Frequently Asked Questions on Textile Screen Printing
Intro text: 45 years of hands-on experience, distilled into the questions I get asked most. Technical, precise, unfiltered answers — from pre-press to curing.
Pre-Press, Emulsion & Screens
Why does the emulsion peel off or wash out during development?
In 95% of cases, this is caused by underexposure or poor mesh preparation. If UV rays (ideal wavelength 365-405 nm, peaking at 395 nm) don't penetrate the full emulsion thickness, the layer touching the mesh won't crosslink. Solution: run a Step Wedge Test, dry the screen with a dehumidifier (humidity <50%), and always degrease before coating.
→ Advanced guides: Pre-Press Basic/Advanced/Professional
How do I eliminate the "sawtooth" effect on printed edges?
Caused by using a mesh count that is too low or stretching the mesh at 90°. Solution: use a higher mesh count, stretch at 22.5° or 45° to the design, and apply an extra coat of emulsion on the print side (face coat) to increase the EOM (Emulsion Over Mesh).
Why won't fine details open up and remain blocked?
Caused by overexposure or light scattering (UV light bypasses the black edges of the film). Solution: reduce exposure time and use a vacuum exposure unit (or heavy weights) to eliminate the air gap between film and emulsion, preventing lateral diffraction.
What are "pinholes" and how do I prevent them?
Tiny dust particles or debris block UV light during exposure. Solution: clean the exposure glass with anti-static products, degrease the mesh thoroughly to remove manufacturing oils, and keep the coating room dust-free.
Why does the emulsion remain sticky or drip hours after drying?
Ambient humidity over 60% or drying the screens vertically. Solution: dry screens horizontally, print-side down, in a ventilated, light-safe room. Gravity pools excess emulsion when dried vertically, creating thick drips that are impossible to dry at the core.
Which emulsion should I use if I print with both water-based and plastisol inks?
If you print predominantly water-based for long runs, use a Pure Photopolymer (SBQ) with high thickness or specific "Water-Resistant" emulsions. If you frequently alternate both inks on the same screen, use a Dual-Cure (SBQ + Diazo), but be aware that pure SBQ resists water abrasion far better.
How do I calculate exact exposure time with cheap or DIY LED UV lights?
Cheap LEDs lack spectral consistency. Use a 21-Step Sensitivity Guide. Expose for an arbitrary time, wash out, and find the perfect step. Multiply your initial time by the guide's correction factor to find your exact time.
Why do "ghost images" remain after reclaiming the screen?
Microscopic ink residue trapped in the mesh intersections or emulsion baked on by flash heat. Solution: use a dedicated "Ghost Image Remover" chemical (often alkaline), let it dwell, and pressure wash.
Tension, Mesh & Preparation
How much does 25 N/cm tension improve print quality over 15 N/cm?
Massively. Higher tension reduces mesh deformation, improving detail, reducing dot gain, and stabilising registration. The "sweet spot" for textiles is between 25 and 30 N/cm. Beyond 30 N/cm, the mechanical stress on the frame and mesh outweighs the qualitative benefits.
→ Advanced guides: Pre-Press Basic/Advanced/Professional
What mesh count should I use for CMYK halftones?
The mesh should be 4 to 4.5 times the halftone line screen (lpi). E.g., 45 lpi requires a 180-200 mesh; 55 lpi requires 220-250. On cotton, prefer the lower end of the range to ensure sufficient ink deposit.
Mesh tension drops during the run, ruining registration: how to fix?
Use aluminium frames (wood warps), let newly stretched screens rest for 24 hours before coating, and replace screens that have been retensioned too many times and lost elasticity (use the finger bounce test).
What mesh for lightweight cotton vs heavy fleece?
Lightweight cotton (smooth): 77-120 threads/cm for a soft hand and detail. Heavy fleece (textured/absorbent): 32-43 threads/cm to push enough ink to cover the fibres.
I use high mesh with water-based inks, but the emulsion breaks out: why?
Water-based ink dries in the mesh, increasing squeegee pressure until the emulsion fails. Solution: increase exposure time, keep the mesh wet with frequent flood strokes, and ensure adequate Emulsion Over Mesh (EOM) — at least 15-20 microns for white ink.
Printing Technique, Squeegee & Setup
The garment sticks to the screen and the print doubles (ghosting): why?
Lack of platen adhesive (tack) or incorrect off-contact. The sticky ink pulls the garment up. Solution: ensure the garment is firmly stuck to the platen and check your off-contact distance.
How many millimetres of off-contact should I set?
