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  1. #1

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    Positive Cyanotypes In-Camera??

    Hi there,

    Has anyone tried to produce positive cyanotype images in camera? I was thinking about coating some glass plates with the relevant solution, and then exposing in camera to produce a positive print.

    I realise that the exposures will be measured in hours (and hours, and hours...), but has anyone tried this and with what success?

    Cheers,
    David.
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  2. #2
    Andrew O'Neill's Avatar
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    Wouldn't you end up with a cyanotype negative rather than a positive?

  3. #3

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    David,

    You should still get a negative as exposure to UV in the highlight areas will darken the sensitised surface. There are formulas for positives (using Ferro instead of Ferricyanide?) but I have not tried them. I did have a go with classic cyanotype and left the camera out in bright sun for a few hours but got nothing. I then realised I had a decent UV filter on the front of the lens which may not have helped!

    Best regards,

    Evan

  4. #4
    Vaughn's Avatar
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    Terry King (historian for the Royal Photographical Society) re-invented an in-camera exposure speed cyanotype process, but it will yield a negative when used in-camera. He holds on to the info tight -- one must pay for the info. But basically, I believe, one coats paper with the Ferric ammonium citrate, expose that in-camera, then develops it in the Potassium ferricyanide. Something along that line.

    Vaughn

    PS...cyanotype rex is the one -- http://www.hands-on-pictures.com/Tutorials/Rex.html
    Last edited by Vaughn; 03-16-2010 at 12:59 PM. Click to view previous post history.
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  5. #5
    willrea's Avatar
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    Googling "Cyanotype Rex" will get you the info you need.

  6. #6

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    I've got the formulas for creating a positive cyanotype - they're from a c1910 book entitled 'Everyones Guide To Photography', which has become my 'bible' to historic processes.

    Evan is quite right in stating that you need to Potassium FERROcyanide, NOT Potassium FERRIcyanide.

    In the spirit of public goodwill (!) I'll post the information here (and you wont even have to pay for it!).

    To sensitise the paper, you need three solutions:

    Solution #1:
    Gum arabic... 96 grains (1 grain = 0.065 grams).
    Water... 1oz (28.4ml).

    Solution #2:
    Ammonio citrate of iron... 240 grains.
    Water... 1oz.

    Solution #3:
    Ferric chloride... 240 grains.
    Water... 1oz.

    Solution #1 must be made up fresh as required. Solutions 2 & 3 can be kept in the dark for several weeks.

    Add 192 minims of #2 to #1, then add 120 minims of #3 (one minim is 0.06ml). Coat the paper as quickly as possible, dry quickly and keep in the dark.

    Expose the paper as normal, the image will appear as bright yellow on a darker ground. Develop the image by brushing on...

    Potassium ferrocyanide... 96 grains.
    Water... 1 oz.

    ...until all the details are visible, then wash under a tap and finally wash in an acid bath...

    Hydrochloric acid... 96 grains.
    Water... 1 oz.

    ...then dry.

    Cheers,
    David.

    PS: Evan, I'm coating the paper with arrowroot tonight, and I'll send it off to you this weekend.
    Last edited by vickersdc; 03-16-2010 at 02:03 PM. Click to view previous post history.
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  7. #7
    Nicholas Lindan's Avatar
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    Diazotypes are a positive process. They are now called blueprints, though properly they should be called 'blue-lines'. They are developed with ammonia, and they do fade over time and exposure to UV. 'Sepia diazos' are brown line positive prints, usually on a translucent base - they can be eradicated (bleached) and are used when one needs to make copies of a marked-up diazo of an original drawing. Sepia diazos have very little fade.

    You can get diazotype materials at a blueprint supply house - http://www.cad-paper.com/category/DIAZOBLUE.aspx
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