At Pulse Merch in Cedar City, we pick spot separations for flat-color logos and simulated-process halftones for photos and gradients, every time, no exceptions. On the garment side, order dark shirts or hoodies, and you need a white underbase built into the separation before anything else happens. Whatever method fits your art, the file that leaves prepress has to carry registration marks and press-ready plates. Skip that step and the job stalls on press, not in the office.
Spot Color vs Simulated-Process Separations: Which To Pick And Why
Spot color separations work when your art is a logo, a team name, or anything built from a handful of flat, defined colors. Each color gets its own plate, ink stays consistent from shirt to shirt, and registration is straightforward because you’re not chasing dozens of halftone dots trying to line up. A three-color construction company logo with sharp edges is a textbook spot job. This is also the most durable long-term approach for anything that needs to survive years of laundering, because thick, opaque ink lays flatter and holds its edge better than tightly packed halftone dots.
Simulated process earns its keep on photographic art, gradients, and anything with more tones than you could reasonably assign individual spot plates. It uses halftone dots at varying sizes to trick the eye into seeing smooth blends and shading, the same principle as a newspaper photo, just tuned for fabric instead of paper. A tour poster with a photo-realistic band image or a sunset gradient behind a logo almost always needs simulated process. Anatol’s breakdown of separations frames this well: choose simulated process for tonal artwork and spot colors for flat-color logos, and that single rule solves most of the guesswork before you even open your software.
True CMYK process, the four-color method borrowed from offset printing, shows up less often in garment work than people expect. It can reproduce photographic detail, but it struggles on textured or dark fabric because the process relies on ink transparency and a bright white base to work correctly. Most shops reserve it for light-colored shirts with detailed full-color art where simulated process would need too many screens.
Cost and setup scale directly with how many screens a job needs:
- Spot jobs typically run a handful of colors, keeping screen charges and burn time low.
- Simulated process jobs often require more screens, including a white underbase and highlight white, which raises both setup cost and press time.
- CMYK process usually needs at least four screens plus additional passes like underbase and highlight on garment work.
- More screens means more registration risk, so simulated process quotes often account for a longer proofing pass.
Software And Tools For Making Separations
Manual separation still has a place. Photoshop with channel masking, spot color plugins, and careful use of the Pantone library gives you total control over every dot, which matters on tricky artwork with overlapping transparencies. Illustrator or a vector PDF workflow handles spot-color logo work cleanly, since flat vector shapes convert to plates without the halftone math that raster art requires.
For production speed, dedicated separation software changes the math entirely. Sep Studio NXT automates both simulated-process and vector PDF separation, and it builds in underbase generation, choke and spread controls, pressmark placement, and ink and textile libraries that plug straight into a RIP for output. QuikSeps covers similar ground with simulated process, true CMYK, and index color workflows, and it lets a shop preview halftones and export film even without a full RIP setup, per QuikSeps’ own feature list.
AI Separations represents the newer automated tier. It generates press-ready plates, including underbase and registration marks, in seconds, and it runs a preflight check nicknamed Print Doctor to flag low-resolution or printing issues before a screen ever gets burned. It’s fast, but automated output on a complex gradient still benefits from a human pass to fix edge artifacts the software misses.
A RIP (raster image processor) is where separations become film or direct-to-screen output. Whichever software you use, it needs to hand off LPI, angle, and trap settings the RIP can read without manual reentry, or you introduce error at the last step of the chain.
Preparing Artwork Files Before Separation
Start with the highest-quality source file you have. Vector art (AI, EPS, or PDF) is ideal for spot work because it scales without quality loss. For raster art headed into simulated process, 300 DPI at final print size is the floor, not the target, since anything softer turns into blurry, indistinct halftones once it hits a mesh screen.
- Flatten strategically. Convert all text to outlines before handoff so no font substitution happens on someone else’s machine, but keep color layers separate until separation is complete.
- Preserve named spot colors. If the client’s brand guide specifies a Pantone, name that swatch exactly in the file. It saves a round of email back-and-forth.
