Unfortunately, my crack will be very visible. I used clear CA so I don't know why its so dark.
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| Author: | Ricardo [ Sat Aug 11, 2007 1:59 am ] |
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I successfully repaired a crack in the waist of a side with CA, but now I am left with a dark line of CA. Is there anything that will dissolve the CA near the surface, and some technique that will hide the glue line? |
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| Author: | Mattia Valente [ Sat Aug 11, 2007 2:56 am ] |
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Nothing I can think of, sorry! Visiblity is one reason to use hide glue (hot) for crack repairs in non-dark woods (in a dark set of EIR, it doesn't much matter...) |
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| Author: | Billy T [ Sat Aug 11, 2007 3:09 am ] |
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Acetone will dissolve CA, but I would test on scrap and wait till others chime in, there may be better way. |
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| Author: | curtis [ Sat Aug 11, 2007 3:45 am ] |
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Hi what is making it dark? is it dirt in the crack? the ca we use dries pretty clear. sounds like one of those fun jobs where you get to scratch all your glue out of the repair you did, clean it out and re-do it! have a gander at frank fords site frets.com for some help, he's the master! good luck, i'd be interested to see photos if its easy enough to do? cheers p.s when regluing (if you go down that route) if the crack doesn't need to be covered with clamps, you can sand over the glue -filling the crack with correct colour dust. I understand you may not be able to do it here but i've had pretty good results with this method before (works great on r/w fingerboard chips) |
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| Author: | Ricardo [ Sat Aug 11, 2007 4:12 am ] |
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Unfortunately, my crack will be very visible. I used clear CA so I don't know why its so dark. |
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| Author: | Ricardo [ Sat Aug 11, 2007 4:19 am ] |
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[QUOTE=Mattia Valente]Nothing I can think of, sorry! Visiblity is one reason to use hide glue (hot) for crack repairs in non-dark woods (in a dark set of EIR, it doesn't much matter...)[/QUOTE] Do you mix dust with the glue? Is hot hide glue the only glue that won't be darker than the wood? |
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| Author: | David Collins [ Sat Aug 11, 2007 4:28 am ] |
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It's possible that the crack was not fully closed and you're seeing the gap which would appear dark, even if slight. If the crack were fully closed it should not appear too dark after it was sanded unless it was a low viscosity CA that really saturated in to the wood around it. If this were the case then you are seeing darker wood there because it is essentially finished. Wipe some naptha on the side to see what the finished color will be - it's quite possible that the darkness will at least come close to matching the rest of the wood when it is finished. |
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| Author: | Ricardo [ Sat Aug 11, 2007 4:30 am ] |
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I wiped paint thinner on it and the crack was darker. So it seems if there were a way I could dig out the CA then I could fill it with something that would match? |
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| Author: | David Collins [ Sat Aug 11, 2007 4:48 am ] |
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That's a tough one, and unfortunately I think with out some seriously delicate patchwork it's not going to go away. I doubt very much that you're seeing any actual dark substance within the crack, but rather the lack of substance. Even a small gap when filled with something clear like CA will appear darker, simply by the light (or rather lack thereof) refracted through the fill. If your sides are thin enough I would bet that the crack would actually look lighter than the finished wood with a decent powered light source behind it. I hate to say it, but the easiest way by far to get rid of the crack is by getting rid of the side. If you're building this instrument to sell, then I would also say it is the cheapest way to fix it after figuring in the cost of your time. It looks like a compression fracture, and unlike a break on the outside of of a bend those will never go away. I say scrap it and move on with a new set of sides. You'll be much happier when the instrument is done. |
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| Author: | Ricardo [ Sat Aug 11, 2007 4:50 am ] |
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Alas, I hate to admit that you are right, but you probably are. I'll get new sides and move on. Thanks David! |
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| Author: | David Collins [ Sat Aug 11, 2007 4:51 am ] |
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I guess I shouldn't have said "scrap it", but rather sunburst the burst the back and sides. Shading is a beautiful thing, and is a wonderful age old tool of hiding defects. If you don't want to burst this one then set it aside for a future project. |
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| Author: | David Collins [ Sat Aug 11, 2007 4:54 am ] |
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| Author: | Joe Beaver [ Sat Aug 11, 2007 5:18 am ] |
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Ricardo Beautifull Koa... worth trying to save I'd say. |
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| Author: | Ricardo [ Sat Aug 11, 2007 5:33 am ] |
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Joe, that was my thought. Maybe I too will be a converter of big boards into smaller! 
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| Author: | Ricardo [ Sat Aug 11, 2007 6:00 am ] |
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I cleaned out the dark stuff from the crack. I have varying colors of koa dust. Which glue should I use to mix it with? |
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| Author: | Greg [ Sat Aug 11, 2007 6:05 am ] |
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Cyanoacrylates, such as Hot Stuff, require a special solvent for effective clean-up. With normal safety precautions, Super Solvent can be used to clean hands or to remove glue spots from clothes or working surfaces. Do not use on lacquer, butyrate, or nitrate-based finishes. 
I think it is actually acetone |
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| Author: | David Collins [ Sat Aug 11, 2007 6:12 am ] |
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[QUOTE=Hesh1956] Not to reopen any old wounds here on the OLF but again I am one who is firmly in the "no CA ever touches my stinkin guitars" (beyond inlaying some dots....) camp.[/QUOTE] Uh-oh. Where's Rick T today? 
