If you'd like to learn how to screen print your own t-shirts, posters, signs and much more then it just takes some understanding of each step. And of course the materials themselves. For the purpose of the blog, we will just assume you have a basic set-up and are ready to start. Keep in mind, there are many different methods, and materials that can be used. However, the steps taken will generally be the same. This is what you'll need to get started.
- Printing press (Manual or automatic)
- Flash cure unit and conveyer dryer
- Ink (Plastisol is the most commonly used)
- Squeegees and flood bars
- Frames and mesh
- Scoop coater
- Exposure unit
- Palette adhesive or spray tack
FRAMES AND MESH
There are various types of screen frames and mesh counts.
Roller Frames: These frames will produce the best quality prints. However, due to the extra hassle of having to tension the mesh yourself, printers who don't have the extra money and time, or just aren't printing anything too complicated may avoid these frames.
Pros: Very high tension = Great quality prints, less issues while printing, faster printing, ink conservation, long life, interchangeable mesh counts, and higher detail in stencils.
Cons: More expensive, easier to break screens by accident due to such high tension, more time needed to retension, (Although if done correct, should only have to be done twice until that mesh has reached its work hardened state)
Aluminum Frames: This is a very common choice of frames due to their light weight, cost, and the fact that it's virtually maintenance free. A solid choice for the average or even above average shop.
Pros: Reasonably low cost, lightweight, easy to clean, low maintenance, and long life.
Cons: Fairly low inconsistent tension range, requires a slower print speed, mesh cannot be changed unless the glue is removed and new mesh is applied.
Wooden Frames: The most common choice for printers who are just starting. Pros: Very low cost, can be made at home with a little effort. Cons: Very low tension, heavy, wood can warp and swell as water and moisture are absorbed, lots of printing issues can arise because of this combination.
CHOOSING THE CORRECT MESH COUNT
It's easy to overlook this step, especially for amateur printers. It's really quite simple to understand. Mesh is measured in tpi (Threads Per Inch). The higher the number, the finer the mesh. The size of the mesh will also determine the amount of ink you will be depositing and also the lpi (Lines Per Inch) that can be printed successfully. It is essentially determining the resolution of your print. Depending on the brand of mesh you are buying, some common mesh counts are 110, 137, 166, 195, 205, 230, 280, 305, 355, 380. It's a good idea to choose low, mid range and higher range meshes to have on hand. And just in case your wondering, the yellow or orange mesh are generally those above 200.
When printing on light colors, its a good idea to use a slightly higher mesh. It will save you ink, give the shirt a softer hand, and ensure the highest detail.
When printing on dark shirts an under-base is normally used. This is a white ink deposit which is printed first and then flash cured so the remaining colors can be printed on top. Otherwise your yellow ink might look kind of green when it's printed on a blue shirt. It's best to use a lower mesh for your under-base, ensuring solid coverage. Higher mesh counts can be used for overprint colors. The under-base artwork is normally contracted by a few pixels to ensure that the overprint colors will completely cover the white.
Fibrillation is a term used when the fibers of the shirt show through the ink on the surface. This is the most common issue that can arise if mesh count is not determined accurately. It can be avoided if your screen has a reasonably high tension, using a low mesh count for the under-base, proper flash times/temperature, proper flood and print speed, and the correct off-contact setting. All of these terms will be discussed in further detail later. It's not as complicated as it may sound so don't get overwhelmed just yet.
Basic rule of thumb: Use low mesh counts for under-bases, simple designs, and thick ink deposit. Use high mesh for detailed designs, light colored shirts, and low ink deposit.
PREPPING YOUR SCREENS
Degreasing: The first and most important step to prepare your screen is Degreasing. There are a variety of different degreasers designed to treat mesh out there. But your household Dawn dish detergent can also be used. It's a good idea to use a CLEAN scrubbing brush when degreasing. You don't want to contaminate your brush with other chemicals, and oils.
First you want to wet both sides of your screen. A power washer is ideal for this step but not required. Then get your brush a little wet and apply a small amount of degreaser to your screen. Begin to work up a lather applying a moderate amount of pressure. The screen will not break on you. Be sure to move the brush in all different directions. Scrub each side for roughly 30 seconds or more. When this is done you'll want to thoroughly rinse the degreaser off both sides of the screen. A good way to check for a well degreased screen is to flood the top portion of the screen with water, it should run down the screen smoothly. If there are little bubbles or spots that break up the water you may need to scrub or rinse a little more thoroughly. Without even knowing it, you have also abraded the screen. Abrading is similar to painting a car or bike. You have to sand, or roughen the surface so that the paint or in this case emulsion will adhere.
Allow your degreased screen to dry. It's best to have a dust free environment with a clean fan, dryer, or dehumidifier. Before proceeding to the next step, ensure that your screen is fully dry. If there is moisture on the screen or frame then chances are it is not. You can touch the edges of the screen if you're in doubt. Avoid running your hands across the middle of the screen, as there are many oils that can be transmitted like this.
This is probably the most critical step in the process. You could be the fastest, most experienced printer in the world, but if your screen is coated poorly your print will also be poor. The way in which you do the coating process will determine the quality of your stencil. The stencil will play a very important role in the edge definition, and the detail in your final print. There are many types of emulsions out there. It's smart to read about some of them to see which one will fit the kind of printing you will be doing.
