Photopolymer plates can be exposed to UV light in two different ways. The most easily accessible source of UV light is sunlight. The advantage of using the sun is that it is plentiful and free. The disadvantage is that you can never be 100% certain that you will have clear skies on the days you want to expose plates and of course night work is not possible. Artists who prefer to work in the evening or who want a more reliable source of UV light may choose an artificial source.
Photopolymer plates need UV-A light for exposures (315-400 nanometers). So if you are purchasing a UV exposure unit you need to ascertain the type of UV light produced by the unit. There are some inexpensive units available via eBay, which are advertised to expose photopolymer plates for foil blocking. They are very successful with line art (black and white) but the florescent tubes are usually too far apart to give a good exposure of tonal images.
Sometimes you can be lucky to purchase a secondhand photopolymer platemaker which is a combined exposure, washout, dryer and post-exposure unit. These can be sourced from flexo platemakers who are selling off old equipment. These units have high-powered 400UV-A florescent lamps, and use a vacuum and diffusion film to get excellent contact between the plate and film positive or film negative.
You can sometimes find old metal halide units which although large have very even light over the whole exposure area, incorporate a vacuum and usually have glass to contact the film to the plate. If you can find one which works great, but if a lamp dies, it can cost a lot to replace it. They are relatively old technology now and finding electricians or technicians to fix them can be difficult especially if you are not in a city.
UV exposure unit – LED unit – Silvi Glattauer
This custom-built UV exposure unit is primarily designed for exposing photopolymer printing plates such as used by the photogravure printing process. (Printight KM73, Printight KM95 and others.) This process requires an efficient and evenly distributed light source over the entire plate area. The unit is also suitable for other similar applications where UV light is required for exposing photo-sensitive substrates.
The UV Exposure Unit was built to provide a UV spectral wavelength output of 365 nm, being ideal for photopolymer printing plates. The 365nm LED strip lighting total 900 LED diodes arranged over a 600 x 450mm area, suitable for up to A2 size plates with space to spare.
UV exposure unit LED – with vacuum and diffusion film
WATCH THIS SPACE – WATCH THIS SPACE
THIS UNIT IS CURRENTLY UNDER DEVELOPMENT IN MELBOURNE, VICTORIA
The vacuum LED unit will have a diffusion film to give good contact between your film positive and film negative and the photopolymer plate.
These units will be available in A2 and A3 sizes. Contact Dianne Longley for progress reports.
Homemade UV exposure unit – with diffusion film and vacuum cleaner attached
I have plans for a UV exposure unit, which can expose up to A2 photopolymer plates, using fluorescent tubes, and a vacuum cleaner. The unit can be made by a person with woodworking skills, but it requires an electrician to do the electrical wiring and would suit home studio use. The file is about 11mb. I can give you access to a Dropbox file for downloading. The instructions are excellent. I used this unit for A5-A2 plates when I lived in Adelaide.
What is the code on the fluorescent tubes in the homemade large UV unit?
The code on the 60cm fluorescent tubes in the large unit is: NEC Blacklight F120SBL 20 watt T10 Japan
What is the code on the fluorescent tubes in the small eBay UV unit?
The code on my smaller unit, using 30cm fluorescent tubes is: F8T5BL Taiwan