I'm one to say that CA glue has it's places. No creep, decent gap filling strength, bonds well to non-porous surfaces, heat reversible, low flexibility, variety of useful viscosities, etc. Still, as Hesh pointed out, it is quite likely to show through most finishes in the future. If the area is saturated and hardened with CA then it will move differently than the rest of the wood through cyclic humidity changes, and generally will show in the crazing as the instrument ages. There are a lot of lacquers like McFadden's however that seem to have a very high plasticizer content and may age better than others. Really though, I would burst it in a heartbeat. Why do you think bursts became as popular with manufacturers as they did? A natural finish is certainly easier to do in theory, but a burst allows for so much room for error throughout the whole building process without any visible effect on the finished product. It's a beautiful thing...... If the existence of the flaw (though it may have no real effect on the finished product) bothers your conscience, mark it down a hundred dollars and sell it as a second. Tell a customer about a flaw that they may never otherwise know about and you'll be golden in their eyes. |
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| Author: | Ricardo [ Sat Aug 11, 2007 6:23 am ] |
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Hesh, I wouldn't sell an instrument with a crack in it. I'll get new sides and move on. Chock it up to learning, expensive as it was. Thanks all for the feedback - much appreciated! 
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| Author: | Rick Turner [ Sat Aug 11, 2007 6:48 am ] |
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I'll use CA wherever it's appropriate, especially when gluing stuff like carbon fiber to wood or for gluing frets in. Of course it's great for inlays. I thought David's first wordless entry here was just perfect. 'Burst it. The more you try to hide that, the more visible it's going to get, and no amount of koa dust, pixie dust, or star dust is going to make that crack disappear under a clear finish. Put a strip of fabric or a spruce pillar behind it. I've seen some very high dollar luthiers' work fixed and bursted around here... Yes, cross grain cracks in flame figured woods fixed with superglue. The work of probably three dozen luthiers comes through our spray booth here in a year's time, and everybody...and I mean everybody has trouble with koa or flamed maple from time to time. Structurally it's probably stronger after it's fixed and backed up! |
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| Author: | Ricardo [ Sat Aug 11, 2007 7:04 am ] |
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David BTW, beautiful sunburst job!!  |
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| Author: | David Collins [ Sat Aug 11, 2007 7:26 am ] |
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[QUOTE=Ricardo] David BTW, beautiful sunburst job!! [/QUOTE]
Thanks, I actually did that burst in one of my previous lives when I was working back in Kalamazoo.
That was a shot of a 40's Gibson L-5, not mine. If a crack is solidly repaired and bursted over, and would have no effect on tone, aesthetics, structure, stability, anything tangible at all...... is there a defect in the end product? While we're at it, if a tree falls in the forest and there is no one around to hear it........
If a mistake can be well repaired with no signs or symptoms remaining, then the existence of the mistake is more a question of philosophy. Punch a big hole in the face of a headstock then made a beautiful inlay to cover it, is it now a flawed unsalable product or is it a custom upgrade? In replacing a fingerboard on a 50's D-18 I drilled a dot about .100" off in one place. I removed the dot, patched it with a cutoff piece of the same fingerboard, and redrilled. It is impossible (not virtually impossible, but truly not possible) for anyone to see. Would you consider the board to be perfect, or does the existence of the repair make it flawed? I say a flaw does not exist unless it can be detected or has an effect. If it holds neither of those properties than I would be challenged to figure out what properties it does have to consider it a flaw. I should say that although I can understand your ideals, I've been moved in recent years to adopt a more pragmatic approach to instruments. Not less caring or particular about relevant details, but being more "down to earth" in deciding what I feel is relevant to an instrument's quality. Granted, the one lingering complication in this particular case would be it's effect on the crazing pattern in that one particular spot in the future. Still this could probably be worked around with perhaps a sizing coat or a shellac sealer with a little extra gum mastic, then flexible lacquer like McFadden. Or it may be no problem at all. As Rick can surely attest to better than myself, many have mythically high assumptions of the perfection of instruments at the top. Great builders aren't infallible, they just know how to deal well with mistakes that may happen. Not trying to push any buttons, just throwing out some conversation starters for a visit to the coffee shop. Burst it man....... |
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| Author: | Ricardo [ Sat Aug 11, 2007 8:15 am ] |
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David, is not unusual to burst koa? |
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| Author: | Rick Turner [ Sat Aug 11, 2007 8:37 am ] |
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I'm not David, but who cares if it's unusual. That makes it worth more. Actually, we burst koa and it's drop dead beautiful. I'll do a kind of "tobacco 'burst" with just US Cellulose "Warm Brown" and "Van Dyke Brown" MEK stains straight on the wood. To go more opaque, you can shoot the stuff onto tacky sealer or mix it in with the finish of your choice. On that one I'd do the wood stained burst first, and then hit the sealer coat to go really dark in the waist, etc. It's kind of a hybrid 'bust techinque. BTW, I should have at least one of my stained-in-th-wood burst jobs up at H'burg. It's a very old timey look, kind of like late teens and Loar era Gibson stuff. |
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