Awards & Engraving

October '18

Issue link:

Contents of this Issue


Page 62 of 84

60 • A&E OCTOBER 2018 lighter and lighter, and before you know it, the whole film slides off its carrier sheet and goes down the drain (hopefully you have a drain screen to catch the debris). So, what happened here? In contrast to the previous scenario, in underexposure, the light did not shine long enough onto the film areas to harden the film, which becomes the stencil itself. Because of that, the film stayed "soft" overall and so stayed water soluble, which causes it to absorb all the water and there- fore letting it slide down the drain. With the dry-process film, you may not be totally aware of the underexposure until it is too late when you attempt to blast it. But really, looking at the underexposed film, you should realize that the image barely has any solid blue/purple areas and that the overall look is light green. The light did not get a chance to break down the film in those areas you want to etch, and you end up with a blotchy image at best. The proper exposure times are impor- tant to pay attention to. With the washout films, you do not have a lot of leeway, maybe 10 seconds in either direction. The dry-process film needs at least 90 seconds to get any satisfactory image; anything under this time will not give you good results. This film allows you to go higher in expo- sure time by even a few minutes before you may encounter overexposure signs. Let me also advise you that the exposure light diminishes in its output of light over time and will eventually affect your expo- sure. When you notice that the quality of your stencils is deteriorating, you only have two choices: either up your exposure time or change the lightbulb. Sometimes, the light will not turn on immediately after you let go of the timer dial, which also affects your exposure. There are several details you have to closely pay attention to. Another important factor: the age of your film. If you are not using your film within a year's time, it may not process properly anymore. You can tell by now that most problems with the processing of photoresist film lie with the operator (that's you) and not with the film itself; read your instructions and pay attention and you will get the hang of the process quickly. © Ruth L Dobbins 2018 Sandcarving Example of an underexposed dry-process film: the image is faint and the areas that are to be blasted are not dark; therefore, the film did not get brittle enough to blast. IMAGE COURTESY IKONICS IMAGING This shows you a side-by-side image of an overexposed (left/top) and an underexposed image with the dry-process film. IMAGE COURTESY IKONICS IMAGING A completely overexposed dry- process film. This is most likely not a scenario you will encounter because you would have to overshoot your time setting by about 300 percent. Here the light has broken down the film so much that even in the background areas the light had penetrated and made the film brittle, which means it would blast away. Also, any areas that are made brittle for blasting will not have a glue left to adhere the film to the substrate. IMAGE COURTESY IKONICS IMAGING A&E

Articles in this issue

Links on this page

view archives of Awards & Engraving - October '18