previous article, we worked out a
number of shapes that the bore of the Potter flute might have been
originally. In this article, we'll try to eliminate some of them
as "impossible", and cast doubt on others as "improbable", in the hope that
a process of elimination will lead us to the "most likely".
Just how bent?
Focus on the compression in
the middle and lower tenons in the graph below. In both cases, we
see that the compression is not limited to the tenon itself, identified
by the vertical dotted lines. It also extends into the adjacent body
wood, in both cases here to the left of the tenons. But now focus
on the upper tenon at image left. Where is the compression to the
adjacent body wood (which in this case will be to the right of the
tenon)? Is it that tiny flat spot, about 10mm wide, between X=40
and X=50mm? Or is it
that extended sloping bit down to about x=140mm? In other words,
is the section of bore between the top and mid tenon supposed to be bent
like that, or is that a by-product of the strangulation at each end?
Check out the family
Imagine this flute was a
human victim, mangled beyond recognition by perpetrator or perpetrators
unknown. Investigators need to know what the victim looked like.
What do they do? Check out the family of course. And we shall do
the same. Surely we can find some other Potter flutes that can
provide some clues? And the answer is .... yes! Check out
Potter's previous model
The Bate Collection in Oxford
holds a fabulously beautiful boxwood flute by Richard Potter, dating
from 1782, just 3 years before he patented the Patent flute we're
looking at in this series. The Bate flute doesn't have a tuning
slide, and has the older square keys with flat leathers for pads.
Because there is no slide, it needed some other way of dealing with the
range of pitches in use at the time. This flute has three "corps
de rechange", left-hand sections of differing length, for that purpose.
So it doesn't just offer us one view of what a Potter flute LH should look
like, but three. Even more exciting is that I have the bore
dimensions for it, kindly drawn up by another Australian, Ken Williams,
in 1984. Sometimes you just strike it lucky!
You can see that flute's bore
illustrated above, as the pink, navy and brown traces in the LH, and the
navy trace for RH and foot. Because the three corps de rechange
are of differing lengths, I've offset their starting points to keep them
connected to the RH section. The short gaps at the start of the RH
and foot sections are because Ken measured in 0.2mm increments of
diameter. So we don't know exactly what diameter the start of
those sections are, excepting they must be less than 0.2 larger than the
next measurement point. No problem for us - we're more interested
in the trends of the bores rather than any one point.
The first thing we notice
about the three LH traces is how alike they are, almost assuredly cut by
the same reamer. The second is how straight they are. There
is no sign of a sudden bend in the LH bore, as we wondered about in the
strangled Potter, shown here in thicker yellow. The third thing we
notice is there is only the most minor sign of bore compression and no
other significant distortion.
This lead me to conclude that
we are in the presence of a flute that has hardly ever been played.
And perhaps of a flute that had a shallow and loose thread wrap that had
never been replaced or augmented. If you don't play a flute, you
have no need to tighten a loose wrap! Acting on a hunch, I asked
my colleague Dr Robert Bigio if he happened to have an image of it
(Robert has taken images of a vast number of flutes at the Bate and
other collections). Sure enough he did and has kindly supplied it:
Richard Potter flute, boxwood &
ivory, 3 corps de rechange
Image by Dr. Robert Bigio, London-based flute maker and researcher
Image reproduced here with permission of the Bate Collection, University
(Robert is a bit scathing
about this image, taken with his older photographic setup, although I
suspect it hasn't sent you screaming from the room. Or at least,
you came back! His newly-released book,
Rudall, Rose &
Carte: The Art of the Flute in Britain sets the standard for flute
photography for the foreseeable future.
And while I'm in promotional
mode, you can find out more about the Bate collection from the
Bate website. And even order
your very own copy of the detailed technical drawings of the Potter
flute to mull over.)
As you can see, the image completely supports
my prediction. The flute is in
magnificent, "as-new" condition, and the loose and shallow tenon thread is pushed back, on
several tenons, exposing the wood below! This is not a flute, it's
a time capsule! And a time capsule with an important message for
us. At least in 1782, Potter intended his LH bore to be straight,
and to join the head diameter with the bore of the RH section.
He did appear to have quite a
different idea of how to deal with the foot. But that's a feature
for a different study.
Potter's Son's flute
And our luck is holding.
The McGee Research Collection has another flute in the Potter family -
this one made by Richard Potter's son, William Henry Potter, sometime
after 1806. William Henry had apprenticed with his father in 1774,
took over in 1806 when Richard retired, and finally retired himself in 1837, dying in 1848, leaving a
fortune of £30,000.
