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Fix a problem · 2 of 5 · 4 min read

Screen-room problems

Pinholes and fisheyesTiny specks of ink printing where there should be none.
Looks like
Tiny specks of ink printing where there should be none. Hold the screen to the light and you’ll see pinpoint holes. Fisheyes are small round voids where wet emulsion pulled away from the mesh.
Likely causes
  • Dust, lint or hair on the mesh, coater or exposure glass
  • Mesh that wasn’t degreased (oils and fingerprints cause fisheyes)
  • Air bubbles from coating too fast, or diazo or dual-cure emulsion not left to de-gas after mixing
  • Under-exposure
  • Coating or drying in high humidity
  • Minerals in hard water (ScreenPrinting.com suggests a filter)
  • Damage or holes in the mesh
Fix it now
Touch up pinholes with block-out or emulsion on the print side and let it dry. If there are many, or they’re in the image, reclaim and re-coat.
Stop it next time
Degrease every screen, keep the darkroom and drying area clean (a closed drying cabinet helps), clean the glass and films, coat slowly, dry fully, and dial in exposure.
More
Emulsion & exposure
Sources: ScreenPrinting.com Help · Chromaline · Chromaline · Avery Dennison
Under-exposed stencilFine lines and small text wash away or look soft.
Looks like
Fine lines and small text wash away or look soft. The squeegee side feels slimy or tacky after washout (Chromaline’s tell-tale sign). Emulsion lifts during rinsing.
Likely causes
  • Exposure too short for that emulsion, mesh and light
  • Emulsion coated too thick for the exposure time
  • Films not dark enough: Chromaline wants a film density (Dmax) above 3.0; the film should look solid black against light
  • Old or badly stored emulsion (refrigerate, don’t freeze)
  • The opposite, over-exposure, makes fine detail refuse to wash out
Fix it now
Reclaim and expose again; Chromaline recommends reclaiming rather than printing an under-exposed screen. Rinse from the print side only.
Stop it next time
Run an exposure calculator or 21-step wedge once for each emulsion, mesh count and light (ScreenPrinting.com targets step 7). Log the times and keep coating thickness consistent.
More
Emulsion & exposure
Sources: Chromaline · ScreenPrinting.com Help · ScreenPrinting.com Help · ScreenPrinting.com Help · ScreenPrintingNow
SawtoothingEdges that should be smooth come out as a zig-zag staircase following the mesh threads, most visible on curves, thin lines and small text.
Looks like
Edges that should be smooth come out as a zig-zag staircase following the mesh threads, most visible on curves, thin lines and small text.
Likely causes
  • A stencil too thin or rough on the print side, so it doesn’t seal against the shirt
  • Under-exposure (extreme over-exposure can also cause it, per Avery)
  • Mesh too coarse for the detail
  • Poor film contact during exposure
  • Light scatter, worse with white mesh
  • Rough washout
Fix it now
You can’t fix a sawtoothed stencil on press. Reprint with a better screen.
Stop it next time
Build enough emulsion on the print side. Coating from the squeegee side pushes emulsion through to the print side, so Avery suggests extra squeegee-side coats, the round edge of the coater, and drying print-side down. Then dial in exposure, use finer and dyed mesh for fine detail, and press the film tight when exposing.
More
Emulsion & exposure
Sources: Avery Dennison · Lawson Screen & Digital · Chromaline · Avient
Stencil breaking down on pressPartway through a run, new pinholes open, edges fray, or emulsion flakes off and ink leaks.
Looks like
Partway through a run, new pinholes open, edges fray, or emulsion flakes off and ink leaks.
Likely causes
  • Under-exposure (Chromaline lists it first)
  • The wrong emulsion for the ink (water-based needs a water-resistant one)
  • Poor films
  • Low mesh tension
  • Harsh solvents or cleaners
  • Temperature and humidity (Chromaline suggests 60–80°F and 30–40% RH for screen-making)
  • Aggressive reclaiming that weakens the mesh
  • Very thick ink, damaged squeegees, too much pressure
Fix it now
Stop and block out small leaks. If the stencil is failing across the image, burn a new screen.
Stop it next time
