What a screen is
A screen is a rigid frame, usually aluminum on production presses, with fine polyester mesh stretched drum-tight across it. The name "silk screen" survives from the days when that mesh was silk. The number of threads per inch is the mesh count: a coarse 110 mesh lets a lot of ink through, while a fine 230 or 305 lets through much less and holds smaller detail.
The mesh is coated with emulsion, a light-sensitive liquid that hardens wherever UV light reaches it. Block the light in the shape of your design and that part of the coating stays soft and rinses out with water. What remains is a stencil: open mesh where ink should pass, hardened emulsion everywhere else. One screen carries one ink for one print location, so a three-color front with a one-color back needs four screens before any underbase is counted.
The process, step by step
1. Artwork and separations
The design is split into one layer per ink, called separations. A two-color logo becomes two black-and-white films; a photo printed on a black shirt can become eight or more. Dark garments usually add a white underbase layer so the colors on top stay bright. File prep is covered in preparing artwork for screen printing, and the separation styles in spot color vs simulated process vs CMYK.
2. Film positives
Each separation is printed as dense black on clear film so it blocks UV light completely. Some shops skip film with computer-to-screen (CTS) systems that print a light-blocking mask straight onto the coated screen. Either way, registration marks on every separation let the printer line the colors up on press.
3. Coating and drying the emulsion
The mesh is degreased first, because oils from hands and old ink stop emulsion from bonding. A metal trough called a scoop coater then spreads emulsion across both sides in a smooth, even layer. Screens dry flat in a dark, low-humidity cabinet, since stray light and moisture both spoil the coating. Coating thickness matters later: a thicker stencil deposits more ink, which is how high-density prints get their height.
4. Exposing and washing out
The film goes onto the coated screen, and an exposure unit floods it with UV light. Too little light leaves a soft stencil that breaks down mid-run; too much closes up fine lines and halftone dots. Exposure times are dialed in for each emulsion and light source with test strips. Afterward a gentle water spray washes out the unexposed design, the screen dries, pinholes are touched up with blockout, and the edges are taped so ink cannot leak around the stencil.
5. Setting up and registering the press
Screens lock into the print heads of a press. The garment is loaded onto a flat support called a platen (or pallet), with a light spray adhesive holding it still. The printer aligns each screen to the registration marks and runs test pieces until every color lands exactly where it should. That alignment is called registration, and on a multi-color job it is usually the slowest part of setup.
6. Flood and print strokes
Ink is spooned onto the screen above the image. A flood stroke pulls a floodbar across the screen to fill the open mesh without touching the shirt. Then comes the print stroke: a rubber squeegee presses the mesh onto the garment and shears ink through the openings. The screen sits a small distance above the garment, called off-contact, so the mesh lifts away right behind the blade and leaves a clean edge. Blade hardness, angle, pressure, speed and the number of strokes all change how much ink lands, and mesh count and print feel explains how.
7. Flashing between colors
Wet ink under wet ink can smear or get lifted by the next screen. A flash unit, an overhead heater, sets the surface of a layer in a few seconds so the next color prints cleanly on top. A flash cure is standard after a white underbase, and many printers print the white, flash it, and print it again for full opacity. Colors that do not need a dry base are often printed wet-on-wet with no flash, which keeps the press moving.
8. Curing in the dryer
The printed garment rides a conveyor belt through a tunnel dryer. Plastisol never air-dries: it only fuses once the entire ink film, not just its surface, reaches the cure temperature on the maker's data sheet. For standard plastisol that figure is commonly 320°F (160°C), and low-cure lines are rated lower, with one major line listing 266–320°F (130–160°C). Water-based ink has to lose its water before it can reach temperature, so it needs a much longer stay in the dryer. Under-cured prints look fine coming off the belt and then crack or wash out, which is why careful printers check with temperature probes or heat strips and stretch- and wash-test samples.
9. Checks, folding and packing
Finished pieces are checked for registration, coverage, placement and cure, then counted by size, folded and packed. When the run is over, ink is scraped back, the emulsion is stripped with a chemical remover, and the mesh is degreased so it can be coated for the next job. Keeping the separations on file is what makes a reorder quicker than the first run.
