Post exposure for Pure Photopolymers helps strengthen the stencil and complete the exposure process. However it should not be substituted for a good initial exposure. It is better to expose the emulsion in the initial exposure for the maximum possible amount of time possible while still achieving good details and resolution. Our emulsion often has wide lattitude of exposure which allows for complete exposure. Under exposing emulsion to achieve all details possible and then relying on post exposure to complete the exposure will never achieve the screen strength that a complete initial exposure followed by post exposure in the sun can achieve. Dual Cures see some added benefit of post exposures along with the heat and drying to get a completely dry stencil. For Diazo the post exposure in the sun is a good drying technique. Pre-stretched Screen users of fine mesh should know that the heat of the sun can cause aluminum frames to expand and increase tension to levels that could pop the mesh. Monitor frames for heat. When I put my light meter in the sun it went past 23,000 watts and was still climbing. When the screen is wet, 20 minutes is enough time in So Cal to dry and post expose. Drying the screen well for discharge and wb along with post is just as important as post exposure. Rushing a freshly made screen to press for discharge will result in breakdown since the emulsion may still have moisture on the inside of the coating.
