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So often I see and hear people asking - what is the best brand of emulsion? Using a good quality emulsion is important, but without a properly prepared film positive, it will be very difficult to get a perfect screen.
When it comes to film positives, opacity most the most important factor. If the ink on your film positive must be dark and dense enough to properly block the UV light emitted from your exposure unit. If it lets light through, it will be very difficult to wash out your stencil.
If the ink is dense enough, it will do its job and block out the UV light, and enable you to rinse out your stencil a lot easier.
Quick exposure is nice, but it is not the most important. If you are trying to get the fastest burn times possible, chances are your stencils will be underexposed.
Under exposure of screens will cost you time & money, and cause undo stress.
If your stencil is not properly exposed and hardened, it can break down during the print process, and you will have to re-burn screens, possibly holding up production and missing deadlines, etc.
Durability of your stencil is most important. When exposed properly, your stencil should last for thousands of prints.
Post expose your screens for added durability. This can be done by simply placing the screen in the sunlight after it is washed out, or back on the exposure unit for a minute or 2. Hitting your screen with full UV light after it is rinsed out will continue to cross link the emulsion, making it harder and less susceptible to breakdown, pinholes etc.