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Florescent Type UV Exposure for ImagOn Question: Has anyone at Maryland Printmakers used flourescent type uv exposure with ImagOn? Howard seems to think it won't work, only a point light source does the job. What is your opinion?
Technical notes offered by Maryland Printmaker, John Murrray: A couple of years ago, we went through the task of finding an answer to this same question concerning exposure unit light sources. I was planning on building a unit. The single point light source will provide the cleanest and most complete rendering of (especially) fine lines from your original transparency material. Accurate and complete rendering when exposing your art work depends on having the exposed areas harden when struck by UV light, and anywhere there is a line or non-white area, there is in effect a shadow or blockage of the UV light which is not hardened. When developed, the unexposed areas slough away, leaving areas that will hold ink. Having a sandwich of transparent film on top of the Imagon coated plate, including and because of the thickness of the transparent material itself, means that some light can sneak in from the sides of the drawn lines and undercut that drawn line, by hardening the Imagon Ultra film immediately underneath the line. This is because there is light coming in from multiple directions. Fluorescent tubes work very well for exposing silkscreens, but not so for intaglio plates. The single point light source will not allow light to sneak in from the sides or underneath the margins of the lines--the single point light it will cast a sharply defined shadow and block the UV light wherever there is a line of artwork (similar to the sun). When developed, the line will be as complete and as distinct on the Imagon Ultra film as it is in the original art on the transparency film. Light coming in from other than a single point will come in from the side and diminish the quality of your image when the plate is developed. The single point light source will definitely give you a better result. Fine lines and details will suffer most dramatically from a soft or diffused light source. Your shading and aquatint will not be as dark as it should be. Also, make sure you are using a vacuum frame to press the transparency (or Mylar film) artwork flat and tight against the Imagon laminated plate. After a lot of reading and research, our group of 4 printmakers chipped in $250 each, and we bought a NuArc 26-1K Metal Halide exposure unit with an integrated UV photodetector cell. It has a digital numeric touch pad for entering a value that represents the number of UV light units for a given exposure. As the lamp deteriorates over time, and the UV output becomes less, the photodetector cell will tell the circuitry to extend the amount of time for the exposure to compensate for the reduced UV light output. This is a very good feature to ensure you have repeatable exposure results. Just using time for calculating your exposures is not nearly as accurate, and you will be constantly recalibrating your exposures to get the desired exposure result. Our NuArc unit has a built in vacuum frame, and does produce about 23 lbs of vacuum, which is sufficient for accurate rendering of the artwork. |
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