British photographic history

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I have a query on the following images and the 'negatives' associated with them? They seem to be some type of copy of the prints but I'm stumped as to the purpose and how these may have been made.
The 'negatives' are all different sizes and have no product markings or identifying notches. They sometimes contain the edges of other images as if the whole was a much larger sheet and on one there is a section that looks as if an exposure test has been made with gradually lightening stripes. There are also finger marks on the 'negatives' that look more than what would have been left by normal handling -rather like a normal film negative would be if handled when wet.
The edges of the images are defined by a heavy almost (but not quite) opaque dark red tape which is now degrading and becoming sticky.
Image subjects vary from what look to be book pages, magazine articles and photographic prints.
There are sometimes corresponding prints on a metallic gold or silver faced paper - the rear of the paper is white and it is thinner than a conventional photographic paper. The prints seem to be a mix of sizes, exactly the same as the 'negative' or sometimes bigger.
They come with no record of who or when they were donated to the archive but this is likely to be before the mid 1980s.
Before I handled them I presumed they were just inverted & photocopied onto acetate but upon examination they seem to be much finer grained and without the density of ink sitting on the reverse (mat) side that such copies would have. The medium itself also seems thicker and more like a neg to handle, but there may be photo-copiers out there that can output to this quality I don't know.
I am presuming some sort of commercial copy process but have no idea what this would be.
Anyone got any ideas??

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These look like the type of negative that would have been stripped in to a plate for printing purposes. From my slightly hazy recollection the film used was thinner than 'normal' photographic cut film. The red tape was used to mask off areas not required for printing. The positives are presumably test prints and printed on to different paper stocks. Someone with a background in pre-digital litho printing may be able to add a more technical explanation.  

Thank you Michael. This is very helpful, as it gives me a direction as to where to direct my research. It is entirely possible that they were donated to the archive from a commercial source so it does make sense.

Michael Pritchard said:

These look like the type of negative that would have been stripped in to a plate for printing purposes. From my slightly hazy recollection the film used was thinner than 'normal' photographic cut film. The red tape was used to mask off areas not required for printing. The positives are presumably test prints and printed on to different paper stocks. Someone with a background in pre-digital litho printing may be able to add a more technical explanation.  

Seeing the red tape here made me feel quite nostalgic. It was used, as Michael has said, to mask off unwanted areas and while that may not seem sensible for a semi transparent tape, almost all printing house processes used orthographic materials, i.e. they were insensitive to red light. Which is why of course they could be handled in a red safelight. The materials were indeed very thin and very shiny and while they came in standard sizes they were often used in large sheets, cut to fit the particular job. So you are definitely dealing with printing house materials and they changed so quickly, especially in the 1960's and 70's that it may not be possible to identify particular processes..... unless you find a printer as old as me!

I should have said, the graduated scale is just that, a strip of exposed film (or paper) that would be exposed (or copied) along with the job so that the printer could keep an eye on the reproduced tonality. It could be used quickly with a densitometer to check the exposure. Kodak produced paper ones, which a photographer would use along with the more familiar colour strip beside a painting in colour transparencies.

Thank you, all and any help is much appreciated here. The items are currently listed in the database that is searchable by the general public as just 'photographic negatives' I'd like to add more detail to this entry to highlight the difference from an in camera neg for those using the database online. Do you have any suggestions as to naming the items - so far not much is springing to mind- Photolithography sheet negative- seems to be the only one I can think of??



Dr. Joe Rock said:

I should have said, the graduated scale is just that, a strip of exposed film (or paper) that would be exposed (or copied) along with the job so that the printer could keep an eye on the reproduced tonality. It could be used quickly with a densitometer to check the exposure. Kodak produced paper ones, which a photographer would use along with the more familiar colour strip beside a painting in colour transparencies.

'Lithographic negative' would be fine.

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