Official Luthiers Forum!

Hi!

I have just received an used Martin D-35 that has a glued crack in the top behind the bridge. The crack is filled with glue as I can feel the hardened glue from inside of the guitar. The repair seems stable. However, the crack in the top finish is either not repaired or the repair has failed. As you can see from the photos there is a deep crack in the finish. How can this be repaired for the best cosmetic result? My local luthier would not touch it as it would be time consuming for him and he tought I could repair it just as good myself. He suggested touch-up pen with amber color in the crack and then seal it with nitrocellulose laquer. Any other suggestions?

I think I would have to clean the laquer edges with a scalpel and would have to fill the defect with some colored filler. Gluboost with amber filler? Touch-up pen? I will level the repair with a razor blade and sand it with 1000/2000/3000 grit and finish with buffing. All suggestions is appreciated.

Regards from Norway

Someone did a terrible job on this one and once there has been a prior, hack... repair lots of shops won't touch it. We wouldn't either. No one wants to get any of it on them so-to-speak reputation speaking.

These cracks generally can be repaired when done soon after the crack invisibly and inexpensively and most of the time you may not be able to see it even without touch-up work, again if done well, well leveled, well closed, etc. This one is way beyond that now.

What does the inside look like, cleats, if so how many, how big, etc? What color is the glue you see too?

From what I can see from here the glue was used as a filler and the crack was not properly closed when glued. This will fail if exposed to drying out again which is likely what caused this crack. It's a very common dryness crack we see on Martins frequently in our neck of the woods, Michigan. Or, in other words the guitar was not properly humidified in a winter and/or permitted to dry out somehow even if there is no winter where it lived.

So what to do now? It's a big can of worms and as I said we would not touch it. My first concern would be the structural integrity of the lousy prior work so that inside look would be important.

After that the only way to improve the looks of this is with a LOT of work, time and effort and if done commercially it would be expensive if you could find someone to take it on. Reopening prior poorly glued joints (if even possible depending on glue used...), cleaning the glue out and this one could not be closed now, too much wood is seemingly missing. So it's open it up, remove all the old glue, make a uniform and open slit and then fill the thing with a hopefully matching piece of wood. Braces may be loose too be sure to check that it's common with these too.

Any attempt to use filler to do anything other than provide a smooth, level top surface effectively cosmetically repairing the lacquer will do just that and only that, repair the finish. The damage to the structure as it is now will show as it does now.

There are people who dabble in Lutherie and are not brick and mortar businesses with proper insurance and guarantees for all concerned including you. These folks often will take on things like this and just as often the results are similar to what we see here.... so be advised AND warned.

If it were mine and I am in the business of advising people what to do with their broken guitars it's how I make my living when not socially distancing... I would 1) learn to live with it and accept it as it is IF.... and only IF the structural aspects are addressed too. Or 2) sell it "as is" and very clearly represent the damage and hack repair work. Or 3) find a real Luthier with a decent reputation who will take it on, the economy has tanked now so some folks are going ugly early these days in doing things they would not normally do. Find a real Luthier and get a quote and if that works for you have it professionally repaired.

FYI the back edge of the bridge should be checked for a gap too and you can use a piece of thin paper or a post-it-note corner to try to push it under the back edge of the bridge and the wings too looking for the beginning of a failed bridge glue joint. This often goes along with this kind of crack and will be important in your opportunity to understand the entire problem here and ALL it's possible associated costs and pitfalls. Check for loose braces too, everywhere....

I would not take this on your self, matching finishes and repairing cosmetic damage is one of the hardest skill sets for any Luthier to learn and it can take a lifetime to do well.

Good luck to you and let us know what you see inside it too please as well as if the bridge is starting to lift on the back edge and wings.

Thank you for your in-depth reply

The thing is, I really like this guitar. It sounds and plays awesome and apart from the crack it is the best acoustic I've played since I started playing for 35 years ago, and I'm 40 now... I would not sell it.

I looked inside and provided a picture. The biggest crack is sealed and glued without cleats. One can see the hardened glue drops underneath this crack. The smaller crack passes light so it is not glued although it seems to be covered in cyanoacrylate from above to fill and flatten the finish flaw. There are no gaps in the bridge and the braces are stable.