Manual vs automatic presses
Both kinds of press make the same kind of print. The difference is who, or what, pulls the squeegee.
| Manual press | Automatic press | |
|---|---|---|
| How the stroke happens | A printer pulls every squeegee stroke by hand | Motorized print heads stroke on a timed cycle |
| Consistency | Varies with the printer's technique and fatigue over a long run | Identical pressure, angle and speed on every piece |
| Color heads | Fewer, which limits colors and flashes per design | More heads, so more colors, flashes and underbase hits in one rotation |
| Where it shines | Samples, short runs, awkward items, hand-controlled specialty work | Long runs, many-color designs, halftone and simulated-process work |
| Speed | Limited by one person loading, printing and unloading | Much faster once registered, especially with a second person unloading |
A skilled manual printer can match an automatic on a simple one- or two-color job. The automatic pulls ahead on long runs and on detailed multi-color art, where every stroke has to match the one before it.
Print faults and what causes them
Knowing the common defects makes it easier to check a delivery and to talk to a printer about a problem:
- Cracking or ink washing out after a few washes points to under-curing: the ink film never reached its full cure temperature for long enough.
- Gaps or white halos between colors mean the screens drifted out of registration, or the separations had too little trap or too little choke on the underbase.
- Specks of ink outside the design come from pinholes in the stencil that were not blocked out.
- Jagged, saw-toothed edges on lines and type usually mean the stencil was too thin or under-exposed, so the mesh pattern shows at the edge.
- A pink or grey cast on white ink over red, black or heathered polyester is dye migration, the garment's dye bleeding into the ink during cure.
- Scorch marks or a yellowed square on a light garment come from too much heat at the flash or in the dryer.
- Fibers poking through the print after washing, called fibrillation, happen when a thin deposit sits on a fuzzy fabric. Smoother ring-spun cotton and a slightly heavier deposit both help.
The inks that go through the screen
Three ink families do most garment work. Plastisol sits on top of the fabric as an opaque, forgiving layer. Water-based ink soaks into the fibers for a softer feel. Discharge ink strips the dye from cotton and replaces it with color. The screen printing inks guide covers all three in depth, and plastisol vs water-based ink puts the two most common side by side. Raised and decorative effects have their own pages: puff and high-density ink and specialty inks such as metallic, glow and foil.
When screen printing makes sense
Screen printing is setup-heavy and run-cheap. Films, screens and registration take the same effort for 24 shirts as for 2,400, while each extra print adds seconds. That shapes when it is the right call:
- Larger runs of one design. Setup is shared across every piece, so the cost per shirt falls as quantity rises. What drives screen printing cost breaks the structure down.
- Spot-color art. Logos, type and flat illustration in a handful of colors are what the process does best, with each ink mixed to a spot color reference.
- Bright color on dark garments. An opaque underbase lets white, yellow or neon read crisply on a black shirt.
- Effects. Puff, high density, discharge, shimmer and glow all come from screen printing inks.
- Longevity. A well-cured print commonly outlives the garment's fabric.
It is a weak fit for one-offs, for many different designs in tiny quantities, and for a different name on every shirt. DTG and DTF handle those without screens: see screen printing vs DTG and types of shirt printing compared. Where a job sits between the two, the method page for screen printing and the one for DTG printing show what each looks like in practice.
What to ask before you order
- Which ink will be used, and does the blank suit it? Discharge, for example, needs reactive-dyed cotton.
- How many screens does the job need once any underbase or highlight white is counted?
- Will you see a mockup with print sizes and placement, and is a strike-off (a test print on the real garment) available for color-critical work?
- How does the printer confirm the ink is fully cured?
- What is kept on file for a reorder: films, separations, or the screens themselves?
Sources
- Wilflex Epic Matte Black plastisol ink, product and cure data (ScreenPrinting.com), checked 2026-10-04
- Wilflex Epic Rio plastisol ink, low-cure range (ScreenPrinting.com), checked 2026-10-04
- Green Galaxy Comet White HSA water-based ink, cure and dwell data, checked 2026-10-04
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