What is Screen Printing?

Screen printing: it might sound like a process designed to make the entryway to your sun room or porch look extra fancy, but that's not quite the case. Screen printing is actually one of the most commonly used techniques for decorating custom items in the promotional products industry. Let’s take a closer look at it in this lesson!

Why is screen printing such a popular technique? The big reason is that it works well with a number of different items. Screen printing can be used on soft fabric products, like t-shirts and tote bags, as well as on products with hard surfaces like tumblers and pens. No matter what kind of promotional item, screen printing is designed to create a crisp, clear logo that stands out.

The Basics

The reason that it's called "screen printing" is because it involves the use of screens, which we hope isn't that surprising. It would be great if manufacturers had giant pens they could use to draw a company's logo in puffy ink on their items, but until they do (and until they make enough to handle a giant production like five thousand t-shirts), manufacturers need a way to force ink onto the item in the shape of a specific design.

One: Your Design Meets The Screen

The first step in screen printing is to get a custom design onto a screen. This is done by spreading a thick green emulsion over the screen, a bit like melted wax. Standing over the green goop and cackling like a mad scientist, "It's alive... IT'S ALIVE!" is optional.

Two: Get Ultraviolet!

Before the emulsion hardens, a machine prints the custom design onto it with UV-shielding ink, which is kind of like sunblock except without the delightful smell of coconut. When the screen and the emulsion are placed under ultraviolet light to dry, the emulsion hardens everywhere except for where the UV-smart ink was applied. The screen gets washed free of any excess emulsion, and finally a negative image of the custom design will be displayed.

Three: Feeling the Pressure

After the transfer process, the screen is placed into a printing machine. A production worker spreads ink in the color of the customer's choosing over the screen. As the items to be customized pass through the printing machine, the colored ink is spread over the design and pushed through the screen (a little bit like pureed food being passed through a strainer). Thanks to the hardened emulsion, the ink only passes through the spots where UV-sensitive ink was applied. Lo and behold—a fully decorated promotional item!

Technical Talk

One of the biggest challenges in screen printing multiple items is proper registration. Print registration refers to the alignment of the screen, along with other parts of the equipment. This alignment ensures a design is printed in the same location on every item, every time. This is especially important if your design has two or more colors. If the registration is off on one of the colors, part of your design could overlap or end up completely detached from the rest of the design! And though "Design in Space" might sound like a great idea for a sci-fi TV show, floating colors really don't do much for the look of a logo. So printers often make registration marks to show where the screen or other parts need to be placed.

Some items go through additional steps like a heat treatment before the printing process, which helps the screen-printed ink better adhere to the item. All items gets dried after the printing is done. And all of them look fantastic!

As common as screen printing is, it’s a pretty technical process! Whoever thought to spread an emulsion across a screen and then treat the screen with a UV-blocking ink must have been a chemistry genius. And because the printing pros keep proper print registration in mind, you get a crisp-looking print of your logo, every time.