Why does index color separation have zero moiré?

Moiré occurs when two or more halftone dot grids interact at similar angles, creating a visible interference pattern. Index separation uses stochastic (randomly placed) square dots, so there is no repeating grid pattern to interfere with the mesh. All channels can output at the same 45-degree angle with no moiré risk whatsoever.

What is the difference between index color and simulated process separation?

Both methods print multiple spot colors to create the illusion of a full-color image. Simulated process uses elliptical halftone dots at different angles and achieves smoother gradients and more photo-realistic transitions. Index uses equal-size square dots, eliminating moiré risk and ink buildup, but produces a slightly more graphic or pixelated aesthetic. Index is easier to print and more forgiving on press.

How many colors does an index separation use?

Index separations typically use 5 to 13 direct spot colors. Unlike CMYK, the inks are opaque spot colors — not transparent process inks. This means index printing works on dark garments without needing a separate CMYK workflow.

How do I output index color separations from Photoshop?

Since the square dot pattern is already embedded in the color plates, output the separations with elliptical dots at 55–65 LPI at 45 degrees for all ink channels. This converts any grayscale area to halftone on output. You use the same angle for every channel — unlike simulated process which requires different angles per color.

Index Color Separation | Zero Moiré

The Technique

What Is Index Color Separation?

Index color separation converts your artwork using stochastic square dots of equal size — completely different from traditional halftone dots that vary in size to simulate shading. Instead of mixing transparent inks, each pixel in the image is assigned to the closest available color from a defined palette of direct opaque spot inks.

The result is a vibrant, sharp print with a distinctive graphic character — slightly pixelated up close, but visually rich from any normal viewing distance. Because the dots are square and randomly distributed rather than arranged in a repeating angle pattern, there is physically no way for moiré to occur.

Index is the go-to method for printers who want color-rich, full-range prints without the angle-sensitive complexity of simulated process. It's particularly popular for fashion apparel, streetwear brands, and any shop that prints high volumes and needs consistent, reliable results on press.

Uses 5–13 direct opaque spot colors
Square equal-size dots — zero moiré possible
No ink buildup — dots sit side-by-side like a puzzle
Works on dark, light, and bright colored garments
All channels output at the same 45° angle
Output LPI: 55–65 lines per inch, all channels identical
Print wet-on-wet — no flash between colors needed

Index square dots (left) vs halftone round dots (right) — zero moiré is built-in to the index method

Real Printed Results

What Index Prints Look Like on Garments

These are actual shirts printed from our index color separations — vibrant, sharp, and consistent on dark fabric.

Index color separation printed on dark shirt — vibrant multi-color screen print result

Dark Garment — Index Print

Multi-color index separation printed on a black shirt. Vibrant, consistent coverage with zero moiré visible at any distance.

Index color screen print sample — square dot stochastic separation on apparel

Index Print — Detail View

Close-up showing the characteristic square dot texture of index printing. Bold, graphic, and vibrant from any viewing distance.

Why Index Wins on Press

Easier to Print. Fewer Problems. Better Results.

Index color separation was developed to solve the biggest headaches in multi-color screen printing. Because the square dots don't create repeating grid patterns, the most common source of print failures — moiré interference — is completely eliminated by design.

Zero Moiré — Ever

Stochastic square dots have no repeating grid pattern to interact with mesh angles. Moiré is structurally impossible, not just unlikely.

No Ink Buildup

Square dots sit side-by-side like puzzle pieces — no overlapping. Ink density stays consistent across the entire print area, preventing muddy areas.

Print Order as a Creative Tool

The print order of colors dramatically affects the final look of an index print. If a color is too dominant, simply drop it lower in the print sequence — no re-separation needed.

Consistent on Any Garment Color

Unlike elliptical halftone dots that can shift visually depending on fabric color, index separations look consistent whether you print on black, white, or any bright garment color.

Simple Output Settings

All channels output at the same 55–65 LPI, 45-degree angle. No calculating unique angles for each ink channel. One setting, all screens — done.

Index color separation — stochastic square dot pattern animation

Index dot pattern

Square dot — index color separation dot shape close-up

Square dot close-up

Output Specifications

Dot Type Square (Stochastic)

LPI 55–65 LPI

Screen Angle 45° — All Channels

Ink Type Direct Spot Colors

Color Count 5–13 Colors

Printing Method Wet-on-Wet

Our Process

From Artwork to Index-Ready File

We handle the color palette reduction and every technical output detail. You get a file that's optimized for your press and ready to output straight to film or CTP.

01

Artwork Analysis

We analyze your design and determine the optimal color palette — typically 6–10 direct spot colors — to best represent your artwork.

