Another Refurbish Project - Renaissance Guitar

I built this instrument - a 'vaulted back' (but not fluted ribs) 4 course renaissance guitar - in 1974 as an experimental project. It was then probably one of the first reconstructions of this type of guitar in modern times.
No four course renaissance guitar survives so the proportions of this instrument were based upon photographs of the Dias five course guitar in London (the museum drawings of the Dias guitar did not become available until 1976) and some 16th C engravings.
In the light of new information, there are a number of details that need to be changed so it has been decided to completely refurbish the instrument. Hopefully there may be some information in the course of this project that might be of some interest to forum members.

Changes to be made include:
1) removal and replacement of the sound board and bracing.
2) replacement of the rose.
3) replacement of the pegs.
4) replacement of the nut and finger board.
5) replacement of bridge
6) shorten and refit the 'peg box'
7) reinforce the vaulted back to increase stiffness.
8) add brace supports and side stiffeners.
9) add 'scoop' or 'cut out' to the sides to provide extra string clearance over the sound hole.

Most of the old oil varnish has been stripped from the instrument - before sound board removal - for convenience. The top was removed in the usual manner using water, a hot iron and thin spatula.

With the top removed the construction of the guitar can be seen. The guitar has been built in the so called Spanish style i.e. the neck and neck joint are made in one piece and the side ribs are glued into slots cut into the side of the neck. With this method the guitar is built, inverted, on a flat base using a solid mold.
The other method used by the early luthiers was to attach the neck separately to the body with a glued butt joint and a nail (or nails). These methods were used for both guitar and violin - a nailed joint being preferred by the French and Italian luthiers like Stradivarius, for example.
I prefer the Spanish method.

The attached images illustrate the two methods. The nailed joint example is on a 17th C Venetian guitar where a single large headed 'clout' nail has been used.
This image has kindly been provided by Daniel Sinier and Françoise de Ridder see under 'Restorations' at

http://sinierderidder.free.fr

The new sound board is made from Sitka spruce and is ready to fit with the bridge and braces glued in place The old sound board was made from western red cedar (a popular choice for lute makers in the 1970s but non authentic).

The bracing is around and above the sound hole to ensure adequate stiffness in this area to prevent the neck from lifting under tension. There are no braces below the sound hole so the sound board is 2.5 mm thick to compensate.

The bridge is from solid ebony with slots - not drilled holes - cut for the strings. There will be additional decorative trim glued to the ends of the bridge.

The pegs have been made from boxwood already fitted to the peg box but require finishing and polishing.

The shallow 3 dimensional rosette has been cut from stiff card and painted gold with colored detailing. No four course guitars survive so it is not known what design of rosette was used - most likely it would have been more like this on one of my vihuelas (see attached image). Nevertheless the 3D rosette provides a nice contrast so - rather than spending time to make another rosette - I will stick with this one.
The 3 dimensional rosette is usually found on five course guitars of the 17th C.

With the fingerboard removed, the next step is to cut off and shorten the peg box and reduce the neck length by about
1 cm to bring the string length to 54 cm. This will give a pitch of about G (A 440) for the instrument

Parchments Strip?

Thanks for the info, regarding the soundboard braces, I saw a parchment strip 1" width glued to the area front of the bridge,
at Baroque guitars and some other, will you glue one like this?

Thanks,
Yaron.

The neck width has been checked with card templates sized for four courses (1 single , 3 double) and six courses - based upon the string spacing now used on my lutes. When the guitar was built string spacing was wider - more suitable for a modern classical guitar. Current string spacing that I today find comfortable is a lot narrower and is very similar to historical lute (fretted) string spacings as well as modern oud (unfretted) string spacings.
Nevertheless, there is insufficient neck width available for a simple conversion to a six course vihuela - so a four course guitar it will remain. The overall string spacing at the nut (with gut or silk strings) will be about 25 mm so the neck can be trimmed back in width to allow about 4 mm on either side of the strings.

The 'peg box' length has been reduced by about 2 cm to be proportionally more historically correct and will be re-attached to the neck with a traditional (for early guitars and vihuelas) 'V' joint. This is a difficult joint to make and fit accurately (in 3 dimensions) so has initially been prepared in the rough with extra material to allow for precise fitting.

