Since traditional 'high UV' light sources (metal halide and mercury vapor lamps) for 'home made' exposure units are becoming harder to find, we have found some LED lights sources that are affordable, safe to use and will work effectively for exposing screens.
Before we discuss LED light sources, we need to discuss some important details regarding light sources in general when building your own exposure unit.
As we have written in a previous article on light sources for exposure units, most people who want to build their own exposure unit mistakenly think that the light source is the most important consideration. It isn't. While the light source will determine what kind of art you can use to make a stencil, the type of emulsion or capillary film that you use is actually more important. If you think of emulsion (or capillary film) as the 'photographic film' used to make your stencil, think in terms of speed and light sensitivity.
Photopolymer emulsion is very sensitive to light. It exposes very quickly and has a wide exposure time range. Manufacturers developed photopolymer emulsion products because they know that many screen printers use an exposure light source that is less than ideal. Photopolymer liquid emulsions (and photopolymer capillary film) work well even with poor light sources. Using a photopolymer emulsion (compared to a diazo-based emulsion) when you have a low UV light source will make a huge difference toward success or failure when making a stencil.
LED lights are becoming more and more popular and look to become the lighting standard in USA. As prices are becoming par with fluorescent lamps, LED lights are becoming more widely available.
For exposing exposing screens, LED lights have several distinct advantages:
- Relatively affordable to purchase.
- Safe to use (they generate very little heat).
- Very economical to operate.
- They last a long time.
LED light sources that have a high lumen output work best for exposing screens and ASPA has found several that will work well as a light source when you are building your own exposure unit.
ASPA has created a short report 'The Best LED Lights for Exposure Units.' In this report, we identify what light sources work best and where to buy them. For more on our report, visit this page.