Conservation of a mid-17th Century English Bass Viol Converted to Cello


Description of the Instrument:

A larger than usual bass viol, English, around 1650, which has been rebuilt as a cello in London around 1750, possibly by a member of the Thompson family of violin makers. It has thereafter suffered massive worm damage and has undergone subsequent repair, much of which is of lesser quality. A non-original, printed label is present which reads:



A fuller discussion of the label follows below.

The Original Parts:


Of the original viol, the belly remains, with a large non-original patch in the centre of the upper bout. The belly is of bent construction, of five tapered pieces of pine, with a single line of dark hardwood purfling around the edge and the remains of a geometrical purfling knot in the upper bout, also executed in a single line of dark hardwood. The remains of this knot can be seen below and to both sides of the non-original patch in the upper bout. There are 2 small, possible original vestiges of linen cloth glued to the inside of the belly. These may be the only remains of the linen strips one would expect to find in an English bent-top viol.

There is no visible evidence of the original bass bar, though there may be marks beneath some of the later repairs.


The sides are original in the lower bout only, but have been cut down in height and somewhat shortened in the process of conversion to cello. The centre bouts and upper bouts are of different wood, all matching, which from the inside, show completely different tool marks from the smoothly planed lower bout rib. It seems clear that the centre and upper bout sides are the work of the 18th century violin maker who converted the viol to a cello. There are several pieces of linen used to repair parts of the sides. There are also 2 vestiges of possibly original linen in the lower bout.

Tail Block

The tail block appears to be original. There is no visible sign of an original tail post, as one might expect on a viol of this period. The endpin hole is not centred and assuming an original, centred position, the ribs would have to be a minimum of 12mm deeper than is presently the case.


The central portion of the back is original. It consists of two book matched pieces of broadly figured maple, with the joint centred and the remains of a geometrical purfling knot aligned on the centre join and executed in a single line of dark hardwood. The inside planed and scraped finish of the original part of the back is in concordance with the inside surface of the lower bout rib, which appears to be original and retains the original viol tail block. Non original pieces have been inserted in the back, in the lower part of the lower bout and in the upper bout, from the bend upwards.





The outlines of both belly and back have been modified in the process of conversion into a cello. This is clear from the purfling line and the variable distance of the purfling to the outer edge. In several places, the purfling runs out of the edge, indicating substantial reductions to the outline of the instrument during its conversion and subsequent repair.

Varnish Analysis

The predominant varnish on the original parts of the instrument is typical of the lesser work of mid to late 18th century London. It consists of a ground of dark red-brown pigment applied to the wood with an equally dark red-brown varnish which is, to a certain degree, alcohol soluble. On parts of the back in particular, in the area of the remaining section of decorative purfling, there are the remains of an earlier and probably original varnish which, under UV light, fluoresces with the characteristic creamy ochre colour that indicates an oil, such as linseed, as part of the ground and an oil based, pigmented varnish above. This area where the original varnish has survived in better condition has also rejected the later varnish to some extent and provides some idea of the original varnish profile.


Identification of the Original Maker

The attribution of this viol to an English maker of the 17th century is based on the style of the decorative purfling knots. The overall outline and CC-hole design seems to belong to the Rose school. Taking into account the choice of wood for the bent top (fir, rather than spruce), the use of a single line of dark hardwood for the purfling, the overall spacing of the broad-edged purfling and the outline in general, this instrument strongly resembles the work of the mid-17th century London maker, William Turner. Several other instruments from Turners workshop are preserved in the Vazquez collection in Trieste and it is on comparison with these that the attribution is made. Another bass viol by Turner in substantially original condition may be found in the Palais Lascaris Museum in Nice.

The large size of this viol and its rather Collichon-like outline and CC-holes create an impression of possible French provenance, but the style of the purfling decoration is not typical French and the other elements point most directly to mid-17th century London and the work of Turner. A date of 1640-50 would be appropriate.

The Original Conversion to Cello

The following parts and repairs seem to be the work of the repairman who originally converted the viol to a cello:

       The scroll and pegbox;

       The neck block and corner blocks;

       The majority of the liners to the back of the instrument;

       The asymmetrical maple soundpost plate, glued to the back in the centre bout and lower corner area. This piece has been glued in place in such a way as to generate a slight arching of the otherwise flat back

       The longitudinal pine strips, glued over the joints in the 5 piece bent top. These are now only partially extant, due to later repairs and modifications. (see drawings below)

       There is a sign, below the lower end of the present bassbar, of an earlier bassbar, somewhat longer and narrower, aligned with the present and in a position that indicates that it was intended for four strings.

       The size of the body was reduced somewhat, during the conversion, as is attested to by the purfling line, which runs out of the current edge in various places on the lower, middle and upper bouts. This will be mapped front and back, to ascertain a possible original outline.

       There remains an 18th century tailpiece and an18th century peg with the instrument. These may well date from the time of the conversion of the cello. (see photo)


Comments Regarding the Conversion.

The parts and repairs related with the conversion to cello are clearly English and mid 18th century. This is evidenced from the way the blocks are cut, so that the ends of the liners tuck into the rebate created (see photo). The liners are flat strips of pine, with a knife cut chamfer, as is common among the London makers. The neck block has 2 holes for screws, the common manner of neck attachment in mid – late 18th century London. All the blocks and liners are of pine and are cut straight off the chisel or the knife. The work strongly resembles that of both Robert Thompson and his sons, Charles & Samuel.

In converting the viol to a cello, the sides have been reduced in height. As mentioned, there is no visible sign of an earlier tailpiece bar as one would expect on viols of this period, though this may have been obliterated in the conversion process, as the instrument has been completely re-varnished by the repairman who converted the instrument to a cello in about 1750. This varnish and dark brown ground are very similar to the work of the Thompson workshop.

