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I have an old metal engraved plate of a picture of my family that was used by the newspaper back in the 1950's. Unfortunately, it has a lot of white type spots of some kind of powder/crystal growth over some of the photo. Is there anyway that I can safely clean the photo plate?

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If this is a thin metal sheet with the picture visible as a negative in slanting light, this plate was used on an offset press and the plate is probably aluminum. The white coating on the surface is possibly just an oxidized surface. Try making a paste with cream of tartar and small amount of warm water to form a paste. With a clean cotton rag try rubbing a spot on a non-critical area and rinse.

(There are commercial aluminum cleaning powders but I can't vouch for their abrasiveness.)

In the movie 'To Live and Die in L.A.', Willem Defoe is a counterfeiter and you can see the entire process of creating a offset plate.

My father had a printing business and I remember these plates quite well.

reference: Kipphan, Helmut (2001). Handbook of print media: technologies and production methods (Illustrated ed.). Springer. pp. 130–144. ISBN 3-540-67326-1.

  • Do you know why Al was used? I'm guessing because Al is softer than steel and hence the engraving tools would last longer. – JenSCDC Nov 19 '14 at 15:36
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    Unless we are talking about a different process, no engraving tools are use. This is a photoengraving process which involved a full size negative made from the original with a large camera, then the negative is laid on a sensitized aluminum (?) sheet and the plate exposed using a brilliant electric arc for a period of seconds. Then the plate is 'developed' by rubbing with some sort of solution that removes a bit of materials. In this references (en.wikipedia.org/wiki/Photoengraving), there was a mention of zinc, so the sheets mat be a metal which is zinc-coated rather than aluminum. – The _traveler Nov 20 '14 at 17:28
  • Got it. I've always just thought that "engraving" was physical and "etching" was all chemical processes. – JenSCDC Nov 20 '14 at 19:34
  • Me, too but I use the terms as I found them. – The _traveler Nov 22 '14 at 1:11
  • Would this be intaglio, if the plates are physically etched, as opposed to photo-litho? [I've worked in the latter industry, using photo-sensitive coated plates, but never seen the former.] – Tetsujin Aug 28 '17 at 12:53

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