Before we talk about the coating process you should know how to use your coater. Many coaters are double sided. They have a smooth edge and a sharp edge. Using the smooth edge will produce a thicker coat and the sharp edge will produce a thinner coat.There are many variables that need to be taken into account when coating. The mesh count, the detail in the artwork, and the type of emulsion being used should all be considered for this step. These things will be better understood and fine tuned as you get more real life experience. For instance, some people may find that wet on wet coating works best for them. (applying 2 coats to the front and 1 to the back is 1 example). Some people also add another coat to the print side after the first coat is dry. These are both effective techniques, it's just determining what's best for you. Here are some good failsafe techniques to use.
1. Fill your coater with emulsion.
2. Position the smooth edge of the coater at the bottom of the print side. Turn the coater up allowing the emulsion to run into contact with the mesh. Be sure there is emulsion touching the mesh all the way across the coater. If not, you'll get an uneven coat or you may even have areas where emulsion is missing.
3. Apply even pressure to the coater and begin moving it to the top of the screen. Don't rush, it should take you around 5-8 seconds to apply your first coat. Coating fast will create more pinholes and a thin stencil which will cause premature breakdown of the screens. Once near the top, move the coater side to side to cut off the flow of emulsion. Wipe any large drips that are present near the top or bottom.
4. Flip and rotate the screen around. Spin your coater around and use the sharp edge to coat the backside of the screen. You can move a little quicker on this side if you'd like. ALWAYS end on the squeegee side. If you need to smooth out the print side with another coat just be sure you add another coat the the squeegee side as well.
5. Dry your screen print side down, just as they will be positioned on the press. Gravity helps pull the emulsion downward creating your stencil. This helps tremendously, screens should not be dried vertically unless there is absolutely no other option. This can cause more pinholes, premature breakdown, and an uneven stencil from gravity pulling the emulsion downward.
This is where you will take the film positives for your artwork and attach them to the screens so they can be placed in an exposure unit to expose the image. In an ideal situation you want your positives to be 100% opaque. Very little or no light should be able to pass through the image. If it does your screen will not wash out as easily as it should, thus creating tiny pieces of emulsion that will be stuck in your image and trap water creating printing issues. We will cover the art separations and film creation in further detail later on. Here is a step by step process that you can take for successful and proper exposer of your screens.
1. There are many methods you can use to attach the films to the screen. The main thing to keep in mind is placing each film (If there are multiple colors) in the same place on all of the screens. Otherwise they might not line up properly once you take it to the press. It's a good idea to use a light table with a grid taped to it. That way you will be able to place each of the film positives in the same place. I'll walk you through the process that works well for me.
2. Let's say I have a 3 color job to print. No under base just 3 colors on a light colored shirt. I have 3 pieces of film. I'll choose one and place it on the center of the grid just as you would be reading it. No need place it mirrored or upside down. Take a couple small pieces of invisible tape and LIGHTLY tape the film to the table. Then take 4 more pieces of invisible tape and tab the ends slightly. (It'll be easier to peel off afterwards) Place them on the corners of the film facing UP so it will stick to the screen.
3. Take one of your coated and dried screens and carefully place it on top of your film. Use the grid as a guide, or even make a jig to ensure that each screen is positioned in the same place. Then put some pressure on the parts of the screen where the upside down tape is positioned. Slowly lift the screen and your film should be stuck to it.
4. Now you are ready to put it in the exposure unit. Being that there are many types of units all varying in power, I highly recommend picking up an exposure calculator. This will help you determine the correct exposure time for the set-up and type of emulsion you are using. Because of all the variances I will not give you an estimation for exposure time. I've used emulsions that expose in less than 20 seconds and others that take 10 minutes.
5. Now your image is done exposing and it's time to wash it out with a hose or power washer. If you are using a power washer for this step just stand back a little and be gentle. You'll want to wet the backside and then start focusing on the image area on the front side of the screen. (flat side) Do not wash your screen out on the reverse side as this can cause the emulsion to weaken, thus creating loss of detail on the side which contains the stencil. Make sure that you have thoroughly washed all the emulsion out of the image area. Once you are happy with the result bring it to a dust free environment with a CLEAN fan or dehumidifier to speed up the drying process. Let the screens dry for a minimum of 45 minutes. Anything less will probably not be a sufficient amount of time to fully dry the screen.
Taping/Prepping screens for print:
Now that your screens are dry it's time for the final step before printing. There are many kinds of tapes you can use for this step. I prefer to use Blue Tape. It's a Polyethylene coated tape which resists inks and solvents and can be easily removed from mesh and frames without leaving behind a sticky residue. It also makes for fast and easy cleanup since it will wipe clean. Other tapes tend to absorb ink and tear easily. Follow the link to this video for a visual of how to and where to apply the tape. Taping Screens
So that pretty much sums up the steps that need to be taken before bringing your completed screens to the printing press. Please DO ask questions and I will be more than happy to help you with them. Come back for a similar step by step instructional post on how to go about setting up a job and printing it. I will include common issues with solutions and proper clean up.