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jdowning
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Restoration of Egyptian Oud - part 3, Soundboard
The soundboard is a real mess but I shall attempt to undertake restoration/ repairs making as little change to the original as possible. Part 1 of
this series includes images of some of the problems and damage to be corrected.
Repair work will include:
- removal, repair, reinstallation of bracing.
- removal, repair, reinstallation of rosettes.
- re-gluing of splits and separated joints.
- patching of broken areas
- rebuilding of the edge tiles.
Before starting, I made a complete digital record of the damaged edges of the soundboard for future reference. The attached images give an indication
of the extent of repairs required around the soundboard edge. On this oud the tiles were originally rebated into the edge for about half the depth of
the soundboard or about 3/4 of a millimeter - similar to edge banding on a lute. Another (unusual?) feature is that the tiles do not extend around the
entire periphery of the soundboard but stop short at the bottom edge of the belly, This part was originally covered by a strip of leathercloth glued
in place.
The soundboard has been subject to repairs and removal in the past so little now remains of the foundation of the original tile installation. Tile
replacement will, therefore, have to be for the full soundboard thickness. The tiles, themselves have also been subject to repairs and replacement in
the past but enough of them remain to indicate the original tile design.
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jdowning
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One consequence of leaving the oud unrepaired for many years (mea culpa!) is that there is consequential damage.
For example, in order to keep everything together in storage, I made the mistake of using 'scotch tape' to 'temporarily' keep the soundboard and bowl
together. The result is that glue from the tape has - over time - been absorbed into the wood and has stained the surface of the soundboard in places.
To remove the staining and 'lift' the glue residues from the wood I used a wax solvent, of the household "Super Goop" variety, applied locally to the
affected area with a Q-tip rubbed in the grain direction of the soundboard and then rubbed dry with a paper towel. This procedure was repeated several
times until most of the stain was removed. The absorbed glue residues were then removed by first coating the area with the solvent, covering with a
piece of brown (absorbant) paper and then applying a hot iron to the area - the softened residues being absorbed by the paper ( an old trick for
removing wax stains). The affected area was then rubbed again with a paper towel moistened in solvent to remove the last traces staining.
This process revealed the bare wood of the soundboard where the glue residue had been removed indicating that the soundboard had been originally
finished in some way to prevent dirt absorption - most likely using a light wax finish(?)
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SamirCanada
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great stuff John Iam glad you restarted on this project.
looking forward to see the updates.
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jdowning
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As the belly is now in a very fragile state it has been temporarily fixed with masking tape to a flat working surface of particle board to protect it
against any damage during handling. Cut outs for the bridge and plectrum guard have been made in the working surface so that the belly can lie flat
and fully supported while being worked upon. Splits in the belly have also been temporarily taped to prevent further damage.
As the original braces are to be preserved, they have been numbered and reference marked so that they may be replaced in their original positions
after repair.
To preserve the oud maker's signature on the rosettes, they have been coated with a clear oil varnish. Without this protection there is a danger that
the signatures might be 'smeared' or otherwise damaged by moisture during the process of un-gluing the braces and rosettes for repair.
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jdowning
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The bars were removed by brushing warm water along the glue joint on both sides of each bar, applying heat locally with a hair dryer and, at the same
time, carefully working a fine artists spatula under and along the glue joint after the glue had softened sufficiently. This had to be done slowly and
with great care to avoid damaging the bars or sound board.
The large quantity of old glue used and left behind by previous luthiers who had undertaken repairs made bar removal a lot more difficult. Full
strength carpenters' hide glue had been used - no thought of any facilitating future restoration work there.!Lots of clean up of old glue remains to
be done.
Many of the bar ends are split or otherwise mangled so they will require glue repairs or patching.
The same strong glue has been used on the rosettes so I have decided to attempt their removal another day,
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jdowning
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I have decided not to try to remove the shams for repair as they are too strongly glued in place and there is too great a risk of doing damage to them
and the soundboard. I shall, therefore, carry out repairs with the shams still glued in place.
In the meantime, does anyone recognise the design which seems to me to be a bit unusual - although there are some 'Arabic' elements? The workmanship
is quite rough.
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Mike
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Your threads are some of my favorite JD! I have really enjoyed watching your pain staking work on this restoration job. Awesome work my friend.
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jdowning
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Hi Mike - thanks for your kind remarks and glad that you find the threads to be of interest. It is my pleasure to share experiences and thoughts with
the many friends throughout the world who make this forum such a success - and to learn a lot from other contributors in the process.
Cheers
John
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bulerias1981
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By the way.. what was the height of the braces?
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jdowning
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The attached image is a sketch drawn to scale of the sound board viewed from underside to show the bracing layout.
The maximum height and width of each brace is shown measured in mm. The cross section of each brace is also shown tapering from maximum width to about
2 mm at the top of each brace (a truncated triangle). The braces are cut away in the usual fashion reducing the ends to a depth of about 8 mm where
each brace meets the bowl - the cut away starts about 7 cm in from the end of each brace. All work rather roughly executed.
