CMYK Plastic Card Printing Explained

Most of our membership cards and full colour plastic cards are printed using the CMYK process — the standard colour method used in commercial printing worldwide. Understanding how it works will help you prepare your artwork correctly and avoid surprises when your cards arrive.

What is CMYK?

CMYK stands for Cyan, Magenta, Yellow, and Key (Black). By overprinting tiny halftone dots of these four colours in varying combinations, a wide range of colours can be reproduced — including realistic-looking photographs. The "K" is used for black rather than "B" to avoid confusion with blue.

If you look closely at any printed magazine, you'll see the individual dots rather than solid colour. This is normal and is how all CMYK printing works. It's worth noting that there is no actual green or orange ink in the process — those colours are created by layering cyan, magenta, and yellow dots in the appropriate proportions.

Because CMYK is a subtractive colour model, you start with a white surface (the card) and subtract brightness by adding ink. The more ink applied, the darker the result.

CMYK vs RGB — Why It Matters for Your Artwork

RGB (Red, Green, Blue) is the colour model used by screens — monitors, phones, tablets. It is an additive model: combining all three at full intensity produces white. RGB has a significantly wider colour range (or "gamut") than CMYK, which is why colours often appear more vivid on screen than in print.

This is the most important practical point: artwork supplied in RGB mode will not print as expected. It will need to be converted to CMYK before printing, and some colours will shift during that conversion — sometimes slightly, sometimes significantly. Bright blues, vivid oranges, and neon greens are the most commonly affected.

Some colours that a monitor can display simply cannot be reproduced in CMYK — these are described as being "outside the CMYK gamut." When an out-of-gamut colour is converted, the printer software gets as close as possible, but there is no workaround. This is an industry-wide limitation, not something specific to us or our equipment.

To avoid issues, set your document to CMYK mode from the outset in whatever software you're using (Adobe Illustrator, Photoshop, or InDesign). Don't design in RGB and convert at the end.

Printing Greys

Grey deserves a specific mention because it's a common cause of unexpected results. A grey made up of C0% M0% Y0% K20% (pure black ink at reduced opacity) will show visible dots when printed. A much smoother result is achieved by using a mixed CMYK grey — a balanced percentage across all four channels. If your design uses grey backgrounds or text, ask us and we can advise the right values for the shade you're after.

Plain Black vs Rich Black

There are two ways to produce black in CMYK printing, and choosing the wrong one for the context can cause problems.

• Plain black (K100 only): use this for body text and small type. If the four printing plates are very slightly misaligned, plain black text stays sharp. Using rich black on small text can produce a coloured shadow effect.
• Rich black (a mix of all four channels): use this for large areas, backgrounds, or design elements where you want a deep, dense black. A common rich black mix is C60% M40% Y40% K100%, though we can advise on the best values for your artwork. Avoid setting all four channels to 100% — this applies too much ink and can cause production problems.

Resolution and DPI

DPI stands for dots per inch and describes image resolution. For plastic card printing, all raster images (photographs, backgrounds, non-vector graphics) must be supplied at a minimum of 300 DPI at the finished print size.

Images downloaded from the web are typically 72 DPI — far too low for print. They may look fine on screen but will appear noticeably blurry or pixelated when printed. If your image looks slightly soft on screen at 100% zoom, it will look significantly worse on the card.

You cannot fix a low-resolution image by increasing the DPI setting in Photoshop without resampling — this adds pixels artificially and does not recover detail that wasn't there to begin with. If in doubt about image quality, contact us before finalising your artwork.

File Types: Raster vs Vector

There are two fundamental types of graphic file:

• Raster files (JPEG, PNG, TIFF, PSD) are made up of pixels. Quality is fixed at the resolution they were created at. Suitable for photographs, but must be 300 DPI at print size.
• Vector files (AI, EPS, PDF from Illustrator) are built from mathematical paths and scale to any size without any loss of quality. Ideal for logos, text, and graphic elements.

We prefer artwork supplied as a high-resolution PDF, AI, or EPS. If your file contains live text, make sure all fonts are outlined (converted to curves) before supplying. This prevents text from reflowing or being substituted if we don't have your exact font installed.

JPEG files are generally not recommended for print due to compression artefacts, though they are acceptable for photographs if supplied at 300 DPI. Word documents are not suitable for print production.

Pantone (PMS) Colours

Pantone (PMS) colours are pre-mixed spot inks that fall outside the standard CMYK process. They're used when absolute colour accuracy is critical — for example, matching a specific brand colour exactly. Pantone also covers metallic, neon, and pastel inks that cannot be replicated in CMYK.

Our standard plastic card printing uses the CMYK process. If your brand uses a specific Pantone colour, we can advise on the closest CMYK equivalent, but an exact match cannot be guaranteed. If Pantone accuracy is essential, contact us to discuss options before placing your order.

Artwork Checklist

Before supplying your artwork, run through this checklist:

• Document set to CMYK colour mode (not RGB)
• All images at 300 DPI minimum at finished print size
• All fonts outlined / converted to curves
• 1.5mm bleed on all sides beyond the card edge
• All important content kept 3mm inside the card edge (safe zone)
• File supplied as PDF, AI, or EPS
• Large black areas using rich black; small text using plain black (K100)

Full artwork specifications and downloadable templates are available on our artwork guides page.

Any questions about preparing your artwork? Contact our team — we're happy to help before you finalise your files.