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I've been given some Metone "photo-sensitised aluminum plates for line or continuous tone". They were made by John Blishen & Co. Ltd. They are Orthochromatic and, according to the box, should be processed using a red safe light. They are 13 x 18 in size. assuming that there is any life left in them (I have no idea how old they are) what could I use them for?
Pete.
Exterior informational photo plaques, like those that used to be found at vista points?
It may be similar to this; www.horizonsisg.com/metalphoto.html
Offset lithography - they are plates for a printing press. Google doesn't come up with anything for 'metone' or 'blishen'. They are likely quite old and may no longer be much good for anything except as sheets of aluminum.Quote:
Originally Posted by Pete Watkins
The emulsion is a polymer that works like dichromated gum.
The plates are placed in a vacuum frame in contact with the negative. They are exposed with a UV light source - a 'plate burner' with a 2 to 4 thousand watt mercury arc lamp. The UV light hardens the emulsion.
The plate is developed in a solvent or caustic that washes away the unexposed emulsion.
The plate is then mounted in an offset printing press:
- The press dampens the plate with water
- The water only sticks to the hardenend emulsion.
- The plate is inked - the ink sticks to the aluminum plate but doesn't stick to the damp gum.
- The ink image is then rolled off the plate and onto a rubber blanket. The blanket is then rolled on to a sheet of paper, transferring the ink image - hence the 'offset' in the name 'offset printing'.
Google for more on offset printing.
For alternate uses the polymer emulsion can be used as a resist in anodizing or etching the plate or you could try a variation on gum-oil or bromoil transfer.
Thanks for all the info. Any ideas what solvent or caustic substance I would use for developing? I've got the UV light and printing frame.
Thanks again,
Pete.
Offset plate materials should be readily available, as offset printing is still widely used. You need to search for a "graphic arts supplies" vendor. The materials are not very expensive.Quote:
Originally Posted by Pete Watkins
See the MSDS for plate 'developers':Quote:
Originally Posted by Pete Watkins
http://www.lacrosselitho.com/ShowPro...91856&CID=1004
Best just to go buy a bottle, methinks.
In the old primitive days a 1% lye solution would work - might give it a try, along with any-old solvent you have kicking around the place.
I have a feeling that these may not be offset plates---I did a bit of offset printing years ago (and even experimented with home-brew dichromated gelatin plates) but can't recall ever encountering orthochromatic sensitization in this context. Since "plate burners" all seem to be made with heavy UV content in the light, and the negatives are (were?) monochromatic, it is not clear what would be gained by having green sensitivity unless they were meant to be exposed by some sort of non-UV flying-spot printer.
It might be worth clipping the corner of a plate and dropping it into photographic fixer; if it starts off milky and turns clear, it is presumably a silver-based material, but if it is transparent to begin with, it is at least something else. I've seen silk-screen latex emulsions that were polymer-based and milky-looking, but they almost certainly wouldn't clear in hypo.
The 13x18 dimensions suggest camera stock; in inches that would be an oddball size, and in centimeters it would be for a very, very small offset press...