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jdowning
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Marinated Wood - an experimental investigation into fluted ribs
Thin and flat, (under 1.5 mm thickness) lute ribs, when bent to shape on a lute bowl mold, will take up a natural, shallow curve, or 'fluting' in
cross section. This is due to the transverse and longitudinal stresses in the bent rib coming into an equilibrium, or balance, state. This feature may
be less pronounced in ribs made from thicker material - as might be found in modern oud construction.
The attached image shows the fluted rib effect represented in a late 16th C representation of a lute (c. 1595) by Caravagio in the Hermitage
museum.
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suz_i_dil
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If you didn't see it, there is a picture of a bowl like this on the forum, on a Tayyar oud.
And thank you for your explanation, I was thinking they had carved the wood...
But by this fact the bowl become not regular too, is this not of a bad incidence on the sound?
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jdowning
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Thankyou suz_i_dil. I have not seen the picture of the Yayyar oud but will look it up. This subject of fluted ribs has been discussed at some length
on the forum (see the topics "Awsome Oud ribs" on the Projects Forum and "Oud with fluted ribs" on the Ouds,Ouds, Ouds forum). However, I want to
start this investigation afresh with a 'clean sheet of paper' and as few as possible preformed ideas - just to see where it might lead.
My objective in this topic is to investigate how far and by what method wood can be bent and formed into deeply fluted ribs without resorting to
carving. As this is a hands on experiment I have no idea, at this point in time, how these experiments will turn out but - success or failure - it
should be a useful learning experience.
Deeply fluted ribs can be found on surviving guitars, vihuelas and small descant lutes (mandolinos) dating from around the end of the 16th C. On these
instruments, the fluting may created by bending thin ribs or by carving thick ribs after bending. The attached image shows a section of carved fluted
ribs on an elaborately decorated early 17th C vaulted back guitar by Magno Stegher dated 1621 (Charles van Raalte Collection, Dean Castle, Kilmarnock,
Scotland). Typically, the body of the instrument is made from many, narrow ribs measuring about
7 mm maximum width.
Fluted ribs, formed by bending, may be found on two, well known, surviving instruments - a guitar by Belchior Dias, dated 1581, in the Royal College
of Music, London and a vihuela cat. E7048 in the Cite de la Musique museum in Paris. (There is some dispute about the designation of these instruments
as guitars or vihuelas but these arguments are irrelevant to this investigation). The attached image shows a section through the central rib of the
Dias guitar drawn to scale having a radius of the fluting about 18 mm and a reverse curve longitudinally having a radius of about 33 inches (838
mm).
This is a shallow longitudinal curve compared to an oud or lute rib, however, the guitar/vihuela ribs have sides that are relatively parallel whereas
lute and oud ribs taper sharply longitudinally. This sharp taper might make it possible to form fluted oud and lute ribs by bending alone although I
am not aware of any surviving early lutes or ouds that have this feature
The current wisdom, however, is that deeply fluted oud or lute ribs can only be made by carving and there are examples of modern luthiers making
instruments in this manner.
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jdowning
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The great advantage of deeply fluted bent ribs is that the ribs may be made very thin (less than 1.5 mm) so the body of the instrument will be very
light but, at the same time, very strong and stiff due to the fluting. It has also been suggested that the fluting, in minimising contact with the
player's body, might improve resonance and sound projection of the instrument.
The following luthiers have made successful copies of the Dias and E7048 guitar/vihuelas so have developed a method for bending the ribs - although I
am not aware of the methods used in each case or if any of these was the method used originally by Dias.
Two of the sites (Batov and Larson) also provide MP3 audio recordings of their vihuela copies so that the impressive sound quality and resonance of
these instruments may be judged.
http://www.lutesandguitars.co.uk/htm/cat12.htm
http://www.vihuelademano.com/
http://daniellarson.com/chambure.htm and
http://daniellarson.com/
and also Rob MacKillop's site at
http://www.songoftherose.co.uk/
This investigation will commence next with some experiments to establish a method for bending fluted ribs as found on the above original instruments.
