Working with spot colours in desktop publishing seems like it should be a straightforward process. In practice, however, there are many potential pitfalls that have to be avoided to produce successful spot colour artwork.
First let's look at how spot colour printing works. First of all it is not like full colour printing. In full colour printing, four colours (cyan, magenta, yellow & black) are used in hundreds of thousands of possible combinations to create full colour printing. In spot colour printing, single colours of ink are used that limit the possible colour combinations to those specific inks. For example, if you had a spot colour job that was being printed in blue ink, the only variations in colour you will see is where the ink has been "screened" to give the appearance of a lighter shade. If you are printing with two colours, you are limited to those two colours and the lighter shades available through screening those two colours.
While there are some limitations of spot colour printing, there are also some advantages over full colour printing:
- Cost- Particularly on shorter runs, spot colour printing can cost significantly less than full colour printing
- Vibrancy and availability of colours. Because of the way spot colours are mixed, there are numerous colours that can be created with spot colour inks that can't be duplicated in full colour printing (particularly vibrant reds). Also, in spot colour printing, there are metallic and fluorescent inks that can't be duplicated in full colour printing
One of the biggest challenges in creating documents for spot colour printing with 2 or more colours is keeping your spot colours specified correctly within your software. To illustrate this point, let's use the example of a flyer that is printed with red & blue inks.
- First, you must specify the red and the blue in your software. In this case we'll use Pantone Reflex Blue and Pantone 032 Red (The Pantone spot colour palette is the standard for spot colour printing).
- After deciding which colours to use, you must make sure to consistently select the "coated" or "uncoated" palette*. If you pick Red 032 cvc (coated) for some items and Red 032 cvu (uncoated) for other items, you will get final separations for each red (some of the items appearing on one separation, some of the items appearing on another). These separations can be both costly and time consuming and this problem has to be fixed before your job can be printed.
- Another challenge for specifying spot colours occurs when you import photos or graphics. First of all, if you have a scan of a two colour logo, it is not going to separate to spot colours. Formats such as tif, jpeg, etc. do not support spot colour separations, so you will have to re-create the logo in a package like Illustrator or Corel in order to create a vector image that can separate (in some cases, eps files can be made into "duotones." This is a fairly complex and technical topic that will be addressed in a coloumn of its own). If you have a colour logo or graphic that can be printed in one of your two colours you will be able to accomplish this (athough you will have to convert it to greyscale or b&w first).
- If you import a b&w or greyscale image, you will have to assign it to either Red 032 or Reflex Blue as it won't separate to either if you leave it black. Most desktop publishing packages will allow you to assign either an outline colour or a fill colour to b&w scans/bitmaps that will then make them separate to the colour you have assigned.
- If you import a spot colour image from a separate application, you have to make sure that it was set to the same colour (including coated or uncoated) in the source application or it will create another separation when you print.
- When you have gotten to a point where you have all your colours properly specified, it's still a good idea to print a set of test separations before creating final output. Even experienced professionals regularly find separation problems in their first test of a file (and it's a lot cheaper and quicker to find and correct any problems before you send the file out for printing).
*Pantone ink swatch books generally contain samples on coated (glossy) paper and a separate section with samples printed on uncoated (matte) paper. The actual ink is the exact same whether it goes on coated or uncoated paper. After 10 years in the industry, I have yet to find a compelling reason why software manufacturers give the option of coated (cvc) or uncoated (cvu) within their software (as it is irrelevant in most regards until the job is actually printed).
Another issue that must be addressed prior to setting up your spot colour print job is whether you will use "quick printing" methods or "tight registration/traditional" methods.
- With quick printing, the printer takes a camera ready output and makes "instant" plastic plates from this output. The benefits of quick printing is that it is usually faster and cheaper on short runs that tight registration/traditional printing. The disadvantage of quick printing is that due to the equipment and plates being used, tight registration is not possible. This generally means that different colours can not touch each other or be close to each other (generally within 3/16"). The term you will often hear for this is "loose registration."
- With traditional printing, using metal plates, very tight registration is possible. The benefits of this are that you can have colours touching each other and/or very close to each other. Also, you get the finest quality text and halftones that can be achieved. With Computer-To-Plate equipment now in use the quality of metal plates is now the standard. Trapping (slight overlap of colours to prevent tiny gaps) is also an issue with tight registration printing. Trapping is something that should be discussed with your printer before your job is printed.
In getting the most out of your spot colour printing, you should learn how to use screens effectively. A one colour print job with the colour being printed in a variety of different shades (ie. 20%, 40%, 60%, 80% & 100%) can have the same effect as multiple colours. A word of caution, however, is that not all colours screen as you might expect. For instance, there is no such thing as a light red. When red is screened back, it becomes pink (which may not be what you had in mind). Most printers have a Pantone book that shows different screen values of Pantone colours. Ask to have a look at this book before you set up your project so you can get predictable results.
We strive to be as accurate and current with our information as possible. Due to the infinite number of scenarios that occur in print & document creation, we can not guarantee that the above information will be correct in all situations.