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jdowning
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Something Completely Different - Metal Bowls - and a Colascione
Some years ago while working for a period earning a living as a heritage tinsmith, I made a copy of a 19th C French guitar by Grobert entirely in
tin-plate complete with brass strings. It was not intended to be played - just for display as a demonstration of the tinsmith's craft.
This time around I thought that it would be interesting to make a working instrument with a metal bowl. Why? - just because I can (or once could when
eyes were clearer and hands steadier!).
The instrument that I plan to make is a Colascione - a long necked lute that was introduced to Europe from Turkey via Italy it is thought around the
mid 15th C - and prevailed in Italy as a popular folk instrument until recent times. This instrument has been chosen because the bowl is relatively
small in size so will be a bit easier (and safer) to handle during the fabrication process - compared to say a full sized oud or lute.
As I have measurements on file of a surviving 17th C Colascione (the Dean Castle Collection, Scotland) it will be used as a basis for this project.
The Dean Castle Colascione has an ivory bowl, 3 strings and a string length of 75.6 cm. - clearly a costly instrument in its day no doubt made for a
rich dilettante rather than a street musician. This is a mid sized or Mezzo-Colascione. See attached images.
Some earlier discussion about the possible origins of the European Colascione is posted here on the forum:
http://www.mikeouds.com/messageboard/viewthread.php?tid=7096#pid438...
The attached engraving by Marin Mersenne, 1636 compares the European version of his time with a Middle Eastern counterpart.
 
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jdowning
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More information about tinware and tinsmithing can be found here:
http://www.mikeouds.com/messageboard/viewthread.php?tid=8565
Although I have in the past made segmented chandelier bodies and fancy fruit/flower bowls from tin plate I have never made a lute bowl from sheet
metal so there is no guarantee that this project will succeed - but no harm in trying.
I will be using tinplate for fabricating the bowl - the stuff that food containers are (or once were) made from - thin sheet steel coated on both
sides with pure metallic tin. The soft tin coating prevents the steel from corroding in moist conditions except in areas that are scratched or damaged
where the steel is exposed.
The tinplate that will be used for this project is 0.38 mm thick (0.015 inch) and is relatively soft so can be easily bent with only finger
pressure.
The tin segments of the bowl will be joined by soldering using a temperature controlled soldering iron (to prevent burning of the tin coating) and a
50/50 lead tin alloy solder that melts easily and sets quickly (a kind of metallic glue) - speed of working is important for this class of fabrication
where two hands often seems insufficient. An acid paste flux (to ensure joint cleanliness during the soldering process) will also be used in the
interests of speed of work. When using lead based solders and acid fluxes it is important to have adequate air extraction facilities to ensure that no
fumes generated are inhaled or come into contact with eyes or skin - and to wear plastic protective gloves.
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jdowning
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The bowl section is semicircular with wider side ribs to increase the overall depth. To simplify the fabrication work the number of ribs has been
reduced to a total of 9 from the original 15. Once the metal bowl has been fabricated the neck and end blocks (of wood) will be 'retrofitted' and
glued into place. Also a conventional wooden end clasp and side strips will be glued to the exterior surface as on the original. These components
provide wooden joint surfaces required for attachment of the sound board - necessary for thin ivory (less than 1mm thick) as well as thinner
tinplate.
As the bowl section is semicircular the central ribs will all be identical and symmetrical. A pattern for the ribs was created first by drawing a full
size section of the bowl to determine the maximum rib width and included angle between the ribs. A rib former was then made by cutting two half
sections of the sound board profile from thin Masonite, hinged together with adhesive tape and set at the included angle (21°) with wooden blocks
glued in place.
The required rib profile is then represented by the inside edges of the former.
The rib profile is then traced onto a paper strip taped over the the former and the edges rubbed with a fingertip tipped in graphite powder (or rubbed
with a pencil).
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jdowning
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The rib pattern on the paper strip is then taped to a sheet of tinplate and the rib profile carefully cut out with a sharp knife. The knife transfers
the rib profile onto the tinplate as a fine cut line in the surface.
The rib pattern is then cut out using hand shears or tin snips following the scribed line exactly - not as easy as it might first appear requiring
practice, good lighting, good eyesight and a steady hand.
Any slight wrinkling of the cut edges is then removed by dressing with a smooth faced hammer on an anvil.
The accuracy of the pattern is all important and must allow for any potential cumulative errors during the course of fabrication as these cannot be
corrected as work proceeds (as they can with wooden rib construction).
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Microber
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Hey John, I like the idea of a metal bowl very much.
But I think some people here in the forum will find it's a crazy project.
I look forward to see more.
Robert
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jdowning
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An essential tool for soldering tinplate is a temperature controlled soldering iron - a cheap soldering iron that can reach temperatures in excess of
1000°F (535°C) will burn the tin coating.