The goal here for me is to make it structurally intact and to minimize the finish flaw so it becomes less visible. I does not need to be 100 % perfect as I regard this guitar as a player, but the flaw is not acceptable now. The local luthier, a well respected guy who builds excellent guitars, will not touch it so I guess I'm on my own on this one.

That is not a big deal, but if you try this with no experience then it will likely turn out poorly. I am not going to give you detailed instructions for repairing this because I don't think you should attempt it. Try to find a good repairman, not necessarily a builder because they may have no idea how to repair guitars.

So as the local luthier here in Norway will not touch it I am on my own. Have no other realistic option than to try to repair it myself. I have some experience, but far from a professional.

So here's my plan:
Re-humidify the guitar. Will start with masking tape and expose the open crack that is filled with CA. Will remove the CA with acetone and try to align the crack. Then glue the crack with liquid hide glue, clamping sideways if needed. After 24 h fill the finish crack with Gluboost and level with a razor blade with taped edges, wet sand and buff. Then cover that crack with masking tape and expose the previously badly glued crack that seems to be filled with some kind of glue. Use Stew-Macs De-Glue Goo to try to remove the glue. Realign the edges of the crack, possible with sideways claping, or steaming the edges to have them swell and glue with liquid hide glue. Small areas with bare wood that is lighter in color than the finished tinted wood will taste a promarker with amber color. When cured I'll use Gluboost to fill the damage in the finish and level, wet sand and buff. Then I'll add cleats.

It will not be 100 %, but hopefully successfully glued and better looking. Any comments to that stategy?

Yes don't do it.

I would argue that the crack should not be closed because it's been open too long and it also appears that one of the two cracks having been forced closed prior likely caused the second crack.

I agree that you should not do this yourself but for who would be doing the repair I would leave the cracks open, clean out old glue, expand the cracks so a uniform piece of wood can be added and add wood. Then I would cleat the inside as needed and conservatively since this is an important area of the top. Five very small cleats or so would be on my mind.

Adding wood not only closes the crack but it glues it back together AND relieves the very same internal stresses on the top that caused the cracks in the first place. Forcing a crack closed that is as bad as these two will only encourage new cracks in short order the next time the guitar gets dry.

Fill the cracks with wood, cleat, check for loose braces and reglue if necessary.

Now here is the fun part and that is the finish touch-up which is a huge reason why this is complicated and not recommended for you to do yourself. You will be attempting to match new nitro to amber old nitro....

So again, as mentioned this needs to go to a pro. If you don't have a pro and you have been absolutely sure that you can't find one I would simply stabilize the cracks open with several small cleats on the inside with reversible glue.

Don't use liquid hide glue it's **** and I would not even use real hide glue because it requires experience and special equipment. Do you know that with real hot hide glue your working time is only seconds? We try to have all clamps in place in 15 seconds or less and preheating can extend this time. But HHG is difficult to use for a first timer, avoid it.

Titebond Original ONLY is what I would recommend for you installing cleats on the inside and then living with it.

Be advised that right now the guitar can be repaired. If you attempt this yourself and screw it up badly you will harm not only the guitar but it's real value over what it has now.

I have to add that we, you are in this spot in the first place because of a poor prior repair by someone who likely did not know what they are doing. Do you really want to go there again with this nice old Martin? No disrespect intended it's my life's mission to try to save guitars from enthusiastic repair folks with zero experience faced with a difficult repair like you have here. Sometimes less is more and buying time can provide you with an opportunity in the future to have a proper repair done by a skilled, experienced Luthier.

PS: Did you check with a piece of thin paper all around the bridge joint to make sure the bridge is still all the way glued down? The bridge pins in your picture are not original suggesting that there has been more prior work in the bridge area.

Thank you for your guidance! Seems that there is more work involved here... The bridge needs to come off and then the cracks must be addressed before regluing the bridge. I guess that less contact between the bridge and the top affects the sound. Is there a risk that the bridge may come flying off if it's not repaired immediately? I guess that less contact between the bridge and the top affects the sound.

I definitely have to convince the local luthier to fix this. He has done a few neck resets before with excellent results so I guess this is manageable for him.

Yeah this is very common and we do around 50 of these every winter often on Martins and we are certified for Martin warranty repair but this is not a warranty repair when the guitar has been dried out OR had prior poor work that needs to be reversed.

