Screen Printing Resource · River City Supply
The Complete Screen Printing Emulsion Troubleshooting Guide
Pinholes, fish eyes, stencils washing out, sawtooth edges, premature breakdown on press — every screen printer hits these problems eventually. This guide is organized by what you're SEEING on the screen, not by what's causing it, so you can find your issue fast and get back to printing.
River City Supply has supplied screen printers since 2008. We've walked hundreds of shops through emulsion problems and know the common (and uncommon) causes. If you've tried the fixes here and you're still stuck, call (512) 454-0505 — we'll help you diagnose it.
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Quick Diagnostic Table
Find your symptom in the left column. The middle column shows the most likely causes. The right column is your first thing to try. For detailed diagnostic steps on each issue, jump to the relevant section below.
| What You're Seeing | Most Likely Cause | First Thing to Try |
|---|---|---|
| Tiny holes in stencil after washout | Contamination on mesh, dust during drying, pinhole air pockets | Degrease before coating, dry in dust-free cabinet, touch up with blockout |
| Circular bare spots in coating | Fish eyes — contamination, oil residue, or poor degreasing | Degrease thoroughly, replace coater if oily, check for static-attracted dust |
| Stencil washes off completely during development | Underexposure (most common), past-shelf-life emulsion, screen not fully dry | Run a Stouffer wedge test, check emulsion mix date, verify drying |
| Stencil too hard to wash out | Overexposure, light source too strong, thin emulsion coat | Reduce exposure time, add more coats, check exposure calibration |
| Jagged or sawtooth edges on stencil | Underexposure, poor coating technique, low-quality film positive | Increase exposure, coat with sharp coater edge, improve film density |
| Halftone dots filling in or dropping out | Wrong exposure for halftone work, mesh count mismatch, underexposed shadow areas | Use proper mesh count (305+ for halftones), step-test exposure |
| Streaks in coating | Dirty/damaged scoop coater edge, uneven coating pressure, emulsion too thick | Inspect/sharpen coater edge, slow steady coating pass, thin if needed |
| Emulsion won't dry properly | Humidity too high, cabinet too cool, coating too thick | Add dehumidifier, raise cabinet temp (under 110°F), reduce coats |
| Stencil breaks down during print run | Wrong emulsion for ink type, no hardener on long WB/discharge run, mesh under tension | Check ink compatibility, apply hardener, verify mesh tension |
| Ghost image after reclaim | Incomplete reclaim, stained mesh, emulsion too long on screen before reclaim | Reclaim within days of last use, use haze/ghost remover, condition mesh |
| Pre-exposure / scumming / haze | Light leak in coating or drying area, screen dried in light, weak yellow safelight | Audit lighting (only yellow safelight), tighten drying cabinet seals |
| Emulsion lifts off mesh during washout | Inadequate degreasing, mesh contamination, hydrophobic mesh treatment | Degrease both sides, mesh prep, ensure full mesh wetting |
Coating & Drying Problems
Most stencil failures actually trace back to problems that happened BEFORE exposure — during coating, drying, or screen prep. Getting these right is the foundation of every successful screen.
Pinholes (Tiny Holes in Stencil)
What you're seeing: Small holes — usually circular, less than 1mm across — visible in the cured emulsion after washout. Most common in fine-detail areas and along stencil edges.
1
Cause: Dust or contamination on mesh during coating
Fix: Degrease thoroughly BEFORE coating. Use lint-free wipes during the entire process. If your shop has dust issues, coat screens in an enclosed area away from production traffic.
2
Cause: Air bubbles in the emulsion from over-stirring
Fix: Let mixed emulsion sit covered for 1-2 hours before coating. Stir with smooth top-to-bottom motion (don't whip). Never stir vigorously.
3
Cause: Dust settling on coated screen during drying
Fix: Use a dust-free, light-tight drying cabinet. Filter the cabinet's intake air. Don't coat screens near sanding, sweeping, or production areas.
4
Cause: Coating emulsion past its useful shelf life
Fix: Check the mix date on sensitized emulsion (4-6 weeks at room temp; 4-6 months refrigerated for diazo and dual-cure). Throw out emulsion that's developed clumps, separation, or unusual color shifts.
5
Cause: Pinholes from mesh imperfections
Fix: Inspect mesh under bright light before coating. Damaged or worn mesh should be retensioned or replaced. New mesh can have manufacturing imperfections — coat both sides for cushion.
✓ Prevention
Most pinholes are preventable with proper degreasing and a clean drying environment. For pinholes that still appear, touch up with Murakami 901 Blockout Red after washout before printing. A few minutes of touch-up saves ruining a print run.
Fish Eyes (Circular Bare Spots)
What you're seeing: Round, dish-shaped spots where the emulsion didn't adhere or pulled away from the mesh during coating. Larger than pinholes — typically 2-10mm across. Often have a slight raised rim around them.
