What Is Screen Printing?

What is screen printing?

Screen printing or silk screen printing was first patented by Samuel Simon in England in 1907. In the beginning, screen printing was used to apply bright colors and patterns to fabrics and wallpaper.

Advertisers soon picked up the screen printing process for their promotions, and the rest is history.

What is Screen Printing Used For?

This printing technique is highly flexible, and you have undoubtedly come across many screen printed items:

  • Screen printing is responsible for most printed T-shirts, uniforms, jackets and other clothing items
  • Glass and plastic containers, like shampoo bottles, are very often decorated by the screen printing process using specialized equipment.
  • Nearly every CD and DVD with an image also employ the screenprinting process.
  • Fine art prints also take advantage of screen printing.

One reason for the diversity of screen printing applications is its ability to deliver bold, opaque colors on a wide variety of materials. 

Different ink formulations allow specific inks to bond with materials such as glass, plastic, and metal. 

The result is a vivid and durable message or image and screen printing in mass quantities.

Even with the advancements in technology and digital printing, screen printing is still the preferred printing process in many printing applications.

Silk Screen Printing for Fine Art Prints

In the 1930s, a group of artists formed the National Serigraphic Society to set themselves apart from commercial screen printing. 

The word serigraphy is a combination of the Latin word for silk and the Greek word meaning to write or draw. 

Even today the term serigraphy typically refers to the use of screen printing for fine arts.

Probably the most iconic artist to use silk screen was Andy Warhol. His screen printed works range from a Campbell’s Soup Can to Marilyn Monroe and Elvis.

According to a 2009 article, his printed work titled Eight Elvises sold for $100 million in a private sale.

Screen Print Example - Eight Elvises by Andy Warhol
Eight Elvises by Andy Warhol

What Equipment And Materials Are Required for Screen Printing?

Regardless of your application or material (also known as the substrate), the basics are always the same.

This is true whether you are printing onto a T-shirt for a gift, a design for your baseball team’s uniforms, or 10,000 custom display pieces; the essential screen printing elements are the same for each.

The Screen

Screen Printing Screens

Modern screen printing does not use silk. Screens for printing use newer materials such as polyester monofilament.

Depending on the image, the screen mesh count may be anywhere from around 120 up to 460 threads per inch. 

Not only are there more or fewer threads, but the higher the thread count, the thinner the screen thread.

Thread thickness is calculated in microns (1 micron is one-millionth of a millimeter). A typical human hair is about 70 microns. 

The 120 mesh is about 125 microns. For fine detail screen printing, the 460 mesh used is about 27 microns. 

The more open mesh and thicker thread allow the printing screens to deposit heavier inks and create a much more substantial layer of ink onto the printed substrate.

The Frame

Screen Printing Frame

The screen must be stretched tightly over a frame before anything can happen with it.

The screen frame may be a simple wooden frame, or a metal frame typically made from aluminum or steel.

Wood frames are not suitable for an automatic printing press. Automated machines require more durable and stable materials.

Special equipment stretches the screen mesh evenly across the frame at a specific tension and angle.

If the material is too loose, it will not perform properly. The printed design will become distorted and inconsistent.

Likewise, if the screen is too tight, it will cause issues with the printed design and make the screen more fragile.

The Emulsion

A light-sensitive emulsion (photopolymer) is applied to the screen once it is properly stretched. The coating process requires specialized equipment designed specifically for screen printing. 

It can be accomplished manually, but this is highly sensitive to technique and takes much practice.

Once this emulsion has cured and is ready to accept your design, the next step is to transfer your design to the screen.

This step is most often done by placing a film positive of your design against the emulsion and exposing it with a high-intensity light source of a specific wavelength. 

A piece of equipment called an exposure frame performs this function. 

A vacuum firmly holds the film against the emulsion, allowing for precise translation of the design on the film to the emulsion on the screen.

Another method of exposing the design onto the emulsion is Direct to Garment (DTG). Many busy commercial screen printing companies eliminate the film and use laser technology to create the image digitally. 

This method saves time by eliminating steps and enhancing accuracy. Again, this process requires highly specialized, costly equipment.

Once the screen is exposed, the unexposed areas are washed out, leaving open mesh where your image will print.

Today’s emulsions are environmentally benign and require only water for processing.

Any areas on the screen where ink can pass through but are not part of the image receive a coating of block out product. 

The block out seals open spaces and pinholes so that only the desired design may print.

The Press

Manual Screen Printing Press

There are three types of screen printing presses.

The most basic is the manual screen printer, which is operated entirely by hand.

Each step in the screen printing process requires the operator to perform that function.

Semiautomatic screen printing machines incorporate some motorized functions such as flooding the screen and cycling the squeegee.

However, these screen printing machines usually require the operator to load and unload the substrates at a minimum.

A fully automated screen printing press will load the substrate, print each ink color, and advance automatically to the next color of ink to be printed.

As each color is printed it is automatically dried before the next color is laid down.

Once the substrate is screen printed with your design it is neatly unloaded.

All this takes place while the screen print operator observes and manages machine settings to maintain quality and production.

