Repairing a crack on the cheap

[jaybp30]

I've got a Stadolin I really like but it has two cracks running from the tail piece to the bridge vertically, one on either side of the feet of the bridge. I had a luthier repair them but he said I should probably replace the bridge with a full contact to lessen strain on the cracks. I didn't. One of the cracks has come loose. I really don't want to put a ton of money into this mandolin but I do like it and would like to keep it from falling apart anymore. The only bracing inside is one horizontal brace just below the bridge. I assume this is what is stopping the cracks from spreading any higher. I am going to get myself a bridge that makes a wider contact but I'd like to sure of the cracks. I don't really care about what it looks like so would using more glue, including allowing some to dry on the top, sure it up any better than doing a neater job just along the inside of the crack? I'd really prefer to do it myself and not pay another $100 on top of the new bridge. It's not a great picture but you can kind of see the cracks come up from behind the tail piece toward the bridge. The one that has come loose is on the treble side. I'd like to continue using .11-.40 strings because it sounds good with them.

[pops1]

The strings may be part of the problem, I would try and use lighter strings and see how they sound. Ask your luthier what kind of glue was used. Leaving glue on top would only look bad and not help. I would get a full contact bridge and have it fit to the top. Good luck.

[ProfChris]

Glue itself is very weak stuff (mostly), so filling the crack with glue won't do much to hold it together. What glue does is to hold two bits of wood which are touching together, and it does that very strongly - so it only works if there's no gap between them!

If those cracks aren't spreading past the brace then I don't think they weaken the top, so I might consider just leaving them as part of the instrument's mojo.

Epoxy will fill cracks, but it won't stick to old glue. So you need to clean out the crack somehow. And if you don't have experience applying and cleaning up epoxy, the top will look utterly horrid when you've finished.

I'd be more worried about why the cracks are opening up. This suggests low humidity where you keep it, which causes the wood to shrink across the grain. If it's shrinking, that might cause other, more structural cracks.

[jaybp30]

I was worried about the humidity. I do have an oasis case humidifier. Do you think 2 would be better.

[Jim Garber]

Those bridges are really nothing to write home about. Keep it in case you want to sell it and the buyer prefers originality and get a good quality bridge. From what I can tell this is a solid wood instrument—one of the better SOLs, probably why the tops cracked.

[multidon]

Loosen your string tension immediately!

You mention your case humidifier, which is a good one. But you don’t mention the case. If it’s one of those chipboard cases it really doesn’t seal well enough for any humidifier to be effective. A proper hard case would be much better. And it doesn’t have to be expensive. A Musicians Friend house brand case will do just fine. The real key is, can you get the cracks to close just by humidifying? Try just humidifying in a tight case and if the cracks close up you’re in business. Let it dry out again a bit so they open up, then you have to clean out the old glue. Try to find out what kind he used. If he used something water soluable like Titebond or hide glue vinegar should remove it. Careful though, you don’t want it slipping around everywhere on the inside. A product called De Glue Goo is basically jellied vinegar and easier to control if you can find it. If he used epoxy or superglue, it will have to be tediously scraped it, very carefully, without removing any wood at all. Tough. Then once the joint is clean, massage in some Original Titebond (not 2, not 3, only original with red label). I’m not kidding. Actually rub it into the crack to make sure there’s enough in there. When you’re done with that wipe off the surface with a slightly damp sponge, place in the tight case with the humidifier, and leave overnight. The humidification should act to close the gap in the crack, effectively clamping it. In the morning, any squeeze out on the top should be able to be removed easily with a damp sponge. And you’re done!

If it were mine, I would try to prevent further damage by using light gauge strings, having a full contact bridge installed, and keeping it humidifier when conditions warrant it. Your oasis is a good choice, but it needs a nice tight case. It doesn’t have to be hermetically sealed or anything, just reasonably tight around the lid.

[jaybp30]

Loosen your string tension immediately!

You mention your case humidifier, which is a good one. But you don’t mention the case. If it’s one of those chipboard cases it really doesn’t seal well enough for any humidifier to be effective. A proper hard case would be much better. And it doesn’t have to be expensive. A Musicians Friend house brand case will do just fine. The real key is, can you get the cracks to close just by humidifying? Try just humidifying in a tight case and if the cracks close up you’re in business. Let it dry out again a bit so they open up, then you have to clean out the old glue. Try to find out what kind he used. If he used something water soluable like Titebond or hide glue vinegar should remove it. Careful though, you don’t want it slipping around everywhere on the inside. A product called De Glue Goo is basically jellied vinegar and easier to control if you can find it. If he used epoxy or superglue, it will have to be tediously scraped it, very carefully, without removing any wood at all. Tough. Then once the joint is clean, massage in some Original Titebond (not 2, not 3, only original with red label). I’m not kidding. Actually rub it into the crack to make sure there’s enough in there. When you’re done with that wipe off the surface with a slightly damp sponge, place in the tight case with the humidifier, and leave overnight. The humidification should act to close the gap in the crack, effectively clamping it. In the morning, any squeeze out on the top should be able to be removed easily with a damp sponge. And you’re done!

If it were mine, I would try to prevent further damage by using light gauge strings, having a full contact bridge installed, and keeping it humidifier when conditions warrant it. Your oasis is a good choice, but it needs a nice tight case. It doesn’t have to be hermetically sealed or anything, just reasonably tight around the lid.

Thanks for the advice. I am going to do exactly this and see how it goes. Right now my case is holding the humidity around 38-39%. I may try and put some kind of rubber insulation around the edge in areas that don't look well sealed and see if that helps.

[pops1]

Put it in a garbage bag with a damp sponge in a plastic bag with holes. Tie a twisty around the bag, for get the case, it will humidify way faster. Keep the mandolin above the bag with the sponge. You can tie the twisty around the bag and the mandolin neck to keep the mandolin from touching the bag with the damp sponge.