" On a piece of patent plate glass lay down by means of paste or
other suitable mountant a piece of paper, tinfoil, or other
material; on this lay in the same manner a second piece a-quarter
of an inch shorter, and so on until a scale of sufficient range
is formed. This being done cut neatly round the edges of the
"scale" to form a clean square or oblong, and paste round this
a frame composed of a number of thicknessess of the same material -
paper or tinfoil - greater by one thickness than the largest
number employed in the scale itself. If tinfoil be used the
scale so produced is ready for employment as a printing surface.
If paper be the material adopted it will be necessary to face it
with tinfoil first before employing it for that purpose.
We have now a matrix from which any number of photometer or
sensitomer scales can be produced by means of gelatinous ink and
ordinary Woodbury printing; and we have, further, this
advantage - that by modifying the quantity of colouring matter in
the ink the scales can be arranged to suit negatives or
transparencies of any degree of intensity. Such scales printed
upon thin plate glass or even paper may be cut into strips, and
each printing-frame in the establishment may be provided at a
very small cost with its own photometer. "
British Journal of Photography, March 7, 1884
hope you find this interesting,
Oh yes, when Woodbury was demonstrating the principal involved
in his printmaking process, he used a glass wedge trough filled
with the "gelatinous ink" to show that: when the gelatin dried,
it created a continuous transition of tone determined by the
thickness of the gelatin.