Grey mottling on Cyanotypes

Discussion in 'Alternative Processes' started by DBP, May 23, 2006.

  1. DBP

    DBP Member

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    I've been experimenting happily with the Printables paper from Freestyle photo (which I found through APUG, so, Sean, your advertisers do get business here). Other than difficulties determining exposure (especially with spring weather here, which can become overcast in 15 minutes), I am pretty happy. But a couple of my prints have dried with a greyish stain in places that looks almost like mildew. Drying times have only been a few hours, so I don't think that is it. Does anyone have any ideas what it is or how to prevent/remove it?

    Also, I spilled a little lemon juice on a print (trying to do too many things at once) and got an interesting yellow cast, which did eventually wash off. Has anyone played with this effect intentionally?
     
  2. Donald Qualls

    Donald Qualls Member

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    The grayish stain might be due to insufficient washing -- if some sensitizer is left in the paper, it will expose (eventually) even in room light; if there's not much of it, it could well look grayish instead of the deep blue that you'd expect from normal exposed areas by the time drying is complete.

    I could be completely off base, too; I haven't done *that* many cyanotypes... :wink:
     
  3. psvensson

    psvensson Member

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    I also got grey mottling now and then, and I'm scratching my head to try to remember what it was. It may have been incomplete drying of the sensitizer, or perhaps when I used a hairdryer on it.
     
  4. Donald Qualls

    Donald Qualls Member

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    When I've used a hair dryer, I found the image washed off -- I think because there was a layer of moist sensitizer under the dry surface, so the color that formed during exposure wasn't bound in the paper surface or sizing.

    Some papers just don't like cyanotype, also -- I don't know if it's buffering agents or something in the sizing, but something converts ferric to ferrous and fogs the sensitizer as soon as it dries. Same thing occurs with some papers on processes that use silver nitrate, such as VDB and salt prints.