verona
Oud Lover
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soundboard crack repair
what is the best way to repair a minor crack in the soundboard, is there a way to do it from the outside, as the soundholes have rosettes?
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Dr. Oud
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you can just rub some glue in the crack. Hide glue is best for this. Be sure to clean up the excess glue before it dries.
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fernandraynaud
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How wide a crack would you feel confident to fix with this method?
Let me explain. I have a crack in a clavichord soundboard, and I see it expand and shrink with changes in humidity, say almost 1 mm at its widest. The
way I was preparing to use is to cut a sliver of the soundboard material, push it into the crack with glue. Then trim it flush with the soundboard.
So is it better to make it wide and use the shim, or make it narrow and use only glue to try to hold it together?
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jdowning
Oud Junkie
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Does the sound board crack affect the acoustic response of the instrument? Sometimes small soundboard cracks are of little consequence acoustically
and structurally - so might best be left alone.
I have maintained/repaired 19th C keyboard instruments with many sound board cracks in evidence that were left as they were - to expand and contract
with humidity changes - without any obvious consequences. For example one 19th C reed organ that I had to fix had a sound board crack about 3 mm wide
(the local Museum's humidity control system had been incorrectly set over the winter period). This was repaired with a flexible rubber cloth patch (to
prevent air leakage) but which would allow the crack to close up again under the more humid conditions of late summer.
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Hank Levin
Oud Maniac
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Crack Repair in Spruce Faces
Sometimes a slight crack doesn't hurt the sound. Sometimes the instrument's bridge will halt the spreading. However, it is likely to spread---even
when it runs up to a cross-brace. Usually a crack is the result of inadequate humidification, although if the wood was not thoroughly dried and
cured before construction, a crack is inevitable.
It's a pain in the butt to get inside an oud or lute to back up a crack from inside, so it's tempting to Q & D the work. Cracks that are handled
by rubbing glue into them are always sloppy looking. Furthermore, this does almost nothing to keep the wood together when the face is again under
tension from low humidity. Also, the old technique of forcing a spruce wedge into a glued crack inevitably results in "tenting" of the face due to
greater pressure on the top surface of the face.
Important Facts:
1.Hot hide glue is the only adhesive I've found that does not discolor spruce.
2. It's important to fix cracks quickly, before the two sides shift to different levels, necessitating cleating from underneath to pull them into the
same level. There are several ways to do that, but I won't get into them here.
If the crack is "hairline" or disappears in humid weather, and you are willing or able to get inside the instrument, wait for a time that it is
relatively dry and the crack is open. Cut thin paper patches about 3/8" to 1/2" wide to back up the crack; if the crack transcends ribs, cut
it in segments to go between the ribs. (You want thin paper because it will be soaked with glue, applied to the back of the crack and allowed to
shrink---and thick paper will absorb a lot of glue, and put so much tension on the underside of the face that it will "tent" when you are done. Thin
paper is plenty strong to hold a thin oud or lute face; that's what's holding the back together! Mask both sides of the crack carefully with masking
tape so you don't smear glue all over the face, and force thin hide glue into the crack. Immediately brush the same thin glue on a section of paper
and on the corresponding surface area of the crack inside the face. Position the paper where it belongs, pat it down with your wet finger and/or the
bristles of a glue brush (you might want to use a different one than the one you are using to apply the glue), and immediately move to the next
section of paper patch. You can kind of see the position of your paper patch using a small mirror, or shining a tiny powerful flashlight from inside
the instrument through the spruce face. You have to move fast, to keep the glue from chilling before you're done. If you suspect that the
glue has chilled, brushing the paper patch with hot water will re-activate the glue. When finished, move the instrument into a relatively humid room
(perhaps where you have been boiling water) to allow the face to expand enough to minimize the crack. Let it sit for 8 hours or so until the glue in
the paper patches is thoroughly dry and contracted.
It takes some skill to not make a big mess inside the instrument with this technique. I recommend a number of "dry" runs before you commence. Good
luck.
If the crack is open, here's a technique I was taught many years ago by Dave (Jose) Rubio when he was in New York. The crack must be opened up just
enough to make the sides of the crack parallel and its insides straight up and down. You can do this with a "diamond deb" type nail file, of the sort
classical guitarists use to shape their nails. The crack must be allowed to follow the grain.
After you clean up the crack as described above, you take a scrap of matching wood, preferably waste from making a top, and choose a section with wide
year lines. You carefully cut a filler strip using only wood from between the year lines, so that when it is smoothed out it will be slightly
too wide to slip into the crack. The splint must be deeper than the thickness of the face, and it should be just a few millimeters longer than the
crack.
Now you place this slightly-too-thick spruce filler into a large vice with smooth, clean jaws, and compress it down to where it's an easy slip fit to
drop it into the crack. Bevel the ends so that when the filler seats, the ends of the crack are nice and clean (rather than black globs of dried
glue). Do lots of dry runs, 'cause when you put this filler in you'll only get one chance.
Mask the sides of the crack with masking tape to keep glue from going all over the face. Apply medium viscosity hot hide glue into the crack and
immediately slide the filler splint into the crack. Press it gently into the crack so that it barely sticks out above the surface of the
instrument face. Press the ends down so the bevels touch the squared-off ends of the crack. The moisture from the hot glue will make the splint swell,
and create pressure inside the crack. However, because the pressure at the top surface is the same as at the bottom surface, it will not tent. Gently
wipe the excess glue off, or squeegee it off from alongside the filler splint, and let it dry for a few hours. This filler should be as strong as the
rest of the face, and should need no backing.
Carefully shave the excess wood from the top of the filler splint down to the surface of the face. Be careful not to cut into the finish, or on an old
oud, into the dark patina of the old wood. You will be left with a "year line" that is undetectable except for its white color.
How to match the filler to the rest of the face? That's a whole 'nother story, that's actually more difficult than the splint! I'll give you a hint,
though, that will work on an old oud. Boil about 3-4 black teabags in a half-cup of water, let it cool, and using a tiny, tiny photo retouch brush,
dab a tiny amount onto the splint until it approximates the patina of your old oud face.
You can see a picture of me doing such a repair on an old Karibyan oud on my website at http://musicaravan.com/images/P1020826.72.jpg
Good luck. Now you know why I charge what I do to fix cracks---so go and get a good humidifier! --Hank Levin
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fernandraynaud
Oud Junkie
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Wow, thank you Hank,
This is a Clavichord, not an oud, and getting at the underside is tricky. Frankly I'm not sure this crack really matters, though I see some settling.
I think I'll make a photo or two. I will digest the fruits of your considerable experience as best I can.
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