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Well, I was closing in with the old Bay State parlor guitar about which I posted a few days back regarding pricing.  As I'm French polishing the back after all those repairs, I'm noticing that there are mat finished lines in the oil sheen left after one of my polishing sessions building up the layers.  I spirit off the oil and notice that my once smoothly filled crack repairs are not smooth anymore, and when I press around, the horror of fresh splits along the repaired cracks become apparent!!!!!  It appears that just the light pressure involved in applying the shellac was enough to crack it back apart in some areas.

When I started the project, I first tried to reglue the broken halves of the back and all the other cracks, I used freshly made hide glue.  This didn't hold for the major splits in the back, so I cleaned out the cracks and splits and started again with LMI white glue.  This seemed to do the trick, but once I got the back reglued to the rest of the body, they started to open up some and spread in some areas.  I took action by using epoxy this time and thought this was the answer....not so it appears.  So, with the cracks being very fine, but clearly separated, I chose super glue as this would run throughout the crack and hopefully solve the problem. 

Also, I've just recently had to repair a new crack along the side near the purfling on the lower bout due, I'm sure, from the added pressure of the back being reunited to the body after over 15 years of being apart. (All cracks and splits have cross patches but the fine short ones near bracings, and they seem fine anyway.

Did I do the right thing here?  Is there something else I should do?  What about chemical incompatibility of three different glues in there?  Is this going to be a playable guitar or not?....I was so very hopeful, even certain, but now I'm freaking out.

Please advise.

Thanks!

Tags: back, crack, cracks, cross, glue, guitar, patches

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I had the same problem with an old Gibson back .It all looked real good untill I started to buff it and then they all apeard again .I think it is because the wood is to thin. Anyway I could not do anything with it. Good luck Bill.""""""""
Maybe try a large cloth path?
Pierre, I'm not sure I understand. Could you please explain?

Thanks!
I think he maens cloth patch .Len
OK, I see what you mean. Thanks.
You're right, sorry!
so i am not into french polishing but i have a question maby an idea to try ?can you put down sanding sealer first to spray it with sanding sealer first and then french polish over the top this process is done with lacquer over the top of sanding sealer to improve the coat, it is applied first to fill large grain instead of a poor filler .if i were dealing with such a crack i would fill it with nitro or sanding sealer first to then proceed with top coat .
I had everything filled up before leveling and beginning the shellac application. Then a couple of days after my first session of shellac application, I noticed the cracks opening up in select areas where once they were entirely smooth. It was more an issue of the wood appearing to be unstable. This poor thing has been through a lot over the years. I sanded down, reglued the cracks, leveled and began again....so far so good, we'll see. I wanted to stay with the shellac as this is the original finish for the whole gutiar, and I don't have a spray booth, so it seemed a win/win. The French polishing itself seems to be going fine, just the cracks have been an issue. Thanks for your thoughts Paul!
john yes thank you for reviewing my post, humidity also may be a player in this game also is it a possibility to supper glue the crack with thin s glue.The french polish is a form of lacquer and should go clear when applying top coat over the supper glue .so that the crack dose not grow or sink after all your hard work is done .also about the repair and staying simple even if the guitar is shellac and needed this re pair, I may conciser a different route even going with nitro, it is a re pair and I some times need to tell my self this when doing my best i hope you find a way cheers phb
John,
It sounds like the main cause of your crack problems is excessively dry wood. Prior to your re-gluing attempts, did you humidify the guitars interior? If the cracks you are trying to repair weren't caused by physical impact (e.g. bumping, dropping), then wood shrinkage due to loss of moisture is your enemy. Try placing a guitar humidifier (either store-bought or I can tell you how to make a homemade one) in the guitar for several days. Restoring moisture to the wood will restore pliability to the wood, making it less prone to new cracks, and will swell the wood fibers overall, closing the cracks you already have, making it easier for re-gluing. Once you've done that, any water-based wood glue (hide glue, Titebond, etc.), should be more than enough to hold the cracks together, and allow you to re-apply your finish. Scott
Once I got the back put back together in early winter, I slowly reunited it with the body with clamps but no glue, trying to get the body used to being friendly with the back again after at least 15 years of separation. During this time I used the sponge in rubber tube style of humidifier. I got the idea of adjusting the guitar dry with only clamps from an article in Frets.com where a warped body was corrected on an archtop. I reglued a back bracing that popped loose recently and reglued the cracks that had opened up, and it's resting with a humidifier in it now. I could do better at maintaining my work space with regard to humidity. I'm going to buy a room hygrometer right away so I know what's actually going on in there. I have a room humidifier, but often forget to fill it and use it, but we've had some rain recently, so I haven't been too concerned. I will keep on top of this more, thanks for bringing it up. Also, William in the first response above, noted that the back might be too thin. I think this is certainly possible as well. It looks thinner than others. Thanks for your input! Much appreciated.
Here in Minnesota where we see literally hundreds of (low) humidity cracks every year we have found that cracks MUST be cleated after rehumidifying and gluing. Otherwise they will reappear.

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