Interesting to think that,
given he started with his dad in 1774, he might have been involved in
making all the flutes we've been looking at. Here's the William
Henry Potter flute:
You can see it's essentially the same as the Richard
Potter we've been following, except in ebony and in slightly better
condition. Indeed, when we see the bore, we realise just how much
in common they have -young Potter's flute in aqua, in the graph
conveniently repeated here:
The only real clear differences we can see are that the
LH top hasn't been cut off, and that the foot bore terminates in a most
unusual curve. Both flutes suffer from similar levels of
strangulation at all three tenons, unlike Richard Potter's early flute
in the Bate. Because the flute under study had been shortened in
the late 19th century, its upper tenon strangulation has moved downhill
compared to the WH Potter, a beautiful proof that at least the
compression under the tenons was not original.
So, in terms of finding out what the strangled Potter's
bore looked like, we're not much further advanced. We have one
flute (or three, depending on how you regard the three corps de rechange) with
a very straight bore, and two with the bent bore. No clear winners
here. Did Richard
Potter introduce a second slope when he invented his Patent flute in
1785, or is the bend in the LH section simply another symptom of severe
strangulation? Perhaps someone else out there has a Potter Patent
flute in better condition they could measure and break the deadlock?
Reality Check I - Is there room for
a straighter bore?
You can imagine that, if the LH bore
were to be enlarged at both ends, the outside diameters of the two tenons
would increase in diameter also. Would they still fit in their sockets?
If not, then surely these theories are blown out of the water! We need to
Seems like that isn't an issue for
the conservative scenarios at the top, or any scenario at the bottom.
Both tenons, now unwrapped, are very free in their sockets, indeed to the point
where you would say sloppy. Measurements indicate that there is about 1mm
clearance - more than a good maker would normally leave. Potter was a very
good maker, so that seems to suggest that that clearance has increased over the
years. As tenons collapse, clearance increases...
But 1mm clearance at the top tenon
may not accommodate the 1.3mm increase in bore diameter we might expect to see
under the boldest scenario. But there might be reason to still wonder. This
flute uses wide bands of ivory to reinforce the sockets. Ivory seems to
shrink even more than wood (it's often cracked because the wood under it didn't
shrink as much), so it might be that any lack of clearance in the barrel socket
could be partially due to shrunken ivory. Certainly that socket is almost
cylindrical, while the RH section's socket is tapered. You can imagine how
much the ivory has shrunk by seeing how much the barrel wood has shrunk,
cracking to expose the slide inside. Yet the ring is still firmly
attached, suggesting it has shrunk at least as much as the wood, and probably
more. The crack is 1.15mm wide at the top shoulder, suggesting a reduction of about
0.37mm on diameter, or about 1.5% . That would probably make the difference needed to
accommodate an emboldened tenon.
Shrunken ivory is suggested also by
the fact that the ivory on the other two sockets has been replaced by metal
bands, probably after the ivory shrunk, cracked and fell off.
This stuff is tricky, isn't it.
If room-to-move proves to be a sticking point (so to speak), we may wish to test
the possibilities by humidifying the barrel too! Hmmm, indeed, why not?
Reality Check II - are the bold scenarios even feasible?
Hang on a minute - get real!
Are we really considering the bold scenarios? Let's do a little
computer modelling first to see if that kind of change is possible....
In our model, we'll assume
the bore started as a straight taper, joining the head bore to the RH
bore. Pink in the graph below. Then we expand the bore by a
specified percentage due to humidity uptake, but let the thread
constrain the area under the tenons to the original size. We'll
assume the section including the Bb and C blocks will be more-or-less
immune from distortion because of the additional rigidity of these walls
lent by the blocks, and because of the distance from the constrained
tenons. Then we'll assume the areas immediately adjacent to the
constrained areas are only 50% constrained (because their wall thickness
is about double the wall thickness of the tenons). Then we taper
the distortion between those and the immune region on the basis of
proximity. Finally, we'll reduce the damaged bore by the same
percentage as we started with.
Note that there are a few
other factors we could throw in, such as the thread retention grooves at
the bottom of the trough, but these would be difficult to model and
probably not make all that much difference to the overall picture.
They might well have a significant effect on the exact shape of the
bottom of the thread trough though.
And what do we get?
Something truly astounding - a match to the as-found bore dimensions
within less than 3%! Compare the blue "as found" trace in the
graph above to the brown "modelled" trace. So even the boldest
does seem feasible.
