Screen Printing Squeegee Illustration Essay

While I’m away on vacation I’m running a series of guest posts on the various printing processes, from digital printing to engraving.  I’ve asked some designers and printers to share their expertise and lots of photos to fill you in on what you need to know about different stationery printing methods. Today I’ve asked two of my favorite screen printing ladies, Carrie and Laurie from Two Trick Pony, to walk us through the screen printing process.  Take it away ponies!

What is Screen Printing?

Screen printing (also known as silk screening) is one of the oldest methods of printmaking, with examples dating back to the Song Dynasty in China.  The process involves creating a stencil of an image on a screen of porous mesh, traditionally made of silk.  A roller or squeegee is used to pull paint-like ink over the stencil, forcing it through the mesh onto the paper being printed.  Unlike the inks used in some other forms of printing, screen printing ink sits right on the surface of paper, resulting in incredibly rich, vibrant color.

The Printing Process

The screen printing process has multiple steps, starting with the process of creating the screen.

The screens are coated with a light sensitive emulsion, and exposed using a positive image.  Your positive can be created in a variety of ways, from digitally printed film, hand-cut rubylith, or hand drawn with ink on acetate.  The positive is positioned directly on the surface of the light table, and the screen placed over the positive, print side down.  The emulsion hardens when exposed to light, and remains soft and water-soluble where the positive blocks the light.  After exposure, we take the screen to the wash-out sink, and rinse away the soft emulsion.  Once the screen has dried completely, we lock the screen into hinges that are mounted onto our print surface.

We align the paper for printing, and mark the location with registration tabs.  Ink is applied directly to one end of the screen in a long bead, ready to be pulled over the screen with the squeegee.

A nice, firm pass with the squeegee forces ink through the mesh, visibly showing on the print side of the screen.  The screen is lowered on the hinges, and the squeegee is used to press the inked mesh flat against the paper, transferring a thin, even layer of ink to the page.

The amount of ink transferred to the paper is controlled by the thickness of the emulsion, so crisp images need a fine, even coat of emulsion to maintain their detail.

Mixing the second color for this particular job was a challenge; we wanted to create the illusion of a 3rd color in the print, so the second ink needed to be transparent and overlay the first color to create a pleasing effect.  We settled on a yellowish green that would create a darker green where it overlapped the blue.

Registration was tight!  The blue and yellow-green had to line up perfectly along the sides of the image.

Printing finally completed, it’s time to cut!  Our cutter, Cooper, was made in 1867, and still works like a charm.

The final piece; poster sized invite, ready to be rolled into tubes and mailed to guests!

Tips and Advice

Like most hand-printing methods, screen printing has a very distinctive look.  Even though the surface is flat, the velvety finish and extreme vibrancy of the ink cannot be replicated with any other technique.  Screen printing can also be used on a variety of surfaces, so anything that has a flat surface can be printed; paper, chip board, fabrics, wood, leather and metal are all viable candidates!

Like any other printing process, screen printing definitely has specific limitations, which makes it better suited for some projects (and not so well suited for others).  Fine details or delicate text can be lost or broken up in the printing process, and large blocks of text can be difficult to print consistently.  Light ink on dark paper works beautifully, but textured papers are out.  Thin papers also present difficulty, as the ink could cause them to buckle or warp.

Thank you so much Ponies!  You can see more of the talented screen printed designs from Two Trick Pony right here!

Photo Credits: Two Trick Pony

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Posted by: noleFiled under: guest posts, screen printing, the printing process

What You Need to Know About Four Color Process Screen Printing

It can be a challenge, but with proper setup you can wow your customers with four color process printing.

January 09, 2017

To create a photorealistic image in screen printing, most printers rely on four color process. That involves printing the four basic print colors — cyan, magenta, yellow and black (CMYK) — in fine, half-tone dots.

Unlike a typical four color print, in which the colors are clearly divided, four color process involves printing wet-on-wet with colors overlapping so they mix and create thousands of different tones.

