Spot Colour and CMYK in the printing process - what's the difference?

This article is not aimed at how to use Pantone Spot Colours, but more of an explanation of the difference between Spot and Process (CMYK) colours.

Spot colours are used in the printing process when a particular colour(s) needs to be accurately represented, such as in a company logo. Choosing a colour is very easy, much like choosing from a Dulux paint swatch at your local hardware store.

The main printing industry standard colour swatch is provided by Pantone^©. If you're using professional graphics software such as, Adobe Illustrator/InDesign/Photoshop or QuarkXpress for instance, then the Pantone colour swatches will already be built-in to your software.

Pantone colours are ready-mixed inks that are identified using a numbering system - Pantone 032 (red), Pantone 485 (red), Pantone 021 (orange) etc. etc. Some of the more popular colours are known by name only - Pantone Reflex Blue, Pantone Purple, etc. as shown in this graphic.

Before we talk more about spot colours, it's important to mention the other main printing process used, which is CMYK printing, a.k.a. Process Colours, or 4 colour printing.

Firstly, in case you don't know CMYK stands for Cyan, Magenta, Yellow & Black (the K stands for 'Key'), the 4 primary colours. So for example, let's say we had an A4 poster to produce which also has colour photographic images used in the artwork. The only way to produce this, using a standard lithographic print process, is to use percentages of each colour to produce the final image. This is all handled automatically for you in your design software.

So, once a printing plate has been generated from your artwork, the job would then be put on a 4 colour printing press. Each of the 4 ink units on the press would hold one of the primary colours. The job would then be produced, in one pass, with the finished poster coming off the press at the other end.

So, whether it's just some black text, photographs or the company logo, this will all get printed together in one pass using the CMYK process.

Well, there's a number of reasons but to keep things concise, here are a couple:

The amount of colours available using the CMYK process is limited. Also, certain colours just can't be produced using CMYK. Pantone 021 Orange for instance, is a well-known problem colour. Instead of the bright orange we see when produced as a spot colour, the orange turns decidely 'brown', when converted to CMYK.

It's not just the blue-chip companies that require their brand being produced in an accurate colour. Anyone who takes their own brand seriously will have a need for their stationery to be produced in consistent colours. This is where a dedicated spot colour comes into its own.

For example, let's assume your logo has been designed in red & black. A popular red is Pantone 032, which is similar to a pillar-box red for those in the UK. The logo will more than likely have been designed in Adobe Illustrator, or CorelDraw etc. A Pantone colour 'book' is selected in the software. There are many colour books available but for our purposes let's say Pantone Solid Coated. (You can select Uncoated if you wish but it won't have any impact on the finished product).

Tip! Choose one colour book, such as Pantone Solid Coated and stick with it. Don't mix any other books or any CMYK artwork. If your'e designing in spot colour, then use that only.

Back to our logo, which we've determined will be designed in Black plus Pantone 032 red. (i.e. 2 colours).

The logo is maybe going to be used on many stationery items, such as business cards, letterheads, invoices, delivery notes, computer forms, labels, envelopes etc. etc.

Some of the more specialist items such as computer forms, multi-part invoices etc. are quite expensive to produce if using a CMYK process, so it's actually much cheaper to produce these using a spot colour process. It follows, that in order to keep our brand colour (Pantone 032 red) consistent across our stationery we really need to have most, if not all, stationery produced in spot colours.

So, if we're thinking of designing a letterhead, it's merely a case of dropping-in the logo, and then using black (which is already used in the logo) for the text. If we want to use small highlights of colour, e.g. a bold E for email, T for telephone etc., then we could colour these in using the 032 red, which is used in the logo also.

Now let's also assume the client prefers text to be done in grey. Rather than select another colour from the grey section of our colour book, (which makes the job 3 spot colours and consequently that bit more expensive), we could simply 'tint' the existing black text by changing the opacity from 100% to maybe 50%. The job will now look as though it's been produced using 3 colours, but we've still only used 2, and kept the costs down for the client. Tints of a main spot colour come in very handy for livening up artwork. For instance, you could take your logo, change all colours to black and then change the opacity to around 5 - 10% and then use this as a 'ghost' image in the background.

Simple stuff, but it can look great!

Just click on: Window (in the main file menu),

select: Swatch Libraries and then Colour Books.

There are often instances where you need to convert existing spot colours to CMYK. This is easily done by selecting them one at a time, (and then using 'Select' > 'Same' > 'Fill Colour' to select all similar colours) and then converting using the 4 colour icon shown below. If you don't see this box, then hit F6 to display it.

Any spot colours left behind probably won't print, so make sure they're all converted, including any 'strokes' that are used.

After converting you can see that Pantone 247 is made up of 36% Cyan and 100% Magenta, with no yellow or black used.

I've only been able to scratch the surface in this spot colour discussion however, if you need any further info please feel free to leave a message in the comment box and I'll do my best to help