The term we use my friend is "scope creep" in so much as the repair that we may believe we need to do often turns into a much bigger deal as you peel back the layers of the onion so to speak.

For the record we not only would not take this on we don't accept shipped in work either so I want to get that out of the way so you know that what I am offering here is out of my own kindness and knowledge. My hope is that you can have some trust in what I am offering in so much as much of the crap on the Internet is absolute BS and often leads to guitars being very severely damaged by poor prior work.

So first off if the Luthier who builds didn't want to do it I would not push anyone into doing it. There are often very good reasons when someone does not want to get outside of their comfort zone and/or skill set. I actually applaud this Luthier for recognizing limitations and scope creep and I wish that many, many more people who call themselves Luthiers would do this too.

With this said you should find a Luthier who specializes in repair work. Many builders will do repair work but they don't specialize in it and also don't eat, drink and live it 24/7 so outcomes may.... not be as good.... as someone who has an excellent reputation for thousands of successful repairs. There are always exceptions.

Although I can't see the guitar in my shop and hands and do my own triage on it based on what we know here this would be my approach for a repair Luthier to repair it:

1). Remove bridge properly and with zero damage. We may find that it's been reglued prior and that the glue used is not reversible so this can be a can of worms because of the existing evidence of lousy prior work.

2). A new one for you the neck angle needs to be checked. I don't recall you mentioning the age of the D-35, how old is it? D-35's and all acoustic guitars for that matter may need to have their neck angle "restored...." an reset after any where from 15 - 30 years. They all usually need it eventually and guitars that dried out often need it sooner as do guitars that had 13's on them all their life.

This could be number one but let's check it because we want to do a good job for you in advising you here. If the neck angle is off it will need to be addressed too and it's a big deal but let's see first, maybe we will get lucky and it's not an issue.

Please take a picture of the saddle in the bridge so I can see how much of the saddle is sticking up from the bridge? Also please measure the distance from the bottom of the high e and low e to the crown of the 12th fret with it tuned to pitch and report back.

Thanks.

3). With the bridge off the cracks would be filled with wood, loose braces addressed, finish touch up completed and possibly a refinish of the top if you really want it to be an invisible repair. These often have a B string crack near the pickguard too so check for that or a curling pickguard.

4). Once the "box" the body is all repaired and the finish touched up then we glue the bridge back on and that's a big deal to do well with Hot hide glue, never the bottled crap.

5). Pin holes are cleared of glue from the bridge reglue and reamed for the 5 degree Martin pins.

6). This should be in number 2 but look at the bridge plate too with a mirror where the string balls sit on the bridge plate inside the guitar. Let me know if it's chewed up and that's a likely thing on these too and would have to be addressed.

7). the instrument is set-up and ready to go. It may need other things too like a fret dress but we can talk about that later.

Let me know what you see and I am sincerely sorry to be the one to tell you that what you have here needs more work than we might think initially. That is often the case. Cracks lead to lifting bridges, poor, deteriorated neck angles are par for the course too as are chewed up bridge plates with lifting bridges. It's a chain of events if you will.

But it is ALL repairable and you cannot buy a new Martin that will have the seasoned sound of this older wood so let's fix her up, let's make her perfect or very good and let's make you happy.

Lastly bridges usually don't fly off unless it's a cedar top or an exception. The failure tends to take some time and be gradual. You can play her this way if you want but please don't exceed 12's for strings to keep the tension down and please also check the bridge for a widening gap monthly. If you see the gap increasing get it repaired.

I think the guitar should not have any string tension on it until it gets repaired. Leaving it strung up like this will cause bellying and warpage of the bridge plate.

I really appreciate your time and expertise. It showed me the underlying problem, and I have decided to send the guitar away for repair in Oslo by a well known professional after the summer vacation when he's available. Will get new original bridge pins and rehumidify the guitar with the two-way system by Boveda.

The guitar is from 2006 with adjustable truss-rod so it is not an old vintage instrument, but still sounds and plays a lot better than new ones. I don't think it needs a neck reset. The action is low, about 4/64" at the high E and 5/64" at the low E at 12th fret without buzzing. The end of a straight egde hits just a little below the top of the bridge and there is still some saddle left so I think the neck angle is ok for now. But now I see that there is a gap in the heel neck. Is this a problem too?

Ynor, probably a good call on the professional repair.

