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Only two formats exist for Chambon printings, both in portrait (upright) orientation.
 | Medium. 5 rows of 12 |
| Long. 4 rows of 12 |
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Unlike previous print methods, a continuous reel of paper was used. The
width of the paper roll was a fixed 13 inches. The step and repeat camera work for
preparing the stamp images used a fixed frame 'window' area of 12 x 6 inches
irrespective of the two layouts. Thus a half inch margin was used either side of the
layout. |
Cylinder layout corresponded to the post office sheet. That is, one complete rotation
of the cylinder produced one post office pane.
Because of the continuous paper roll, the comb perforator operated on the paper during
printing, continuously. This meant that the interpane gutter, separating each printed
pane, was also the exact size of a stamp. This gutter was conveniently guillotined to
produce the individual post office sheets.
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| Portrait |
5 x 12 medium format |
Landscape |
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| Portrait |
4 x 12 long format |
Landscape |
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Note that the actual printing layouts are
portrait oriented. |
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Cylinder sizes.
It should be noted in the above examples that 4 'long' stamps exactly matched 5
'medium' stamps in height. The width of both long and medium stamps was fixed at exactly
one inch (including perforation).
This 'exactness' corresponded to the allowable window size of the step and repeat
camera. However, the long format cylinders were slightly larger to accommodate the extra
height of the long stamp interpane blank gutter, which needed to be the same size as it's
stamp in order for the continuous comb perforator to operate correctly.
Serial Numbers
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Two printheads were used. Each printing alternate panes. One printhead was
positioned 2 units in, the other 3 units in, from the lower right corner. There is no
significance to these numbers, they were individually set to random values at the
beginning of a print run and were used internally for gross audits. |
Autotrons
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Multicoloured, photogravure printing consists of
using one to several separate cylinders, each responsible for an individual colour ink.
The fast drying inks are printed by each cylinder in turn as the continuous roll passes
under it. Along the left side of some issues are coloured bars or lines. As
experience grew, these were introduced to detect the proper operation of each colour
cylinder and that the flow of ink was correct. The earliest issues did not have these
autotrons. In the case of reprinted values, such as the 2/5d Wren, the later white paper
printing (which was confusingly issued first) has autotrons, the cream paper does not. |
Perforations
Only one perforator gauge was used, 13½x13¼. Naturally, on Landscape (upright) images
the measurement is 13¼x13½.
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