1
Cause: Oil or silicone contamination on the mesh
Fix: This is the #1 cause. Hands transfer oils from skin to mesh — wear gloves. Hand soap, silicone-based mold releases, and certain mesh treatments can leave residue. Aggressive degreasing usually solves it.
2
Cause: Contaminated scoop coater
Fix: Oils from previous coatings can contaminate your scoop coater. Clean the coater with mineral spirits or stencil remover before each coating session. Inspect the edge for residue.
3
Cause: Hand contact with mesh after degreasing
Fix: Always wear nitrile or latex gloves after degreasing. Skin oils transfer instantly and cause fish eyes. Same applies to handling the frame edges — oils migrate.
4
Cause: Static-attracted contamination during drying
Fix: Low-humidity environments build static on mesh that attracts airborne contaminants. Maintain 40-60% relative humidity in coating and drying areas. Anti-static brushes can help in dry climates.
5
Cause: Solvent residue from previous reclaim
Fix: Aggressive reclaim chemistry can leave residue that interferes with new coating. Rinse screens thoroughly after reclaim. Some shops mesh-prep with a mild degreaser after reclaim and before coating.
✓ Prevention
Fish eyes are almost always a contamination issue. The fix isn't more emulsion — it's better mesh prep. Adopt a consistent degreasing protocol, wear gloves, and inspect screens under bright light before coating. Catch contamination before it costs you a screen.
Related products: Degreasers · Screen cleaning chemicals
Streaking or Uneven Coating
What you're seeing: Visible streaks, ridges, or unevenness across the coated stencil. Often shows up most clearly on the squeegee side when held up to light.
1
Cause: Damaged or dull scoop coater edge
Fix: Inspect the sharp edge of your scoop coater regularly. Nicks, gouges, or dulling create streaks. Replace or have the edge resharpened. Aluminum coaters last longer than plastic but eventually wear too.
2
Cause: Inconsistent coating pressure
Fix: The scoop coater should be held at consistent angle and pressure throughout the entire upward pass. Stopping and starting creates streaks. Practice smooth single-pass coating on sacrificial screens.
3
Cause: Emulsion too thick or too thin viscosity
Fix: Some emulsions become noticeably more viscous if they've been refrigerated or stored cold. Bring to room temperature 30 minutes before coating. Conversely, thin emulsion (past shelf life or contaminated) won't hold a clean coat.
4
Cause: Coating with the wrong edge of the scoop coater
Fix: Most scoop coaters have a sharp edge (for the print side) and a rounded edge (for the squeegee side). Using the wrong edge produces uneven coating. Check the coater profile if you're unsure.
5
Cause: Air bubbles in the emulsion
Fix: Bubbles from recent mixing or transfer cause local thin spots. Let emulsion settle 1-2 hours after any transfer or stirring before coating critical screens.
✓ Prevention
Coater maintenance matters. Inspect your scoop coater's sharp edge weekly — a 30-second inspection prevents a week of bad screens. Keep a backup coater on hand so you're never coating with a damaged edge under deadline pressure.
Emulsion Won't Dry Properly
What you're seeing: Coated screens stay tacky for hours longer than expected, or appear dry on the surface but smear when touched. Often correlates with high-humidity weather or seasonal changes.
1
Cause: Humidity in coating/drying area too high
Fix: Above 60-70% relative humidity dramatically slows drying. Install a dehumidifier in your coating room. Target 40-55% RH for fast, consistent drying. Cheap dehumidifiers from any hardware store work fine for typical shop sizes.
2
Cause: Drying cabinet temperature too low
Fix: Cabinet should be 95-105°F (35-40°C) for optimal drying. Below 80°F drying takes 2-3× longer. NEVER exceed 110°F — pre-curing destroys photopolymer emulsions.
3
Cause: Coating layers too thick
Fix: Multiple wet-on-wet coats can take significantly longer to dry than single coats. Each subsequent coat slows the previous one. For thick stencils, dry between coats.
4
Cause: Poor airflow in drying cabinet
Fix: Stagnant humid air around screens slows drying. Install a small fan in the cabinet to circulate air. Ensure the cabinet has an exhaust vent — don't seal it completely.
5
Cause: Coating area too humid (storms, summer)
Fix: Texas and Gulf Coast shops know this well — when ambient humidity spikes during storms, drying slows dramatically. Time your coating sessions for lower-humidity windows when possible, or compensate with stronger dehumidification.
✓ Prevention
Climate control is essential. A simple temperature/humidity monitor in your drying cabinet (inexpensive from any hardware store) tells you in 30 seconds whether your environment is on spec. Most drying problems are environmental, not emulsion issues.
Pre-Exposure or Fogging During Drying
What you're seeing: Stencil washes out only partially. Image areas that should wash out cleanly appear hardened or refuse to develop. Often a gradual problem that builds across multiple screens before being noticed.