- Pick the right working color mode. Accept RGB client files, but do the actual separation work in a mode that maps cleanly to spot or CMYK plates rather than trying to eyeball conversions.
- Lock transparency effects. Drop shadows, glows, and blend modes need to be rasterized and accounted for in the separation, not left live, or they’ll separate unpredictably.
- Add registration and crop marks. Every plate needs consistent pressmarks in the same position, plus bleed if the design runs to the garment edge.
Shops that receive vector PDFs with pre-named spot colors spend noticeably less time on manual fixes than shops working from low-res JPEGs pulled off a phone. That single difference in file quality is the most common reason one job’s proofing takes ten minutes and another takes an hour, a pattern Pulse Merch’s own file checklist was built to prevent before it starts.
What LPI And Screening Settings Actually Do On Press
Lines per inch, or LPI, controls how fine your halftone dot pattern is, and it has to match your mesh count or you’ll fight moiré patterns and dot gain for the whole run. Coarser mesh (110 to 156 mesh) generally pairs with 35 to 45 LPI, while finer mesh (200 mesh and up) can handle 55 LPI or higher for detailed simulated-process work. Vendors and separation software document these pairings because guessing wrong shows up immediately as a fuzzy, muddy print.
- Use elliptical or round dot shapes for most simulated process work; they hold detail better than square dots at small sizes.
- Rotate screen angles between channels (commonly 15, 45, 75, and 90 degrees) to prevent the layered dot patterns from creating visible moiré.
- Cap highlight dots around 3 to 5 percent tone and shadow dots below 90 to 95 percent, since anything past that either disappears in exposure or fills in during printing.
- Go coarser on textured or heavy fabric like fleece, and finer on smooth cotton or performance polyester where the weave won’t fight your dot structure.
Our own halftone sampling checklist exists because these numbers aren’t universal. A setting that looks perfect on a proof sheet can still block up on press if the ink viscosity or squeegee pressure shifts even slightly, which is why we sample before committing a full run.
Underbase, Trapping, And Registration That Hold On Press
A white underbase goes down first on any dark garment, and it needs enough opacity, generally two passes with a flash cure between them, to keep colors printed on top from looking muddy or gray. Skimp on the underbase and every color on top reads dull no matter how good the separation looks on screen.
Choke and spread control how much adjacent color plates overlap or pull back at their edges. A typical choke on a white underbase runs about 0.5 to 1 pixel smaller than the art on top of it, which prevents a visible white halo around your colors. Spread works the opposite direction, slightly growing a shape so it fully covers the layer beneath, and it’s what keeps small text or thin lines from showing gaps when registration drifts even a hair on press.
Registration marks need to sit in the same fixed position on every single plate, ideally outside the print area so they don’t interfere with the final image. Press operators align to those marks first, then check a test print against the approved proof before running production quantities.
Pro Tip: Stage your darkest overprint colors last and keep flash cures consistent between passes. Uneven flash timing is the single most common cause of ghosting, where a faint double image appears because the ink underneath shifted slightly before the next color hit it.
Exporting Separations For Film Or Direct-To-Screen Output
Getting a separation from your screen to a usable plate comes down to matching your export format to how the shop actually exposes screens.
- Choose the right export format. EPS or PDF files with pressmarks work for vector spot jobs; high-resolution TIFF positives are standard for halftone work headed to film; layered PSDs still get used for shops doing manual channel editing.
- Set your RIP correctly. LPI, halftone angle, ink simulation profile, and trapping settings all need to transfer from your separation software, not get reset to RIP defaults.
- Decide between film and direct-to-screen. Film positives remain reliable and let you hold onto physical proofs; direct-to-screen (CTS) skips film entirely and often produces sharper dot edges, but it demands the exposure unit be calibrated correctly.
- Check the proof against your checklist. Verify registration marks align, the underbase covers fully, choke and spread read correctly at the edges, and the recommended mesh count matches what’s specified before a single screen gets burned.
Skipping the proofing step to save twenty minutes is how a 500-shirt run turns into a 500-shirt reprint.
