Direct Stencils (Capillary & Emulsions) Fault finding guide

Detail filling in

Detail filling in Cause Remedy UV light Use of white mesh Use dyed mesh and increase exposure UV light

Detail filling in Cause Remedy Positive UV light UV light Poor contact between positive and stencil Remedy Improve vacuum Check positive is right reading Ensure backing sheet removed Positive in good contact with the stencil Undercutting caused by positive in poor contact with the stencil Positive UV light UV light

Fine detail filling in Cause Remedy Positive UV light Light undercutting on high Rz stencil Remedy Use Capillex Use higher solids stencil Add additional wet on dry coats Positive UV light

Detail filling in Cause Remedy UV light Poor light source geometry Increase lamp distance Reduce reflected light UV light Light more perpendicular to the stencil

Detail filling in Cause Remedy Dust between positive and stencil Ensure positive and stencil are clean by using a clean room wipe or Teknek roller Positive Dust UV light

Detail filling in Cause Remedy Over exposure Poor wash out Reduce exposure Many stencils benefit from a final wash with a high pressure gun at 1m distance, especially water resistant stencils No resolution improvement at different exposures indicates a washout issue

Detail filling in Good diazo Badly decomposed diazo Cause Diazo decomposed by heat or age Remedy Ensure diazo is stored between 3oC and 20oC and is within 2 year shelf life Good diazo Badly decomposed diazo

Cause Remedy Difficult to washout Gross over-exposure Excessive drying temperature Coated screen fogged by light Low density positive Remedy Reduce exposure Dry coated screen at max. 40°C Store coated screen in dark or under safelight Re-make positive

Pinholes - Emulsions Cause Air entrapment during coating Air entrained in the emulsion Air developing in the trough Bits in the emulsion Remedy Ensure emulsion fills the mesh during print side coatings Ensure the pot has fully degassed before coating Reduce coating speed Metal stirrers gouge the sides of the pot on sensitising. Use the wooden stirrer provided

Poor Adhesion Cause Remedy Diazo Correctly dried stencil Inadequate drying prior to exposure Remedy Dry coated screens thoroughly. Do not dry unexposed screens in the same cabinet as wet screens Diazo Correctly dried stencil Underdried stencil Strong stencil with all diazo sites cross linking PVOH Weak stencil with some diazo sites reacted with water UV

Cause Poor Adhesion Remedy Use Autotype exposure calculator to find correct exposure time Ensure has correct UV output and lamp has not aged Cause Under-exposure

Poor Adhesion Cause Under exposure Remedy Increase exposure time

Poor Definition Cause Remedy Poor edge quality of positive Incorrect exposure Use of white mesh Remedy Remake positive Expose for optimum time Use dyed fabric

Mesh difficult to reclaim Remedy Increase exposure to optimum If reclaim is required do not use A and B Hardener Check stripper is correct concentration 2-4%, for very water resistant stencils err on the higher side, so 1:25 stripper concentrate should be used at 1:15 dilution Change solvents used with the stencil Cause Under-exposed stencils are more difficult to reclaim A and B Hardener used Stripper incorrect concentration Stencil fusing