1
Cause: Light leak in the drying cabinet
Fix: Even small light leaks slowly pre-expose emulsion during drying. Inspect cabinet seals, door gaskets, and any vents. Cover light leaks with black tape. Black-painted interiors absorb stray light better than reflective surfaces.
2
Cause: Wrong lighting in the coating area
Fix: Standard fluorescent, LED, and daylight all emit UV that pre-exposes emulsion. Switch coating-area lighting to yellow safelight bulbs (sold for darkroom use). Even brief exposure to white light during coating can fog screens.
3
Cause: Coating area exposed to natural light
Fix: Windows, skylights, even reflected sunlight from doorways can fog emulsion. Curtain off coating areas. UV-filtering window film helps.
4
Cause: Screens transported through bright areas
Fix: Carrying coated screens from coating room to drying cabinet through a brightly-lit production floor exposes them. Plan your shop layout to minimize this transit, or carry screens covered with black fabric.
5
Cause: Yellow safelight is too bright or wrong wavelength
Fix: Some 'yellow' bulbs aren't true safelights. Use bulbs specifically sold for screen-printing or darkroom use. Lower the wattage if the safelight area is bright enough to read by — that's too much light.
✓ Prevention
Audit your shop's coating/drying light environment. Walk through with all the safelights on at night — anywhere you see a light leak, a screen is being slowly fogged. For long-term emulsion storage and shelf life issues, store sensitized emulsion in a refrigerator.
Exposure Problems
Exposure is where most diagnosable problems show up — but exposure is also the most-blamed and least-tested step. Before adjusting anything, run a Chromaline 21-step Stouffer wedge test on your specific setup. It takes 5 minutes and tells you exactly what your shop's correct exposure time is.
Stencil Washes Out Completely (Loss of Adhesion)
What you're seeing: The entire emulsion film, or large portions of it, washes off the mesh during development. Sometimes feels slimy or transfers color to your fingers during washout — a key indicator.
1
Cause: Underexposure (most common cause)
Fix: The emulsion didn't cure fully through its thickness. Run a Stouffer 21-step wedge test to find your shop's correct time. Increase exposure in 25% increments until the stencil holds detail without washing out.
2
Cause: Inadequate mesh degreasing
Fix: Emulsion can't adhere to oily or contaminated mesh. Degrease properly before every coating — both sides, with a soft brush, until you see foam, then rinse thoroughly.
3
Cause: Past-shelf-life emulsion
Fix: Sensitized diazo and dual-cure emulsions have 4-6 weeks shelf life at room temperature. Photopolymer emulsions degrade more slowly but still expire. Check the mix date on the container — discard expired emulsion.
4
Cause: Screen not fully dry at exposure
Fix: Wet or damp emulsion can't cure properly. Verify screens are bone-dry before exposure. If your shop has humidity issues, increase drying time and use a dehumidifier.
5
Cause: Water pressure too high during washout
Fix: Excessive pressure tears the stencil off before development finishes. Use a gentle spray at first, gradually increasing pressure only on stubborn areas. Pressure washers should be used cautiously and at distance.
6
Cause: Water temperature too hot
Fix: Hot water (above 100°F) can soften and remove cured emulsion along with the unexposed areas. Use lukewarm water — 90-100°F (32-38°C) — for washout.
7
Cause: Pre-exposed or outdated film positive
Fix: If your film positive has fogged areas (gray instead of clear in the image areas), insufficient UV passes through to expose the emulsion. Check film clarity. Inkjet positives degrade over time — print fresh ones for important jobs.
✓ Prevention
This is the most common emulsion problem and the most preventable. A Stouffer wedge test on every emulsion change and every exposure-lamp replacement keeps you dialed in. If you've never tested your exposure setup formally, the wedge test is worth more than any troubleshooting article.
Stencil Too Hard to Wash Out (Overexposure)
What you're seeing: Image areas that should wash out cleanly resist development. Stencil details — especially fine lines, small text, or halftone shadow areas — fill in or refuse to open up. May require excessive scrubbing.
1
Cause: Exposure time too long
Fix: The most direct cause. Reduce exposure time in 25% increments. Run a Stouffer wedge test to find your true optimal time — most shops have more latitude than they assume.
2
Cause: Light source too strong or too close to screen
Fix: Higher-intensity LED or metal halide lamps cure faster than older fluorescent units. If you've upgraded your light source recently, exposure times need to come down proportionally. Distance from light to screen also matters.
3
Cause: Emulsion coat too thin
Fix: Thin stencils have less material to cure — they reach full cure faster than thicker ones. If you're getting overexposure with the same time that worked before, check that you're coating to the same thickness.
4
Cause: Film positive too thin/translucent in image areas
Fix: If the 'black' areas of your film positive aren't truly opaque, UV passes through them, exposing what should remain unexposed. Hold positives up to bright light — image areas should be solidly opaque, not gray.