What Actually Goes Wrong In Production
The single most common mistake we see is client art pulled straight from a website at 72 DPI, then blown up to fit a full chest print. It looks fine on a monitor and turns into a soft, pixelated mess the moment it hits halftone screening, because there’s no detail in the file to screen in the first place. We catch it before separation, but it costs everyone time that a proper vector file would have saved.
The second mistake is color count creep on small runs. A client wants an 8-color simulated-process design for a 24-piece order, and the math just doesn’t work; screen charges alone can cost more than the shirts. We’ll usually recommend simplifying to a 3 or 4 color version that still reads well but doesn’t burn the client’s budget on setup they’ll never earn back in per-unit savings.
On durability, the tradeoff between plastisol and water-based or discharge ink is real and worth understanding before you pick a decoration method. Heavy plastisol lay gives you vivid, opaque color that holds up to washing, but it can crack over time on fabric that stretches a lot, think fitted athletic wear. Water-based and discharge inks sit softer into the fabric and feel better against skin, but they need compatible fabric and careful chemical handling to perform consistently.
The ink cracked at the shoulders within a season of regular wear because heavy plastisol doesn’t flex well with that fabric’s stretch. The fix was resetting expectations: for high-stretch performance fabric, embroidery or a softer ink formulation holds up far better than a heavy simulated-process print ever will.
- Low-resolution source art is the top cause of muddy halftones.
- Too many colors on a short run kills the budget before it kills the print quality.
- Heavy ink lay on stretch fabric is a durability risk, not just an aesthetic choice.
- Embroidery outperforms printing for logos on structured items like caps and jackets where flex isn’t a factor.
What To Put On Your Spec Sheet When Ordering Separations
Send your shop a spec sheet, not a vague description, and the quote comes back faster and more accurate.
- State your desired method up front: spot color or simulated process, not just “make it look good.”
- Include exact Pantone references or ink brand names if you have brand color standards to hit.
- Confirm garment color, since dark garments trigger underbase requirements that change both cost and screen count.
- Note your print area size and placement so mesh and screen size get chosen correctly the first time.
- Specify deliverables you expect back: press-ready PDFs, flattened TIFFs, a proof sheet, or full auto-separation handled in-house.
Turnaround and cost both scale with color count and underbase requirements, so a simple 2-color spot job will always move faster and cheaper than an 8-color simulated process piece on dark garments. The biggest red flag in a job request is vague art references, “make it pop” with no file attached, since that guarantees a slower quote and more revision rounds than a request that arrives with a clean vector file and a filled-out spec sheet.
Cleaning Up Separations After Automatic Processing
Automated tools like AI Separations and Sep Studio NXT get you most of the way there fast, but they aren’t the finish line on complex art. The most common cleanup pass involves edge artifacts around small text or fine lines, where automated masking sometimes leaves a faint halo or slightly jagged edge that a manual touch-up in Photoshop fixes in minutes.
Trapping is the second area worth a manual check. Automated software applies a default choke or spread value across the whole design, but a logo with both fine text and bold shapes often needs different trap values in different areas. We’ll manually adjust choke on small text separately from the broader shapes to keep both legible and clean.
Halftone dot cleanup matters most in shadow and highlight areas. Automated separation sometimes lets shadow dots blow out past 95 percent tone or highlight dots drop below the printable minimum, and both extremes cause detail loss on press. Pull those channels into a levels or curves adjustment and pin them back into a printable range before sending the file forward.
Color channel isolation is worth a final pass too. Automated tools occasionally bleed a color slightly into an adjacent channel on complex gradients, which shows up as unwanted tint in an area that should be clean. A quick channel-by-channel review catches this before it becomes a wasted screen.
Handling Gradients And Blends Without Losing Detail
Gradients separate into halftone dot patterns that gradually change size across the transition, mimicking the visual effect of a smooth blend using nothing but varying dot density. The trick is making sure the gradient’s tonal range fits within your printable dot range, generally 3 to 95 percent tone, so neither end of the blend drops out or blocks up on press.
