Indirect Film Troubleshooting Guide

Slow Drying:

 

Possible Problem	Solution
Improper blotting	Use newsprint pad; change bottom sheet 5 - 6 times
Poor air circulation	Use cool air fan
Excessive relative humidity	Dehumidify drying area

 

Emulsion delaminates during washout:

 

Possible Problem	Solution
Developer concentration low	Mix fresh Ulano A & B Developer; use correct size package and amount of water; use only Ulano brand developer
Developer too cold	Keep developer at room temperature. Cover developer tray to prevent cooling from evaporation. Put bottle filled with hot water in corner of tray.
Washout temperature too high	Use thermometer. Water should feel a little warmer than body temperature
Exposed through wrong side	Film should be exposed through backing sheet
Underexposure	Perform Step Wedge Test; check age of bulb

 

Poor adhesion:

 

Possible Problem	Solution
Improper fabric preparation	Degrease all fabrics; roughen and degrease synthetics
Fabric too coarse	Use finer fabric
Over / underexposure	Perform Step Wedge Test
Improper blotting	Use pad of newsprint and firm pressure. Use buildup board
Excessive washout temperature	Use thermometer
Excessive washout pressure	Use aerator nozzle

 

Pinholes:

 

Possible Problem	Solution
Underexposure	Perform Step Wedge Test; check light output
Dust	Clean positives, contact glass, film backing
Poor adhesion	See above
Particles in washout water	Use aerator nozzle, plus water prefilter or strainer
Particles in ink	Avoid coarse frit or pigmented ink
Moisture in thinner or washup solvent	Avoid condensation during solvent storage. Use best grade ink and solvent.
Mesh too coarse for stencil details	Match mesh count to fineness of detail.
Off-contact too high	Stretch fabric tight for proper snap at minimum off-contact.
Poorly stretched fabric	Check proper fabric tension.

 

Stencil Brittleness:

 

Possible Problem	Solution
Stencil dried out	Humidify printing area in winter; use glycerine treatment.

 

Poor Resolution (Loss of Detail):

 

Possible Problem	Solution
Poor vacuum contact	Check vacuum; use board behind film in soft-blanket vacuum frame.
Light reflectance	Use black backup sheet behind film if vacuum frame blanket is of light color.
Poor light source	Upgrade light source.
Poor positives	Check optical density, especially with pen or airbrush positives.
Light too close	Minimum exposure distance should be at least 1½ times image diagonal. Increase exposure distance.
Overexposure	Perform Step Wedge Test.
Poor washout	Check washout procedure - duration, pressure, and temperature.

 

Poor Definition (Edge Sharpness):

 

Possible Problem	Solution
Insufficient washout	Wash out thoroughly and chill.
Heat from light source	Increase exposure distance.
Improper developing	Check developer concentration.
Excessive drying heat	Use cool air only.
Positive oriented incorrectly	Emulsion side of positive must contact film backing during exposure.
Excessive blotting pressure	Blot gently with a pad of newsprint.
Underexposure	Perform Step Wedge Test

 

Stencil cracking or Brittleness:

 

Possible Problem	Solution
Low humidity	Humidify work area; use glycerine treatment
Excessive drying heat	Use cool air only
Excessive off-contact	Stretch fabric better
Marginal adhesion	See Poor Adhesion above
Overexposure	Perform Step Wedge Test

 

Emulsion wrinkling while developing:

 

Possible Problem	Solution
Spent or low concentration developer	Mix fresh Ulano A and B Developer; use only Ulano brand developer.
Developer temperature too low	Control developer temperature.

 

Scumming; Difficult Washout; "Open" areas not printing:

 

Possible Problem	Solution
Insufficient washout	Check washout duration and temperature.
Overexposure	Perform Step Wedge Test
Insufficient chilling	Chill in room temperature water for 30 seconds after washout
Poor positive density	Check positive
Film pre-exposed	Use yellow safelights; store film only in tube or box.
Residue from previous stencil	Review stencil removal procedures.
Insufficient vacuum	Check vacuum pressure
Wrong washout temperature	Use a thermometer
Poor light source	Upgrade light source
Excessive blotting pressure	Use thick pad of newsprint.

 

Stencil edges standing up:

 

Possible Problem	Solution
Overexposure	Perform Step Wedge Test
Improper screen preparation	Review preparation procedures.
Improper blotting	Use firmer pressure on newsprint pad. Use only newsprint to blot.
Excessive drying heat	Use cool air only.

 

Stencil sticking to substrate:

 

Possible Problem	Solution
Ink drying too fast	Retarder / thinner needed
Trapped moisture	Dry stencil more thoroughly; dehumidify press area; dust the stencil bottom with talcum powder
Electrostatic attraction	Ground press. Humidify press area.

 

Poor stencil wear:

 

Possible Problem	Solution
Improper screen preparation	Degrease all fabric; roughen and degrease synthetics.
Excessive off-contact	Improve fabric stretching.
Under / overexposure	Perform Step Wedge Test.
Ink too coarse	Avoid coarse frit or pigmented inks.
Substrate abrasion	Clean substrate; tape jig edges.
Water in ink or washup solvent	Check for water.
Improper wash up	Washup from squeegee side.
Excessive squeegee pressure	Lower off contact distance; check fabric stretching.