If this step is successful, the investigation will then move on to explore the possibility of making fluted oud or lute ribs by bending alone.
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suz_i_dil
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A bit technical for me, just let me wish good luck in your investigation.
Very interesting research, indeed all the oud I tried which were really sounding great to my ears were all very light instruments.
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jdowning
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Thinness of the bowl seems to have been a feature of early ouds as it was for lutes according to Arabic/Persian accounts during the Mediaeval period
in Europe. The accounts do not state 'how thin is thin' except to record that the ribs were made thinner than the soundboard. This may imply a rib
thickness of under 2mm. This does not necessarily mean that early ouds had faceted bowl exteriors like the lute - they could still have been made like
modern ouds starting with relatively thick ribs that are then shaped to give a smooth rounded bowl exterior. If this was the case then the bowl might
then have been shaped on the interior as well - to produce a uniform thin wall thickness.
BTW, I was unable to locate a picture on the forum of a Yayyar oud with a fluted rib bowl - all of the images posted seem to be of ouds with a
conventional smooth rounded profile.
The first stage of this investigation will be to establish a method for bending and forming the "inverted saddle", fluted form of rib found on the
16th C vaulted back guitar/vihuela examples posted . The attached image is a sketch representing the required general shape of this type of rib.
Constraints to be applied in the investigation are:
- the method must be one that could possibly have been used by luthiers of the 16th C.
- the method must be a process that will not result in deterioration of the structure or physical properties of the wood. However, removal of some
residual materials from within the cell structure of the wood (extractives - waxes, resins, mineral salts etc.) may be acceptable if found to be
beneficial in improving bending properties.
- after bending, the geometry of the wood shall be fixed and permanent - within a reasonable tolerance (recognising that all wood expands and
contracts with humidity/temperature variation)
There are a number of possible bending procedures which may or may not work successfully. These are to be considered, tested and evaluated separately.
All methods will require the wood to be temporarily softened and/or made 'plastic and remain in that state long enough for the wood to be clamped to a
mold of required shape without splitting or breaking.
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suz_i_dil
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Here is the pictures I was talking about :
http://www.mikeouds.com/messageboard/viewthread.php?tid=2686#pid290...
Hope it may help you in your research.
Regards
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jdowning
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Thanks suz_i_dil. Those are nice examples of ouds with fluted ribs but the question is - is the fluting of the ribs created by carving the ribs after
assembly into a bowl or by bending prior to assembly? If they are carved - and I suspect that they are - then the inside of the oud bowl will be
'smooth'. In other words the bowls are conventional except for their carved outward appearance. This can easily be verified by viewing the interior of
the bowls through the soundholes (Samir?).
Luthier Foad Jihad (?) of Iraq makes similar oud bowls. The fluting of his ouds is confirmed to be achieved by carving not bending (see "Awsome Oud
Ribs" on the Oud Projects forum).
If a method can be found to successfully flute oud or lute ribs by bending, then another alternative might be not to flute a rib but to reverse the
direction of the transverse bend from a 'cupped' fluted section to an arch. A rib curved across its width in this manner might be used to efficiently
produce a conventional smooth surfaced oud bowl having very thin ribs of uniform thickness. Just a thought at this stage though.
A very useful and informative reference about wood, its structure, properties and commercial applications is available for free download from the U.S.
Forest Products Laboratory at
http://www.fpl.fs.fed.us/documnts/fplgtr/fplgtr113/fplgtr113.htm
This is the Wood Handbook, a publication dealing with wood as an engineering material but which can be selectively downloaded chapter by chapter if
the engineering applications are of no interest.