Fine detail: 1.0-1.5 mm. Lightweight cotton (water-based): 1.5-2.0 mm. Heavy fleece/thick garments (plastisol): 2.5-3.0 mm. Off-contact guarantees immediate "snap-off" of the mesh.
Ink smears/bleeds after 3-4 passes: how to fix?
Ink builds up on the underside of the screen due to excessive squeegee pressure, too acute an angle (<45°), or zero off-contact. Solution: set squeegee to 75°, increase off-contact, and wipe the back of the screen.
What squeegee hardness (Shore A) should I use?
Fine details/halftones: 75-85 Shore A (flexes less, maximum resolution). Solid coverage/underbases: 60-65 Shore A (deposits more ink).
How does squeegee angle affect the print?
A sharper angle (45°) deposits more ink but blurs edges. A vertical angle (75°-90°) gives sharp edges and minimal deposit. Use 60-65° for solid coverage, 75-80° for halftones.
How to perform a flood stroke with water-based inks?
Lift the screen (off-contact), tilt the squeegee to 30°-45° with minimal pressure. The goal is merely to fill the mesh openings to block out oxygen, not to push ink onto the garment.
How much squeegee pressure should I apply?
The absolute minimum required to clear the mesh. If ink is bleeding onto the platen, the issue is almost always insufficient off-contact or collapsed mesh tension — not too much pressure.
→ Free guide: Printing/Inks — Squeegee Angle & Pressure
Inks, Halftones & Chemistry
Plastisol forms clumps on the squeegee instead of rolling: why?
Plastisol is thixotropic; it needs mechanical shear to become fluid, especially if the shop is below 20°C. Solution: stir the ink vigorously in the tub before putting it on the screen and keep the shop at a stable 22-24°C.
Water-based ink dries in the screen: how to unblock and prevent it?
Don't scrape! Use warm water and a soft brush. To prevent: add a retarder (max 3-5% to avoid destroying thixotropy), mist with demineralised water, and keep the mesh flooded when pausing.
White ink on black garments is transparent: how to get opacity?
Use a low mesh count (43-55 threads/cm) for maximum deposit and ensure an EOM of 15-20 microns. Print a double pass with a flash cure in between. Never add water or thinners to high-opacity white — it destroys coverage.
→ Advanced guides: Inks Basic/Advanced/Professional
→ Podcast: Inks, Chemistry & Sustainability — One Hit White
→ Podcast: Textile Applications, Fashion & Finishing — White on Black
I added too much additive and the ink drips through the mesh: how to recover?
You exceeded the 5% additive limit, destroying the surface tension and thixotropy. Solution: mix the ruined ink with fresh, unthinned base ink to restore the viscosity.
Metallic or glitter inks block the mesh immediately: why?
Geometric error: the particle size is larger than the mesh openings. Solution: use very open meshes (15-34 threads/cm for thick glitter, 62-77 for metallics) and a soft squeegee.
How to achieve a "soft hand" without losing opacity?
Use dedicated "soft hand" inks, increase the mesh count, or add a soft-hand base additive. Never use plasticiser to soften the hand — it ruins opacity and inhibits proper curing.
How much dot gain is acceptable in textile screen printing?
Between 15% and 25% on mid-tones is controllable. Above 30%, tonal reproduction is compromised. The goal isn't to eliminate it, but to measure it and create compensation curves in your RIP to linearise the process.
What is the true limit of printable detail on fabric?
It depends on the substrate. On tight, smooth cotton, you can hold 0.15-0.20 mm details. On open or textured fabrics, the physical weave of the fabric becomes the limiting factor, not the screen.
Substrates, Polyester & Special Phenomena
White ink on polyester turns pink/yellow (Dye Migration): how to stop it?
Above 130°C, heat sublimates the disperse dyes in the polyester, which gasify and penetrate the white ink. Solution: print a "Barrier/Blocker" under base first, cure at the lowest possible temperature, and use "Low-Bleed" white inks.
→ Advanced guides: Inks Basic/Advanced/Professional
After washing, the cotton print is covered in fuzz (Fibrillation): how to prevent?
Short cotton fibres from carded (not combed) cotton break through the ink film during the wash cycle. Solution: use high-quality combed cotton, apply a transparent "flat" base to glue fibres down before printing, or flash and press with a hot press.
Polyester shrinks during flash curing, ruining registration: how to fix?
Polyester is heat-sensitive. Solution: lower the flash power and time, increase the distance between the flash head and the garment, and use strong spray adhesive on the platen to anchor the garment.