I once read about a technique for repair of wide top cracks that need a splice to fill the defect. I wish I could remember the source (I recall maybe a French violin maker? - might be wrong). I have never tried it myself, and I would be interested in opinions from Hesh and others. You first clean out the crack and remove old glue and dirt. Then cut a splice of suitable material (in this case sitka) which is a bit wider than the crack. The trick is that you then crush this long splinter of spruce by placing it on a hard surface and rolling the shaft of a screwdriver along its full length. You want this squashed sliver to be able too fit loosely into the crack. Liberally coat the whole sliver with hot hide glue and then just set it aside to dry. Later, dry fit the sliver into the crack and then use steam (e.g. wet cloth and a clothes iron or soldering iron) to swell the crushed fibers of the spruce and simultaneously reactivate the HHG. "Et voila" - the splice expands to tightly fill the void and gets glued in at the same time. Scrape/sand the surface flush. Of course you still have the problem of finish repair - but it always seemed to me to be a neat trick to fit the splice. Anyone else heard of this, or tried it?

I just make a splint to fit the crack then glue it in but that's an interesting idea, maybe useful in some cases, don't know.

_________________
Steve Smith
"Music is what feelings sound like"

Good plan Ynor and you are very welcome, happy to help. The action is great. I would set this guitar up for a finger style player with 4/64th" for the high e at the 12th, what you have now and 5.5/64th" for the low e at the 12th". So the neck angle is fine.

The gap in the heel is troubling tough and Martin would have never shipped it that way which suggests that it's had more prior work and maybe it's even had a neck reset prior. The gap is caused by a poorly fitted dovetail joint and again Martin would never let it leave Pennsylvania this way. The Martin warranty changed a few years ago to no longer cover neck resets unless there has been a manufacturing or material defect. Martin now believes what my business partner and I have always believed and that is a neck reset is just part of normal though expensive and expected maintenance of an acoustic guitar.

If the gap at the heel is not from any form of abuse or mishandling or prior work there would be a warranty claim there but only for the original purchaser who is registered with Martin to the guitar.

Regarding the bridge in a perfect world none of us would suggest that a guitar could be played a bit more with a lifting bridge but that's not my reality or experience. Some bridges can have this gap for years with nothing getting worse. I would have it properly repaired but I believe that you could gently play it with 12's as I indicated prior for a short while and enjoy her before sending her off for repair.

Mark interesting technique and I would have to see it done and know more about outcomes before ever providing anyone with what my take is. My world is a bit different from what's interesting or different my world is all about tried and true as well as reasonable approaches that consistently produce excellent results. We are entrusted with the valuable personal property of others and as such not only do we have a responsibility to do no harm we also have an ethical requirement in our view to never use anyone's personal property for our learning curve. It sounds like an interesting approach though for sure.

We've been pioneering another novel technique by the way that involves ep*xy of all things to fill an open crack with color matched ep*xy with back joint reinforcement like strips cleating the crack open and preventing the ep*xy from falling through the crack. This is for cracks that would be filled with wood but this is simpler, less expensive, fast and when appropriate for the instrument, say a $300 Yamaha a lot more economically feasible than a $300 bill to add wood and do finish touch up.

Elderly Instruments who are our pals and they have ten Luthiers, Dave my business partner used to work there after he taught Lutherie for the Gallop School of Lutherie Elderly is who came up with the ep*xy fill method and who we got it from. We've done it maybe 30 times now with great results.

Anyway there are lots of approaches but generically speaking this one needs to be filled, not closed which would induce more stresses and likely crack again. Any decent method that accomplished this doing no harm and hopefully being invisible when done is a good day. This guitar is also a "player" my personal favorite kind of guitar and a few war wounds only tend to lend cred.

That's funny Hesh, I do this too for a low cost repair on a low cost instrument; just did it on one I've got in the shop. I clean up the crack, put masking tape on the inside over the crack and then tape on each side of the crack on the outside and finally tint the epoxy and then fill the crack. Finish off with normal cleats. Pretty easy to get the epoxy proud of the crack and then just level in the usual manner. Fast and works good.

_________________
Steve Smith
"Music is what feelings sound like"

Very cool Steve and that's exactly how we do it too. It makes a nice, smooth, level repair and quickly too. The epoxy may show a little but it sure looks better than what we see here.