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jdowning
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Wood is complex structurally but simply put, is comprised of longitudinal fibres which are hollow, tubular cells with the cell walls made of cellulose
compounds - a kind of sugar. The cells make it possible for transfer of nutrient containing sap within a tree. The cells are joined to each other with
'lignin'. Lignin, softens at temperatures above 170 C/ 340 F but in the presence of moisture, the softening temperature of lignin is lowered to below
the boiling point of water (100 C/212 F).
In a softened state, the wood cells may be compressed considerably but stretched very little before failing.
Lignin may also be temporarily softened with chemicals.
The objective of this first part of the experimental process is to try to get a general feel, quickly, for what bending procedures may or may not work
in practice. Samples of seasoned American walnut and Maple - quarter sawn - measuring about 35 mm wide by 135 mm long by 1.2 mm thick (1.375 X 5.30 X
1/16 inches) were prepared, planed smooth both sides.
A 'male' mold, (the type used by luthier Dan Larson), on which the test pieces will be formed - representing the geometry of the central rib of the
16th C Dias guitar - was cut from a piece of pine. The mold is about half the length of the Dias rib for preliminary test purposes - to save time and
material. This mold configuration is the easiest to manufacture - quickly made by cutting the longitudinal curve on a bandsaw and then shaping the
cross section with a rasp. The longitudinal curvature of the mold was made with a radius of 27 inches (656 mm) - tighter than that of the original
Dias rib (33 inches/ 838 mm), to allow for some anticipated 'spring back' of a bent rib after release from the mold. The longitudinal curvature was
accurately measured using a set of standard draughting curves.
The attached image shows the completed test mold. The nails in the side are convenient anchor points for the string that will be used to tie down the
sample to the mold
So - ready to go for the first test.
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Peyman
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This is really interesting. I had no idea that's one way of making the fluted ribs. Looking forward to the experiments.
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jdowning
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The first test was to heat dry, seasoned wood samples to above the softening temperature of lignin. This is the technique familiar to all luthiers -
it works very well in two dimensional bending using a heated bending iron where the curve of the flat rib may be induced - little by little - by
heating and cooling to permanently set the required curve.
On a much larger scale, this technique was used by Naval shipyards - in the days of wooden sailing ships - to bend massive timbers. The heavy timbers
of oak - up to 4 inches (100 mm) in thickness were buried in sand in a furnace heated to the required temperature and left for several hours. After
'soaking' at the required temperature, the timbers had attained sufficient flexibility so that they could be relatively easily bent into a required
curve. (It is very likely, these ship's timbers would have had a moisture content at or above the air dried saturation limit of about 20% which, in
turn would have helped to soften the wood for bending).
Thin rib blanks cool very quickly and so lose their flexibility (in a few seconds) when removed from a heat source. Using a convenient heat source
(hot air gun) it was found impossible to manipulate the test piece on the mold quickly enough without each test piece splitting in two. Two samples -
quarter sawn and flat sawn - both failed. Test failure #1!
For this method to work, the rib blank would have to be subject to a constant, uniform high temperature, forced into the contours of the mold by some
means and then allowed to cool. This might be achieved using an electric heat blanket and pressurised, heated molds or by heating the mold and rib
blank in an oven together with, say, an heated, flexible, heavy sand bag (or a string of metal weights) to provide the required forming pressure. As I
do not have an electric heating blanket (and neither did 16th C luthiers) the former option has been discounted. The latter option might work but is
too complicated for consideration right now. There must be an easier way?
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jdowning
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Wood, when freshly cut and full of sap ('green' wood) - dependant upon the species, - may be soft and flexible enough to be formed to shape on a mold
where it will permanently attain (within limits) the shape of the mold on drying and seasoning. The disadvantage of this method is that it is slow and
the wood may be subject to cracks and splits during the drying process unless carefully controlled. Also, slab cut wood is less stable than quarter
sawn under variable humidity conditions.
For information and interest, here is an image of a sample of wood (vinewood) that was slab cut from a 2 inch (50 mm) stem earlier this year and
allowed to air dry. Note that the sample, on drying, has naturally attained (almost!) the ' inverted saddle shaped' geometric profile that is the
objective of these test - without using a mold!!