The bottom bout rib is a single piece of plain maple, still retaining the original viol tail block. There is a cut-out for a saddle, with indications that this has been enlarged from a smaller, earlier saddle.

The tail pin hole is not centred in the side, but is placed 60mm from the back-side joint. Given the current rib height of 112mm, a centred pin hole would suggest sides of 120mm depth as a minimum. The size of the viol would indicate sides of around 130 – 140mm originally.

Another characteristic of the reduction of the ribs is that the bend in the upper back, which originally would be expected to have a sharp angle of between 10 & 20o, has been  reduced to a curve which reduces from 114mm at the break to 90mm at the neck, rather as one sees on some double basses. This seems to be a design feature of the 18th century conversion, given that the corner blocks are all from that time and that the back liners are still partly original and run beyond the break.

It is likely that the sides were completely disassembled for the conversion (with the exception of removing the tail block) and that the sides were cut down and re-fitted to the modified back. This procedure would seem to follow the usual 18th century English assembly system for violin family instruments, which uses the back as the base for construction.

The corners of the sides currently show signs of having been chamfered, rather than lapped.  As the body size was also reduced during the conversion and, given that the lower bout is a single, original piece, this chamfering may be considered to be the work of the violin maker doing the conversion.

The pegbox and scroll are 18th century English and are currently spliced onto a late 19th or early 20th century neck. The scroll model follows the characteristic Stainer pattern, current in mid-18th century London and strongly resembles the work of Robert Thompson or his sons. The varnish is also typical of the Thompson workshop, being a dark red brown on a brown pigment ground. The whole instrument was re-varnished this dark pigmented red-brown colour at the time of the conversion and there are signs of an earlier, possibly original varnish of superior clarity and lighter colour, in the area around the purfling knot on the upper centre of the back. Small patches of the same varnish and golden ground appear on other areas of the back.


The Label

The instrument contains a printed paper label which is not original and is glued to the unoriginal soundpost plate that was added at the time of the cello conversion. The label consists of a baking piece of hand-laid paper 84mm in length, onto which 2 rectangular printed sections of similar paper are glued (see photos). As well, due to damage to the upper edge of the label resulting from later repairs to the instrument, a portion of reversed text has become visible. This text is actually printed in a similar, Roman serif font, on the reverse of the backing piece. There are also 4 hand-written letters on the label, which are readable left to right.



Below is the reversed text from the top right-hand corner under normal and infra-red light. 

P1010164 reversed croppedSnapshot3 Potter IR

Worm flight holes through the label indicate its presence in the instrument before the worm damage occurred. This worm damage occurred after the conversion to cello, so the label may have been assembled and glued in by the maker who did the conversion or shortly after.

Later Repairs and Alterations

Following the conversion to cello about 1750, this instrument has passed a long period of disuse and poor storage, during which it was very severely damaged by woodworm attack. All parts of the instrument show signs of this attack and the following parts are now absent, most likely due to collapse of the wood from this attack:

       A central section of the upper bout of the belly

       The back above the bend

       The back below the widest point of the lower bout

       The neck from which the present pegbox and scroll were taken.


The quality of this later work is generally quite poor and at times, amateurish. It is not possible to accurately determine the sequence of works undertaken after the worm damage was sustained, but work of a superior quality seems to have been undertaken in the early 20th century, possibly by Domenic Vlummens, the Antwerp maker and repairer, who lived in London in the 1920s and 30s. The bridge which came with the instrument (see documentation) carries his stamp and the work of fitting a new neck is of reasonable quality and would date from this period.

Condition on Completion:

The instrument was restored as a cello, retaining the early 20th century neck and bassbar. Otherwise the instrument was fitted up as a mid-18th century cello with a period style solid ebony fingerboard and using the 18th century tailpiece which came with the instrument. The one early peg in the set present on arrival was copied in fruitwood and an end button was made to match, the finish being black stain and varnish as per the original.

An ivory nut and saddle were fitted and the instrument fitted with a French style bridge similar to the Vlummens bridge that came with the instrument a soundpost of diameter 11mm was prepared and fitted. A set of period style gut strings were fitted and the instrument provisionally tuned 3 semitones below modern pitch. At this pitch the instrument appears stable and has a warm and strong sound on all strings.

Recommendations for Care and Maintenance:

Pitch and Tuning: Due to the fragile nature of the restored body, it is recommended that the instrument not be left permanently at pitch. Recommended playing pitch is 3 semitones below modern pitch. For display and storage purposes the instrument should be tuned a fifth lower than the recommended playing pitch.

Humidity control: The recommended humidity range for display and storage is 35 – 65%RH. Above and below these limits care should be taken to maintain a microclimate around the instrument and case. This is most important in dry summer weather to avoid stress to joints and possible cracking or seam separation.

If displayed, the instrument should be in a stable humidity environment away from direct sunlight and in the lower storey of a multi-storey building. A hygrometer hanging near the instrument is strongly recommended.

If hanging the instrument for display, support from the scroll using a soft cotton cord and pad the point of contact with a wall using felt attached to the wall with double sided tape.

Ian Signature

Ian Watchorn;  22nd. September 2014

Belly inside & out     Belly%20inside

P1010062     P1010061

     Back%20Outside  Back & Sides Inside

P1010033                P1010122


Back & sides



P1010141  P1010179


P1010243         P1010242




P1010046      P1010094   P1010076





final 1A     final%202A     final%203A


final%2010A     final%2014     final%2018A