The pegbox V joint is in the final stages of fitting - a difficult an time consuming joint to make but unavoidable in this case where the original pegbox is to be reused. Ah well nothing like a woodworking challenge!

I have made this type of joint before on a vihuela that I built in 1977 - a scaled down version of the then only known surviving 16th vihuela from a monastery in Guadalupe now in the Musée Jaquemart-André, Paris. A working drawing of the instrument made by luthier Maish Weisman in 1974 shows a 'V' joint - cut the full depth of the pegbox - reinforced with a wooden dowel.
A similar joint is noted on the 16th Dias guitar in London on the drawing made by Stephen Barber in 1976.

I made another smaller vihuela the following year (1978) but, because of the difficulty in making the 'V' joint, this time around the neck and pegbox were made in one piece and the 'V' joint simulated with knife cuts. This is a much simpler solution so I did wonder at the time why the 16th C vihuela and guitar makers chose to go to all the trouble of making a complex 'V' joint rather than going with this obviously much simpler, cost effective (and potentially stronger) 'one piece' solution.

It can be seen from the attached images that the 'real' 'V' joint can be distinguished from a 'simulated' joint by either the discontinuity or continuity of the wood grain running across the joint.

Luthier Alexander Batov has examined the pegbox joints of both the Dias guitar and the so called 'Chambure' vihuela in Paris (that also has this style of 'V' joint) only to conclude that both these instruments - judging from the wood grain continuity - do not have 'real' 'V' joints at all but that they are 'simulated'
So when I thought in 1978 that I was cheating (to save time) by making a simulated 'V' joint this would appear in fact to be the historically correct method! We live and learn!

Detailed images comparing the joints of the Dias and Chambure instruments can be found here

http://www.vihuelademano.com/vgcrossroads.htm

The vaulted back of the guitar is thin and currently too flexible. In order to stiffen the back of the guitar 15 mm wide strips of close weave cotton cloth have been glued over the rib joints using high bloom strength hide glue.
In order to keep everything in alignment while the glue dries and cures (and shrinks!) - a simple jig slipped over the 'waist' of the guitar should to the job.

If this extra reinforcement is not sufficient 3 or 4 additional strips of cloth may be glued across the width of the back.

Additional reinforcement of the back has been provided with four cloth strips glued across the width of the guitar body. Shrinkage of the hot hide glue has caused the sides to close in by a couple of mm.

The sound board has been fitted by trimming the brace ends to be a precise fit to the sides. The correct alignment of the sound board to the neck is then maintained with two wooden pins (tooth picks) - one drilled into the bottom block the other into the neck. These pins - after the sound board has been glued into place - will be covered by the fingerboard and a decorative inlay at the bottom of the sound board.

The pegbox has been glued to the neck after completing fitting of the 'V' joint (a difficult joint to make - not to be recommended!). The top of the pegbox will be covered with a
2 mm thick Boxwood plate - further reinforcing the 'V' joint. This will match the fingerboard that will also be made from Boxwood.

With the sound board aligned and the registration pins in place it is time to align the bridge in preparation for gluing it in place.

A card template representing the exact string length and outside string width at bridge and nut is used to position the bridge. Double layers of masking tape placed in front of and behind the bridge provide a temporary register for the bridge to prevent sliding out of alignment when being glued.

A flat block of wood is temporarily taped underneath the bridge as a support for clamping and the clamping arrangement tested with a 'dry run' (always a good idea when working with fast setting hide glue).

The bridge is of the traditional guitar slotted design - slots cut rather than holes drilled for the strings. The ends of the bridge will be finished with decorative circular end pieces separately glued in place. The end pieces are made from a short tube of Ebony with a contrasting Boxwood core (turned on a lathe but could also be done by drilling a hole in a piece of Ebony and then shaping the exterior by hand after gluing in the core for support). This assembly will be thinly sliced with a razor saw to form the individual end pieces.

The bridge and rosette have been glued in place using hot hide glue.