Short, tight gradients (a quick fade from one color to another within an inch or two) are the riskiest, because there’s less room for the dot pattern to transition smoothly. Stretch the gradient over more physical space when the design allows it, and the halftone transition reads far cleaner on fabric.
Multicolor blends, where one gradient shifts through several hues rather than light-to-dark on a single color, need extra attention to screen angle assignment. Each color channel needs its own angle to avoid the dot patterns stacking into a moiré pattern right where the blend is most visible. This is also where a coarser mesh can actually hurt you, since fewer dots per inch means less room to render a smooth transition, so gradient-heavy art often pushes a job toward finer mesh even if the rest of the design would tolerate something coarser.
Owner-Operator Perspective: When Automated Separations Are Enough
We hand-edit separations when the client’s logo has fine text, tight registration tolerances, or a gradient that automated tools handle roughly. Automated separations from tools like AI Separations are genuinely good enough for straightforward simulated-process photo art or simple spot logos, and we’ll accept that output without touching it on those jobs.
The line is quality threshold, not price. A repeat corporate client running 500 polos wants consistency across every reorder, so we’ll manually verify separations even when the automated version looks fine at a glance. A one-time event shirt with simple art doesn’t need that level of scrutiny. The tradeoff is turnaround: manual review adds a day, sometimes two, but it’s the difference between a reorder matching perfectly and a client noticing their logo shifted slightly six months later.
— Cohen
Getting Production-Ready Separations From Pulse Merch
Pulse Merch handles color separations in-house in Cedar City, which means your job doesn’t sit in a queue waiting on a third-party prepress vendor before it ever reaches a screen. We build spot separations for flat logo work and simulated-process halftones for photo and gradient art, with underbase, choke and spread, and registration handled as part of the standard workflow, not an upcharge you find out about later.
When you request a quote, expect us to ask for your source art, confirm garment color and print area, and send a proof before anything goes to press. That’s how we catch a low-res file or a color count problem before it costs you a reprint. If you want to see how the full production process fits together before you commit to an order, our screen printing process breakdown walks through what happens between your approved art and a finished shirt. Ready to move forward? Get a quote and tell us what you’re printing, and we’ll tell you exactly what file we need back from you.
Sources
For deeper technical grounding, Anatol’s guide to screen printing color separations covers the fundamentals of ink roadmap planning. For software specifics, review Sep Studio NXT’s feature set, QuikSeps’ separation tools, and AI Separations’ automated workflow to compare what each platform actually automates versus what still needs a human hand.
- A Guide to Screen Printing Color Separations
- Sep Studio NXT – Screen Printing Software | Freehand Graphics
- AI Color Separation & Quoting Software — No Photoshop | AI Separations
FAQ
What is the best color separation software for screen printing?
There isn’t one universal answer since it depends on your workflow and art complexity, but shops generally split between full manual control in Photoshop or Illustrator, semi-automated suites like Sep Studio NXT and QuikSeps, and fast automated tools like AI Separations. Pulse Merch handles separations in-house using a mix of manual editing and automated tools depending on the job’s complexity.
Do I need to flash cure between colors when screen printing?
Yes, most multi-color jobs need a flash cure between colors, especially when printing wet-on-wet over an underbase, because it partially sets the ink so the next color doesn’t bleed into it. Skipping or shortening flash time is a common cause of ghosting and muddy color mixing on press.
How can I separate colors in an image?
You separate colors by either isolating flat colors into individual spot plates (best for logos) or converting an image into halftone dot patterns across multiple channels to simulate tones and gradients (simulated process). Anatol’s separation guide breaks down both approaches as the standard methods used in textile screen printing.
What is color separation in printing?
Color separation is the process of breaking artwork into individual plates, one per ink color or halftone channel, so each can be printed in sequence to reconstruct the full design on the garment. It’s the step between finished artwork and screens ready to go on press.
How much does it cost to have separations done professionally?
Cost depends on color count, underbase requirements, and file complexity rather than a flat rate, since a 2-color spot job and an 8-color simulated-process job on dark garments require very different setup work. Pulse Merch quotes separations as part of the full production estimate once we see your art and garment specs.