5
Cause: Bleed-through from glass-side exposure
Fix: If your exposure unit has reflective surfaces near the screen, UV can bounce around and expose from unintended angles. Black-paint reflective surfaces near exposure units. Use a black backing board behind screens during exposure.
✓ Prevention
Overexposure is easier to fix than underexposure — you reduce exposure time. But it tells you your setup has more cure power than you need, which means you also have more exposure latitude. That's a good problem to have. Step-test exposure on a wedge to find your real optimal time.
Sawtooth or Jagged Stencil Edges
What you're seeing: Stencil edges look jagged, fuzzy, or stepped instead of clean and sharp. Most visible in straight lines and large area edges. Halftone dots may have ragged perimeters.
1
Cause: Coating thickness mismatch with mesh count
Fix: Thin coats on coarse mesh produce sawtooth from the mesh threads showing through. Higher mesh counts (230-355) hide sawtooth better. Add more emulsion coats for coarser mesh.
2
Cause: Coating with wrong scoop coater edge
Fix: The sharp edge of the scoop coater goes against the mesh for sharp stencil edges. Using the rounded edge produces softer, less defined edges. Verify your technique.
3
Cause: Underexposure causing weak edges
Fix: Edges of stencils need full cure to hold definition. Underexposure shows up first at the edges. Increase exposure time and test.
4
Cause: Mesh tension too low
Fix: Loose mesh allows the squeegee to push the stencil edge down during printing, causing inked-edge bleed that looks like sawtooth. Check mesh tension — should be 18-25 N/cm for textile work.
5
Cause: Film positive poor quality at edges
Fix: Inkjet positives can show stepped edges from the printer's resolution. Print at maximum DPI. Vector art reproduces cleaner than rasterized art at small sizes.
✓ Prevention
Sharp stencil edges require all three of: high-quality film positive + proper exposure + good coating technique. None of these alone is enough. For demanding work (fine lines, small text, athletic graphics), invest in all three.
Related products: Screens, frames & mesh · Films & positives
Halftone Dots Filling In or Dropping Out
What you're seeing: Halftone dots — especially in shadow areas (high percentage) or highlight areas (low percentage) — disappear, merge together, or fail to develop properly. Most common in CMYK process and simulated process printing.
1
Cause: Mesh count too low for halftone resolution
Fix: Halftones need high mesh counts to reproduce dots properly. Rule of thumb: mesh count should be 4-5× your halftone LPI. 65 LPI halftones need 260-325 mesh; 55 LPI needs 220-275. Lower mesh causes shadow fill-in.
2
Cause: Exposure not optimized for halftone work
Fix: Halftones require precise exposure — both underexposure and overexposure damage dots. Step-test exposure with halftone targets, not just solid areas. The 'right' exposure for solid graphics may be wrong for fine halftones.
3
Cause: Film positive density insufficient
Fix: Halftone positives need strong black for shadow dots. Inkjet positives often lack sufficient density — try printing through a positive enhancement spray or use specialty inkjet inks. Laser-printed positives have density issues.
4
Cause: Stencil thickness wrong for halftone work
Fix: Thicker stencils make halftone dot reproduction harder — the dots get 'walled in' by emulsion thickness. For halftone work, use thinner stencils (1 coat each side, no additional builds).
5
Cause: Squeegee pressure or angle causing dot gain
Fix: On-press, excessive squeegee pressure or wrong angle pushes ink between halftone dots, causing them to merge. Lighter pressure, sharper squeegee angle (75-80°), and harder durometer help.
✓ Prevention
Halftone work is where shops can find their printing limits. If you're regularly losing halftone detail, consider whether your equipment is matched to the work. Sometimes the right answer is moving to higher mesh, better film, or process-rated emulsion. Sometimes it's accepting that 85 LPI is beyond your shop's current capability.
Related products: Screens & mesh · Films & positives
Washout & Development Problems
After exposure, the unexposed emulsion needs to wash out cleanly while the exposed emulsion stays put. Issues at this stage often look like exposure problems but may have other causes.
Scumming or Haze in Image Areas
What you're seeing: After washout, the image areas (which should be completely open) show a faint film, residue, or cloudiness. Looks like the image didn't fully wash out. Visible most clearly when holding the screen up to light.
1
Cause: Incomplete washout / underexposure combination
Fix: Counter-intuitively, sometimes scumming appears with underexposed screens because the partially-cured emulsion in image areas is harder to wash out. Increase exposure and wash longer. Use a wet vac to remove water and any residue.
2
Cause: Excess humidity during screen drying
Fix: Humidity above 50% causes emulsion to absorb moisture, which can re-cure during exposure. Add a dehumidifier — target 40-50% RH. Even a small bathroom-sized unit handles a typical shop.