How do I print on Nylon or synthetics without it peeling off?
Nylon is non-porous. Solution: use inks specifically formulated for nylon or add a nylon catalyst/bonding agent (5-10%) to your ink. The catalyst creates a covalent cross-link bond that bites into the synthetic fibre.
Ink spreads like an oil slick on sports polyester: why?
Uncontrolled capillary action on smooth synthetic fibres. Solution: thicken the ink with a viscosity builder, use a hard squeegee (75+ Shore A), and reduce pressure.
Can I use water-based inks on technical polyester (sportswear)?
Highly discouraged. The water content reactivates dye migration, and adhesion is poor on hydrophobic fibres. Use anti-migration plastisol or specific water-based inks with a catalyst.
Registration & Multi-Colour Printing
Colours don't align (misregistration): what are the main causes?
Uneven mesh tension, unstable platens, varying off-contact, or using paper films that expand with humidity. Always use polyester films for exposure and ensure all screens have identical tension.
Why does a perfectly registered job drift during the run?
Thermal expansion of the press, mesh tension loss, or ink buildup. Solution: use aluminium frames, monitor tension, and keep the production room climate-controlled (22°C).
How much does fabric stretch affect registration?
Massively, especially in CMYK. Stretchy fabrics distort under squeegee pressure. Solution: use aggressive platen adhesive and minimise squeegee pressure.
When to use a flash cure between colours, and when to avoid it?
Use it for light colours over a white under base, or when colours overlap. Avoid it for dark-on-dark (wet-on-wet) printing. Warning: over-flashing creates a glassy surface that prevents the next layer from adhering (delamination). A correct flash leaves the under base dry to the touch but still "tacky" under pressure.
How do I handle CMYK registration with water-based inks?
It is nearly impossible on a manual press because the pauses allow the ink to dry. It requires an automatic press, retarder additives, and a humidified environment.
→ Advanced guides: Graphics Basic/Advanced/Professional
Curing & Post-Print
The plastisol print washes out: why, even if it went through the dryer?
Undercuring. The ink must reach 160°C at its core. Causes: belt too fast, deposit too thick. Pro tip: use Low-Cure inks that polymerise at 130°C-135°C, drastically reducing the risk of undercuring on heavy fleece and synthetics.
How do I verify curing without expensive tools?
Stretch Test: stretch the cold print — if the ink cracks, it's undercured. Wash Test: wash at 60°C. Thermo-strips: adhesive labels that permanently change colour at 160°C. Warning: laser IR pyrometers only measure surface or air temperature; to measure the ink core, you need a contact probe (Donut Probe).
How do I cure without a conveyor dryer?
Heat press: 165°C with silicone paper for 35-45 seconds at light pressure to avoid pushing ink into the fibres. Iron: for hobby use only. Domestic oven: not recommended due to toxicity and inconsistency.
Prints stick together when stacked: why?
Ink not completely cured or stacked while still warm. Plastisol, if not fully fused at the core, remains thermoplastic and reactivates with residual heat. Solution: let prints cool completely on aerated racks.
The print remains tacky to the touch even after heat: is that normal?
No. It means there was partial thermal shock, or the ink is low quality with an excess of free plasticisers migrating to the surface.
Process Control, Economics & Quality
How do I linearise a screen printing process?
By measuring the actual printed dot gain and creating compensation curves in the RIP. This transforms an artisanal process into a measurable, repeatable industrial one.
Which variables affect the final colour most?
White underbase opacity, dot gain, deposit thickness (EOM), fabric absorbency, and curing temperature. The white underbase is the most underestimated variable.
What is the real cost of working with low-tension screens?
Hidden costs are enormous: longer setup times, higher ink consumption, waste and reprints. The cost far exceeds the investment in a tension meter and quality frames.
What is the main cause of productivity loss?
Process variability. Every time a variable — tension, humidity, viscosity — changes, the operator wastes time compensating. Stability beats speed.
Why do modern, expensive presses produce mediocre results?
Because automation only amplifies the existing process. If the process is not standardised — from tension to dryer temperature — the automatic press will produce waste in series, faster.
What are the 10 parameters that determine 80% of the final result?
1. Mesh tension — 2. Mesh count — 3. Thread diameter — 4. Emulsion thickness (EOM) — 5. Off-contact — 6. Squeegee hardness — 7. Squeegee pressure — 8. Ink viscosity — 9. Curing temperature (at the core) — 10. Substrate stability.
→ Podcast: Fundamentals of Screen Printing & Process