The bridge end pieces have been decorated with a star branding iron - easily made by filing the end of a steel rod with a triangular section file.
The branding iron is first heated with a propane torch, tested for correct temperature on some scrap wood and then applied to the piece. Temperature should be just sufficient to form a clear burnt depression after applying the hot iron for a couple of seconds.
The end pieces have been glued with hot hide glue - a drop of glue being applied to the sound board only. Each end piece is then stuck on the end of a needle (to facilitate handling) and applied to the glue. Each piece is then held in place with finger pressure for a couple of minutes until the glue gels.

With the glue pot in action, the rosette has also been glued in place.

All set for gluing the sound board in place - next

Before gluing the sound board it was decided to 'scorch' the underside (of the unbraced area below the sound hole) with a hot iron as an experiment and as an extension of the scorching tests reported in the recent topic "Burnished Soundboards" (Advice , Tips and Questions" page 3).

Scorching is found on some surviving Baroque period guitars but the reason for this is something of a mystery.

To scorch the sound board an old style (non electric) 'iron' was used - made from a small block of copper attached to an iron rod fitted with a wooden handle (an old file handle). The iron is heated using an external source such as an open flame. A propane torch was used here.
The hot iron was tested for temperature on a scrap of spruce (just sufficient to discolour the surface of the wood) and then quickly rubbed over the whole area of the sound board below the sound hole - avoiding the area immediately under the bridge (risk of softening the glue).

After scorching, the sound board became slightly 'crowned' (i.e curved upwards) from being originally flat. The crowning occurs around the edges of the sound board for about 4 cm with the central portion of the sound board remaining flat.
So was this the purpose of scorching - to crown the sound board (in the absence of bracing shaped to to achieve the same purpose)? Deliberate crowning of the sound board is found on modern classical guitars and some of the old surviving ouds.
Therefore, was the purpose of scorching an unbraced guitar sound board done to achieve an acoustic performance improvement?

Overnight temperatures were Minus 11°C and with wood stove heat, Relative Humidity is steady at 55% so the sound board was glued in place this morning.

A low Bloom strength hot hide glue was used - well diluted - so that setting time was increased and strength decreased. Nothing special about the procedure (if hot hide glue is used - as it should be).
The joint faces and ends of the braces were coated with glue and the sound board placed in position with the alignment pins in place. By this time the glue has 'gelled' so has to be remelted to make a viable joint. Working around the sound board joint - little by little - using a hot iron applied to the upper surface of the sound board, the glue was remelted and the joint clamped in place using strips of masking tape. Traditionally glued paper strips - scorched in place with the hot iron - would have been used in place of masking tape. Masking tape is a bit more convenient - but not necessarily better.

Tomorrow - after the glue has completely cured - the masking tape will be removed and the joint inspected. Any areas (if any) where the joint has not properly closed will be reworked with the hot iron.

With the sound board glued and trimmed to size, the next step is to cut and fit the pegbox head plate. The head plate is a thick veneer glued to the upper face of the pegbox to strengthen the 'V' joint and for appearance. I have a lot of old boxwood stock in sawn billets (the older the better for boxwood as it takes years to fully season) so will make both the fingerboard and head plate from this material.

As boxwood comes from a small diameter tree the sawn billets are not wide enough for a head plate so a blank has been made from two book matched pieces about 3 mm thick. (The head plate will be later be planed down thinner than this after it has been glued in place).
These are first jointed with a plane on a 'shooting board' and then glued with hot hide glue. No clamps are required - the two pieces - with glue applied to the joint surfaces - are first rubbed together (to squeeze out surplus glue) and then held together (on a flat surface) with finger pressure for a couple of minutes until the glue gels. This is the so called 'rubbed joint' familiar to woodworkers who use hot hide glue. All quickly done and uncomplicated - a benefit of hot hide glue joints.

After 24+ hours to allow the glue to fully harden and moisture content in the area around the joint to stabilise, the surplus glue on the surface was removed with a scraper blade.

