Re: gravure plates under vacuum
I think all great artists are closet engineers as well. You certainly qualify as both Susan! Let me see if I understand correctly. You put masonite on the bed and a piece of burnished foamcore with a window on top of that, and then put the film and plate in the window in the foamcore. This means there was nothing physically touching the top of the transparency to hold it to the plate and that the only thing keeping it there was gravity and whatever the vacuum pressure was able to do? How large was the plate and film you used? 5x5 as well? Can't wait to see the results of your experiment! Wonder if it will work with Krene...though I'd hate to have to reinstall the glass into the vacuum frame. Jon SusanV wrote: Hi ya'll, Jon, I did the experiment you suggested with a piece of virgin km73 and pictorico ohp under vacuum. I watched as the vacuum pulldown advanced, right along with the splotchy look of the contact between plate and film. dark areas where the film contacted (maybe too tightly?), and lighter elsewhere. I came to realize that the darker areas seemed related to the plate and film being drawn up against the glass of my exposure unit very tightly. (Jon, this would go along with what you've said about too much vacuum being a problem) I wondered if the lighter areas were indeed close enough for a sharp exposure. I couldn't stop the darker splotches from happening even by using as little as 5"mercury pressure... the moment the sandwich raised up and touched the glass, the splotches appeared. At this point I should maybe describe my vacuum/exposure bed because I'm not sure if they all work this way... The actual pebbled surface bed of the frame is rather thin and flexible, and during vacuum drawdown it rises up, lifting the plate and film up to come in firm contact with the glass, which rests on a raised rubber gasket around the perimeter of the bed.. So... how to draw a vacuum for close contact, but not caused the sandwich to be pressed together physically by contacting the glass. I placed a piece of masonite, maybe 11x14" on the vacuum bed. Then I cut a 5x5" window in a similar sized piece of foamcore, and placed that on top of the masonite. (To allow air to escape I used a burnisher to draw some deep indentations in the underside of the foamcore, radiating out from the window to the outside edges.) I then put the plate and ohp positive in the window (no powder), and turned on the vacuum. The vacuum drew down to 22" pressure, and the window and masonite under it didn't allow the plate to rise up to the glass!!! The film maintained a totally measle free, even, light tone... even after an extended drawdown time (like 3 minutes or so). I exposed the plate, developed, etc... and when I printed it, there were no measles. What's more... there is very fine detail in this image, and it was ALL there, crisp and sharp as can be! There was definitely close enough contact with the film without it being physically pressed together. The vacuum was enough. So for me, I think this is going to be my solution to the measles. I'll post this test print to my blog later, including some closeups of the sharpness of the detail. susan susan gravure blog at www.susanvossgravures.blogspot.com website www.dalyvoss.com
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