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  • Writer's pictureChiara

UV continued

Despite being separated from the RMIT University Print Studio, thankfully we have not been separated from the staff. Rob Dott, one of our technical officers, did some extra helpful research for me. This article has useful information about UV light sources for printing, but Rob also found me a supplier for a different sort of UV light source. I was soon on the phone ordering a blacklight blue 20w compact fluorescent bulb from GMT lighting. The output from this bulb is mainly in the UV A spectrum (365nm) which is safe for human exposure and optimum for cyanotype exposure. The question remained as to the adequacy of the output. However the bulb can be fitted to a regular desk or bedside type lamp and doesn't have the heat and dangerous UV issues of the halogen light, so long exposure times need not be a problem.

It took several wedge tests and a bit of patience before I got this result:

The upper strip is the area covered by (blank) transparency film since the film does block a small amount of the light. The fact that the darkest area covered by film (upper left) is not as dark as the darkest section in the lower strip (bottom left) demonstrates that I still have not achieve optimum exposure at 7 hours. I ended up trying some 8 and 9 hour exposures without repeating the wedge tests since each test was taking me an entire day.

My initial cyanotype tests with the BLB bulb were done in my studio, but in order to control the exposure I had to black out my windows and glass door with makeshift curtains. I soon got tired of that and shifted the set up to my bedroom where I can pull down the blinds and close the door. I also invested in an electrical timer plug to save me from being ruled by my alarm clock.

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