The exact profile of the pegbox was traced onto a piece of paper to make a template - by rubbing a finger around the edge of the pegbox. This outline was marked on the head plate blank with a pencil and then cut slightly oversize with a fretsaw fitted with fine tooth blade.
The plate blank was tested in place to ensure that adequate material was available for final trimming to size.

As this is a 'retrofit' project, the peg holes will be re-drilled (through the plate) after the head plate has been glued in place.

The head plate has been glued to the pegbox with diluted hot hide glue (same as for gluing sound board) - all done in the kitchen as the unheated workshop - with snow on the ground outside - is too cold for gluing operations. The good quality, but inexpensive plastic spring clamps - quickly applied - are ideal for this work.

With the head plate glued in place the peg holes must be drilled though the plate from the back of the peg box - using the existing peg holes as a guide. The centering of the drill must be precise so a 'transfer' centre punch was used to mark the exact centre for the drill through each peg hole. Transfer punches come in sets of increasing diameter in steps of about 0.4 mm and cost about $10 - inexpensive for a precision tool. A handy tool for both metal and woodworking.
The woodworking drill is a single spur type that cuts a clean straight hole - slightly undersized in diameter. The holes were cut using a hand drill so that the point of the drill could be felt to engage exactly in the punched centre marks before drilling.
The drilled holes were then 'cleaned up' with a peghole reamer.

Box wood is a hard and brittle wood so that the inevitable slight chipping around the drilled holes was removed by scraping the surface of the head plate with a cabinet scraper. The surplus material around the edge of the plate was then removed by filing to finish the job.

Next to prepare, fit and glue the fingerboard.

As usual - great work

A preliminary check on string action has been undertaken to determine the thickness and taper of the fingerboard blank (thicker at the nut end than at the neck joint).
A piece of nylon string was attached to the bridge, tied to a peg and tensioned. The correct nut height was set with packing.
At the bridge the string height was raised by filing the slots at an angle - one advantage of a slotted bridge that cannot be done with a drilled bridge.
The string action is measured with an easily made tool. This is just a small strip of hardwood cut with a slender taper calibrated in half millimeter steps (measured with precision calipers). The metal key ring is just so that it does not get lost among the other wood shavings.

Checking the sound board with a straight edge revealed a high spot over the 'neck block' which was removed with a cabinet scraper. The guitar has been made with a sound board 'scoop' - found on some old ouds , lutes and guitars - to avoid risk of string contact with the rosette when the sound board is distorted under full string tension.
Interesting to note that with the sound board glued in place the 'scoop' remains despite the convex sound board profile induced by the previous sound board scorching. This may be a result of the hot iron application when gluing the sound board in place - causing scorching of the upper face of soundboard edge? It will be interesting to see how all of this might affect the acoustic response of the completed guitar.

Current string action - with the neck planed and scraped straight and flat - is measured at 3 mm which will probably increase a bit under string tension so is about right. From these measurements the fingerboard will be made with a taper - thickness at the nut end 4 mm and at the neck joint
2 mm.
Final finishing of the finger board surface and action adjustment will be done after the fingerboard is glued to the neck.

The pre-shaped finger board has been glued to the neck with hot hide glue.
To minimise warping of the fingerboard from moisture of the glue during the gluing operation (moisture causes the surface of the wood to swell temporarily), the upper surface was first moistened with a damp cloth and glue only applied to the neck.

Low bloom strength glue was used - well diluted so that it runs from the glue brush in a continuous stream and does not gel too quickly.

Spring clamps and a flat 'caul' (block of wood to apply an even pressure) were used to clamp the fingerboard in place with two pins inserted first at the nut end to ensure the finger board did not slide out of alignment as the clamps were applied.

Another method of applying clamping pressure (without using a caul) would be to quickly wind string (or rubber surgical tubing) tightly around the fingerboard and neck for the full length. Long flat woven bootlaces that have some elasticity or stretch would work well enough. This method takes a bit more practice, however.

After allowing 24 hours for the glue to cure and moisture in the wood to dry out and stabilise the finger board and sound board surfaces and edges will be trimmed to size and finished. The sound board edges will be tapered slightly but left without a half binding inlay. This might be added later if improvements to acoustic response are considered necessary.

