Dendrochronology and
the Dating of Violins
Dendrochronology, which
may be defined as the dating of the year rings of wood, has only
recently been employed in the dating of violins. In 1953, Lottermoser
and Meyer attempted a relative dating of Italian stringed instruments by
comparing the year-ring patterns of three violins, though actual dating
was not achieved until the 1980s by Corona, Schweingruber, and Klein
[1]. In 1994, when I curated The Violin Masterpieces of Guarneri del
Gesù exhibition at the Metropolitan Museum of Art in New York, I
invited one of the world’s leading dendrochronologists, Dr. Peter Klein
of the Ordinariat für Holzbiologie of the University of Hamburg, to date
the spruce tops of the twenty-five violins assembled for that
exhibition. Among the conclusions gleaned from Klein’s findings are that
Giuseppe Guarneri apparently did not use well-aged wood in making his
instruments (the last datable ring is often just a few years earlier
than the date on the violin’s label) and that he occasionally used
mismatched pieces for the tops (whether this was by design, disinterest,
or carelessness remains a matter of conjecture).
I met Dr. Klein many years before the Guarneri exhibition, for in the
1980s and 1990s, he was often invited to the Metropolitan Museum of Art
to date panel paintings and other wooden objects. In dating musical
instruments for the Department of Musical Instruments (including
violins, viols, lutes, guitars, and harpsichords), I never had any
reason to question his findings, which were always in agreement with my
assessments regarding age and attribution. A few years after the
Guarneri exhibition, I employed his services in dating the wood used to
make the “Messiah” violin. Though he initially determined that the last
datable year-ring of that instrument was 1738 (which postdated
Stradivari’s death in 1737), members of the violin trade maneuvered him
into temporarily retracting his findings in exchange for an opportunity
to re-measure the “Messiah’s” year-rings at the Ashmolean Museum.
However, because of a dispute that developed during that session, he was
unable to leave the Ashmolean with his measurements. Klein now declines
to date violins, which is a great loss to those of us who formerly
relied upon his expertise and objectivity. (Prior to publishing Klein’s
results [2], I submitted the raw data to Dr. Peter Ian Kuniholm, a
dendrochronologist on the faculty of Cornell University, who confirmed
Dr. Klein’s dating.)
Following Klein’s controversial dating of the “Messiah,” Mr. John
Topham, and subsequently, Dr. Henri Grissino-Mayer entered the fray and
claimed to have found an earlier date that re-established the
“Messiah’s” authenticity. Lacking Klein’s proprietary master chronology,
Topham and Grissino-Mayer employed what they termed a “floating
chronology,” which was derived from year-ring measurements taken from
the “Archinto” and “Kux-Castelbarco” Stradivari violas. Unfortunately,
their floating chronology only extended to 1685, and as
dendrochronologists Angelo Mondino and Matteo Avalle later pointed out,
this did not permit Topham and Grissino-Mayer to discover a more
compelling statistical match further along in time [3]. In 2005 Mondino
and Avalle asserted that the last year-ring of the “Messiah” grew in
1788, fifty-one years after the death of Antonio Stradivari, though in a
more recent study, they claim to have discovered an even later date,
1844 [4].
Disturbed by the multitude of conflicting dates, I decided to delve
more deeply and directly into this dating technique in the hope of
learning more about it and, perhaps, determine why dendrochronologists
have arrived at so many different dates for the “Messiah.” In 2007 I
purchased the Synchro Search computer program and the accompanying
Manual of Dendrochronology Applied to the Dating of Musical Instruments
written by Angelo Mondino and Matteo Avalle (Cremona Books, 2005).
Synchro Search is a graphing and statistical program for comparing
year-ring data with established master spruce chronologies. The program
disk includes a number of master chronologies that are in the public
domain, including the Ötztal-Obergurgler, Siebenlist-Kerner Ötztaler,
Obersaxon-Meierhof, Schweingruber, and Malcolm chronologies, which are
among the chronologies that have been used in dating violins. In using
the Synchro Search program, the graphed year-ring dimensions of the
violin in question can be advanced with the click of a computer key
against graphs of any of the master chronologies until a match is
found. The program automatically computes statistical data, including
Gleichläufigkeit (similarity or G index), Pearson’s r
correlation coefficient (see below), Student’s t, mean
sensitivity, serial correlation coefficient, overlapping index, and
linear regression. The program can also be set so that the computer will
locate the best matches, which is very convenient when master
chronologies are hundreds of years in length.
