Insufficient degreasing of the mesh

Dust particles on the stencil carrier

Poorly mixed photo-initiator (diazo) and emulsion (inhomogenous coating)

Coating too fast can trap air in the mesh openings. (Formation of bubbles leads to premature printing failure)

Emulsion insufficiently dried before exposure

Exposure time too short. Failure to compensate for a highly light-absorbent diapositive

Intensity fall-off in the exposure lamp. (Measure the output using a light integrator)

Insufficiently sensitised emulsion. Incomplete dissolution of the diazo component in water. Some of the diazo sensitiser remains undissolved in the bottle

Caution at very high humidity! The coated screen may feel completely dry, but is only superficially dry due to the high air humidity. Allow for longer exposure times under these circumstances

After coating, leave corase meshes to dry overnight at room temperature

This can occur with white mesh. Use a dyed mesh. Compared to white mesh, dyed screen mesh require a 50 – 100% exposure increase

Only use non-reversed positives