Visit a print shop. I did and their salesman was only too glad
to show me around. Modern lithoplates have a precoated
photosensitive polymer that is cured/hardened with intense white
light. The precoated plate is masked with a photonegative film
and exposed in a light box. The plate is then washed with water
and the uncured polymer in the masked areas dissolve out. The
plate is then etched with mild acid (nitric?). The depth of the
etch is barely the thickness of the ink on a page. The old
style Italgio etching is deeper and you can probably simulate
that by letting the acid work longer although the thickness of
the aluminium lithoplate at 0.5mm limits what you can achieve.
Pioneering photographer used to make their own emulsified glass
plates with silver nitrate in cellulose acetate solution. Early
lithoplates were thin brass plates. Perhaps this is one route
you can investigate.
Another possibility is to use precoated photosensitive copper
plates used for making electronic circuit boards. You can mask
your design with a photopositive or negative and use sunlight to
cure the polymer. Unexposed polymer is washed off with water.
Ferric chloride is used to etch the plate and all the necessary
supplies are available from the same source. The thicker copper
coating will allow a deeper etch. The product can be used as a
Kelvin Mok (firstname.lastname@example.org)
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