Fix exposure first and match the emulsion to the ink. For long water-based runs, use a hardener or post-exposure per the emulsion maker. Use a gentle press wash on press.
More
Emulsion & exposure
Sources: Chromaline · ScreenPrinting.com
Ghost image or haze in a reclaimed screenA faint stained shadow of the old design stays in the mesh.
Looks like
A faint stained shadow of the old design stays in the mesh. A heavy ghost can print or block light in the next exposure.
Likely causes
  • Under-exposed emulsion that locks in when reclaim chemicals hit it
  • Low tension, so more pressure forces pigment into the threads
  • Abrasive scrubbing
  • Reclaiming screens that are still wet
  • Hot solvents like lacquer thinner
  • Ink left to dry in the screen
Fix it now
A haze or ghost remover can help, but they’re harsh: follow the label and wear protection. A light stain that doesn’t block light may not matter, and some ghosts never fully come out.
Stop it next time
Expose fully (post-exposure per your emulsion’s directions), clean ink out right after the job, avoid hot solvents, and don’t let emulsion remover dry on the screen.
More
Emulsion & exposure
Sources: ScreenPrinting.com · ScreenPrinting.com Help · Screen Printing Magazine
Sources for this guide (50)
  1. ScreenPrinting.com Help, Pinholes and fisheyes
  2. Chromaline, Causes of pinholes during screen making
  3. Chromaline, Underexposed screen tech tip (PDF)
  4. Avery Dennison, IB 8.34 silkscreen troubleshooting guide (PDF)
  5. ScreenPrinting.com Help, Over- vs. under-exposure
  6. ScreenPrinting.com Help, How do I figure out exposure times?
  7. ScreenPrinting.com Help, Why can’t I burn my screens correctly?
  8. ScreenPrintingNow, Using the 21-step wedge
  9. Lawson Screen & Digital, Direct emulsion troubleshooting checklist
  10. Avient, Print technique guide, 2023 (PDF)
  11. Chromaline, 10 common reasons for stencil breakdown on press
  12. ScreenPrinting.com, Printing with plastisol vs. water-based ink
  13. ScreenPrinting.com, Get rid of ghost images
  14. ScreenPrinting.com Help, How do you reclaim screens?
  15. Screen Printing Magazine, Preventing and removing haze
  16. International Coatings, Preventing moiré patterns
  17. Screen Printing Magazine, Ten tips to help avoid halftone moiré
  18. Solutions for Screen Printers, Halftone angles demystified
  19. Impressions, Troubleshooting screen printing (2018)
  20. Screen Printing Magazine, Catching the on-press culprit
  21. ScreenPrinting.com Help, Why is my print fuzzy?
  22. Ink Kitchen, Why out of register? Let me count the ways
  23. ScreenPrinting.com Help, What’s considered good mesh tension?
  24. ScreenPrinting.com, Registering water-based and plastisol prints
  25. Davis International, Common issues
  26. PrintWiki, Mesh marks
  27. Lawson Screen & Digital, Eliminating fibrillation
  28. Texsource, What is fibrillation?
  29. Fujifilm, Fibrillation in plastisols (PDF)
  30. ScreenPrinting.com Help, How do I pick the right mesh count?
  31. ScreenPrinting.com, High contrast with discharge inks
  32. Signs101 forum, Just started screen printing again
  33. ScreenPrinting.com Help, Water-based vs. plastisol
  34. Lawson Screen & Digital, Plastisol ink FAQ
  35. Lawson Screen & Digital, Reducing plastisol ink build-up
  36. Screen Printing Magazine, Anti-build-up additive
  37. PIA/SPTF, Textile plastisol curing troubleshooting (PDF)
  38. Lawson Screen & Digital, Curing plastisol inks
  39. ScreenPrinting.com Help, Why does ink crack in a stretch test?
  40. ScreenPrinting.com Help, Why does ink look faded after washing?
  41. Screen Printing Magazine, Curing comes clean through wash testing
  42. International Coatings, How do I test to make sure my inks are properly cured?
  43. ScreenPrinting.com, What is dye migration?
  44. ScreenPrinting.com, Decoding poly white and dye blocker inks
  45. Lawson Screen & Digital, Testing polyester for dye migration
  46. Lawson Screen & Digital, Low-cure screen printing ink
  47. Ink Kitchen, Scorching heat, scorching shirts
  48. ScreenPrinting.com Help, Can you over-cure plastisol ink?
  49. Screen Printing Magazine, Figuring out flash-curing parameters
  50. Wilflex (Avient), Ink curing tips (2020, PDF)

Where sources disagree, the page says so.