Whether you need a simple tabletop mechanism for single ink color, or a fully automated screen printing machine capable of multiple colors, the screen must be mounted securely and accurately.

You don’t want the screen to move while printing, as this will distort the design. Also, the positioning must be consistent for each print.

A manual press does not require any electricity. Semiautomatic machines and fully automatic machines do require power.

Most all of them require more than a 110 V outlet.

More sophisticated equipment will require a 220 V two-phase service to support all the mechanics and drying units.

The Squeegee

Screen Printing Squeegee

Once the screen is mounted correctly and aligned, the proper squeegee blade is selected.

Most squeegees today are made from high-grade polyurethane, which is exceptionally durable.

With heavier inks and lower mesh counts, a softer squeegee is in order.

Higher mesh counts, thinner inks, and more detail require much harder material.

Manual screen printing is done with a handheld squeegee using proper technique to achieve consistent results.

With automated screen printing equipment, the squeegee blade is mounted directly to the press where the angles and pressure are a part of the setup.

These settings create a much more consistent result in the quality of the print compared to manual manipulation.

The Ink

As mentioned above, the substrate is the primary determinant of the proper ink formula.

Screenprint inks usually have a strong pigment and create bright, intense colors.

You can also create custom ink colors for branding and other purposes.

Some inks create a puffy finished product popular in some apparel printing. There are metallic inks and florescent colors as well; the options are nearly endless.

While some inks will air dry, most formulations are either heat set or UV cured.

Multicolor and fine detail screen printing is well-suited to UV curing.

In this process, the inks are dry almost instantly.

Rapid curing prevents the ink from spreading (flowing), enhancing detail, and allows for the next color to print immediately.

How is Screen Printing Done?

The Printing Process

The equipment is ready, ink is on the screen, and you are prepared to pull your first print. The substrate (what you are printing onto) is securely mounted directly below the screen.

There may be a mechanism to secure the substrate, or it may be secure using spray glue. In garment printing, this platen functions much like an ironing board.

Once your substrate is in place, the screen is lowered and rests slightly above the surface of your substrate.

This spacing is known as off contact and is highly critical for the quality of your print. Too high, too low, or an uneven gap will all distort the image, making multiple colors impossible to align.

The ink is drawn across the image from front to back. On a manual press, the squeegee performs this function. Automated machines use a flood bar that cycles down and forward then raises as the squeegee comes down and draws back, creating the image.

As the squeegee comes down, it forces the mesh into contact with the substrate and pushes ink through the mesh at a specific angle.

Then as the squeegee moves forward, the mesh releases from the substrate and is ready for the next cycle.

Once printing is complete, the next step is to cure or dry the ink. With UV inks, drying occurs during the print process. In all other cases, the printed item will go into an appropriate dryer or be placed on a drying rack to air dry.

Cleaning Up

This part of the process will also vary widely. More significant operations will have screen washing and reclaiming equipment. 

The screen may be cleaned of ink and filed to be used later. Alternately, the emulsion may be removed so the mesh can be coated and used again. Often, frames are recycled, and new fabric stretched on the same frame to be used repeatedly.

Most high production facilities will not reuse screens. This practice is especially true in the case of more fragile higher mesh count fabrics. The screen can lose its tension with use, and defects often develop in both the emulsion and the mesh—these defects can create significant loss of time when trying to reuse screens. 

That is the process for screen printing. There is a lot of science used along with technique when working with silkscreen printing. But, the basic principles are elementary and have been around for centuries.

Frequently Asked Questions

Is Screen Printing Expensive?

With all of the specialized equipment and materials, you might think that screen printing is a very costly endeavor.

Silkscreening is by far the most economical method for printing on many different surfaces and products.

The technique also scales well, meaning that the setup costs are about the same for a single T-shirt as they are for five dozen shirts. The larger the quantity, the lower your unit price will become.

The specific requirements, the quantity, turnaround time, and your vendor will all factor into determining your cost.

Generally, however, screen printing is a reasonably economical process. If your project is well-suited to the silkscreen process, there is likely no more cost-effective method.

Is Screen Printing or Digital Printing Better?

New digital technologies are providing some stunning images on garments and many other items.

Unlike screen printing, where many steps, equipment, and varying supplies are used, digital printing requires only a digital file.

Fewer steps and fewer components make digital quicker and less costly to set up.

This abbreviated process results in less expensive short runs and samples. However, digital printing is less scalable as the costs do not decrease significantly with larger volumes.

At the same time, digital does offer features that silkscreen just cannot deliver. Features such as personalization and sequential numbering make digital the only option in some cases.

Digital printing also creates a different type of image, which may be more appropriate for some kinds of work.

Digital and screenprint are merely two types of printing; one is not fundamentally better than the other. They each have their pros and cons. The real question is which one is best suited for your project.

More Information

There is much more that goes into the screenprinting process; with many details and elaborate calculations required for optimum results. But, you need not wander too far into the weeds to understand this robust form of communication and art.

After reading this post, you should have enough information and insight regarding screenprinting to proceed with confidence in your next project. It’s time to get creative and exercise some of your new knowledge!