While some of these issues may also be caused by other factors, incorrect screen exposure time is of great importance. By comparison, the main problem associated with over-exposure is that the screen may not wash out properly and fine detail will be lost.
While manufacturers do provide guideline exposure times, it is rare that their guidelines are for the exact make and model of your screen exposure unit, or indeed for a suitably coated screen with high emulsion over mesh (EOM), which means that trial and error is the order of the day. It is therefore important that you have a procedure in place to test all your emulsions to ensure correct screen exposure time is used at all times.
Follow these steps for proper use of this calculator1.) How long do you think it will take to expose your screens? 60sec? 120sec? 180sec? You can often refer to manufacturer recommendations for estimated times. For this example we will use 120 seconds. 2.) Divide that time by 6 (ex: 120sec / 6 = 15 seconds) 3.) Tape this Exposure Calculator to your screen and Expose for the amount of time from Step 2 (ex: 15 seconds). 4.) COVER Row #1 with cardboard & Expose screen again for same amount of time (15 seconds). 5.) Slide the cardboard down so that its COVERING Rows 1 & 2. 6.) Expose again for the same amount of time (15 seconds). 7.) Continue sliding the cardboard down covering rows 1, 2, 3, and so on until Row 6 is exposed. 8.) Washout image area with water and select the row with the clearest detail across the entire row. 9.) Multiply that row number by the number of seconds from Step 2 (15 seconds) You now have an accurate way to dial in your exposure times.
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