The wood of the braces is quite light (low in density) - similar to cedar wood. The grain of the braces in cross section runs roughly parallel to the
face of the sound board i.e across the brace - as is usually found in old surviving lutes (not vertical as in modern guitars).
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Mehran
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Sweet, are you resuming this restoration then?
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bulerias1981
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jdowning, thank you..
Interesting. I have another image of this oud, but without the bracing heights. ( I supposed you just added that now?)
I'm curious about the effects of braces running vertical grain to horizontal on the soundboard.
If this oud is 100 years as you believe, its interesting to see the measurements being very standard, and still common place today in ouds.
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jdowning
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I am currently clearing out the room where the oud and lots of other stuff have been stored as well as my workshops - so that there is more space to
work. This meant that I had ready access to the braces and yesterday added this information to the original drawing (that was made back in 1975).
The horizontal grain of lute braces may just have been that the braces had been cut from the same pieces of quartered wood as the thin split sound
board billets? The other advantage is that with the grain in the horizontal direction the joint surface of a brace is less absorbent than is the case
with vertical grain so creates a somewhat stronger glued joint but I doubt if there is much advantage either way - structurally or acoustically.
This is one of a number of instrument and non instrument related projects currently 'on the back burner' awaiting further action as time and
motivation permits. Perhaps this would be a good time to pick up the threads of this project - once the room clearing up work is out of the way.
The plan will be to rebuild the edge of the sound board - to the width of the original edge tiles - with sections of 2 mm thick sound board spruce
(after cutting away the remains of the original tiles) - with grain direction matching sound board grain direction. After repairing and refitting the
sound board, the spruce 'banding' will then be rebated to half depth and new tiles fitted - slightly wider than the original in order to overlap the
spruce/sound board edge joint for strength. This way the original half banding arrangement will be replicated.
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jdowning
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After having made progress in clearing some workspace today I have decided to pick up the thread again on this project (the work needs to be done
sooner or later).
The next step is to clean all residual glue from the braces and sound board - starting with the braces. Once the glue has been cleaned off it will be
possible to assess the extent of damage to the braces and the repair work required. The intent is to use the original braces.
The glue residues are hard and brittle and have been applied in excess. Chipping away the glue with a knife or chisel is not an option due to the risk
of tearing and damaging the relatively soft but brittle wood of the braces.
The method for glue removal is to first brush water onto the heavy glue deposits, apply a wet thin cotton cloth over the glue and then apply a hot
iron to the cloth. The hot iron (at about 450°C) instantly generates steam that quickly softens the glue. The softened glue is absorbed into the
cloth, the cloth then sticks to the iron allowing the soft glue to be wiped off the brace with a sliding action of the iron. This procedure is
repeated bit by bit using fresh cloth as it becomes contaminated with the absorbed glue.
This is a slow but quite efficient process.
The cleaned braces will be left to dry for several days.
The braces have been numbered in pencil (Arabic numerals from 1 to 6 - not counting the half braces on either side of the large sound hole). Every
effort will be made to preserve these original markings. Brace #1 is below the bridge and #6 is at the neck block.
Note that the cross grain of the braces is not perfectly parallel to the sound board surfaces but varies between about 30° to about 45° from
horizontal.
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jdowning
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With the braces cleaned up some of the typical damage requiring repair can be seen.
Brace splits occur when the sound board is carelessly removed - a combination of driving a hot spatula into the end of the brace and attempting to pry
the sound board loose before adequately softening the glue at the end of the brace with moisture and heat. The damage is easily repaired however.
Not sure how the ends of two of the braces became so 'chewed up' over time but this will be fixed with a small 'splice' repair.
With the braces cleaned up, next step is to clean up the underside of the sound board to remove all surplus glue. This was achieved using the same
damp cloth/ hot iron procedure used for the brace clean up as previously mentioned.
The attached image shows the area under the fingerboard inlay before and after clean up with glue and the original paper reinforcement removed
Removal of the glue is made more difficult because the whole underside of the sound board had been originally scored with a toothing plane. Not sure
why the sound board underside was finished in this way - possibly just to ensure a uniform flatness but without then going to the extra trouble of
planing out the grooves as would be the usual practice in sound board thicknessing.
More to follow.
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jdowning
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The shams were covered in excess glue and had been 'repaired' in the past with 'globs' of glue spread over the splits and cracks.
Due to the fragility of the sound board the shams are to be repaired in situ.
Excess glue was again easily removed with the damp cloth/hot iron technique. The glue 'globs' were picked out with a dentists pick after the glue had
been softened. The open cracks will eventually be filled with matching wood.
One problem with use of water and heat for removing braces and excess glue is that the accumulated dirt of ages - in grained in the sound board wood -
mixed with the water can cause unsightly 'watermark' staining on the sound board outer surface.
