Separations are key to the screen printing process. This is especially the case if a customer wants to hand a digital file to a screen printing services company and expects to get precise results. If you're preparing to ship a project to a printer, you should understand these four aspects of the use of separations.
Foremost, the idea centers on the use of colors. You will be specifically separating the main colors in the image. If you're printing a face from a photograph on a T-shirt using a four-color process, for example, the separations will usually be cyan, magenta, yellow, and black. This process is often called CMYK with the K referring to the black level in the image.
When a screen printer creates a product for a customer, they do so in layers. These layers are separate screens representing each of the colors. If you're using white letters and a red border to offset them, for example, the printing company would likely create two screens. One screen would be for the white ink, and the other would be for the red. They'd lay down one of those two first in an initial production run. Once that layer dried on all the shirts, they'd then do another run with the red ink to complete the process.
Virtually all modern screen printing starts with digital files. Fortunately, companies that produce most of the software tools for creating these files understand how screen printing services work. Various programs allow you to create color separations in digital files.
This will give you a better idea of how the layers will come together after the print runs are done. Notably, you may want to do the separations on your own and then send them to the printing company if you have very specific requirements. Otherwise, you will have to rely on their graphic artists to tweak the separations.
Making the jump from your computer screen to the printing company's screens and then on to the printing process can create some misunderstandings about which colors you want. Once more, the digital world has an answer, and that is the use of color profiles. A color profile is a digital system for matching output across devices.
If you wish to create items and then send them to a third party, it is best to use the same color profiles as they do. Contact your preferred printing company and ask them for a copy of their profile so you can plug it into your system.