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Question:
When
I was travelling by air recently, the glass
fell off of my watch. Is this very common
and why did it happen?
Jody
Abrams, Devon, England
To
have the glass fall off of your watch is certainly
annoying, although the reason for this fairly
uncommon event can be easily explained. Watches
that are designed to be water-resistant prevent
water from entering the case. That is obvious.
But, it also means that air cannot enter the case
either. In addition, the air that is already inside
the case cannot get out. Therefore, the pressure
inside of a watch is the same as the ambient pressure
at the factory where it was assembled. And, because
the watch is air-tight, this pressure will not
change.
If you are in an aeroplane flying at an altitude
of 10,000 meters, you still have enough oxygen
to breathe because the cabin pressure is maintained
artifci-ally using air compressors. If the cabin
loses this pressure, oxygen masks will drop from
the overhead compartments. However, the air pressure
in a plane flying at this altitude is not the
same as it is on the ground. It would simply be
too expensive to keep the cabin pressurized to
such an extent. In general, airlines maintain
the pressure inside their aircraft equivalent
to that at the top of a 2,000 metre high mountain.
As a result, when the aeroplane begins its descent
towards the airport, many change when the aeroplane
took off since its ascent was more gradual and
their ears would have had more time to adjust
to the decreasing pressure.
Getting back to watches… Unless they were
assembled at 2,000 meters of altitude, water-resistant
timepieces maintain the ground pressure. When
they are taken in a craft flying at 10,000 metres,
their internal pressure will therefore be higher
than that of the cabin. From a theoretical point
of view, they should have a tendency to explode.
Of course, we don’t find watches exploding
in flight, although from time to time, we do observe
that the glass is ejected from the case thus allowing
pressure equalization. If this happens, it is
probably due to a weakness in the construction.
With modern watch production, however, the glass
should not fall out. Normally manufacturers test
their watches under conditions of reduced ambient
pressure (such as in an aeroplane) as well as
under conditions of increased pressure (such as
under water).
In your case, the manufacturer of your watch should
be responsible for this imperfection and should
offer to repair the piece at no charge. In addition,
even if there was only one such problem with his
products, a conscientious manufacturer should
review the manner in which all glasses are mounted
in their cases.
Question:
What
does the expression “guilloché”
mean?
Alfred
Lo, Brisbane, Australia
The
term 'guilloché' is a French term that
means 'engine-turned'. However these days,
the French word is often used in English when
dealing with the subject of watchmaking. It
is used to describe a technique for engraving
a particular type of ornamental motif on an
object. Generally, this design consists of
wavy and interlacing lines that cross at regular
intervals.
This shimmering pattern is created using a
machine called a 'tour à guilloché',
or 'rose-engine' in English. This apparatus
is particularly ingenious and can combine
several types of movements to obtain varied
decorative patterns. We can get a myriad of
designs by using different combinations of
cams mounted on the axis of the rose-engine.
The fixed feeler-spindles push on the various
cams, causing the lathe mounted in the cradle
to oscillate laterally while turning in front
of the stationary engraving tool mounted on
the other side of the device.
The most classical form of the guilloché
motif is the 'barley-corn' pattern. It is
shown in Figures 1a and 1b.
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| Figure
1a: The first machining stage and the
beginning of the second stage for the
barley-corn pattern using the guilloché
technique. In reality, the machining starts
at the edge of the inner central zone
to be left blank then moves outward. |
Figure
1b: The finished barley-corn pattern using
the guilloché method. The inner
central zone has been left blank. |
This
design can be off-centred to leave a space
for the addition of a monogram, logo or brand
name (see Figure 2). Abraham-Louis Breguet
often used dials that had been finely decorated
with the barley-corn pattern in his watches.
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| Figure
2: The back case of a pocket watch that
has been decorated with an off-centred
oval guilloché technique leaving
a blank elliptical area near the base. |
Figure
3: An example of the 'flinqué'
pattern, or a design composed of radiating
scallops made by an engine-turning or
guilloché technique. |
In
general, however, most dials were decorated
with a pattern consisting of radiating scallops
or festoons with twelve spokes. This type
of guilloché design is called 'flinqué'
in French but is now also used in English.
Figure 3 illustrates a good example of this
type of engraving. The engine-turning technique
can also be used to obtain straight lines
as well as to create inter-esting geometric
decorations, as shown in Figure 4.
This technique may also be used to approximate
classical engraving, for example, to make
arrangements of leaves or flowers, complicated
geometric designs and even portraits. Figure
5 shows an excellent example of a highly detailed
and intricate guilloché piece of art.
This plaque contains elaborate ornamentation
and portraits that were made around 1850 by
Alcide Nicolet, a craftsman known for the
high quality of his very special work.
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| Figure
4: The guilloché method can also
be used to obtain straight lines and geometrical
patterns as seen on the case of this pocket
watch. |
Figure
5: This plaque was created around 1850
by Alcide Nicolet, and shows the many
intricate and detailed possibilities for
the engine-turning or guilloché
technique. |
Already
in 1819, rose-engine machines were operating
in La Chaux-de-Fonds. A letter written by
Auguste Courvoisier to his brother Frédéric
describes a reception given for the Royal
Prince of Prussia when he visited the small
town: ‘The Royal Prince was presented
with a gold medallion. On one side was a portrait
of the King that had been made by Henri Banguerel
using the same guilloché technique
that was used in decorating small boxes. The
Prince seemed very satisfied, as much as with
his gift as with the battalion and the repast
that was prepared in his honour at the town’s
offices.’ I might add in the interest
of historical detail, that, ironically, the
recipient of this letter was none other than
the future leader of the rebellion that provoked
the separation of the Neuchâtel region
from the Prussian empire.
The guilloché devices, which were the
most highly perfected in their day, could
also mass-produce medallions in addition to
making objects with very complicated relief
designs. The depth of penetration and motion
of the engraving tool were guided by a feeler-spindle
attached to a hand-crafted model of the motif.
In the last century, these techniques were
very highly appreciated and often used to
decorate timepieces. Today, how-ever, they
have lost much of their lustre as the demand
for watches with smooth clean lines continues
to grow.
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