Re: solarplate images up on my website
Jon, Is this a manifistation of Newton Rings? In a message dated 2/20/07 12:25:28 AM, jon@terabear.com writes: Measles...good analogy. Notice the difference though. Chris' measles are dark in the light areas, while Susan's are white in the dark areas. Chris: http://czaphotography.com/img/learning/solarplate/Guncompare.jpg Susan: http://bp1.blogger.com/_K_E_8kwTNvw/RdqEKwry8dI/AAAAAAAAAA4/trtOOQWlZ3g/s1600-h/radish01.jpg My .02 cents/sense is the causes are related, but are manifested for different reasons. I've suffered through both of them. Both have to do with uneven contact during exposure, as you may have guessed. Susan, however, unlike Chris, is using a vacuum frame. Contact should be flawless, right? Wrong. Why, has to do with the "tackiness" between OHP and the KM73 plate which was documented in my procedure. Took me about a year to figure this problem out, but my excuse is I had to go between Boulder and Denver once a week to actually print the tests, like Chris. But, I'm not as bright as her either. Susan: If you want to test this, take a virgin KM73 plate with the mylar removed, and a virgin piece of OHP (without an image printed on it), sandwich them under the vacuum frame and hit the switch on the vacuum. I'll bet you see a similar, but subtle pattern of patches manifesting like leprosy within the first minute of drawdown. The aquatint screen, unlike your image transparency, is made of real film and doesn't have this issue, but the OHP is tackier against the KM73 plate and this is the problem. The remedy for me has been baby powder, very lightly dusted over plate with a hake brush (Jan gave me the idea several years ago). If you were using baby powder, the other key is to not let the image exposure draw down too exceedingly long. I basically wait until the Krene goes flat against the bed, then hit the exposure switch with no extra drawdown time beyond that. Since the screen exposure is not the issue, you can draw down on it as long as you want. I do things in this order: Remove mylar Expose Screen to plate Dust plate with baby powder Expose Image to plate (minimal drawdown time) Washout normally Hope that helps. I've got some other things I'm testing out to help with the OHP issue with the KM73 plates and will report back if I come up with anything better than the above. Best wishes, Jon Best Wishes, Mark Nelson Precision Digital Negatives - The System PDNPrint Forum at Yahoo Groups www.MarkINelsonPhoto.com
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