1. Direct Stencils (Capillary & Emulsions)
Fault finding guide

2. Detail filling in

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

4. 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

5. 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

6. 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

7. 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

8. 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

9. 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

10. 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

11. 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

12. 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

13. 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

14. Poor Adhesion
Cause
Under exposure
Remedy
Increase exposure time

15. 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

16. 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