First design free for new accounts. See the proof before you pay. How it works

Vector art conversion

Color Separation for Screen Printing: Spot, Sim Process and Index

We prepare color separation for screen printing as film-ready files: one positive per screen, with the white underbase, chokes, halftones and registration marks already built, so you can output films and burn screens without rework.

On this page
  1. What color separation for screen printing means
  2. Three types of separations
  3. Spot color separations
  4. Simulated process separations
  5. Index separations
  6. Underbase for dark garments
  7. Choke, spread and trap basics
  8. Halftones
  9. Registration marks and film-ready output
  10. Pricing and turnaround
  11. What to tell us when you order

Separations decide how a print looks long before ink touches the shirt. A clean set registers easily, holds its detail on press and prints with a soft hand. A rushed set means extra screens, fill-in, visible underbase and wasted shirts. Our screen printing separations are built by people who think about the press, the mesh and the garment, not just the artwork.

What color separation for screen printing means

Color separation splits a design into one layer per ink. Each layer is printed as a black positive on clear film, and each film exposes one screen. Solid areas print as solid ink, and tones are made with halftone dots. The separations also carry everything the printer needs to line the screens up: registration marks, the color name and the print order.

Three types of separations

TypeBest forHow it printsPrice
Spot colorLogos, text, team designs, flat graphicsEach color is a solid shape or simple halftone in its own ink$25 up to 4 colors, then $5 per extra color
Simulated processPhotos, painted and detailed illustrations on light or dark garmentsA set of spot inks with overlapping halftones that blend into full colorQuoted
IndexDetailed art where you want a bold, grainy look and easy registrationSquare dots of the same size placed side by side, one ink per dotQuoted

Spot color separations

Spot color separations cover most garment work. Each ink is a separate, solid vector shape, colors are specified by Pantone name, and where two colors meet they are trapped so no gaps show on press. If the design uses a tint, such as a lighter version of one ink, it becomes a halftone on that same screen instead of an extra color.

Clean vector art is the starting point. If your artwork is a low-resolution JPG or a screenshot, it needs to be redrawn first; order logo vectorization on the same order and we separate from the new vector file.

Simulated process separations

Simulated process separations reproduce full color art with a limited set of spot inks, often somewhere between six and ten screens including the underbase. Each ink gets its own halftone channel, and the overlapping dots blend visually into shades and gradients. Sim process works well on dark garments where CMYK process printing struggles. Because the number of screens and the work involved depend heavily on the art, simulated process separations are quoted after we see the file.

Index separations

Index separations convert the art into square dots of a single size, each dot assigned one ink with no overlap. The result looks slightly pixelated up close and bright from a distance. Index is forgiving on registration and works well on manual presses. Like sim process, it is quoted per design.

Underbase for dark garments

On dark garments, most ink colors need a white underbase printed first, flashed and then overprinted. Without it, colors look dull and sink into the fabric. A good underbase is not just a white copy of the design:

  • Choked slightly smaller than the top colors so no white edge peeks out.
  • Knocked out where the design uses the shirt color itself, which keeps the print lighter and softer.
  • Halftoned under darker top colors that do not need full white behind them, which reduces ink deposit and improves hand.
  • Paired with a highlight white, printed last, when bright white areas need extra opacity.

If you print discharge or other water-based inks that do not need an underbase, say so in your order notes and we build the separations for that process instead.

Choke, spread and trap basics

No press holds perfect registration, so separations build in small overlaps. Spreading (also called trapping) makes a lighter color slightly larger so it tucks under a darker neighbor. Choking makes a shape slightly smaller, most often the underbase, so it hides under the top colors. The amount is small, usually a fraction of a millimeter, and depends on your press, garment and mesh. Tell us if your shop uses a specific trap width and we build to it.

Halftones

Garment screen printing uses much coarser halftones than paper printing. Common settings:

SettingTypical choiceWhy
Line screenAbout 45 to 65 LPICoarser dots hold better on fabric and on typical garment meshes
Mesh matchMesh count roughly 4 to 5 times the LPIHelps dots sit on the mesh without dropping out
AngleCommonly around 22.5 degreesReduces moire between the dots and the mesh threads
Dot shapeElliptical or roundElliptical dots give smoother midtone transitions

Very small highlight dots and very small shadow gaps tend to drop out or fill in on press, so we keep tonal ranges inside what the mesh can reproduce. If your shop has standard LPI, angle or mesh counts, add them to the order and we use them.

Registration marks and film-ready output

Every separation set is delivered film ready:

  • One black positive per screen, including underbase and highlight white
  • Registration marks in the same position on every film
  • Each film labeled with the ink color, Pantone name where specified, and the print order
  • A composite preview showing the design on the garment color
  • Output at the print size you ordered

We deliver digital files only. You output the films on your own film printer or send the files to a film output service.

Pricing and turnaround

Spot color separations are $25 for up to 4 spot colors, plus $5 for each additional color. A six color job, for example, is $25 plus two extra colors at $5 each. Tell us the garment color so the proof shows every screen, including any underbase and highlight white, before you pay. Simulated process and index separations are quoted.

Standard turnaround is 24 hours, with rush (12 hours) and express (6 hours) available. For quoted work, the clock starts when you accept the quote. Shops ordering separations every week can also add redraws, DTF files and embroidery through the same dashboard, as described on our page for print shops.

What to tell us when you order

  • Garment colors the design will print on
  • Ink colors, by Pantone number if you have them
  • Print size and placement
  • Your press setup: manual or automatic and the number of heads
  • Preferred mesh counts, LPI and trap width, if your shop has standards
  • Ink type, such as plastisol, water-based or discharge

For the full range of vector work, including redraws and custom art, see vector art conversion.

Need seps for your next run? Upload the art and see your separation price before you submit.

Frequently asked questions

What LPI should I use for screen printing halftones?

Most garment printers use about 45 to 65 LPI. Lower values are easier to hold on common meshes and on textured fabrics, while higher values show finer detail but need higher mesh counts and tighter press control. A common rule is a mesh count roughly 4 to 5 times the LPI.

Can you separate a photo for screen printing?

Yes, with simulated process or index separations. Both reproduce photographic tones with spot inks and halftones. The number of screens depends on the image and the garment color, so photo separations are quoted after we see the file.

Do you print the films or burn the screens?

No. We deliver digital, film-ready separation files. You print the films on your own film printer, or send the files to a film output service, and burn the screens in your shop.

What is the difference between choke and trap?

A choke shrinks a shape slightly so it hides under the colors around it, which is how an underbase is usually handled. A trap, or spread, grows a shape slightly so it overlaps its neighbor. Both cover small registration shifts on press so no gaps or white edges show.

Can you match specific Pantone ink colors?

Yes. Each film is labeled with the Pantone ink name you specify, and the composite preview uses those colors. Mixing and matching the physical ink happens in your shop, so the final color depends on your ink system and garment.

Do water-based and discharge prints need different separations?

Often, yes. Discharge ink removes the garment dye, so many designs on dark cotton do not need a white underbase at all. Water-based inks can also need different halftone and trap choices. Tell us the ink type in the order and the separations are built for it.

Send us your logo. See the proof before you pay.

Flat prices from $14, every machine format included, and a 24-hour standard turnaround. Your first design is free up to $24.

Start an orderPrices