After fitting the fingerboard the instrument has been trimmed and fine sanded prior to finishing.

The register pin hole at the 'tail' end of the sound board left after gluing the sound board has been filled with an ebony plug (left over from another project) - purely cosmetic. The register pin hole on the neck has now been covered by the fingerboard.

Another item left over from other projects is an ebony 'tail button' - turned free hand on a lathe from some scrap ebony. This will be fitted later. The tail button is for the attachment of a shoulder strap to help support the guitar when playing - the instrument being too small to hold across the legs in the usual manner.

The entire guitar is to be refinished. As I recall there was a problem with the varnish originally used, way back in 1974, which did not cure properly - remaining slightly 'sticky'. To make matters worse, I may have wax polished over the varnish to counteract the problem - but cannot remember - so, regardless, all of this has to be removed.
After wiping the surfaces of the body and neck with a grease remover fluid ('Goo-Gone') they have been sanded with fine 'open coat' papers (3M) until all visible traces of old varnish/wax deposits (seen as slight 'clogging' of the sandpaper) have been removed.

The sound board and fingerboard will remain unvarnished but will be burnished to a gloss finish. The rest of the guitar will be finished with a hand rubbed 'TruOil' type varnish.

Two boxwood burnishers have been made - one for general burnishing the other to get into tight corners around the bridge. The surface of each burnisher is slightly rounded - as are the edges - to ensure the sound board is not marked or scored.
The burnisher working surfaces were then polished to a mirror finish on a piece of burlap sack cloth.

The burnishers are rubbed with light hand pressure in the direction of the sound board grain and quickly result in a glossy surface finish of the sound board.
Having messed around with a number of hopeful sound board finishes (like egg white distillate) I am coming around to thinking that the old lute sound boards were finished in this way i.e. without any kind of varnish or other applied substances. And so might have been the old ouds? Over time (centuries) the sound board wood will oxidise naturally to the dark brown colour seen in the surviving lutes and together with the polished sound board surface gives the appearance of having had some kind of finish applied when there never was.
The burnished surface should also discourage local dirt accumulations on the sound board if regularly kept polished with a soft cloth.

With the old finish all (hopefully) removed a first coat of 'home made' rubbing oil varnish (see 'Make Your Own 'Tru-Oil' Varnish' on this forum) has been applied to the back and pegbox. The neck will be varnished separately later - just for convenience in handling.
Three coats will be applied initially - allowing 24 hours to dry between each coat - followed by rubbing down between successive coats with fine 3M 'open coat' sand paper to fill the open grain of the 'mahogany' ribs.
The wood used is not a true mahogany but was cut from a highly figured piece of a pseudo mahogany ('Utile') rescued (at low cost) from the 'odds and ends bin' of a local wood supplier. Utile wood is quite similar in Specific Gravity and structure to true Central American Mahogany. The wood grain is quite open so varnishing could take some time - six or more coats perhaps.

The overall appearance with the contrasting 'flamed' Sycamore ribs should be quite dramatic - overstated even.

Attempts to finish the body with a 'rubbing varnish' have been abandoned. The resin/oil content of the highly figured Utile wood - used for the back and sides - is preventing the varnish from drying properly - this is the problem originally encountered when the guitar was first built - a problem common to oily woods like Brazilian Rosewood, Cocobolo etc. The varnish would likely dry eventually but this might take weeks, months or years even.
The neck and pegbox - cut from plain grained Utile - do not seem to have this problem.

The solution (hopefully) is first to strip off the varnish that has already been applied and to remove as much of the surface oils as possible. This was done with a fast drying lacquer thinner containing Toluene that will dissolve waxes. It will also dissolve some plastics - including Nitrile gloves - so cheap polythene protective gloves were necessary. After removing the varnish coats the surface was rubbed down with 400 grit 3M open coat sand paper and then wiped over again with the lacquer thinner. This was repeated until no clogging of the sandpaper was seen and all stain (oils and waxes) was removed from the wood surfaces.