3
Cause: Poor positive-to-emulsion contact during exposure
Fix: Air gaps between the film positive and the emulsion cause light scatter, which partially exposes image areas. Check your vacuum frame — pump pressure, blanket condition, glass for scratches. Verify positives are emulsion-side down.
4
Cause: Pre-exposure of the film positive or emulsion
Fix: Light leaks during coating, drying, or storage cause partial pre-curing that appears as haze. Audit lighting in coating/drying areas. Check the safelight area for white-light leaks.
5
Cause: Light scatter through mesh fabric
Fix: White or light-colored mesh reflects UV around image areas during exposure, partially exposing them. Switch to dyed (yellow or orange) mesh for fine-detail work — it absorbs scattered UV instead of reflecting it.
6
Cause: Old or damaged exposure unit glass
Fix: Scratched, hazy, or contaminated glass scatters UV unevenly. Clean glass thoroughly before each session. Replace glass if it has significant scratches or yellowing.
✓ Prevention
Scumming is often a combination problem — humidity + light leaks + light scatter. Fixing one cause may not be enough. Audit your full coating/drying/exposure workflow as a system. Switching from white to dyed mesh alone fixes many scumming complaints.
Related products: Screens & mesh
Weak Stencil (Won't Survive Printing)
What you're seeing: Stencil washes out cleanly but feels thin, soft, or breaks down within the first dozen prints. May show wear at edges where the squeegee passes. Different from washout breakdown — the stencil exists but lacks durability.
1
Cause: Underexposure (the silent cause)
Fix: An under-cured stencil washes out but lacks the cross-linking that gives it print durability. The stencil exists but its molecular structure isn't fully formed. Increase exposure time until the stencil holds together through hundreds of prints.
2
Cause: Emulsion coating too thin
Fix: Thin stencils on coarse mesh can't hold up to print pressure. Either add more coats (especially to the squeegee side) or use a higher-solids emulsion that builds thickness per coat.
3
Cause: Screen not fully dry during exposure
Fix: Damp emulsion can't cure to full strength. Verify drying — when in doubt, add another hour. A dehumidifier in the drying cabinet prevents this entirely.
4
Cause: Wrong emulsion for ink chemistry
Fix: Pure photopolymer emulsions can be too weak for aggressive water-based or discharge inks. For these ink types, use a dual-cure or PVA-SBQ emulsion, and consider a hardener for long runs.
5
Cause: Stencil thickness wrong for mesh count
Fix: High mesh counts (305+) need thinner stencils; coarse mesh (110-160) needs thicker. Wrong combinations produce stencils that work briefly but fail. Match coating to mesh.
✓ Prevention
For demanding work (long runs, aggressive inks, fine detail), apply Murakami MS Hardener after exposure and development. The reclaimable hardener treatment compounds stencil durability without permanently locking up your screens.
Related products: Emulsions · MS Hardener
Stencil Bridging in Fine Detail
What you're seeing: Fine lines, small text, and detailed graphics fail to wash out completely. Adjacent lines merge into single thicker lines. Letterforms with thin counters (interior spaces in 'a', 'o', 'e') fill in.
1
Cause: Stencil too thick for the detail size
Fix: Thick stencils 'bridge' across small openings during washout. For fine detail work, use thinner coats (1 coat each side, no buildup). Higher solids emulsion can help by building strength without excess thickness.
2
Cause: Mesh count too low for the detail
Fix: Coarse mesh threads obstruct fine detail. For text under 8pt and lines under 1pt, use 305+ mesh count. The mesh count limits the detail you can reproduce — fundamental constraint.
3
Cause: Underexposure of small details
Fix: Small image areas need slightly less exposure (more washout time) than large areas. Severe underexposure causes fine detail to bridge while solid areas develop normally. Test with detail-heavy positives.
4
Cause: Excessive water pressure damaging fine areas
Fix: Aggressive washout can blast cured emulsion bridges that weren't fully washed away, producing apparent bridging where the stencil actually opened correctly but the detail was damaged. Use gentle pressure on detail-heavy screens.
5
Cause: Film positive resolution insufficient
Fix: Inkjet positives at low DPI render fine detail with stepped edges that look like bridging. Print at maximum DPI. For very fine work, professional film output service may be needed.
✓ Prevention
Define your shop's minimum detail capability based on equipment. Most textile shops can reliably hold 6pt text and 0.5pt lines with 305 mesh and proper exposure. Customers asking for finer detail than that should be told the limits — or the work outsourced to specialty shops with finer equipment.
Related products: Screens & mesh · Films
On-Press Stencil Problems
Sometimes the stencil washes out perfectly but fails during printing. These on-press failures usually involve mismatch between emulsion type and ink type, or insufficient stencil durability for the print run length.
Stencil Breaks Down During the Print Run
What you're seeing: Stencil starts printing perfectly, then degrades partway through the run — edges soften, image becomes less crisp, print quality drops noticeably. May see emulsion debris in the print or on the squeegee.
