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.
They are much rarer now but 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.
There are many UV units suitable for exposing photopolymer plates that have UV fluorescent tube lights and more recently LED UV lights. Most have a vacuum included with the unit. Some have more powerful UV lights in them than other units. A LED UV unit from China (purchased by a colleague) was taking 40 minutes to expose a photopolymer plate. She purchased new LED lights and significantly reduced the exposure time. Finding an electrician to replace the strips of LED lights is a bit challenging.
A2 and A4 UV exposure units using LED lights – 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. The A4 unit has LED strip lighting total 450 LED diodes arranged over a 300 x 275mm area, suitable for up to A4 size plates with space to spare.
LED UV exposure units available from Silvi Glattauer.
Further Information contact Silvi Glattauer – 0417 377 962 or silvi@silvi.com.au
Click image to view video of exposure unit.
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 UV fluorescent tubes, a diffusion film 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.
FAQs
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
I asked Silvi Glattauer what I should purchase if I need to replace low power or slow LED UV strips with UV LED lights specifically for photopolymer plates?
365 NM LED STRIPS: High quality SMD2835 365nm
DC12V IP20 UV led strip,
4.8W/m
elson@vlikelighting.com
VLIKE LIGHTING TECHNOLOGY CO.,LIMITED
6/F,Building5,TianFuAn Industrial,
Xixiang,Bao’an,
ShenZhen,China
Tel: +86 755 2974 9129