But what was that "specified
percentage"? I found in my model that I needed a 7% swelling and
subsequent shrinkage rate to produce the match reported. Is 7%
change feasible? Not in one sitting, perhaps, but in a case of
serial strangulation, perfectly feasible. Three cycles of just
over 2% each would do the job nicely, Inspector.
Now that we've seen the bold
scenarios supported, doesn't that also cast some doubt onto the
conservative scenarios? Why would the damage caused by over-tight
thread-bands be limited to just the tenon below? Surely some
distortion of the adjacent wood is inevitable. Try this simple
analogue. Support a thin rule on two pencils, about 50mm (2") in
from the ends, on your desk. The pencils represent the tenon
shoulders. Now press down at each end, about 25mm (1") in from the
ends of the rule. This pressure represents the constraining thread
band. Watch the centre of the rule as you do it - does it remain
still? No, it rises as the pressure goes on. This is because
the rule has finite stiffness - it refuses to bend meekly around the
pencils - the whole thing prefers to adopt a curved shape. The
same will apply to the flute section - the finite stiffness of the wood
will ensure that the compression and thus the damage is taken over a
broader area than just the point of pressure. The conservative
scenarios are not looking good...
Of course, the bolder the
scenario we end up supporting, the more our "moderately strangled" flute
is being reclassified as "seriously strangled". The criteria I had
proposed for the threshold of seriously strangled was 1mm reduction in
diameter. The aqua and violet traces would meet that criteria on the top
tenon, and those plus the orange trace in the mid tenon.
And this is one I had classified as just a "moderately strangled" flute. Sobering, eh?
A cold shower
Now, of course, we shouldn't
necessarily expect that restoring a flute to its original shape will
necessarily make it a better tuned flute for our modern purposes than it would
have otherwise been. Mr Potter didn't intend his flute to play at
A 440, although with that very long tuning slide he was certainly
keeping his options open. The barrel extension on that flute is
27mm, so even if he never intended to let you see the naked metal of the
head tube, he had allowed for about 27Hz variation in pitch. So,
even starting at the low pitch of the day, A440 might be within range.
By way of comparison, Ken
Williams estimated that the three bodies on the Bate Potter were
intended to play at ~418, 427 and 436Hz. Our flute was a little
shorter, and is now, because of the high pitch era modification it
suffered, considerably shorter! So it's a bit hard to know what to
expect. But, if we want to have any chance of
understanding what he was aiming at, we need to get back to his
dimensions. And of course, the same applies to flutes by all the
What about the rings?
In these series, we've been
concentrating on the compressive effects of thread bands. But what
about socket rings? If a thread band can prove to be a barrier to
expansion, surely a metal or ivory ring is even more? Why don't we
see the same compressive effects under the metal rings?
Answer is that we do.
But it's not so noticeable. Look at the RH section in the "bore as
found" graph, reproduced here. It's the section from around X=210
to X=340mm. At the 210 end of the section, we see a small amount
of compression. At the other end of the section, we see a
thread-wrapped tenon from around X=310 to 330 with a lot more
Surely that makes no sense!
If a band of pliable thread causes problems, surely a strong band of
unyielding metal has
to create more? It's a fair question, and one we need to
investigate and be able to answer convincingly. I have a few theories,
half-baked at best, which I'll share with you until we can investigate
Theory 1 relies on the
difference between playing and weather-induced swelling. You'll
remember from the first series that we tested two ways that moisture
levels in a flute could be increased. We found that
simulated playing was a far more efficient way of getting moisture into
the wood than putting the flute in a humidified environment. The
area under the tenon thread is bore, which gets nice and wet when you
play. The area under the socket ring is socket, protected from
direct application of moisture by the tenon of the connecting piece.
So it only gets moist by conduction from the adjacent bore area, or from
humidity in the air.
Theory 2 is that the
compression under the ring is largely confined to the socket. The
socket wall is thin, and therefore relatively flexible, while the rest
of the body wall is thick and therefore much stiffer. The socket
probably protects the bore by going a bit bell-mouthed. We do see
a little compression at around X=210, but nothing compared to that under
the tenons. We often come across bell-mouthing in old flute
sockets. That's the annoying situation where it's hard to get the
tenon in, but once there, the joint is loose and floppy. Now we
can see why it happens.
Theory 3 relates to serial
strangulation. When the tenon shrinks, the joints get loose, and
the owner adds a bit more thread to tighten them up, initiating the next
cycle of serial strangulation. But if the socket shrinks, the joints
get tighter. The owner might react by removing some thread off
that tenon, but that won't affect the socket.
