What file format is best for screen printing artwork?

Adobe Illustrator (.ai) or .eps files are the industry standard for screen printing. They're fully vector, scalable without quality loss, and support proper spot color separation. PDFs are sometimes accepted but should be saved from Illustrator with editable content preserved. Never submit JPEGs or PNGs as final screen printing artwork files.

Do I need to separate colors myself before sending to a screen printer?

Not always — many shops will separate for you, sometimes for a fee. However, providing properly separated, Pantone-assigned artwork dramatically reduces errors, prevents color surprises, and speeds up production. If your design has more than 4 colors or includes halftones, professional pre-separation is strongly recommended before submitting to any shop.

What is an underbase and when do I need one?

An underbase is a layer of white ink printed first on dark garments. Without it, the garment color bleeds through translucent inks, muting your colors. Any design printing on black, navy, charcoal, or other dark fabrics needs a white underbase layer. It should be slightly choked (reduced) to prevent white halo around the design edges.

What resolution should screen printing artwork be?

Vector artwork doesn't have a resolution — it's resolution-independent. If your design includes raster elements (textures, photos), they should be at least 300 DPI at final print size. For halftone elements, the raster resolution needs to be at a minimum 8–10x the intended LPI — so for 45 LPI halftones, your raster base should be at least 360 DPI.

How many colors can a screen print have?

There's no hard limit, but cost increases with each color since every color requires its own screen. Most shops accommodate 1–8 spot colors comfortably. Simulated process printing can achieve photographic results with 6–8 carefully separated spot colors. Designs exceeding 8 colors are often better suited to DTF or DTG printing for cost efficiency.

What is trapping and why does it matter for screen printing?

Trapping compensates for the slight misregistration that naturally occurs between color passes on a screen printing press. Without trapping, a tiny shift can expose the garment or underbase between two adjacent colors as a white or garment-colored gap. Typically a 0.25–0.5pt spread or choke on lighter colors is sufficient for most garment screen printing applications.

Can I use gradients in screen printing designs?

Yes, but gradients must be converted to halftones — a field of dots that simulate the gradient through varying dot size. The halftone frequency (LPI) must be matched to the shop's mesh count. Gradients that simply fade to the garment color are the easiest to handle. Gradient-to-gradient transitions require simulated process separation and are significantly more complex to produce.

How to Prepare Artwork for Screen Printing

Screen printing rewards preparation. When your artwork is set up correctly, a skilled press operator can pull clean, vibrant prints all day. When it isn't, you get ink bleed, misregistration, blown-out halftones, and a shop that adds rush fees every time your files land in their inbox.

This guide covers everything a production artist or shop owner needs to know about preparing artwork for screen printing — from file format basics to advanced color separation and trapping.

Why Screen Printing Artwork Is Different From Other Print Processes

Unlike inkjet or laser printing, screen printing lays ink down one color at a time through a physical mesh screen. Each color in your design requires its own screen, its own exposure, and its own pass through the press. That physical reality drives every artwork requirement in this process.

Artwork that works perfectly in digital formats — a JPEG, a PNG, a layered Photoshop file — can be completely unusable for screen printing if the colors aren't separated, the edges aren't clean, or the resolution isn't matched to the halftone frequency the shop uses.

"I've seen files come in from major agencies that were completely unusable for screen printing. Beautiful-looking designs, but the colors were blended RGB gradients on a flattened layer. We had to rebuild them from scratch." — Common feedback from screen print production departments.

Step 1: Start With the Right File Format

The gold standard for screen printing artwork is a vector file — specifically an Adobe Illustrator .ai or .eps file with all fonts outlined and no linked images. Here's why:

Infinitely scalable — a vector file can go from a chest logo to a billboard without losing a pixel of sharpness
Clean, hard edges — the pen tool paths that define vector shapes are mathematically precise, which translates directly to clean screen edges
Editable color channels — each spot color lives on its own layer or swatch, making separation straightforward
No rasterization artifacts — no anti-aliasing, no soft edges, no blending modes that fall apart at film output

If your artwork starts as a raster (JPEG, PNG, PSD), it needs to be properly vectorized before screen printing setup can begin. A low-quality auto-trace won't cut it — the paths need to be clean, anchor points minimal, and curves smooth.

→ Get your logo properly vectorized for screen printing

Step 2: Convert Colors to Spot Colors (Pantone)

RGB and CMYK are for digital printing. Screen printing uses spot colors — individual, pre-mixed ink formulas, usually referenced by Pantone Matching System (PMS) numbers.

Here's what the conversion process looks like in practice:

Assigning Pantone Colors

Open your Illustrator file and open the Swatches panel
Delete all global swatches that aren't part of your design
For each color in your design, select all objects of that color and assign a Pantone Coated or Uncoated swatch
Name each swatch clearly: PMS 186 C, PMS 123 C, White, Black, etc.
Set each swatch to Spot Color (not Process) in the swatch options

Underbase White

If you're printing on dark garments, your shop will need a white underbase — a layer of white ink printed first to make overlying colors opaque and vibrant. This should be a separate layer in your file, often created by merging all color objects, expanding, and slightly choking them (reducing by 0.5–1pt) to avoid white halo.