Also, this vinewood has no visible seasoning splits or cracks.
The reason that this sample has taken a fluted profile is because of the differential grain length across the slab cut section - shorter at the bottom
of the sample than at the top so that the shrinkage on drying is less at the bottom than on the top of the section (see the bottom two images of end
grain). The longer the grain length the greater the amount of shrinkage. Also, as the transverse stresses induced by this natural curvature must be
balanced by an equal and opposite stress, an opposing longitudinal curve can be seen in the sample.
This is test #2 which may have some useful future application.
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Clayton
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Always fascinating and I love your scientific method of exploration... illustration, and documentation! I think that vinewood really has some
potential. I like the way it feels. This is a great thread... I love the look of the fluted lute back and might really be interesting on an Oud.
Keep up the good work.
-Clayton
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jdowning
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Thanks for your interest Peyman and Clayton.
This exercise began a couple of weeks ago when searching for a method to soften wood - not in order to bend it - but to make it easier to slice across
end grain in preparation for microscopic examination of wood grain structure. A perfectly clean cut is required and most seasoned woods are too hard
and require softening. Freshly cut ('green') wood, on the other hand, may be cut cleanly without prior treatment as the structure is soft - the cells
being full of sap and the cell walls saturated with liquid matter.
A method used to soften dried wood samples is to boil them in water until the sample sinks - an indication that the cells of the sample are fully
waterlogged. At this point the sample has - in effect - been 'reconstituted' to its 'green' state (like adding water to dried food). The boiling of a
small sample may take up to an hour or more depending upon its porosity and density. Some wood species, however, are so hard that they require a
further softening treatment prior to boiling (see 'Identifying Wood' by Bruce Hoadley, Taunton Press). This may be accomplished by first soaking a
specimen in a 50/50 solution of alcohol and glycerine for several days.
Cutting of a sample must be done immediately after a sample has been removed from the boiling water.
Clearly, this treatment does not permanently modify the cell structure of the wood under examination and so is reversible.
Boiling or steaming wood at atmospheric pressure (temperature 100 C/ 212 F) is a well known method for softening wood prior to bending - used by boat
builders and furniture makers for example. In building wooden boat hulls, the softened planking may be subject to bending in three dimensions - curved
and twisted.
I have used this method in the past for bending replicas of 19th C wooden hay rakes and offset broad-axe handles - the heating chamber being simply a
one gallon metal can half filled with water with a piece of metal duct pipe stuck in the top. This device was placed vertically on a camping stove,
the water brought to a boil and the wood to be bent suspended in the 'steam pipe' until soft enough to bend. 'Speed is of the essence' here using a
prepared jig into which the softened wood must be quickly clamped before it has a chance to cool and reharden to a permanent bend.
Oud or lute ribs may also be bent by this method but - being so thin - tend to lose heat and reharden quickly.
Curious to find out if pre-soaking a sample of wood prior to boiling might delay the the hardening of boiled, plasticised wood I extended my search
further afield to find out if there might be fluids other than water and alcohol that could be tested as a pre-soak agent. Use of glycerine (a kind of
soap) is not under consideration here due to the possibilty that its presence in wood might adversely affect gluing properties.
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Peyman
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I tried this method once with maple strips about 3 mm thick: I soaked them in water for 24 hrs, then used a heat gun to bend around a plywood form. It
worked very nicely. This method really didn't work for rosewood and walnut (might have had something to do with the grain). I now use an electric iron
(for ironing clothes).
I also read about a method called "cold bending." It's used with violins. They soak the strips for a week then bend them over a form and let dry.
Apparantly it works as I have read the same with some Persian instrument makers who soak in water and don't heat anything. The drying time is probably
long.
The other method that I read about is used in frame drums and banjo rims. The wood is soaked with Ammonia and that softens it. Then it's bent over a
form. I think it's probably not a good method for bending since ammonia is particularly nasty.
