Back by popular demand, the noted trainer and consultant Charlie Taublieb shares his secrets for HD success.
To get the best results, I apply the emulsion twice. I use a squeegee for the first coat to attach the film, and then I apply a double coat of the same emulsion to the inside of the screen using a round-edge scoop coater to ensure a good bond between the film and emulsion. You can dry the screen between the two steps if you like, but it isn’t necessary. But be sure the screen is dry before exposing it, remembering that you are creating a very thick stencil. With a heated drying cabinet, depending on the settings and the humidity in the screenroom, it should take about an hour. It will take several hours without a heated cabinet, and you might consider letting the screen dry overnight.
Avoid using weak light sources such as fluorescent tube units to expose thick-film screens. You might be able to get such an exposure unit to work, but the exposure times will be very long and the edge definition will probably not be as good. I prefer using metal-halide lamps in the range of 3000 to 6000 watts, allowing 90 seconds for each 100 microns of film thickness; this means a 400-micron film would take 6 minutes to expose. I’ve had mixed experiences using LED exposure units for this application, with results that have varied widely depending on the manufacturer. My advice is to talk to your stencil system supplier and test.
After exposing the screen, I like to let it soak in a dip tank filled with water for about 5 minutes. This isn’t necessary, but will make it easier to wash out the screen. Then I use a 1000-psi pressure washer with a V-shaped nozzle from about a foot away. Wash only the side that has the film attached to it. After washing is complete, dry the screen thoroughly. I prefer vacuuming my screens dry.
Ink Selection and Job Setup
There are several different types of HD formulations – inks, gels, and bases. HD printing is most commonly done with plastisol, but over the past few years, several water-based ink lines have been introduced that are also designed to achieve raised effects.
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