When buying an exposure unit, there’s a lot to consider. One big question many printers have to answer is which type of exposure unit to purchase: vacuum or compression units. What are the differences between them? Which shops benefit from each type? This blog will outline the differences between vacuum and exposure units, and which unit belongs in different shops.
WHAT IS A VACUUM EXPOSURE UNIT?
The purpose of a vacuum exposure unit is to create the best, tightest positive contact between the light source, glass, film, and emulsion. Having tight, strong contact to the point where the black ink in the film is almost embedded into the emulsion means that light cannot wrap around the film well. The end result is a straight, clean burn with sharp edges. Vacuum units provide the best detail resolution.
WHAT IS A COMPRESSION EXPOSURE UNIT?
Compression exposure units require a bit more finesse to create great detail. To replicate the downforce of a vacuum unit, place weight on top of the lid or foam to add compression to the film, screen, and emulsion layer. This creates the tightest contact possible.
Compression exposure units do not achieve the same level of positive contact as vacuum units, but they still perform well. Edges may be a little rough from time to time, but the stencil will still rinse out well and produce an acceptable print. For best results, printers should use emulsions with diazo, called dual cure emulsion. The diazo is a resolution and detail enhancer and helps sharpen edges. Diazo solves all exposure problems.
ART AND EXPOSURE UNIT NEEDS
Halftones, CMYK, sim process, and highly detailed prints need a vacuum exposure unit. Capturing the tiny details in these designs requires the tightest positive contact between the film and the screen. The vacuum will achieve the best results for these kinds of prints.
Compression exposure units are best for spot color prints like block text. To produce a print with a bit more detail, make sure to use diazo-mixed emulsion.
The bottom dollar matters, even when choosing an exposure unit. Vacuum exposure units are more expensive than compression exposure units. There’s nothing wrong with starting out small and affordable, then working up to a bigger, better unit later.
THE DARKROOM MATTERS
In the end, the darkroom composition matters more than the exposure unit sitting in it. The darkroom needs to be light-safe, warm, and dry for screens to turn out properly. Having the optimal darkroom environment is more important than having a tricked-out exposure unit.
Screen printing starts and ends in the darkroom. The environment is just as important as the equipment inside it. The better the screens are, the easier it is to print. Printers should invest in equipment that fits budget and printing needs, dial it in, and prepare to upgrade when possible.