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jdowning
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Thanks Peyman.
As Ammonia is already on my list of 'pre-soak' liquids to test lets start with that first. A modern commercial method used to temporarily plasticise
wood is to soak it in liquid ammonia. This apparently softens the lignin (without heat) to the point where the wood can be permanently formed into
extreme shapes not possible using conventional wood bending methods. However, as liquid ammonia boils at minus 33 C it must either be kept under
pressure in a vessel and/or refrigerated to keep it liquefied. Nevertheless, it may still be feasible to soak thin wood strips (fror the required
minute or two) in the ammonia liquid as it boils off at ambient conditions of temperature and pressure. This would have to be done in a laboratory
fume chamber where the ammonia gas given off could be safely conducted to atmosphere. By all accounts this process would likely work in producing the
desired fluted oud or lute ribs. It might be possible to obtain liquid ammonia from, say, a commercial refrigeration company but the stuff is way too
hazardous to mess around with for a back yard project and it is considered to be an environmental hazard to boot. Furthermore, as liquid ammonia was
not a material available to 16th C luthiers, its use is automatically discounted for the purposes of this investigation.
Household ammonia is a solution of ammonia gas in water - from 5% to 10% by weight - readily available, 'off the shelf' in local stores. However,
experts state that household ammonia is useless for plasticising wood - liquid ammonia must be used to be effective. Nevertheless, I have included
household ammonia on my list of liquids to test as some claim to have had success in using this product to reversibly soften wood.
Ammonia salts (for example sal-ammoniac or ammonium chloride, found in volcanic regions) have been known from very early times - known to Greeks and
Romans and mentioned in Arabic texts as early as the 8th C. Mixing sal-ammoniac with quicklime (prepared by roasting lime - a technology known to
earliest prehistoric man) produces ammonia gas. This was reported by the 15th C - but was probably earlier knowledge. So, it is likely safe to assume
that by the Mediaeval era in Europe, the equivalent of household ammonia would have been known and available.
Ammonia gas is also produced by the natural decomposition of excreted animal wastes so burying wood samples in a farm manure pile might be an
alternative possibility - but one that I am not ready to explore right now!
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jdowning
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As alcohol has been mentioned as a wood softener, I have included white table wine on my list - around 15% ethyl alcohol by volume. Again, this would
have been a liquid available to early civilisations.
Also included is household white vinegar - sour wine - also available to the ancients.
In my search, I came across a reference where the engineers at JVC had discovered (after a search of 20 years) that after immersing panels of Birch
wood in Sake (Japanese rice wine) the wood became flexible enough to form into cones that they use for Hi-Fi loudspeakers. Distilled spirits of
alcohol apparently do not work (so forget about using a shot of Jack Daniels or single malt whiskey - thankfully!). Sake is more of a beer than wine
as it is subject to a double fermentation process - not using yeast to convert starch to alcohol in a single fermentation, as in the case of wine but
instead using the fungi Aspergillus oryzae - naturally present (like yeast) in the environment. Sake comes in various types - some with added alcohol
content - and the JVC engineers, understandably do not go into further detail but they reckon that it is the presence of this fungi strain in the Sake
that, somehow, does the trick.
With curiosity getting the better of me, I bought a bottle of cheap 'table' Sake from a local store (about 15 % by volume alcohol with no added
alcohol) for testing. Well, to be honest, I just wanted to sample the Sake as I have some doubts as to wether or not it will work!
Cheers! Salut! Disappointing, however, to find that the beverage is not to my taste.
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jdowning
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So, if it really is the Aspergillus genus in sake and not the ethyl alcohol content that is responsible for softening the wood, I looked for
alternative fluids where active residues of the genus might be found. Soy sauce might be one. However, a pharmaceutical product by the trade name of
"Beano" - made from another strain of the genus Aspergillus terreus - readily available 'off the shelf' for those unfortunates with socially
unacceptable digestive problems, has been selected for testing - i.e without the alcohol content of Sake.