To seal the wood, three coats of Orange Shellac have been applied - wiping on with a cloth pad and allowing three hours or so to dry between coats. The Shellac will be allowed to fully dry in a warm kitchen for another couple of days. The surfaces will then be rubbed down with 400 grit sandpaper and re-coated with Shellac. This operation will be repeated for several coats until the required finish is achieved.

I do not use premixed Shellac (it has a limited shelf life of about 6 months. If too old it may not dry) but always prepare my own fresh stock - in small quantities as required - from Orange Shellac flakes that have an unlimited shelf life. Orange Shellac is good for darker woods. The Shellac flakes are dissolved in ethyl alcohol. I purchase both Shellac flakes and an alcohol based Shellac thinner (not the same stuff as the above lacquer thinner) from Lee Valley Tools.
The Shellac is used in various dilutions - known as 'cuts' - measured in pounds of Shellac dissolved in a gallon of alcohol - 5 lb, 3 lb, 1 lb 'cut' etc. Best to apply dilute solutions and many coats.
For this project a 2 lb cut Shellac was first mixed (14 grams of Shellac flakes in 70 c.c. of thinner). This was used for the initial sealer coats. The finishing coats will be a more dilute solution of about 1lb cut.

The shellac coatings have successfully sealed the grain and fully dried.
An oil varnish could be applied over the sealing coats (but not a varnish containing polyurethane as it will not stick properly to the shellac). Rubbing oil varnish should not be used as the shellac will prevent it from penetrating into the wood.
It has been decided, however, to finish the instrument with only shellac.

The first step is to fill the open grain of the Utile wood. This is done by first sanding away most of the shellac coating trying not to cut through to the wood underneath. 400 grit open coat paper is used for this which generates a lot of very fine yellow dust (which is powdered shellac). This powder is left on the surface of the wood and worked into the grain with a cloth pad dipped in thin 1 lb cut shellac - using a small circular motion of the pad (a bit like French polishing) - soaking the pad at regular intervals as the shellac dries quickly. The shellac will then be left to dry for a day in a warm kitchen and the procedure repeated until the wood grain is completely filled. This should take about 3 or 4 coats - and a few days.

After several coats of shellac each allowed to dry for 24 hours or more and then rubbed down with 400 grit paper - the wood grain is filled and sealed.

Three final coats of 2 lb cut shellac were then applied with a cloth pad - this time without rubbing down between coats - and allowed to dry thoroughly for a few days. This left a glossy surface with streak marks and dust inclusions that were removed by rubbing down with 0000 grade steel wool. This is done with fingertip control - working over small areas at a time - until all streak marks etc are removed and the whole surface has a uniform sheen. Strong incident light is necessary in order to see all surface imperfections as work proceeds. Steel wool - even of this finest grade cuts quite quickly so care must be taken not to cut through the shellac coat to the wood underneath.
Shellac is not a particularly durable finish and will discolour if in contact with moisture or alcohol (although easily repaired if this happens) so has been given a thin protective coat of hard furniture wax. The wax is applied by putting a small piece in cotton cloth to form a pad - working in small circles over the entire surface. After drying for half an hour the wax is then polished to a nice satin sheen with a soft cloth.

This is essentially a shellac varnish finish - not a 'French Polish' shellac finish (that is far too glossy for my taste).

The nut will be made from a quantity of cattle leg bone pieces cleaned and prepared about 18 months ago (see "Making Bone Nuts from ,Scratch' on this forum).

The bone is pretty hard and irregular in shape so is (safely) cut roughly to size by hand with a metal cutting saw and a filed with a wood rasp (file).
The pieces have been checked with a magnifying glass to ensure that there is no bone porosity which would make a piece unsuitable for use as a nut - not only because of the tiny holes but because they likely still contain fat or grease deposits. Areas where the inside of the bone is 'cratered' rather than smooth are where porosity is most likely to be found and so should be avoided.

Two pieces that seem to be without porosity have been cut and - to be absolutely sure they are grease free before use - have been immersed in lacquer thinner (a mixture of Acetone, Methyl Ethyl Ketone and other solvents) where they will remain for about a week. If all grease is not removed from the bone then it may 'leach out' later and soak into and damage the surrounding wood of the neck.

