25 May Top Tips to Improve T-shirt Print Quality
One of the reasons I like working in this industry is that it has a great mixture of art and science. There is a craftsmanship feel to it that is palatable on the production floor. Over the years of managing production, and even back when I was an art director, there are a few things that would commonly show up in print process that would need to be corrected on press. Some of these are really simple and easy, some are a little more complex. I’m sure I’m going to leave off something, so please add yours to the comment section below!
Registration – There are a lot of steps to check if you are having registration issues. The problems could be as simple as the screens just aren’t lined up correctly, or it could be something more elusive such as low tension screens, one of the platen’s that isn’t leveled, an artwork problem, or any number of things. A good operator should be able to set up a job on press in about five minutes per screen on average.
The best trick is to start with the simplest and that is to make sure you are registering the screens together using registration marks. I know some shops don’t use them as they don’t want to tape them off, but that savings is quickly diminished if you are having difficulty getting the job set up as the screens won’t line up. At a minimum, these should be above and below the art and large enough to be seen through the screen. Make sure your screen room blows these out completely, and doesn’t block them out during the quality control/pinhole hunt step. These marks should line up exactly center with the platen. Dial these in one at a time.
Also there is plenty of long standing on-press registration tricks you can use. Some printers will print the black or underbase screen on a junk shirt, platen or on a clear tape coated platen and quickly flash cure the print. They then will use this to register the other colors.
Using more advanced screen prep tools such as a computer-to-screen imaging system, Tri-Lock, pin-registration systems or other devices will help reduce your registration time, as the screens will be imaged perfectly registered to one another as a set. You just need to use your micros to dial them in usually. If your platens are not perfectly centered on your press arms, you could have registration and off-center issues, so watch how you lock in your platens.
If you are having problems registering your image on screen, the best method to determining what could be the issue is to review each screen individually to see where the problem could be. Only change one thing at a time. I’ve seen too many operators get frustrated as the image won’t register, as they adjust two or three screens at a time and then review the result. It’s a moving target if you do it that way as there are too many variables. It’s actually faster to slow down and use your brain. Try it!
Color Matching – These days most jobs have ink colors specified with a vast array of Pantone colors called out. Smaller shops may just offer a stock set of colors, but even they will be asked occasionally to match a particular PMS color. There is an ongoing debate for charging for a PMS match, as larger shops see it as a simply a task that has to be accomplished and have built the infrastructure to handle it; while the smaller manual shops aren’t set up and usually charge a fee. The smaller shops are the ones that usually have “a guy” that has a certain eye for mixing color, and don’t see the need to change. To me, that’s foolish as you want to make the task as easy as possible and remove the step away from a particular person and toward being a standardized function of your shop that can be trainable.
To build your ink room set up for quick and easy color matching you only need a few tools. The primary tool that is needed is a really good scale that measures to .01 and can be zeroed out. Get one that is stainless steel for easy cleaning.
Most ink companies have an ink system that allows you to build your Pantone color by using a base plus an assortment of pigments. To mix a color, you simply type in a PMS number into a computer workstation in your ink room and the list of ingredients will appear. You enter the quantity of ink you want in the bucket and the system will tell you exactly how much of each ingredient to add by weight. Place an empty bucket on the scale and zero it out. Then add the base per the requested weight and zero it out. Then, each required pigment is added, zeroing out each time. Mix up the ink when finished and it will exactly match the required PMS color in the volume of ink you need for the job. Average time to mix is usually about four minutes for a batch of one gallon or less.
Ink Coverage – Believe it or not your ink coverage is mostly dependent on a combination of the mesh selected for the job and the thickness of the emulsion on the screen, rather than how much squeegee pressure you are using. Using so much pressure that your squeegee bends over like the letter “L” doesn’t contribute much more ink to the situation…and actually could start contributing to other problems.
Tons of articles (even books) have been written about the subject of “Emulsion Over Mesh” or EOM, which I’m not going to dive too deep on this blog. Frankly, they are much better than what I could write. The short version is that the emulsion you add to the screen creates a channel. During the printing process when you flood your screen, you are filling that channel with ink. If you have everything on press set up correctly, you need just enough squeegee pressure to sheer the ink through the channel and onto the t-shirt. You shouldn’t be driving the ink through the screen like a hammer and nail.
Want more ink down on the shirt for an underbase screen? Try adding one more coat of emulsion to the screen (print side) during the prep stage. Some shops even use capillary film for a thicker stencil for a “one hit white”.
While the screen certainly plays an important role in your ink coverage, so does your squeegee choice. A softer squeegee will likely send more ink onto the shirt, while a harder squeegee won’t. When there are ink issues on press, one of the first questions I might ask is what type of squeegee is the operator using currently? Too much dot gain could be the result of using a softer squeegee.