1
Cause: Wrong emulsion for the ink type
Fix: Water-based and discharge inks attack standard photopolymer emulsions. For these inks, use a dual-cure or PVA-SBQ emulsion. Plastisol-only emulsions can't survive long water-based runs — check the product's ink compatibility before the next job.
2
Cause: No hardener applied for long water-based/discharge runs
Fix: For water-based or discharge runs over 200 impressions, Murakami MS Hardener dramatically extends stencil life. Apply after exposure and development, then cure in sunlight or 100°F hot box. Reclaimable, so screens aren't lost permanently.
3
Cause: Stencil underexposed (slow failure mode)
Fix: An under-cured stencil may print fine for the first 50-100 impressions but lacks the structural integrity to last. Increase exposure time and test on the next screen.
4
Cause: Squeegee pressure too high
Fix: Excessive squeegee pressure abrades the stencil surface during printing. Reduce pressure to the minimum needed to deposit ink — many shops run higher pressure than necessary. Sharper squeegee blade angles also help.
5
Cause: Squeegee blade damaged or contaminated
Fix: Nicked, hardened, or contaminated squeegee blades catch on the stencil and tear it. Inspect blades — replace or sharpen as needed. Wipe blades between print runs.
6
Cause: Aggressive cleanup chemicals between print stops
Fix: Some on-press cleaning sprays can soften emulsion if used too aggressively or left in contact too long. Use mild on-press cleaners and wipe quickly.
✓ Prevention
Match your emulsion choice to your run length and ink type BEFORE coating. For predictable long runs with water-based or discharge inks, plan to use a hardener. The 10 minutes spent applying hardener saves the screen and the production schedule.
Stencil Edge Lift During Printing
What you're seeing: Edges of the stencil image (or the entire stencil at the frame edges) lift away from the mesh during printing, causing ink to bleed into areas that should be masked. Different from breakdown — the stencil is intact but separating.
1
Cause: Inadequate mesh degreasing before coating
Fix: The stencil only adheres as well as the mesh allows. Skipped or inadequate degreasing produces stencils that look fine on first inspection but lift under press conditions. Re-establish a consistent degreasing protocol.
2
Cause: Mesh contamination from previous reclaim
Fix: Aggressive reclaim chemistry can leave a hydrophobic film on mesh that interferes with new emulsion adhesion. Use a mesh-prep / mesh-conditioner product after reclaim and before coating.
3
Cause: Stencil too thin for the printing forces
Fix: Very thin stencils flex during printing and can lift at edges. Add an extra coat to the squeegee side for press durability.
4
Cause: Ink chemistry attacking the stencil
Fix: Same root cause as breakdown — wrong emulsion for the ink type. Discharge and aggressive water-based inks can lift edges of unsuitable emulsions within dozens of prints.
5
Cause: Mesh tension too low
Fix: Slack mesh allows the stencil-mesh bond to flex during squeegee passes, eventually fatiguing the bond. Check mesh tension — retension or replace if below spec.
6
Cause: Blockout incomplete around stencil edges
Fix: Untouched edges of coated emulsion (the area between your image and the frame) can lift first and propagate inward. Apply Murakami 901 Blockout Red to the perimeter after washout.
✓ Prevention
Edge lift almost always traces back to mesh prep. A consistent degreasing protocol — applied to every screen, every time — prevents most edge lift. Skipping degreasing because 'this screen looks fine' is the most common avoidable shop mistake.
Ink Bleeding or Staining the Stencil
What you're seeing: During printing, ink color appears in stencil areas that should be sealed. May see color migration along stencil edges, into fine detail, or showing through the back of the stencil onto the platen.
1
Cause: Stencil too thin for the ink type
Fix: Thin stencils don't fully seal against aggressive inks. Especially common with discharge inks and some water-based formulations. Build thicker stencils (more coats on squeegee side) or use higher-solids emulsion.
2
Cause: Pinholes letting ink through
Fix: Small pinholes you missed during touch-up let ink through. Always inspect screens under bright light after washout and touch up pinholes before printing.
3
Cause: Stencil pre-stained from previous ink
Fix: If a screen wasn't fully reclaimed between jobs, residual color from the previous ink can bleed through during printing. Always fully reclaim AND haze-remove between different ink colors.
4
Cause: Off-contact too high or too low
Fix: Wrong off-contact distance can cause ink to wick along stencil edges during squeegee separation. Adjust off-contact to your standard for the press.
5
Cause: Excessive squeegee pressure or dwell time
Fix: Pushing too hard or too slowly during the squeegee pass forces ink into stencil weak points. Use lighter pressure and faster passes.
✓ Prevention
Pre-print inspection: hold the screen up to a bright light source and look for pinholes, thin spots, and damaged areas. 2 minutes of inspection prevents 20 minutes of cleanup from a bleeding stencil mid-run.
