Simulated Process vs Spot Colour: Which Separation Do You Need?

When a screen printer or DTF shop sends us artwork for separation, the first question we ask is almost always the same: is this spot colour or does it need simulated process?

The wrong answer costs you screens, ink, and time. Here's how to tell the difference quickly.

What Is Spot Colour Separation?

Spot colour separation takes artwork that is made up of flat, solid areas of colour and splits each colour into its own channel. Each channel prints as a single, 100% coverage layer — no halftone dots, no optical mixing.

A typical spot colour job is a brand logo with three or four solid Pantone colours. The red is red. The black is black. There's no blending, no gradient, no photographic depth.

When to use it:

• Logos with flat, named colours (Pantone, CMYK solid)
• Text-based designs
• Artwork that will be reproduced across multiple colourways with colour swap requirements
• Any job where Pantone-accurate colour matching is critical

Spot colour separations are precise, predictable, and straightforward to burn and print. They're the right tool for clean, flat artwork.

What Is Simulated Process Separation?

Simulated process uses small halftone dots — printed at specific angles and frequencies — to trick the eye into seeing a full range of colours from a limited ink set. The dots don't mix on the substrate; they mix optically in the viewer's eye.

This is the method used for complex, photographic, or illustrative artwork: portraits, landscapes, gradients, anything with tonal depth. It's called "simulated" because it simulates photographic colour reproduction using screen printing inks rather than CMYK offset inks.

A typical simulated process separation produces 6–8 channels: an underbase white (on dark garments), a highlight white, and 4–6 colour inks. The exact count depends on the artwork complexity and how many colours you want to keep.

When to use it:

• Photographic or photorealistic artwork
• Complex illustrations with gradients and blending
• Artwork going on dark or coloured garments
• Any design where the colour is built up through tonal variation rather than flat fills

The Most Common Mistake

The most common mistake is asking for spot colour separation on artwork that cannot be separated into flat channels — usually because the original file is RGB and full of anti-aliasing, gradients, or photographic textures.

You can see this in two ways:

1. Open the file in Illustrator and look at the swatch panel. If the colours are named Pantone codes, it's likely spot-colour ready. If there are hundreds of unnamed swatches or the artwork is a raster image, it almost certainly isn't.
2. Zoom in on an edge between two colour areas. Spot-colour art has a clean, hard edge. Simulated process art has a soft transition or you can see individual pixels blending.

A Quick Rule of Thumb

Ask yourself: can I count the colours?

If you can look at the design and name every colour in 10 seconds — "red, black, white, and a mid-grey" — it's probably spot colour.

If the design has depth, photo-realism, or you couldn't begin to list every shade — it's simulated process.

What About CMYK and Index Separation?

These are less common but worth knowing:

• CMYK uses only four channels — cyan, magenta, yellow, and black — and works correctly only on white or very light garments. It's the screen printing equivalent of offset print reproduction.
• Index separation replaces halftone dots with a grid of solid squares. The result is fully opaque and works on any garment colour, making it ideal when the same artwork needs to print on 5 or 6 different shirt colours without reformulating.

When You're Not Sure, Ask

Submit your file with a note about your print environment — garment colour, number of colours you want to use, and the press mesh count. We'll review the file and tell you which method suits it before quoting. There's no charge to find out.

The separation method determines everything downstream: ink count, screen count, cost, and what the finished print can look like. Getting it right before you burn any screens is always worth a quick conversation.