In my investigation of this dating procedure, I did not wish to muddy
the “Messiah” waters any further, so I decided to use Synchro Search
in an attempt to establish the age of a large (17½”; 444 mm) viola,
apparently Brescian, that the late Jacques Francais attributed to
Gasparo da Salò (1540-1609). Making year-ring measurements of an old,
heavily restored violin or viola top can be difficult. There may be
“patches coming through” made with transplanted or later wood, painted
year-rings, as well as dents, scratches, and heavily discolored or
retouched varnish that obscure the grain. One must be aware of seams,
wings, and grain direction. If even a single year-ring is missed, this
can prevent the discovery of a match with the master chronology, so one
must be very careful in measuring. At that time, Klein used a little 7X
loupe fitted with a metric scale that came in contact with the surface
of the instrument. The advantage of this device is that it can be
carried around in a pocket; the disadvantage is that it must be pushed
along the surface of the instrument as one moves from year-ring to
year-ring. When using a loupe, it is necessary to call out the
measurements to a recording secretary, and this is another
inconvenience. I devised a piece of equipment that is more accurate and
convenient to use, though unfortunately, it is cumbersome. It consists
of a low-power stereo microscope (mine is an Amscope 7-45X on a boom
stand) with one eyepiece fitted with a cross-hair reticule. Below the
microscope, a violin/viola cradle (International Violin Co. #T-97) is
attached to a 250 mm rack-and-pinion linear translation stage (Edmund
#R56-796) that is linked via a brass angle bracket to a 12”-300 mm
Mitutoyo Digimatic linear scale with SPC output (see Figures 1 and 2).
To use this device, I clamp the instrument (with its strings, bridge,
and tailpiece removed) in the cradle and start by aligning the earliest
year-ring (which is typically the ring at the edge of the lower bout of
the instrument—though one should carefully check the year-ring shading
to make certain of the orientation) with the cross hair in the
microscope’s eyepiece. Using the rack-and-pinion of the translation
stage, I then carefully align the next year-ring against the cross hair
and press the button on the linear scale’s output device. This enters
the measurement into a Microsoft Excel spreadsheet, which I have
programmed to subtract the previous measurement from the last one
entered, so that I wind up with a column of year-ring widths. Most
violins have tops made with book-matched slabs of spruce, so one must
stop at the center joint. These tabulated widths should then be
multiplied by a factor of 100 so that the graphed data can be more
readily compared to the master chronologies (dendrochronologists work in
units of 1/100 mm, so 1 mm is expressed as 100) [5]. The column of
figures must then be copied out of Excel as a text file (.txt file
extension) so that the data can be compared against any of the master
chronologies that are supplied with the Synchro Search program.
Returning to the Brescian viola: I compared my 74 measurements of
year-rings from the treble side of the instrument to the following
master chronologies: PCAB Giertz Obergurgler 1276-1974, LADE Siebenlist
Obergurgler 1511-1974, PCAB Schweingruber Obersaxen 1537-1995, and Media
46° 1276-1994. I employed a straightforward matching of the year-ring
sequence with these master chronologies and did not use indexing,
segmentation, or any of the other statistical manipulations that
dendrochronologists often resort to. Tabulated below are the final
dates for the viola’s treble-side sequence where there was 60% or better
Gleichläufigkeit (G index or similarity) with each of the master
chronologies. This was chosen as a cutoff point because it represents a
degree of probability of over 95%, and because this percentage of
agreement between the year-rings of an object and a master chronology is
sometimes considered a “match” in dendrochronological reports and
literature [6]. The reader may be surprised by the number of “matches”
that were found:
Final
Year Gleichläufigkeit
PCAB Giertz
Obergurgler 1350 62.3%
1417
61.6%
1445
65.7%
1463
65.7%
1500
61.6%
1522 62.3%
1540 60.2%
1554 64.3%
1572 65.7%
1583 63.0%
1600 62.3%
1618 61.6%
1732
63.6%
1756
62.3%
1758
65.7%
1839
63.6%
1863
62.3%
1901
65.0%
LADE Siebenlist
Obergurgler 1511 62.3%
1665
65.0%
1680
62.3%
1704
63.0%
1732
63.0%
1750
60.9%
1792
60.2%
1810
60.9%
1826
63.0%
1826
65.7%
1834
65.7%
1949
65.0%
PCAB Schweingruber
Obersaxen 1690 61.6%
1756
65.0%
1758
62.3%
1784
64.3%
1810
65.0%
1895
63.0%
1925
60.9%
1953
67.8%
1959
60.9%
Media
46° 1522 62.3%
1551
63.6%
1572
63.0%
1611
60.2%
1625
60.2%
1657
70.5%
1665
65.0%
1696
60.9%
1710
60.9%
1712
62.3%
1732
60.9%
1754
62.3%
1756
63.6%
At 60%
Gleichläufigkeit or higher (representing a probability of 95% or
better), 52 matches were found, and at 65% Gleichläufigkeit or
higher (representing a degree of probability of around 99% or better),
13 matches were found (with final dates of the series ranging from 1445
to 1953). It is also disconcerting that the PCAB Giertz Obergurgler,
LADE Siebenlist Obergurgler, and PCAB Schweingruber Obersaxen master
chronologies produced very few dates in common (1732 and 1756); the
Media 46° chronology exhibited several concordances (1522, 1572, 1665,
1732, and 1756), but this would be expected as it is a composite derived
from over thirty chronologies, including the other three that I used.