Four color process screen printing takes some additional time, knowledge and setup, but screen printers who offer four color process printing are rewarded with beautiful prints that can wow customers. You’ll need to take careful steps as you choose and color-separate your artwork, choose the right substrate, set up your screen printing machine and print your images.

Quality Artwork is Key to Success

While all good screen printing begins with good artwork, quality artwork becomes even more important when printing a four color process. It’s imperative that you use a high-resolution image for your four color process jobs. In fact, many screen printers will use oversized images to achieve the level of detail they need for these screen printing jobs.

When separating the colors for your screens, you’ll need to change some of the settings in your separation program, as most programs default to settings ideal for printing on paper. First, you will need to make sure your color separation is set to CMYK. You also will need to verify that the cyan, magenta, yellow and black formulations used by your program line up with your inks. Some ink companies offer plugin files that will sync the colors in your graphics program with their ink colors.

The four CMYK colors - cyan, magenta, yellow and black - are
combined to create beautiful results with four color process printing.

You also will need to adjust screen angles for each color in the following range: 5 percent for yellow, 55 percent for cyan, 22 percent for magenta and 80 percent for black. The most common line count used for screen printing is 26.6 lines per centimeter. Halftone dots need to be set between 15 and 85 percent density. Finally, the dot shape will have to be adjusted; the elliptical shape is usually used in screen printing, as it works well within the squares created by the screen mesh.

Substrate Really Matters

In four color process screen printing, the substrate matters. Four color process printing is recommended for light — usually white or cream-colored — garments, as the different color variations do not stand out on dark garments. However, it is possible to print a good four color process image on a dark substrate with a white underbase, but it is not commonly done. Your chosen substrate should have a tight weave so that the individual dots have a surface on which to print; though you do need to be wary of heavy-duty materials woven of thick threads, as they can interfere with the detail of the half-tone dots.

Pay Attention to Details in Setup

Four color process work is incredibly detailed. Because of that, you will be laying down the finest coating of each ink color, and your screen printing machine setup will reflect that. Four color process screen printing requires densely woven screens, and most experienced screen printers recommend using 305 mesh count, or even slightly higher. The point weave, or thickness of the mesh, also should be fine — 34 micron is a good rule of thumb for a 305-count screen.

It’s also crucial to make sure that your screen tension is adequate. Loose screens budge during printing, rather than snapping cleanly away from the ink, causing blurring and improper color mixing. The screen tension should be around 25 Newtons per square centimeter; screen tension should not be less than 22 or more than 30.

The right squeegee goes a long way
towards getting great four color process results!

Because you are laying down a light layer of half tones with four color process screen printing, you want to create as little off-contact distance as you can. An off-contact distance of 0.040 inches is recommended. A 70- to 75-durometer squeegee should be used to create a good ink shear, and the squeegee and flood bar angles on your screen printing machine should be set to around 15 degrees.

Printing

When it comes time to print your four color process job, you will print from the lightest color to the darkest, so your color order will be yellow, magenta, cyan, black. If you are printing with a white underbase, you will print that first. Because the goal with four color process screen printing is to have the ink colors blend to create a myriad of tones, you will print wet-on-wet. There is no flashing between colors, unless you are printing a white underbase, and in that case, only the underbase is flash cured.

The biggest challenge in four color process screen printing is laying down the same amount of ink on each substrate to create consistent images. Because of that, automatic screen printing machines work best for four color process printing. However, it can be done successfully on a manual screen printing press, but you must be careful to use only one print stroke per color, and the ink must be lifted and not allowed to retouch the stencil once the print has been made. To lay down only a light layer of ink, use a gentle print stroke with the squeegee at a low angle.

Your first four color process job can provide your shop with a major challenge, but by using quality artwork and the right garment, and by setting up and carrying out your screen printing process carefully, you will be awarded with a beautifully detailed screen print. Looking for the right equipment to get started? Let's talk screen printing!

Tags: screen printing equipment setup, screen printing methods

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