The best tool for the job is made by the 'Weller' company (W60P - W100P series). Temperature is controlled by an ingenious system that depends upon
loss of magnetism of a magnet at a critical temperature (the Curie Temperature). In the 'Weller' iron this phenomenon is used to operate a switch to
turn off power when the tip of the iron reaches a fixed temperature (600°F, 700°F and 800°F) dictated by a ferromagnetic sensor in the tip.
For this project I will be using a Weller W60P iron with a 1/4 inch chisel tip operating at 700°F.
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jdowning
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Having made the rib pattern the ribs are marked out by tracing around the pattern placed on a sheet of tinplate using a sharp pointed scriber. Each
rib is then accurately cut out by hand with tinsnips and the edges dressed smooth with a hammer - as described for making the pattern.
Each rib is then easily bent by hand to roughly the required contour (the sound board profile).
No mould is required to fabricate the bowl. Each pair of ribs is held edge to edge and 'tacked' in position with spots of solder - working along the
length of each rib joint from one end to the other.
Once each rib has been tacked the joint on both sides is coated with a thin film of acid paste flux and the soldering iron is then run the full length
of the interior surface melting the spots of solder as it goes into a solid homogeneous joint.
The attached image shows the first three ribs assembled.
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jdowning
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The ribs are now assembled and trimmed to form the basic bowl. Total time to reach this stage would be an afternoon's work - say about six hours for a
relatively experienced worker starting with marking out the ribs.
As the weather has turned frigid it is currently not comfortable to work in my workshop so this will be a good time to assess the structural viability
or otherwise of the bowl and to decide whether or not to proceed further with this little project.
The rib joints are very thin (about 0.4 mm) and relatively fragile so can separate if the bowl, in its current state, is subject to flexing. Some
additional joint reinforcement might, therefore, be worthwhile as a precaution. First thoughts would be to reinforce each joint with small soldered
tabs of tinplate spaced at say 5 cm intervals along the joint. We will see.
 
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rootsguitar
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Artful! It's one thing to think of such a project but you are uniquely able to create this instrument.
I look fwd to hearing the sounds and hope you can continue with the project.
I know this may be a tangent but it could be possible to fill the bowl with a small amount of water and create an unusual effect by striking it then
plucking the strings.
The Metallic Bowl Effect " MBE" :
http://youtu.be/d-u-BUuhtMM
Water could be added through the rose
Happy new year!
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SamirCanada
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wow John! that's a very interesting project! I wonder about how it will sound as well!
so will it be a spruce top or a tin top?
@samiroud Instagram
samiroudmaker@gmail.com
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faggiuols
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Jdowning
Your arguments are always interesting!
I wish I had two days every day to read them with care ..
I printed that about silk strings but they are not even halfway .. you update it faster than I can read it.
anyway thanks because you share your studies with all members ..
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jdowning
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Although the guitar that I made was all tin plate - including the top and braces(!) - it was never intended to be functional musically.
The intent here is to only make the bowl of tin plate - the remainder of the instrument will be of conventional wood construction including the top
and bracing of spruce. The Dean Castle Colascione has a separate inset rosette like an oud so this will have the same arrangement that will allow
testing of different sound hole diameters (to determine optimum air resonance frequency). The neck joint will be made vertical (like an oud) a simpler
arrangement found on some other surviving Colasciones - not sloping as on a lute. There will after all only be three strings so the width of the neck
joint may be reduced accordingly.
I do not expect that a metal bowl will have any acoustical effect not otherwise found in a conventional wooden bowl - but of course it will be
impossible to make any meaningful comparison in the absence of an equivalent all wood instrument.
Advantages of a metal bowl might be low cost and speed of fabrication. Also the ribs may be decorated by engraving, acid etching or embossing although
here everything is to be kept plain and simple. A metal bowl might also be easily copper electro plated at low cost if so desired.
Tinware of the 19th C was often coated with several layers of a hard baked on varnish that was supposed to imitate Japanese lacquer work - known as
japanned ware - very popular for the time period. This finish was both durable in preventing corrosion as well as decorative. This is the finish that
I likely will apply - but using modern self curing varnishes.
Although I shall measure bowl volume (before gluing on the top), so that air resonance frequency may be accurately calculated, adding water to the
bowl on the completed instrument with a spruce top would obviously not be a good idea (but would have been possible with a tin plate top).
A happy, healthy and successful new year to all.
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jdowning
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Here is a video of a duet of Colascione and Baroque guitar that might be used to compare the sound of wooden and metal bowl versions - although the
instrument in this recording is a larger and with 4 strings.
https://www.youtube.com/watch?v=Dx_joJkG6rI
A surprisingly strong sounding bass accompaniment.
