Screen Printing Process
The screen printing process includes many steps. Of course, there’s the actual printing of the shirt, piece of apparel, bag or item, but there is also much, much more to it than that. There’s also extensive set-up, configuration, tear-down and more involved, and each step must be done carefully and meticulously if you want the absolute best final product.
Let’s take a look at how the screen printing process works, from start to finish, now.
The separation process – during which the artwork is separated into layers and prepared for printing onto film positives - is different for each type of screen printing. Depending on which type of printing you choose, there could be any number of film positives produced, and the number of film positives produced directly correlates to the number of screens you need to finish the job.
Here’s how each separation process works:
- Spot color – Spot color is for projects that have basic, solid color fills – ones that are easy to identify and separate. For these, separation works like this: Open your image file, and separate each color into a different layer. If there are two colors in the design, you’ll have two layers. If there are 10 colors, there will be 10 layers. Spot color works with any color of ink, so it’s a good option if you have a simple design and a client who wants very specific pantone colors.
- 4 color process – The four-color process works like your ink jet printer – using shades of cyan, magenta, yellow and black to print the desired design. This is generally only used on white or very light fabrics, as the color of the material can interfere with the mixing of the inks. Unlike with spot color, you don’t need a layer for each individual color with the 4-color process. Instead, you need one for C, M, Y and K (cyan, magenta, yellow and black.) If you are printing on a dark material, you may need a fifth layer for white ink, too. Because you are limited to four colors in this process, it may be difficult to achieve an exact replica of your desired artwork color-wise, but as long as the layers are separately probably, it should come pretty close.
- Simulated process – The simulated process is for intricate and complex designs. It uses Pantone ink colors in varying halftone percentages, then layers them to create new colors. With the simulated process, you don’t need a layer for each color or even for each shade. Instead, you separate your image into the number of screens you have available (make sure account for flashing and have enough available space on the press if necessary). Try to separate the layers into general hues, and aim to mimic the original artwork as close as possible.
- Halftone – Halftone printing uses shading, gradients and small, barely visible dots to create the desired design. It can help deliver a very realistic-looking print – especially on photos and other images.
Once you’ve separated your image, the layers will need to be printed onto transparent film positives, which will act as stencils and will be placed over your screens. Let’s look at how that process works now.
- The first step is to set up your screens. These are created by stretching polyester fabric over a frame, usually made of aluminum or wood. The fabric used should have a high thread count, and it must be very tight, so it won’t budge when you start to lay the ink over top.
- Now, it’s time to create the photo negatives. Place your film positive over a screen, and apply an ultraviolet sensitive photo emulsion to it. Then, expose this to UV light (either naturally or by using UV light bulbs), and it will harden, creating the perfect “stencil” for your print. Do this for each of your layers, and be sure to take every step possible to keep additional light from hitting the screen. This could affect the quality of your negative.
- Next, you need to wash the emulsion out of your screens – this is what leaves behind a stencil, which you will use to print your design. A pressure washer will deliver the best results. Then, you need to let the screen completely dry before setting up your prints.
- Once the screens are dry, it’s time to put the screens on your press. This can be a tedious process, especially if you have multiple colors. Each screen will need to be properly registered so that every color is aligned properly. If this isn’t done, it will mess up the design, and your print won’t come out as planned. After you’ve registered the screens, you can tape off the registration marks on them, and you’re ready to start printing.
- Now, push your desired ink through the screen using a squeegee, and you’ll have the first layer of your print! You’ll need to repeat this with each color your image has, sometimes you need to flash (dry) the ink in between each round. This prevents running and mixing of colors.
- Finally, you’ll need to run your printed item through an electric or gas dryer to fully cure the inks. Different inks cure at different temperatures, so make sure you choose the proper settings for your ink. If your print isn’t cured correctly (or completely) it can cause the image to crack after it goes in the wash.
- After this, you’re done! You image is printed, and the item is ready for use!
If you’re going to be screen printing for a while, you probably don’t want to throw away all those screens after a job – that would be wasteful (and expensive.) Instead, you can recycle them. Simply rinse out the screen and make sure all ink is removed. Then, remove the hardened emulsion. You may need a professional-grade emulsion remover to do this, but it will help immensely.
You’ll also want to clean the screen, to ensure that no unwanted flecks of ink, dirt or debris get on your next project. Just use a small brush, along with some degreasing product and water, and scrub the entire screen down. Let it dry thoroughly before using the screen for another project.