Is it worth preparing cattle bone at home rather than buying nuts 'ready made' from luthier supply houses? Probably not.

In the meantime work on finishing the pegs and fingerboard surface will proceed.

The fingerboard has been levelled with a cabinet scraper and then given a slight curve or 'crown' across the width to ensure that the tied frets fit tightly against the surface of the fingerboard.

The guitar has been temporarily fitted with an old ebony nut and old nylon strings (plus a silk 'bourdon' bass string on the 4th course) and brought up to tension (ranging from 3.5 Kg course #1 to 2.8 Kg for courses #3 and #4). Temporary graduated diameter nylon frets (cheap fishing line - 0.8mm to 0.5mm - much cheaper than gut but not as good) have also been fitted. This is to assess if any further adjustments may be required to the string 'action'.

Under full string tension, the temporary nut can easily be pushed from side to side with finger pressure (due to the shallow angle of the pegbox - unlike an oud). As this might result in an inefficient transfer of string vibration, the bone nut that will eventually be fitted will be set tightly in a shallow channel.

The boxwood pegs require finishing by rounding off sharp edges with fine sandpaper. Further finishing should not be necessary as the peg heads will become 'burnished' with use. The ends of the pegs are slotted (rather than drilled) in the traditional way (no need for small diameter drills for pegs or bridge). In order to facilitate tuning when using gut or silk strings, the diameter of peg projecting above the pegbox may be reduced in diameter but, for now, the pegs will be left unmodified.

With a string length of 55 cm the maximum pitch of the top string - if traditional gut or silk - would be g' at A415. Initially PVF strings will be used so maximum pitch of the top string might be raised to a' - just to establish the optimum pitch for the guitar.
The 4th course could be unison or octave tuned - another factor requiring some experimentation for best results.

In the meantime - to hear how a renaissance guitar might have sounded at its finest - do a Google search for videos of Massimo Lonardi playing Renaissance Guitar - from the Spanish and French 16th C tablatures.

The degreased nut blank has been tightly fitted into a shallow rebate and trimmed to size ready for filing the string grooves. The rebate has been sealed with shellac and the nut will be glued in place with dilute hot hide glue to endure perfect seating and prevent any movement when under string loading.

To be absolutely certain that the nut is completely free of grease it will be left to soak for a few more days in pure acetone a relatively non toxic solvent (but highly inflammable).

To demonstrate the need for perfect degreasing of home prepared bone a few cut small pieces (previously cleaned by boiling in detergent followed by soaking for days in purified gasoline) have been soaking in Lacquer thinner for about a week - this brand being a mixture of Toluene, Methyl Ethyle Ketone, Methanol and Acetone. The liquid during this time has turned 'cloudy' in appearance due to thousands of what seem to be air bubbles but which are probably water/grease globules extracted from the bone. So this solvent mix is pretty effective. Pure Acetone is supposed to be better.

With the nut fitted the grooves for the strings have been cut with a needle file. It helps to have temporary strings fitted and up to tension to hold the nut in place during this operation.
To ensure consistent depth of the grooves a metal strip just over 1 mm thick has been placed in front of the nut so that the file does not cut too deeply. After filing the string slots have been polished with a thin string dipped in a fine abrasive ('rottenstone' - used for final polishing of a varnish finish).
The nut has been glued in place with a small 'dab' of hot hide glue.

The pegs shank have been burnished to a polished finish using burnishers made from small blocks of boxwood drilled and then cut to the correct taper with a peg reamer. Each peg is put in the burnisher and rotated by hand - being careful not to push the peg into the burnisher too tightly - to avoid jamming the peg. This compresses the wood fibres to ensure a smooth action of each peg when finally fitted.

The peg ends have been reduced in diameter by filing a groove with a needle file. This is to make tuning less sensitive - particularly when using gut or silk strings. It also helps prevent the annoyance of nylon strings tending to pop out of the peg slot before a string is brought up to tension.

Other finishing touches - the tail button has been fitted, a push fit and my makers brand has been burnt into the sound board just below the fingerboard.