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jdowning
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'Beano' (continued) - contains the enzyme, Beta-galactosidase (from the Aspergillus terreus fungus).it is reported that "the pulp and paper industry
benefit from the enzyme production capabilities of certain fungi to soften wood fibres - including lignin biodegradation". The enzymes break down the
cellulose (sugars) of the cell walls apparently. Don't ask me how - I am not a biochemist!
The solution strength that I have arbitrarily chosen to use for the tests is three 'Beano' tablets to 20 ml (cubic centimeters) of water.
The final choice of pre-soak fluid for these initial preliminary tests is Methanol or wood alcohol - again, readily available off the shelf. Methanol
(distilled from wood) was used by the Ancient Egyptians in the embalming process for mummification so was well known to early civilisations. I chose
this because it is a concentrated alcohol and - because it is derived from wood - which seems to be appropriate for these trials. All guesswork at
this point in time.
Methanol must be handled with plastic gloves in a well ventilated place as inhalation of the fumes and absorption of the fluid through the skin, can
prove to be dangerously toxic.
So - with my workshop now smelling faintly of a brewery, we can now move on to the next phase.
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patheslip
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Late night disconnected thoughts:
Horrified to learn sake involves Aspergillus. This fungus can kill. I put some fallen leaves in plastic bags to encourage breakdown. When I opened
them I must have breathed in the spores. Ended up in hospital. Another gardener died from the same thing this year.
I shall avoid Japanese restaurants.
Returning to our moutons: fungus softens wood prior to digesting it. The change is permanent. Is this what you want?
Bending wood: I made a coracle from ash, heating the wood in a plastic drainpipe filled with steam from a modified pressure cooker. Very tricky
holding that hot wood and bending it into shape. How did the shipwrights do it with much bigger planks? Luckily for us ouds are measured in
millimetres not inches.
Good luck with the project
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Peyman
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Interesting investigation with the materials.
Ammonia is definitely not a good idea.
What about using those veneer softeners? I didn't search how they work but is worth looking into, since the ribs are so thin.
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jdowning
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Thanks for your constructive observations Peyman and patheslip.
The pre-soaking or 'marinating' of the wood samples began over a week ago and bending of the samples has begun. As I only have a single mold, bending
tests are sequential and are being completed at the rate of one per day. It will be a few days before this initial trial is complete so I shall post
the full findings then.
In the meantime I have started to reconsider the potential of using 'green' wood more seriously than earlier in this thread. Peyman has confirmed that
some luthiers, East and West, cold bend instrument ribs (presumably in a softened state) and allow the ribs to dry on a mold where they take up the
shape of the mold permanently. Green wood is used on instrument bowls that are carved from a solid block as the wood is softer and easier to carve.
The initial carving brings the wall thickness close to finished size and the bowl is allowed to slowly season and dry before being finished to final
dimensions. In general, most luthiers work with well seasoned wood in instrument construction to avoid all kinds of potential problems with wood
splitting etc. Nevertheless, if soft and flexible 'green' wood is used (unheated) in order to successfully conform to a complex three dimensional
shape - like a fluted rib - and then allowed to dry and fully season on a mold before being assembled into an instrument there should not be a
problem. Due to the thin wood sections being contemplated the natural seasoning period might be relatively short - a month or two perhaps. This would
potentially be a far more efficient procedure than working with fully seasoned rib blanks, softening them by some means and then trying to heat bend
them to shape. Heat bending particularly presents handling difficulties.
Some woods do bend easier than others which might have something to do with cell diameter and distribution. The large diameter early wood cells tend
be thin walled whereas the small late-wood cells are thick walled. So wood with a greater proportion of large diameter early wood cells might be
relatively easier to bend. Note the macro section of vinewood posted above. It is comprised mainly of large diameter cells and the wood is very
pliable even when cold and dry (see 'Wood Fit for a King' on this forum). Woods with small, widely distributed cells such as Beech are much stiffer
and harder to bend.
