Screen E-Book (.PDF) - MacDermid Autotype

Getting the right exposureThere is always a compromise between exposuretime and achievable resolution becausethere is always some scatter withinthe system. As you increase exposure tocreate a harder stencil you automaticallystart to reduce the resolution.Comparing exposure times with white andanti-halation dyed meshWhite mesh transmits and scatters light,yellow and orange mesh absorb the wavelengthsneeded for the crosslinking reaction,but scatter far less of the light.This means that dyed meshes require longerexposures (up to 4x for some yellowmeshes) but give better resolution anddefinition. Light scatter increases withmesh count and exposure time.This makes using dyed mesh particularlyimportant for fine detail resolution on finemeshes.Poor contact with positiveThe contact between positive and stencilshould be as perfect as possible, inadequatecontact results in light undercutting,more so when combined with poor lightgeometry.66