Ink Count and Cost

Every color is a screen, and every screen adds cost. A good production artist always tells the client: 6 colors costs roughly double what 3 colors costs when factoring in screen fees, setup, and press time. Designing with ink count in mind is a real service.

Step 3: Color Separation — The Heart of Screen Printing Prep

Color separation is the process of splitting your design into individual layers, one per ink color, so each can be output to its own film positive and burned to a screen.

Spot Color Separation

For flat-color designs (no gradients, no photographic elements), spot separation is straightforward:

Each color lives on its own layer
Objects are filled with 100% spot color, no transparency
Overprint settings are used intentionally — black is typically set to overprint, lighter colors are knocked out

Simulated Process Separation

For photographic or gradient-heavy designs printed on garments, simulated process uses halftone dots of spot colors to simulate a full-color image. This is a specialized skill:

Requires dedicated separation software (Separation Studio, Spot Process, or manual Photoshop channels)
Halftone frequency (LPI) must match the mesh count — a 160-mesh screen typically handles 45 LPI; a 230-mesh can push 65 LPI
Dot shape matters: elliptical dots blend better at midtones than round dots
Maximum ink density per color rarely exceeds 85% to avoid ink starvation and muddy prints

→ Have our team build your color-separated files from scratch

Step 4: Halftones and Gradients

Gradients are one of the most common artwork problems in screen printing. A gradient that fades to white, for example, needs to be converted to a halftone — a field of dots that get smaller and smaller as the gradient fades.

Key Halftone Specs

Mesh Count	Max LPI	Best For
110 mesh	35 LPI	Heavy ink deposits, specialty inks
160 mesh	45 LPI	Standard plastisol, most garment printing
200 mesh	55 LPI	Fine detail, discharge printing
230 mesh	65 LPI	Fine halftones, water-based inks

Always confirm LPI and dot shape with your print shop before finalizing halftone artwork. A mismatch between your file output and the shop's preferred mesh count causes moiré patterns — that shimmering grid pattern that appears when halftone frequencies interfere with the mesh.

Step 5: Trapping

Trapping prevents white gaps from appearing between colors due to slight misregistration on press. Even a well-maintained press can shift 1/32" between colors — and that's enough to show garment between two adjacent ink layers.

How to Trap Correctly

Spread trap: Expand the lighter color slightly (0.25–0.5pt) so it overlaps under the darker color
Choke trap: Shrink a lighter shape inside a darker background
Overprint: Set black and very dark colors to overprint so they print on top without knocking out the layer beneath

In Illustrator, use Object > Expand Appearance, then Pathfinder > Unite to combine shapes before applying manual traps. Automated trapping in Illustrator's Trap filter is a starting point, but manual trapping is more reliable for complex designs.

Step 6: Artwork Sizing and Safe Zones

Screen print locations have standard size constraints:

Full front chest: Up to 12" × 14"
Left chest: 3.5" × 3.5" to 4" × 4"
Full back: Up to 13" × 15"
Sleeve: 3" × 11" (varies by garment)

Always set up artwork at 100% print size in your file. Never ask a shop to scale your artwork to fit — this shifts any embedded raster elements, throws off halftone frequencies, and can break trapping values.

Step 7: File Delivery Checklist

Before you send files to a screen printer, run through this checklist:

→ Use our free Artwork Readiness Checklist

Real Production Scenario: The 6-Color Band Shirt

A regional concert promoter came to us with a PNG of a band logo — full-color, gradient sky background, hand-lettered type, about 1200×800px at 72 DPI. The client wanted 500 shirts, black garments, 6 colors max.

Here's what we did:

Rebuilt the type from scratch in Illustrator using the closest matching typeface, then modified letterforms to match the hand-lettered original
Simplified the gradient sky into 3 flat spot colors that simulated the gradient without requiring halftones
Assigned PMS colors: 286 C (blue), 1235 C (gold), 7417 C (red-orange), 877 C (metallic silver), Black, White underbase
Set up the underbase: merged all layers, expanded, choked 0.75pt, placed on bottom layer
Trapped all adjacent colors: 0.35pt spread on lighter colors
Output at 13" × 15" (full back) and 4" × 4" (left chest)

The shop printed all 500 pieces with zero remake requests. That's what proper prep looks like.

Common Mistakes to Avoid

Sending RGB files: RGB colors shift unpredictably when converted to Pantone by the shop
Using raster effects in Illustrator: Drop shadows, glows, and blurs create transparency that breaks separation
Ignoring minimum stroke widths: Lines thinner than 0.5pt can plug or lose definition on press
Forgetting to outline fonts: Missing fonts get substituted automatically, breaking your layout
Not communicating ink type: Discharge, water-based, and plastisol each have different coverage and underbase requirements

→ Submit your files for a free artwork review before sending to your printer

The Bottom Line

Preparing artwork for screen printing isn't just about making something look good on screen — it's about building files that a press operator can actually use. Spot colors, clean vectors, proper trapping, correct LPI halftones, and a delivered-at-size file are the difference between a smooth production run and an expensive headache.

If you're not confident your files meet these specs, don't guess. Get them reviewed by a production artist who does this every day. Send us your files and we'll tell you exactly what needs to be fixed — no charge for the review.