I have no experience with veneer softeners so don't know how they work but will check it out as a possibility.
The possibility of Aspergillus in Sake being the active ingredient for bending wood is just a quote from the JVC engineers. I doubt if there would be
any fungus residue remaining in the beverage - which is why I questioned if it is the alcohol that is the active ingredient. However, I wonder if the
action of the fungus during the fermentation process results in production of enzymes (as in the case of 'Beano') that do remain in the drink and are
an active constituent in softening the cell walls of the wood?
I think that partial softening of the wood cells by controlled immersion in a bacterial 'soup' might be an acceptable possibility. Immersion of
freshly felled logs in water to prevent splitting and insect attack (known as ponding) is standard practice in the logging industry. It has also been
found that action on the ponded logs by bacteria in the water can result in degradation of pit membranes in the cell walls allowing freer transfer of
fluids through the woods. Useful for wood that is to be chemically pressure treated but also with possibilties for impregnation of the wood with other
fluids - such as pre-soak fluids in our case.
All this has reminded me about another old method of preparing and using green wood - practiced by the North American Indians to make baskets from
Ash. The freshly felled Black or Swamp Ash tree section is first immersed in a stream (freshly felled Ash dries and end checks very quickly after
felling - within an hour in my experience). After remaining immersed for a time (not sure how long but can find out. Many days or weeks as I recall)
the log is taken from the water, the bark removed and the whole surface of the log pounded with wooden mallets. The pounding causes the wood fibres to
separate along the growth rings so that long, thin strips of the still soft wood may be peeled from the log. The process is repeated to remove
successive layers, gradually reducing the log diameter until too small to be used. The thin flexible wood strips (about an inch or so wide) are then
tightly woven into baskets (or chair seats ) and allowed to air dry and harden in place. The end grain direction in this case is across the width of
the strip (not quarter cut).
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patheslip
Oud Junkie
Posts: 160
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Location: Welsh Marches
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Your remarks about ponding bring to mind some other old country practices. Elm wood, from this once ubiquitous tree, was ponded to make it water
resistant. The large branches, which hollow naturally, were widely used for pipes and village and farm pumps and hollowed out pieces of trunk for
water troughs.
Withy branches are still ponded for basket making in those damp parts where the willow grows well. They're tied in bundles and laid in water for a
year and a day.
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jdowning
Oud Junkie
Posts: 3485
Registered: 8-2-2006
Location: Ontario, Canada
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Checking out veneer softeners - one apparently effective home made softener is made by mixing 8 oz glycerine and 8 oz denatured alcohol in a gallon of
water. This is essentially the same as recommended by Hoadley for softening wood by pre-soaking mentioned in an earlier posting - except that it is a
50/50 mix without water added. I was incorrect in thinking that glycerine was a kind of soap - it is a kind of alcohol so should not have adverse
effect on gluing properties. Glycerine is derived from the soap making process as a byproduct left in the boiling vat after the soap has been skimmed
off. Apparently glycerine was not identified until the late 18th C which should disqualify it from consideration here. However, it is very possible
that the impure glycerine containing liquid could have been used in earlier times - it's just that it wasn't known as glycerine. The impure liquid
contains about 25% of common salt (sodium chloride) that at one time was crudely purified by repeated boiling in open vats, removing the salt that
crystallised on the sides - a simple process well within the capabilities of earlier civilizations.
So glycerine is back on the list of pre-soak possibilities.
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jdowning
Oud Junkie
Posts: 3485
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Location: Ontario, Canada
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I should mention that sale of denatured alcohol (for example ethyl alcohol with 10% methyl alcohol added to blind or kill anyone foolish enough to
drink the stuff), is restricted in Canada so is not an option for use in these tests. Methylated Spirits is (or used to be) readily available in the
U.K. and unrestricted - the same applies in the U.S.A. apparently.
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