Forgotten in its old age

by Aditya

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As someone who 'knows about photography' I've been handed some old metal (possibly copper?) plates which look like they were at one time used for in a printing press for some kind of short run, but I'm more than happy to be corrected.

They've been stored in a box in a church for quite a while and have a few mucky bits on but otherwise seem to be in fairly good condition.

Printing plate sample

I'm looking to identify what they are and recommendation on best practices for cleaning & storage.

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This question appears to be off-topic because restoring printing plates aren't photography related. It's really more of a metalworking question. –  AJ Henderson Sep 3 '13 at 13:38
    
If not here then where in the SE network would you guys suggest that restoring and preserving these photographs would be better placed? –  James Snell Sep 3 '13 at 17:52
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I think it's just not clear to people that these are photographic plates. You're in the right place for that. –  mattdm Sep 3 '13 at 18:02
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I don't think this is any different from restoring an old photograph in any other medium. –  mattdm Sep 3 '13 at 18:16
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I'll add my two cents to this already extended discussion in the comments(this does seem on topic to me). 1.) Not all questions fit on an SE site, and just because it doesn't fit on one well, doesn't mean we leave them open here 2.) Just because no one here currently may be able to answer a question, does not make it off topic. –  dpollitt Sep 4 '13 at 3:13

1 Answer 1

up vote 4 down vote accepted

I recognize these. I've made them. It is a copper printing plate. They are screened for use directly onto the paper, probably in a letterpress since they are flat.

They are made by exposing a print (copy) in a large process camera with a vacuum back to hold the film perfectly flat during a long exposure. The resulting very dense high contrast "lithographic" film is then contact printed onto a sensitized copper plate (gum bichromate process). The plate is put into an acid etch bath that eat away the exposed portions and leaves the unexposed portions (a dot screen) in a relief. Ink sits on the high spots that hit the paper when an inked plate (That's what you're looking at) and paper are pressed together in a printing press.

There's more but you'll find everything on the Internet. If not, I can answer any question you may have. I've done it and taught it. I still have a press in my living room that would accept it and make a nice print from it. :)

Edit: I see there're tacks on the edges. They hold the thin chamfered etched copper plate onto a piece of wood - probably plywood - to raise the surface to the international standard type height of 0.918 inches.

Cleaning is easy, wipe it with a slightly oily (keroscene) rag. Store flat or on edge. Caution: Copper is a soft, easily-scratched metal. Once scratched, cannot be repaired. For durability, copper plates were chrome-plated.

This would've made a nice cross post with the graphic design group, too.

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