of information must appear on the movement for identification
The maker's mark, the calibre reference number, the various hallmarks
as well as personal information may be engraved on the plate,
the bridges or the watch case.
Engraving is also used to personalise and enhance the aesthetic
appeal of a watch. Motifs may therefore be engraved on a watch
for purely aesthetic purposes.
Engraving: the method
Engraving is a decoration performed in relief or by hollowing,
by hand or by machine, chemically or by other procedures used
on metals such as steel, brass, copper, gold, silver or platinum.
Given the complexity of this work, hand-engraving with a burin
is mostly used for one-of-a-kind creations or small series. Skilled
engravers must have in-depth knowledge of drawing techniques and
the constant practice which is the only way of achieving the required
level of skill and dexterity.
Engraving is practised by incising the material using an
instrument called a burin or graver. There are several sorts:
blade-shaped with two rounded faces, flat with two plate faces
and the cutting edge intersected by a third face which thereby
broadens the tip of the burin; and gouges which are flat gravers
with a groove-shaped hollow.
Currently, most engravings such as those for numerals and letters
appearing on movements are done by numerically controlled machinery.
The engravings are drawn on plans like a part to be machined.
The plan is then fed into computer-assisted design software in
order to decode the machine language required to execute the path
of the tool (engraving-cutter).
One can also engraving using acid. To do so, the part to be engraved
is covered with a varnish sensitive to ultra-violet rays and then
placed on a negative film representing the drawing one wishes
to engrave. After flattening the film over the part, it is exposed
to ultra-violet rays which uncovers the portion that is to be
attacked by the acid. The part is then soaked in acid which will
only attack that specific portion. Depending on the desired depth
of engraving, a particular mixture will be made. Chemical engraving
enables the creation of very precise motifs that are only a few
tenths of a micron deep.
The letters, numbers or shapes to be engraved are formed on metal
plaques or stencils which serves as a guide. They are linked by
a leverage system carrying a tool (diamond, burin, milling-cutter)
which provides a scale reproduction of the initial shapes, letters,
numbers or decorative patterns.
A laser beam strikes the matter by bidirectional scanning governed
by a programme pre-recorded on a numerically controlled machine.
The engraving may be performed by machine for productivity reasons,
since the mechanical sped makes the cost price lower.
The style of mechanical engraving is not the same; it can be recognised
by its outlines which are flatter and less vibrant than those
done by hand, since no machine could ever replace the authenticity
of hand craftsmanship.
Moreover, some scrolling effects cannot be done by machine or
do not create the same effect, since the precise gestures of the
craftsman polish the matter while cutting into it. It is also
to touch up machine engraving by hand, using a well sharpened
burin to eliminate the mechanical and unattractive appearance
which machines may produce.
Chasing is a particularly delicate and spectacular type of decoration
generally used for extremely high-end plates, bars and bridges,
or on the case itself. It might be seen as a kind of engraving
of decorative patterns executed in relief with a bevel-edged steel
blade calls a chaser or chisel.
The entire work is done by hammering and repoussť work performed
by hand. This type of work calls for dexterity, know-how and a
great deal of patience.
Chasing gives an absolutely unique character which simply cannot
be reproduced by mechanical means. Currently, stamping has replaced
hand chasing. The result achieved is clean and free of burrs.
This mechanical method is suitable for large series and the middle
of the range but once again does not permit any aesthetic personalisation.