The 1657 date (which has the highest Gleichläufigkeit of 70.5%
and a probability of 99.9%) is of interest because violas of this large
size were still being constructed at this time, though if correct, it
would rule out Gasparo da Salo as the maker, as he died in 1609.
However, I should point out that I subsequently discovered a date of
1805 with a considerably higher Gleichläufigkeit of 75.3% using
the CEBR Schweingruber Ceader Valley (Cipro) chronology. I must admit
that I did not initially seek a match with this master chronology
because its synchronization dates extend only from 1675 through 1981,
and my inclination was to search for dates using master chronologies
that had earlier starting points. This only demonstrates that one may
inadvertently overlook a master chronology because its inclusive years
would appear to fall outside the date that one hopes or expects to
find.
In general, my
experiences with the Alpine master chronologies supplied with the
Synchro Search program (which include the PCAB Siebenlist-Kerner
Ötztaler and PCAB Gierz Obergurgler chronologies that were employed by
Grissino-Mayer, et. al., in fixing a date to their floating chronology
when attempting to date the “Messiah”) have not yielded overwhelmingly
convincing, or unique matches with a number of Italian instruments that
I have tried to date [7]. The reason for this may be due to the fact
that these master chronologies were constructed from wood samples taken
from Alpine regions or altitudes that do not have precisely the same
climatic conditions as the locale where the Cremonese and Brescian
makers obtained their wood, which I believe was likely from the Italian
Alps directly north of Brescia. Many of the master chronologies in the
public domain are derived from wood found in the Ötztal and Obergurgl
mountain ranges, which are close to Innsbruck, Austria. It is also
possible that the Synchro Search program itself is at fault-some
dendrochronologists have been critical of certain of its statistical
operations, including its method of calculating Pearson’s r
correlation coefficient and Student’s t [8]. However,
determining Gleichläufigkeit is fairly straightforward, and it is
often the only measurement cited in dendrochronological reports,
including those of Peter Klein. Yet another reason for the failure to
discover singular matches may be due to underlying flaws in the
technique itself—that it is simply not precise enough to pin irrefutable
dates on relatively short sequences of year-rings.
In conclusion, I
would strongly advise violin historians, authenticators, appraisers, and
purchasers to be wary of the dates that are being published in auction
catalogs, certificates, and scholarly journals. I would also suggest
that dendrochronologists produce reports that contain considerably more
statistical detail, and if they arrive at several possible dates for an
instrument, they should report all of them; moreover, they must never
rule out dates that they have been prompted to believe lie outside the
probable period of manufacture.
_____________________________
1. Lottermoser W and
Meyer J, “Über die Möglichkeiten einer Dendrochronologie von
altitalienischer Geigen,” Instrumentenbau-Zeitschrift 12 (1958):
295-297; Corona E, Ricerche dendrocronologiche su due violini del XVIII
secolo,” L’Italia For. e Mont., XXXV, 3 (1980): 112-115;
Schweingruber F H, Tree Ring Basics and Application of
Dendrochronology (Dordrecht, 1983); Klein P, Mehringer H, and Bauch
J, “Tree-Ring Chronology of Spruce Wood and Its Application in the
Dating of Stringed Instruments,” Icom Committee for Conservation 7th
Triennial Meeting Copenhagen 10-14 September 1984 Preprints (1984):
84.1.69-84.1.72.
2. Pollens S, “Le Messie,” Journal of the Violin
Society of America 16.1 (1999): 75-101.
3. Mondino A and Avalle M, Manual of Dendrochronology
Applied to the Dating of Musical Instruments (Cremona, 2005):
85-107.
4. Mondino and Avalle, Manual of Dendrochonology,
pp. 85-87; Mondino and Avalle, New Dendrodating Procedure Exercises
(Cremona, 2009): 91-92.
5. Below are the raw measurements taken from the viola
multiplied by 100:
236,189,175,165,119,135,140,173,169,150,116,176,190,169,202,174,132,205,
193,205,212,204,200,216,215,220,188,198,156,161,205,188,167,157,172,193,
151,181,189,244,196,199,173,214,177,214,183,182,192,171,166,195,181,171,
205,168,185,175,127,172,151,170,162,170,225,237,260,274,257,262,245,116,
128,175.
6. Bernabei M, Bontadi
J, and Rossi Rognoni G, “A dendrochronological investigation of stringed
instruments from the collection of the Cherubini Conservatory in
Florence, Italy,” Journal of Archaeological Science 37 (2010):
195.
7. Mondino and Avalle, Manual of Dendrochronology:
68.
8. I would like to thank Peter Ratcliff for pointing this
out. Personal communication, 2010.
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