Related products: Murakami 901 Blockout Red · Emulsions
Reclaim Problems
A screen isn't done until it's been reclaimed properly. Reclaim issues affect every subsequent coating, so getting reclaim right protects your future stencils.
Ghost Image After Reclaim
What you're seeing: After reclaiming a screen, a faint outline of the previous image remains visible on the mesh. The stencil itself is gone, but a 'ghost' image is dyed into the mesh threads. New stencils may show this old image during printing.
1
Cause: Ink residue stained the mesh during printing
Fix: Ink dyes accumulate on mesh during long print runs, especially with discharge and some water-based inks. Use a haze/ghost remover after stencil removal. This is a separate step from emulsion reclaim.
2
Cause: Screen left too long before reclaim
Fix: Reclaim soon after printing ends. Mesh staining gets worse the longer ink residue sits. Same-day reclaim is ideal; within a week is usually still recoverable.
3
Cause: Incomplete stencil removal before haze treatment
Fix: Apply haze remover ONLY after stencil remover has fully cleared the emulsion. Mixing the two chemistries on a partially-reclaimed screen produces poor results.
4
Cause: Insufficient haze removal contact time
Fix: Haze removers need adequate dwell time to penetrate stained mesh fibers. Follow the product's specific instructions — usually 5-15 minutes of contact before scrubbing and rinsing.
5
Cause: Hard water minerals interfering
Fix: Some hard water deposits in your shop water can interfere with reclaim chemistry. If your shop has very hard water, consider a water softener or filter for screen reclamation.
✓ Prevention
Add haze/ghost removal as a standard step in your reclaim protocol — not just when ghosting is visible. Preventive haze removal keeps mesh cleaner long-term and extends overall screen life.
Related products: Screen cleaning chemicals
Emulsion Won't Fully Reclaim
What you're seeing: Stencil remover doesn't completely dissolve the cured emulsion. Pieces of stencil remain stuck to mesh even after scrubbing and rinsing. New emulsion coats over the residue don't adhere properly.
1
Cause: Emulsion + hardener combination requiring specific reclaim
Fix: Permanent hardeners create essentially permanent stencils. If you used a permanent hardener, the screen may be lost. Reclaimable hardeners (like Murakami MS) require following their specific reclaim instructions exactly.
2
Cause: Wrong reclaim chemistry for the emulsion type
Fix: Diazo, dual-cure, and photopolymer emulsions sometimes respond best to different reclaim chemistries. Stencil remover labels list compatible emulsion types — verify match.
3
Cause: Old, dried-out stencil
Fix: Emulsion left on a screen for months becomes harder to reclaim. Try multiple passes of stencil remover with scrubbing between applications. Sometimes longer dwell time alone solves it.
4
Cause: Insufficient contact time / dwell time
Fix: Apply stencil remover, then let it work — often 5-10 minutes — BEFORE scrubbing. Most users scrub too quickly. Let the chemistry do the work first.
5
Cause: Inadequate water pressure for full removal
Fix: After chemistry works on the stencil, you need adequate water pressure to flush out the dissolved emulsion. A pressure washer or strong spray nozzle helps significantly for stubborn screens.
✓ Prevention
Reclaim screens promptly after printing. Adopt a consistent reclaim protocol (stencil remover → haze remover → degreaser before next coating). Skipping the degreasing step before recoating produces stencils that fail unexpectedly.
Related products: Screen cleaning chemicals · MS Hardener (reclaimable)
Permanent Mesh Staining
What you're seeing: Mesh threads themselves have absorbed ink color or chemistry, leaving a permanent stain that haze remover can't fully eliminate. The mesh works mechanically but shows the previous color. New stencils may bleed the stain through.
1
Cause: Mesh has reached end of useful life
Fix: After enough print cycles, mesh fibers lose elasticity and develop permanent staining that can't be reclaimed. Plan to retension or replace mesh as standard maintenance. Most textile mesh lasts 50-200 reclaim cycles depending on chemistry exposure.
2
Cause: Used the wrong reclaim chemistry for that ink
Fix: Some specialty inks (certain water-based dyes, pigment inks) need specific reclaim chemistry. Verify your reclaim products are rated for your ink types.
3
Cause: Hot reclaim chemistry set the stain
Fix: Some haze removers warn against use with warm water — heat can set certain dyes into mesh permanently. Read product instructions and follow water temperature recommendations.
4
Cause: Screen was used past reclaim point
Fix: Once mesh is significantly stained, continuing to use it just adds more stains and damage. Recognize when a screen has reached the end of its useful life and retension or replace.
✓ Prevention
Track your screens' reclaim cycles. Most shops never count, but a simple sticker or marker on the frame tracking 'reclaim count' helps you plan replacement before staining becomes a quality issue.
