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| Posted on 1/30/08 at 06:29 AM | |
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You wrote an excellent summary of your process. The fact that your stencil is holding in the mesh means your lamp is doing it's job. Emulsion is easy. If it doesn't wash out, it was crosslinked somehow. If the emulsion washes out - it wasn't exposed with enough UV-A energy, so it dissolves with water and goes down the drain. Yellow mesh may double the exposure required for white mesh. I have never found any advantage to dyed mesh below 200 threads per inch. It could be that your positive is not opaque enough for the longer exposure of the One Coat + diazo and yellow mesh. As an experiment, coat a small area of a sacrifice screen. Dry it and then wash out the stencil without exposing. Measure the time it takes and that is the time it should take to develop an exposed stencil. On your next exposure, tape a dime to the stencil to see if the dark areas of your positive are failing you and letting UV-A energy through to the stencil. The dime will stop all UV energy and will demonstrate the best washout. If the area covered by the dime doesn't wash out, you have exposed the stencil to UV energy or heat energy and the stencil is resisting dissolving with water and going down the drain. If the areas covered by your positive don't wash out at the same speed as the area covered by the dime, UV energy las leaked through and cross linked the stencil. Power washers can help speed things up, but the fact that you have a ragged edge means you are tearing out the weaker part of the stencil with water pressure, not dissolving unexposed stencil. I could kick your front door open instead of using a key, but that always leaves a mess. Can water pressure dissolve sugar cubes faster than low pressure water? [Edited on 1/30/08 by richardgreaves] ____________________ Richard Greaves, ASPT Ulano Corp. New York Technical Services 718-943-1338 direct | |
  
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