To remove these stains (and a great deal of accumulated dirt) the offending areas are rubbed with a moistened cloth dipped in Pumice powder. Pumice
powder is a very fine abrasive (volcanic ash) used for final polishing of varnished finishes. The fine powder picks up the dirt producing debris
similar to that produced by a pencil eraser. Eventually the whole outer surface of the sound board will be cleaned up in this manner.
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jdowning
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The damp cloth/ hot iron technique requires a plentiful supply of rags that are discarded when contaminated with the old glue.
We are, of course, removing old hot hide glue in this project.
The surface of the hot iron also picks up a lot of the glue so must be cleaned at intervals. This is easily done - after the iron has cooled and
disconnected from the power supply (!) - with hot soapy water and nylon bristle scrubbing brush.
This work could just as easily be carried out without a fancy, thermostatically controlled, electric iron - using just a plain iron heated over a
flame but - of course - an electric iron is more convenient and a bit safer.
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bulerias1981
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The average top thickness was 2mm?
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Marina
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jdowning
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The average sound board thickness is probably less than that and the edge - due to repeated removal of the sound board for past repairs - is thinner
still. The 2mm edging is just to give me room to play with before final thicknessing.
I cannot recall if I have previously surveyed and recorded the sound board thickness so will do this for the record and post the results later for
information.
Note that the measured thickness (about 1.5 mm if I recall correctly) will be somewhat greater than the minimum average due to the toothed surface - a
caliper measurement only recording the 'peaks'.
Did the maker use a toothing plane to produce a more flexible sound board without significantly reducing overall sound board mass or was he just
taking a short cut to save construction time? Another possible reason for a toothed surface is that it provides a greater surface area for gluing the
braces.
For those unfamiliar with a toothing plane, attached is an image of my antique toothing plane. Note that the blade is set at a very high angle and is
scored on the back face with vertical grooves to produce 'teeth' along the cutting edge. In use the teeth score the surface of the wood into fine
grooves. These planes were once used to work wood with difficult grain before final finishing using a regular plane or cabinet scraper (to remove the
grooves). They were also used to prepare a wood surface prior to veneering the plane levelling the surface and grooving it to provide a greater
surface area for gluing. Some luthiers use the toothing plane as part of the sound board levelling process.
Toothed plane blades can be purchased from Lee Valley Ottawa designed to fit their regular planes but at one time the old blades came in three grades
- Fine, Medium and Coarse.
In this case the oud maker failed to remove all of the original saw marks from the underside of the sound board - again a sign of rough workmanship -
out of sight out of mind!
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SamirCanada
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Sweet looking plane John.
looking forward to follow this thread.
@samiroud Instagram
samiroudmaker@gmail.com
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jdowning
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Here is the sound board thickness plot giving the nominal thickness in millimeters - measured with sound board calipers.
Due to the age of the sound board it is possible that the thicknesses were even greater than measured here.
These thicknesses are of the same order as those found on surviving lutes of the 16th/17th C.
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bulerias1981
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Interesting thickness scheme. Slightly heavier on the right side.
What do you mean the thicknesses are of the same order?
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jdowning
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By 'the same order' I meant the same order of magnitude and distribution as the measured sound board thicknesses of the old surviving lutes where
thicknesses can range from 1.1 mm in the case of lute #M154 in the Germanisches National Museum, Nurnberg by Laux Maler to 2.4 mm in the case of a
large lute by Matheus Buechenburg #142/470 in the Museo Bardini, Firenze.
These thicknesses should be regarded with some caution as the surviving sound boards - some nearly 500 years old - likely have lost some of their
original thickness in the passage of time due to dessication of the wood and repeated removal and refinishing of the sound boards for repair. The
general pattern is that the lute sound boards are thicker around the edges and a bit thinner in the centre. However it should be noted that the
central area around the 'cut in' rosette(s) can be as thin as 1 mm to facilitate cutting of the rosette.
In the case of the Laux Maler lute #M154 it is suspected that originally the sound board was quite a bit thicker. A recent discovery of another lute
by Laux Maler has a sound board thickness averaging 2 mm (see http://sinierderidder.free.fr under 'Restorations').
A further complication is that lute making in the 16th and
17th C was big business and there is evidence that some of the prominent makers (Laux Maler included) purchased components like sound boards - already
prepared with rosettes cut in - from specialist suppliers. So, it is not known if the old lute makers originally deliberately (for acoustic benefit ?)
created thick and thin areas or if the sound boards (with the exception of the thinned areas around the rosette) were originally pretty well uniform
in thickness.
I also have to doubt that the maker of this project oud - judging from the rough workmanship of the sound board - attempted any kind of refined sound
board 'tuning' by adjusting thicknesses. If he did then he may have 'got it wrong' by making the bass side thicker than the treble whereas the reverse
should (theoretically) have been the way to go.
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Yaron Naor
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Again...
That's another superb work of yours with so much details...
Thanks a lot
Yaron Naor
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