxidize naturally with exposure to the sun and air but most of the finishes we use yellow too. 



I would be tempted to just leave it and let nature take it's course but since it belongs to someone else I would probably add just a bit of tint to get it a little closer to the rest of the top. You might wipe down the area with naphtha or alcohol  to get a feel for the finished colors.


When I tint a repair, I don't try to get the depth of color I need in one application. I like to keep the stain light and thin and work my way up to the color I want. The alcohol dries so quickly that it doesn't take much time.  I prefer to leave it a bit lighter than the surrounding wood and I like to check it in direct sunlight to get a better feel for how well it actually blends.  In the end, leaving it a bit light is better, time will blend it all together.


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