This is confirmed in an early 18th C publication by Ernst Gottlieb Baron ('Study of the Lute', 1727 - translation by Douglas Alton Smith) where he
criticises his contemporary Herr Mattheson for suggesting that the lute was lousy for accompaniment of singers in church or opera as it cannot be
heard - the colascione being more suitable. The author counters sarcastically "He .. forgets that the colascione .. is only the bass of a lute, and
could not be more than the whole instrument, especially since it is quite reasonable that more can be done with many strings than with three, four or
six courses. But it is a fault in his nature that he was not able to perceive the special delicacy in chamber music accompaniment with the lute
...."
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jdowning
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The main additional structural component is a baffle plate located at the neck block position. This has been cut from tin plate and soldered in
position. The little soldering tabs on the baffle were cut using a 'nibbler' or 'notcher' tool that can cut where tin snips cannot go (a tool used by
electronics workers for hand cutting circuit boards). The space behind the baffle will be filled with wood slices epoxy glued in place as a
retrofitted neck block.
Total weight of the completed metal bowl is 320 grams.
Apart from the wooden neck block, wooden strips are to be epoxy glued around the upper edge of the bowl to provide a gluing surface for the sound
board. Assembly of the sound board to bowl and other wooden components of the rest of the instrument will then use conventional hot hide glue.
 
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mavrothis
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Really enjoying this! Can't wait to hear the result!
mav
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jdowning
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Thanks Mav - let's hope the end result does not disappoint!
The main obstacle to progress will now be weather as I am reluctant to spend on inefficient electrical heating of my workshop when it is minus 30° C
outside. On Sunday the temperature may be on the plus side so will plan to complete metal work on the bowl then.
There is not a lot of information available about the surviving originals. Thinking ahead, the sound board bracing is likely to have been
uncomplicated. A sound board X-ray of the 19th C Colascione MIR 912 in the Germanisches Nationalmuseum, Nürnberg shows three substantial braces - two
on each side of the sound hole and one just in front of the bridge. I plan on this smaller instrument to only have two braces (providing sound hole
support) with the sound board 3 mm thick at the centre tapering to about 2 mm at the edges.
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narciso
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Yet another very interesting project, and fine workmanship, as ever! Thanks for sharing jdowning!
A while back on this forum there was a discussion about what sort of relevance the material used for the ribs has on sound.
I can't seem to find the thread unfortunately, but I remember someone pulled in a physics argument to the effect that the material is irrelevant
because the shell structure is stable with respect to vibrational excitations, i.e. those vibrations which propagate in the soundboard
That seemed to me a bit oversimplistic because even if the bowl shell remains inert in that sense, then taking the physics perspective a little
further one still has to consider the absorbance/reflectance boundary conditions (b.c.'s) on sound waves incident at the bowl surface. These are
likely to be quite sensitive to differences in the rib material; they arguably control the character of the marked reverb effect one hears from ouds
in particular ( much stronger than that of a guitar body)
I wonder if it will be possible able to draw any qualitative conclusions in this respect on the basis of your work here with tin ?
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nedal
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Hey John, that is a very Interesting Project, that might interest you to, Mr. Phillip Shahin from Tarshiha, Palestine had made Ouds with a
Carbon-fiber Bowl.
this is a video with Mr. Tareq al Jundi trying those Ouds
https://www.youtube.com/watch?v=hTa0NpgL7Uo
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jdowning
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Thanks for your interest and comments everybody.
narciso - perhaps the discussion that you had in mind is here?
http://www.mikeouds.com/messageboard/viewthread.php?tid=14572
nedal -there is also some mention of the plastic bowled ouds by Mr Shahin (and others). No doubt the discussions about this and that of instrument
acoustics will continue (and continue to be unresolved).
I don't expect that a metal bowl will have any detectable influence on the sound produced compared to that of a wooden bowl all other factors being
equal (which they can never be). This project will not provide any qualitative conclusions in respect of different bowl materials.
I am curious about why lutes with such a small bowl should perform so well (i.e. to be clearly heard) as bass continuo instruments in large auditoria
(churches, opera houses and the like - or in open spaces as an instrument of the streets) as historical record would have it. The sound board surface
is small in area so one might expect low frequency sound projection due to this component to also be muted? This then would leave the strength of
projection of the air resonance component of the bowl (that I am particularly interested in here). I suspect that the relatively high position of the
sound hole (relatively closer to the neck block) typically found on this type of instrument may have something to do with it. We will see.
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narciso
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Thanks jdowning for digging up that relevant thread. I think I'd seen a different one previously, but the gist of it was the same.
