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Re: giant photogram Q
Hi list what follows was sent to me BUT should have been sent to Emily Kate
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>I'd suggest using cyanotype, although it won't be black, but it is so much
>easier to work with. I know someone (Jane Reese) who did large cyanotypes
>using old photographic background paper for a children's workshop many
>years ago (which have appeared I think in some of the histories, and I
>think may be in the collection at George Eastman House.) Her biggest
>problem was getting the paper she had prepared in USA across into Canada
>where she was doing the workshop.
>A garden hose is all you need to develop it, and it only takes a few
>seconds before it is insensitive to light, though you need to wash it
>longer.
>All photograms are negatives of course, and you could in theory contact
>print them to give positives, but there are practical difficulties with
>large photograms in maintaining contact (a sheet of plate glass would be
>heavy enough to do this) and also because large sheets of paper need to be
>fairly heavy weight to allow handling, so they need a long exposure.
>If you want your final result to be black and positive you could try
>making a cyanotype negative and printing this onto a normal photographic
>paper.
>If you really need a black (or at least dark brown) image you should use
>the Vandyke (brownprint) process:
>A 90 g ferric ammonium citrate in 330ml water
>B 15 g tartaric acid in 330ml water
>C 38 g silver nitrate in 330ml water
>Dissolve all chemicals, mix A + B well, then add C slowly with constant
>stirring. Store in brown bottle in dark cupboard.
>Handle with gloves as it stains.
>Coat the paper away from sun or fluorescent lights - for a large print I'd
>try using a sponge. Avoid brushes or rollers with metal parts. Hang to dry
>in subdued light or darkness.
>Expose to get good highlight detail (you will lose some). Coat oversize
>(or a separate sheet at the same time on the same paper type) so you can
>trim some for tests to establish correct exposure.
>Develop by water wash - but the washings will stain and are poisonous, so
>you need more care than with blueprint. 2-5 mins.
>Fixing may not be absolutely necessary, but it does usually darken the
>print in any case. Use a very dilute plain hypo for a short time - 20
>grams per litre sodium thiosulphate for a maximum of 5 minutes, then wash
>for at least half an hour in running water.
>Good luck
>Peter Marshall
>Photography Guide at About http://photography.about.com/
>email: photography.guide@about.com
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