Printing Your T-shirts: An Overview

You've picked your textiles, created a t-shirt design and placed your order. So what happens next?

The first step in getting your design onto a t-shirt involves printing films for the various colors used. A graphic artist will look at your artwork and determine the best method of printing the colors.

The two main methods of printing colors are spot colors and four-color process. Spot colors are individual colors that are printed separately. There are 100's of pre-mixed colors and an infinite number of colors that can be mixed to specification (e.g. Pantone Matching System colors).

Four-color process physically blends four colors (Cyan (sky blue), Magenta (hot pink), Yellow and Black) on the textile to create a large variety of colors. Four-color process, also known as CMYK, is used to simulate photographic work and graphics with sophisticated shading and textural effects. A hybrid form of printing known as simulated process is sometimes used, combining components of both process and spot color printing.

The graphic artist creates transparent acetate films of each color and prints them in black along with registration marks and identifying information. The films are then collected into an envelope with printing instructions and sent to the be burned onto screens.

Each color of your t-shirt design is then exposed via a high-intensity lightbox onto a fine mesh screen that has been coated with photosensitive emulsion. These screens were initially made from silk, thus the origin of the term silkscreen. When the emulsion is exposed, it hardens and becomes insoluble to water. The black sections of the acetate film prevent light from getting to the emulsion immediately beneath them. Those sections not exposed will dissolve in water. The screen is placed in a high-pressure washing unit where the unexposed sections of emulsion are washed out of the screen. What remains is, in effect, an intricate stencil for that particular color of ink.

While the Art Department is working on your films, your t-shirts are being ordered from wholesalers. Sometimes this can be a challenge; calls can be made all across the country looking for a particular size or color of t-shirt. When the textiles arrive, they are counted in and checked against the order for accuracy and then taken to the screen printers.

A multiple-head press holds a number of screens from as few as four to as many as sixteen. The screens are arranged radially and rotate over palettes that the t shirts are loaded on. There are both automatic and manual presses; on automatics the rotation is handled by pneumatics while smaller manual presses are physically rotated by the printer. Each screen is placed onto a bracket, or head, and locked into place. The printer then carefully adjusts the printed images from each screen until they are all in correct alignment for the final, combined image. The correct color of ink is added to each screen and is forced through the screen's openings by pulling a squeegee from the bottom of the screen to the top. A number of different factors affect the final silkscreen print result, including the hardness of the squeegee, the angle and force of the pull used, and the type of ink used.

After printing, your t-shirts are run through a high-temperature dryer to cure the ink so it will bind to the fibers of the material. A final test print is approved by the graphic artist working on your design, and the run of t-shirts is printed.

Printing On The Dark Side: Four-Color Or Simulated Process?

Printing a full color image on a dark shirt is one of the hardest jobs a screen printer faces. Regular four-color process uses transparent inks: Cyan (sky blue), Magenta (hot pink), Yellow and Black) which print in various percentages, blending together to form a wide range of colors. While this process works beautifully on a white shirt, the results can be disappointing on dark shirts, requiring a white underbase and multiple passes of colors ending up with a thick ink layer and muddy color. While good four-color process can be done on a dark shirt, to do so takes a great deal of experimentation, time, and tweaking during the print run. But there is another way to achieve similar results much more easily.

Simulated process uses opaque inks and in more than just four colors, often between six and eight (usually White, Red, Yellow, Green, Dark Blue, Light Blue, Gray, and Purple). Simulated process colors are usually printed wet-on-wet, with few flashes (a drying process while the shirt is still on the press). For example, to create a flesh tone simulated process would use a mixture of tan, opaque yellow and possibly white. Since the colors are opaque, the dark background becomes a non-issue (or at least much less of one). And if individual, particular colors are needed (for example a exact shade of red for a business logo) they can be mixed to specification and individually printed.

So why would you want to use four-color process at all? When done correctly and successfully, it is the most accurate version of full color reproduction. And for shops with smaller presses with fewer heads available, the multiple colors required for simulated process may not be possible at all. Also for subtle, nuanced art with slight changes in tone, such as pastels, the bright, solid colors of simulated process do not work well.

While screen printing images on dark shirts may be difficult, the results can be amazing and are worth the time and effort involved regardless of which type of printing you use.