Related products: Screens, frames & mesh · Screen cleaning chemicals
Prevention Checklist (Stop Problems Before They Start)
Most emulsion problems are preventable with a consistent workflow. Print this list and post it in your screen-making area:
✓
Degrease every screen before coating
Most stencil failures trace back to skipped or inadequate degreasing. Make it a non-negotiable step.
✓
Run a Stouffer wedge test on every emulsion change
Takes 5 minutes. Tells you exactly what your exposure time should be. Skipping it costs hours of troubleshooting later.
✓
Monitor humidity in coating/drying areas
Target 40-50% RH. An inexpensive humidity monitor pays for itself the first time it prevents a bad batch of screens.
✓
Keep the drying cabinet under 110°F (43°C)
Higher temperatures pre-cure emulsion. Install a thermometer in the cabinet.
✓
Use yellow safelight in coating and drying areas
Standard room lighting slowly fogs emulsion. Switch all bulbs in screen-making areas to true yellow safelight.
✓
Label sensitized emulsion containers with mix date
Sensitized diazo and dual-cure emulsions have 4-6 weeks shelf life. Knowing the date prevents using stale emulsion.
✓
Inspect every screen before printing
Hold up to bright light. Catch pinholes, thin spots, and edge issues before they ruin a print run.
✓
Touch up pinholes with blockout BEFORE printing
30 seconds of touch-up prevents 30 minutes of cleanup mid-run.
✓
Match emulsion to ink type
Plastisol-only emulsions don't survive water-based or discharge runs. Read product specs before coating.
✓
Apply hardener for long water-based/discharge runs
Murakami MS Hardener is reclaimable — no permanent screen loss. Compounds stencil life for runs over 200 impressions.
✓
Reclaim screens promptly after printing
Mesh staining gets worse over time. Same-day reclaim is ideal. Add haze removal as a standard step.
✓
Track reclaim cycles per screen
Mesh wears out. Replace before staining becomes a quality issue. Mark frames or use a simple log.
Tools & Products Referenced in This Guide
If you don't have these on hand, they're worth keeping in your shop. Each one solves a common problem covered above.
Screen Degreasers →
Essential for clean stencils. Apply before every coating. Cheap insurance against pinholes, fish eyes, and edge lift.
Chromaline Exposure Calculator (Stouffer Wedge) →
The single most important diagnostic tool for any screen-printing shop. Tells you exactly what your exposure time should be in 5 minutes.
Screen Cleaning Chemicals →
Stencil removers, haze/ghost removers, and reclaim chemistry. Different formulations for different emulsion types and ink chemistries.
Murakami MS Hardener →
Post-exposure stencil hardener. Reclaimable. Pair with any emulsion for extended water-based and discharge runs.
Murakami 901 Blockout Red →
Touch up pinholes and mask frame edges. Red color shows clearly against blue stencils. Essential pre-printing touch-up product.
Screen Printing Emulsions →
Browse the full emulsion lineup. Different chemistries optimized for different ink types and workflow priorities.
Screens, Frames & Mesh →
Quality mesh is the foundation of every stencil. Different mesh counts for different work — coarse for heavy deposit, fine for halftones.
Films & Positives →
Quality film positives are non-negotiable for clean stencils. Inkjet film, laser film, and waterproof options.
When to Call for Help
If you've tried the relevant fixes above and you're still stuck, call us. We've helped hundreds of shops diagnose emulsion problems and we usually figure it out in a 10-15 minute phone call. There's no charge for support.
Tech Support Without the Runaround
Call (512) 454-0505
River City Supply · San Antonio, TX · Supplying screen printers since 2008
Monday-Friday · 9am-5pm CT · [email protected]
When to Contact the Emulsion Manufacturer Directly
For very unusual issues, manufacturer technical support has deep formula-specific knowledge we don't always have. If your problem is highly specific to one brand's chemistry, going direct to the manufacturer is sometimes faster:
Murakami Screen Products →
Chromaline Screen Products →
Saati Screen Products →
Kiwo Screen Products →
Ulano Screen Products →
CCI Screen Products →
Chromaline Screen Products →
Saati Screen Products →
Kiwo Screen Products →
Ulano Screen Products →
CCI Screen Products →
A Note From River City Supply
Emulsion problems are frustrating because the symptoms often look similar but have different root causes. The same "stencil washed out" symptom can come from underexposure, contaminated mesh, past-shelf-life emulsion, or excessive water pressure — each requiring a different fix.
The biggest lesson from helping hundreds of shops with emulsion issues: test your setup formally with a Stouffer wedge before you blame the emulsion. Most shops adjust 3-4 variables when one accurate test would tell them exactly which variable is the actual problem.
If you're still stuck after trying the relevant fixes above, call us at (512) 454-0505. We're not on commission to sell you anything — we just want to help you fix the problem.