02

Color Reduction

We reduce the artwork to the index palette, adjust brightness and contrast, and optimize for the selected ink colors and garment substrate.

03

Index Separation

Each color channel is separated using stochastic square dot conversion. White underbase created for dark garments. Print order recommended.

04

File Delivery

Delivered as a layered PSD with named channels, PANTONE® ink numbers, output instructions (55–65 LPI, 45° all channels), same day.

What's Included

Everything in Every Index Separation

Index color separation is a technically precise process that requires careful color palette selection and proper dot conversion. Every separation we deliver has been hand-optimized for print-on-press performance — not just technically correct, but tuned to print beautifully on your specific setup.

Pro tip on print order: With index printing, the print sequence is a powerful creative lever. Printing a color early in the sequence means it will be partially covered by later inks — printing it last makes it dominant. We include a recommended print order with every separation, but you can experiment to fine-tune the final look without re-separating.

Index color separation (5–13 colors)

White underbase for dark shirts

Highlight white channel

PANTONE® ink specifications

Color & brightness correction

White balance adjustment

Print order recommendation

Output settings included

Named PSD layers/channels

Fast turnaround

When to Choose Index Over Simulated Process

Index is the better choice when you want easier printing, lower moiré risk, and a bold graphic aesthetic. Simulated process produces softer gradients and more photorealistic transitions. For fashion prints, streetwear, and high-volume runs — index wins on consistency and simplicity.

Works on Any Garment Color

Unlike elliptical halftone separations that can be affected by the shirt's color bleed, index separations deliver consistent results on black, white, bright, and pastel garments. The direct spot color inks block what's underneath.

How It Compares

Index vs Other Separation Methods

Each method has its strengths. Index color is uniquely suited to shops that prioritize press consistency and want to eliminate moiré risk entirely.

Feature	Index Color	Simulated Process	Spot Color	CMYK
Moiré risk	✓ Zero	Low (careful angles)	✓ None	Low (standard angles)
Works on dark garments	✓ Yes	✓ Yes	✓ Yes	✗ No
Photo-realistic gradients	Good (graphic style)	✓ Excellent	✗ Flat only	✓ On white
Ink channels	5–13 direct	6–10 spot	1–12 solid	4 CMYK
Screen angles	All at 45° — simple	Different per channel	No halftone	4 precise angles
Dot gain issues	✓ None	Needs compensation	✓ None	Needs compensation
Starting price	$25	$25	$15	$20

Common Questions

Index Color Separation FAQ

What is index color separation?+

Index color separation converts artwork using stochastic square dots of equal size instead of traditional round or elliptical halftone dots. Each pixel is assigned to the closest available color from a defined palette of 5–13 direct opaque spot inks. The result is a vibrant, graphic-style print with zero moiré risk — structurally impossible with square dots because there is no repeating angle grid to interfere with the mesh.

Why does index color have zero moiré?+

Moiré occurs when two repeating dot grids at similar angles create a visible interference pattern. Traditional halftone separations use round dots in regular grids, which is why precise screen angles are critical. Index dots are square and randomly distributed — there's no repeating pattern to interfere with the mesh. You can print all channels at the same 45-degree angle and moiré is physically impossible.

What is the difference between index and simulated process?+

Both use multiple spot colors to create the appearance of a full-color image. Simulated process uses elliptical halftone dots at carefully offset angles, producing smoother gradients and more photorealistic transitions — ideal for portraits and detailed photography. Index uses equal-size square dots at one angle, making it easier to print, completely immune to moiré, and producing a bolder, more graphic aesthetic. For fashion prints and high-volume consistent runs, index is often the better choice.

How do I output index separations from Photoshop?+

Since the square dot pattern is already embedded in the color plates by the separation process, output all channels using elliptical dots at 55–65 LPI at 45 degrees. Use the same angle and frequency for every single ink channel — unlike simulated process where each channel needs a different angle. This uniform output setting converts any grayscale area to halftone and keeps all channels consistent. We include specific output instructions with every file.

Can I adjust colors after receiving the file?+

Yes — and this is one of the best features of index printing. You can adjust the final look on press simply by changing the print order. Printing a color earlier in the sequence means subsequent inks will partially cover it, making it less dominant. Printing it last makes it the most prominent. This lets you fine-tune the visual result without re-separating the artwork. We include a recommended print order, but experimentation is encouraged.

Is index color right for every design?+

Index works best for designs with bold colors, strong contrast, and a graphic character — streetwear, fashion prints, pop art, and illustrative designs. It's not the ideal choice for very delicate gradients, skin-tone-heavy portraits, or designs where photographic smoothness is critical — for those, simulated process will produce better results. When you submit your artwork, we'll recommend the method that will look best in print.

Index Color
Separation

What Is Index Color Separation?