As you say, it is hard to see how a small tin bowl could have delivered a loud basso continuo
Perhaps it was assembled as a cage rather than as a sealed shell? This would free up vibrational modes of the ribs, such that amplification could be
achieved by resting on an auxiliary resonating chamber
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jdowning
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I am not aware of any surviving members of the lute family that have any such a complexity of bowl construction narciso. The Dean Castle colascione
that I examined first hand did not, neither do the examples in the Germanisches Nationalmuseum MIR 912.
http://www.europeana.eu/portal/record/09102/_GNM_662380.html
and MIR 911 (note also the x-ray images showing the brace arrangements)
https://www.europeana.eu/en/item/09102/_GNM_662343
It should be remembered when considering the interior surface of lute and oud bowls that the larger instruments have the rib joints reinforced with
paper strips glued in place with hot hide glue typically covering at least 50% of the interior surface of the wood - the remainder of the wood surface
is coated with hard hide glue. So if the bowl interior is thought to be a reflective surface nowhere is the wood of the bowl exposed.
Instruments with smaller bowls such as mandolins often had the entire interior surface covered with paper glued in place with hot hide glue. The Dean
Castle colascione is an example.
As I currently visualise it, for a bowl structure to produce audible sound it would have to be free to vibrate in the air (like the bottom plate of a
violin or less so that of a guitar). However any such vibration would be effectively damped by the body of the player.
Furthermore the primary driving force behind bowl flexing (if any) might be the strongly pulsating low frequency air resonance mode (that might be
felt by the player). A stiffer bowl might flex less than one that is less stiff structurally (so here relative rib material stiffness and thickness
might possibly play an insignificant part) - the former case increasing the air resonance frequency for a given sound hole diameter and the latter
lowering the air resonance frequency. More significantly, a luthier might (should) adjust the air resonance frequency by altering sound hole diameter,
the number of sound holes and the position of the sound hole(s) to suite the acoustic objectives sought in the instrument under construction.
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jdowning
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Another historical reference to the colascione is found in 'Musurgia Universalis' by Athanasus Kircher, Rome 1650.
The attached image shows a three string colascione (here named a colachon) alongside a theorbo - the colascione being a longer instrument (assuming
that they are engraved to about the same scale). Oddly the tuning of the colascione is given as c', c'' and g'' which means that if strung in gut
string length would have to be about 30 cm or so - hardly a bass continuo instrument!
The fret spacings are interesting if drawn proportionally to scale.
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jdowning
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Now that the metal work of the bowl is complete the wooden interfaces - neck block, tail block, end clasp and side strips - must be configured, shaped
and glued in place.
The neck block is made from 9 mm thick slices of 'yellow poplar' (it is not a poplar but a species of magnolia tree) - rescued years ago from an old
desk found thrown in a 'dumpster'. This is a relatively soft but stable and easily carved wood. Each slice was sawn out roughly to size with a coping
saw and then shaped to fit by carving with a knife and finished with a small woodworking rasp. Grain direction of the slices is arranged to cross like
plywood. High precision of the fit is not required as the slices will be glued in place with gap filling epoxy.
The block is left well oversize for final trimming after all of the other wooden additions to the bowl are finally in place.
 
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jdowning
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Searching for more information about the three stringed colascione/colachon (not the German 6 course, lute like, callichon or gallichon of Baron's
era) this discussion on the 'Forum des Musiques Medievales' may be of interest.
http://www.apemutam.org/forum/viewtopic.php?f=13&t=396
Unfortunately the general consensus is that as there is no known surviving written music for the colascione - it being an instrument of the street
musician or associated with the itinerant Comedia dell Arte theatre groups - it will be impossible now to recreate the music or performance style of
the instrument as it was in the 16th and 17th C.
So once this project is completed I can feel free to experiment unhindered by 'historical correctness' restraints!
The Kircher engraving of a colachon would seem to have been copied from Mersenne (?) complete with the tuning arrangement of an octave and a fifth and
the strange fret configuration. The fret configuration may be misleading as there is some historical evidence to suggest that the fret spacing was
approximately equal temperament as for the lute.
I have checked the Mersenne original text but can find no description of the fret spacing for a colascione although he does number the frets in his
engraving of the instrument.
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jdowning
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Further research reveals that there is one surviving manuscript of music for colascione - or rather the 'soprano' version known as the colascioncino
tuned an octave higher than the larger colascione (its string length being about 50 cm). Domenico Colla and his brother Bresciani toured Europe giving
recitals during the second half of the 18th C - Domenico being a virtuoso player of the 2 string colascioncino (played with a wood bark plectrum) .
There are six sonatas written for the instrument with bass accompaniment (colascione or guitar?) - a some pages from the sonatas are attached for
information. Fancy stuff - I could not find recordings on YouTube - too difficult for modern performers perhaps?
This attempt to present the colascione as a high art instrument appears to have failed, the instrument being then regarded as a curiosity by the
audiences although the skill of the performers was appreciated.
See FoMRHI Comm 2027 - link on page 5 of this topic.
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