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  1. #11

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    Yes after a little hunting, the taxidermy suppliers came up trumps. The formaldehyde looks like it will work out much cheaper than alum too; in cost terms anyway, not sure about health!

    I have not tried chrome alum, but the potassium (and also ammonium alum which I have a little of) do harden the gelatine over time and in a small concentration (about 10% relative to the gelatine) can be quite effective; the solution is very clear too so does not itself stain the paper in any way. Unfortunately, by the time I get to 10% concentration, the cyanotype behaviour has changed quite noticeably. I am not sure if it is the mild acidity of the alum but the image looks and behaves very similarly to when using a strong acid wash to develop the print. The apparent speed of the sensitiser is increased by at least a stop (which is useful), but I find that I get blue in the water that attaches itself at random on the print, clouding the highlights. The yellow sensitiser is also sometimes very hard to wash out, although the poor washing behaviour is erratic and unpredictable.

    I have found with 3% of alum to the weight of dry gelatine, the impact on the developing is minimal and although the gelatine mix is only slightly thickened, it is much easier to size the paper first time from the water-leaf state. With just plain gelatine (3% in water), the water-leaf paper is exceptionally fragile after brushing on the first coat and I have made many holes in the sheets. Interestingly, if I sensitise a sheet of paper and leave it in the dark for a few days before I expose it, with gelatine-only coated paper, the yellow goes a fraction darker, but the paper works fine. The gelatine-alum paper gets really quite green within 2 days and then has a blue 'fog' when you use it. I have some gelatine-formaldehyde paper in the dark now to see how it behaves.

    The gelatine-formaldehyde coats the paper much more satisfactorily and the paper can withstand a warm water wash well too, which will make any of my alum paper fall apart. The coating process is a little trickier though as I do it wearing thick rubber gloves. I am experimenting with different concentrations and methods so will let you know which is most effective.

    I look forward to seeing the print David and I will let you know when it arrives.


    Best regards,

    Evan

  2. #12

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    I seem to have had a lot of failures dealing with cyanotype on glass, but here's one that did work! Although, it's not exactly as I wanted it, it's good enough to serve as inspiration for me.

    It's a 5x7 image on glass, then put in the photo-frame with a white backing paper.



    Cheers,
    David.
    PS: I've got some more glass cyanotypes printing right now as I'm trying to make the most of the sunshine!
    Creative Image Maker e-magazine is back! Find out more at http://creativeimagemaker.blogspot.com

    Thank you.

  3. #13

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    That looks really great David! Looks like your perseverance is paying off.

  4. #14

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    Quote Originally Posted by rorye View Post
    That looks really great David! Looks like your perseverance is paying off.
    You spoke too soon! I had another four failures today :0(

    Funnily enough, the best one so far has been with food gelatine as a substrate - just about everyone that I've used photo-gelatin and chrom alum has failed. I'm beginning to think that gelatin only allows the cyanotype solution to soak into it (and the chrom alum prevents that).

    Cheers,
    David.
    Creative Image Maker e-magazine is back! Find out more at http://creativeimagemaker.blogspot.com

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  5. #15

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    Nice work David, keep trying. Have you tried to: prepare double strength (or 1.5x) stock solutions, mix 1A+1B coating solution, dilute this coating solution 1:1 with gelatin and use this on a glass previously coated with hardened gelatin?

    A note: Cyanotype image needs oxygen to repair itself from the fading effect of ambient light, therefore make sure the image on glass has access to air. If not, you'll have a gradually fading image after local oxygen is depleted...

    Regards,
    Loris.

  6. #16
    Barry S's Avatar
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    Here's a crazy idea. Try making a weak negative by printing with a plate you've already made, and putting on a black backing for a ....Cyanbrotype.

  7. #17

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    Loris: I did try a mix using 2ml gelatin & chrom alum, and adding 5ml cyanotype sensitiser to it. It just washed off the glass. I even tried refrigerating the glass, in case the gelatin was softening due to being sat out in the sun to expose. No difference.

    However, I will try your idea of hardened gelatin, with a gelatin/cyanotype layer on top - I'll let you know what happens.

    Barry: now it's funny you should say that, as the image posted above shows a weak positive that didn't really come to life until I'd backed it with the white paper!

    Cheers,
    David.
    Creative Image Maker e-magazine is back! Find out more at http://creativeimagemaker.blogspot.com

    Thank you.

  8. #18
    Robert Hall's Avatar
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    Have you tried the trick of the wet plate practitioners?

    The glass plate is cleaned first with rotten stone (or pumice) to allow the glass to be as clean as possible.

    This helps to keep the emulsion on the glass.
    Robert Hall
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    Technology is not a panacea. It alone will not move your art forward. Only through developing your own aesthetic - free from the tools that create it - can you find new dimension to your work.

  9. #19

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    Quote Originally Posted by vickersdc View Post
    ...
    However, I will try your idea of hardened gelatin, with a gelatin/cyanotype layer on top - I'll let you know what happens.
    ...
    David, if you use sun as the lightsource the heat would be a real concern. Maybe you can print under open shade, there will be still plenty of UV coming from the blue sky. (Printing times will be longer for sure, but manageable I think - I mean if you can tolerate something like 1 - 1.5 stop speed loss...)

  10. #20

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    Quote Originally Posted by Loris Medici View Post
    David, if you use sun as the lightsource the heat would be a real concern. Maybe you can print under open shade, there will be still plenty of UV coming from the blue sky. (Printing times will be longer for sure, but manageable I think - I mean if you can tolerate something like 1 - 1.5 stop speed loss...)
    When it takes 1+ hours to print anyway, a bit longer won't make any difference! I'm now thinking about when I did the most successful print on to glass (which happened to be the very first one I did) - it may well have been an overcast day and would definitely have been cold outside.

    Robert:

    Thanks for the tip with the pumice - but doesn't that result in scratched glass?
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