GCM 240 Lecture Notes - Lecture 10: Prepress, Relief Printing, Surface Tension
17 Dec 2016
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Non-i(cid:373)age area: does(cid:374)"t pri(cid:374)t, accepts water (cid:894)hydrophilic(cid:895) Purpose: to keep non-image areas of the plate clean from ink: to desensitize the plate to ink. Fountain solution is composed of: water (95-99%, gum arabic (preserves the plate, phosphoric acid, buffet (controls ph, wetting agent (reduces surface tension, antimicrobial additives. Check ph normally acidic ph of 3. 5 5. 5. Conductivity (measured in micromhos) is the best measure of proper concentration: the amount of things dissolved in water, ph can remain stable due to buffer but conductivity an go up. Fountain solution must be compatible with: inks, plates, and substrates. Fountain solution is applied to the plate by the dampening system form rollers before the plate is inked. Always print with the minimum ink required to achieve target density and minimum fountain solution required to keep the plate clean. Catch-up or dry-up: non-image area dries up and starts receiving ink. Slow ink drying: excessively low ph, excessive fountain solution.
