Very often during the packaging design process, clients ask the following question: Why is the use of special inks so important? The answer to this question is obvious to most print designers, but for normal people who don't have experience (or obsession) with inks and printing processes, is not obvious at all. The importance of this in packaging goes to eleven.
But first, a quick recap on inks.
CMYK vs Pantone
To make it as simple as possible, let's say that CMYK or process printing is a full-color printing method using only four inks (Cyan, Magenta, Yellow and Black) that mixed up in different percentages will form thousands of different colors.
What is usually called "Special Inks" is usually referred to Pantone colors. Pantone is a catalogue of color for printing. To know what a Pantone color (called PMS for short) looks like, you need to look at a Pantone book (this is really the only way). Often times, PMS colors will look very different on screen, plus colors in general change a lot from one screen to another. PMS colors are supposed to print exactly like chip on the book. So you have to trust the book. Not the screen. And get color proofs.. but we'll get there.
PMS colors and Packaging
DULL VS BRIGHT
Probably the most important thing when you compare CMYK and PMS colors is that it's really hard to achieve bright, sharp colors with CMYK. Bright colors in packaging are very important, they need to be eye catching to get customers attention on shelf. Plus most of buying decisions on shelf are made based on color.
Imagine if Coca-Cola's iconic red was sometimes a bit orange, sometimes purple-ish, sometimes... well, you get the idea. This is what would happen if they used CMYK. The fact is that it's very hard for printers to get the same color over and over again, especially using CMYK.
Color consistency in packaging is important because it contributes to brand recognition. The better the recognition the faster your customers will find it, and the faster they find it the faster they'll buy it. Using PMS colors will also ensure that the entire palette (for example for different varieties of the same product) looks cohesive.
KNOCKOUT AND REGISTRATION
Let's use Coca-Cola's example again: Their labels usually are their iconic red (PMS 484 C) with the logo "knocking out". What you see inside the logo is the actual substrate, not white ink (unless it has a white plate, but let's not get too technical here). We call this "knocking out", basically where the printer doesn't print. If using offset printing, PMS 484 C will be just one plate, which equals to one run.
When using CMYK, we would need 4 runs instead of one, and they would all have to hit in the exact same place so avoid registration problems.
IN THE END, IT'S JUST WORTH IT
It's kind of a myth that using PMS colors is a lot more expensive than just CMYK. Trust me, I've seen tons of quotes with and without them. Before you request for a quote, you need to ask the printer if they can use Pantone colors, and if so how many inks total can be printed. Keep in mind big quantities always keep prices low, if you're going to do a short run it might not be worth it.
If you're printing a lot of a certain PMS color, it's always a good idea to ask for "draw-downs". These are proofs of color printed on the actual substrate. This is always a good idea because the natural color of substrate will affect color tonality.
At the time to decide what to do, PMS or not PMS, I will always recommend PMS. If possible, it is always to control as much as we can. In the end the ultimate goal is for your packaging to look as good as possible because the better it looks, the better will sell.