A little serial strangulation might apply to the sockets of this
particular flute. Note that, in both RH and foot, the original
ivory socket rings have cracked off and got lost, and have been replaced
by brass rings. We don't know how well the repairer prepared those
rings. If, as I have reason to suspect, he made them undersized and hammered them on, they might
well be a fresh source of compression.
Theory 4 goes to the
differing nature of the thread band and ring. When the socket wood
shrinks under the ring, the ring suddenly exerts no more pressure, and
shrinkage will probably stop. The more elastic thread band
probably continues to exert some pressure, so shrinkage continues longer
each moist cycle.
And of course, Theory "n"
tells us that all these things are involved.
But what about the rings on the foot?
Aha, reckon you got me, huh? When we look at the
first bit of the foot bore (X=330 to 350), we see no sign of compression
at all. So, how come? Just take a look at that section of
the foot in the image below:
That's where the bulge which forms the hinge block for
all three foot keys, and which runs completely around the foot at this
point. Nothing is going to crush such a mighty block of wood!
That's not to say someone didn't try. When I removed
the brass ring, I found a cylindrical crack running back into that block
at the diameter of the wood under the ring. I suspect whoever
replaced the missing ivory band with a brass one simply hammered it on
to the tapered piece of wood remaining,
causing the wood under the band to separate from the inside of the
And, at this stage I'm not sure what to make of the very
end of the foot bore. It almost looks like it was intended to be
horizontal at about 10.4mm for the last 45mm, from X=425 to 470.
Could that dip near the end be the result of compression under the foot
ring? We may have to look at that issue separately.
Let's imagine that we decide
that the only damage this flute has suffered is to the tenons. So
we go with the ultra conservative scenario "just fix the tenons". But
let's say we were wrong. Supposing the compression of the thread
band squashed not only the tenons but a considerable part of the nearby
body. If we take the compression off the tenons, we also take it
off the adjacent body area. Any expansion to the tenons may cause the
adjacent bore to enlarge. So even just fixing the tenons might
reveal that the bore has moved too. So it's possible that, even in making the wrong call, we will
still learn what really happened. It's rather comforting isn't it
- we can afford to press on even if we don't quite know what we might
ever happened to that cornerstone of Tea Party ideology - the Right to Remain
Serial strangler clues
I had great hopes, when
pulling the thread off the RH section tenon, that I might be able to
find clues to a serial strangulation. I most carefully sought out
the end of the thread using a needle probe under the zoom dissecting
microscope, and lifting the thread away gently with fine tweezers.
But the thread was so compressed, it broke at points where it crossed
other threads, so I was not able to be sure how many separate lengths of
thread were involved.
But, when I finally reached
the tenon, it became clear that the entire thread band had been replaced
a number of times. I counted at least 6 slashes in the wood that had been made
with blades since the tenon had been combed. Some straight and
full length, some at wild angles, some in the form of tangential slices.
We can say with confidence that frequent vigorous thread removal and replacement
was a part of its history.
A Plea for Moderation
Finally, let's here a voice
in favour of a moderate expectation. Check out the undamaged and
lightly damaged flutes in the survey graph reproduced below. The
Geo Rudall Willis Fecit (dark green) seems perfectly happy to be pointing at about 18.1,
but then, it's a small bore flute. The Anon Pratten (light blue)would have come
out around 18.3mm, if it weren't for the bridging taper, which might not be
original. The RC7120 (navy) seems from this graph to be heading for an
opening of about 18.7mm. Just as it's clear they have suffered little
or no compression, there doesn't seem to be evidence that these flute
bores were aiming for the head diameter.
At this stage, I think we have to
accept we still don't know that the bore should look like, other than the conservative
scenario, "flatten the tenons" in the graph reproduced below looks rather too conservative. It might just be that we'll have
to rely on recognising a credible bore shape when we see it, either from
measuring and graphing it, or from its performance.
But it hasn't been wasted
effort. We've considered a lot of possibilities, and will be well
armed to venture forward, antennas twitching. Knowing that even if
we achieve a moderate scenario (say the orange or red trace), our poor
flute will be saved from strangulation.
But maybe you can see
something I've overlooked? Do feel free to get in touch!
In our next exciting episode,
we'll look at ways of proceeding from here. What are the options
for action, and which option should we take? We'll see that even
that requires a lot of consideration. You might remember me
warning in the first series that realistic (as opposed to in extremis)
studies would take a lot of thought and a long time. Was I wrong?