Print Hand – “Hand” is the industry term for how the ink feels on the shirt after printing and curing. A lot of shops have moved to using waterbased ink because it gives the final print that soft, retail hand that is very popular currently. Essentially with each screen and color you are printing on the shirt, the thicker the deposit of ink will be. Sometimes this is an issue, sometimes not. If want to achieve a softer hand on the print here are some tips:
Use a higher mesh count for the screen. The higher the mesh, the less ink will be deposited onto the shirt. For underbase screens, try using a 156 instead of a 110. Screen selection isn’t automatic, and is image dependent as some mesh choices you might want to make won’t be completely successful. The only way to learn is to experiment and see what works for you.
Try using a different ink base to increase the ink viscosity. Finesse base, Chino base…even adding some curable reducer to the ink you are using will work. The idea here is to “thin” the ink down to improve how it flows onto the shirt substrate. Be careful though…inks are formulated to work a certain way on purpose. When you start introducing additives to the ink, you may change the property of the ink and have some unintended consequences if you aren’t careful. Opacity and curing issues being the top two issues in most cases.
Roller squeegees. This after-market device works great and we have them on all of our automatics. After you print your underbase and flash the shirt, use a roller squeegee in the cool down station. This flattens the ink that has just been gelled by the flash unit and sets up the printed ink nicely for taking on more colors. You can also achieve this yourself by using an unexposed screen, a squeegee, and some base. Set up the screen like normal with the squeegee. The base gives the squeegee something to move around and reduces friction. Underneath the screen tape a big sheet of Teflon (like the kind you use for your heat press cover.) A roller works better, but this technique will work in a pinch.
Keeping Things Straight – Your shirt print quality is sometimes only as good as your loader. Getting the shirt straight in in the right position on the platen is a basic step in printing, and often overlooked until the client complains about crooked or off-center imprints. Let’s face it, loading a t-shirt press is a monotonous and robotic like process, and it’s easy to lose focus and get distracted on what you are doing. Look at these in your shop:
Speed. If your press operator can’t handle the speed of the press, misses boards and has questionable image location results, it may be that they have the speed set too fast. Printing a bunch of misprints quickly is never better than running the press at a speed where quality counts. All too often in production the emphasis is on how many impressions are printed during the shift. Start keeping a discrepancy log with misprints, quality control and other issues and you’ll quickly see that these errors can add up fast. Slow down for better quality!
Ergonomics. Skilled press operators know exactly what they like in a work station area. A good, thick spongy mat under their feet. Some music to print with. A most of all a properly positioned cart or table full of shirts. As every printer is a different size, let them adjust this to what they like. Shorter printers sometimes can’t handle the same mountain of shirts that a taller printer will churn through. Some printers like the shirt openings facing them, some like it the opposite way. There isn’t a hard and fast rule except one – comfort counts. Good print quality for loading comes for being comfortable and relaxed in the process. Make sure there is room for them to operate and adjust along the way.
Mark Your Boards. Good press operators instinctively know where and how to load the shirts for the best print. However, they don’t stop there. For great results, mark your boards where the collar is to drop, where the center of the shirt will be, or any other landmark that is a concern. Have a T-square, ruler, tape measure, and some markers ready. If you are trying to line up a landmark on the shirt such as a seam, top of the pocket or other item a great trick is to use lasers. You can get lasers that will project dots or lines from any hardware store. These can be magnetically positioned onto the metal part of your press and the line will project down onto the board. Use two and form a cross for positioning pockets.
Pinholes & Screen Problems – Why is it that most shops will staff their worst employees in the screen room when it is such a keystone part of the entire printing process? Granted it is by far the grubbiest job in the building, but if you staff your screen room with great, process minded people you can eliminate a lot of on-press challenges with screens.
A good number of issues stem from improperly cleaned screens, emulsion coating, exposure issues, and failure to wash out the emulsion correctly. There are many variables that go into making a great screen, but one thing is certain and that is you can judge the craftsmanship of a screen-print shop by how they run their screen room. What emphasis are they placing on standards and controlling variables? Top shops are very particular about their screens, and go to great lengths to perfect the outcome by introducing more precision in this area.
If you are having challenges with your screens on-press, take the initiative and double back to the screen room and look for the cause of the issue. For example, pinholes can be the result of dust and smudges on the glass of the vacuum table. How often is that cleaned? By the way, one of the most overlooked benefits of going to a computer to screen system for imaging is the fact that you no longer need the vacuum step in exposing the screens, so the dust on the glass problem is eliminated…therefore so are the pinholes.
Artwork – Your art staff can help you control your print quality in many ways too. It helps if they understand and comprehend the mechanical process of printing. Their knowledge and understanding of what happens on press will greatly influence the decisions that they may be making in creating the art that will be printed later. They absolutely need to understand why you flash cure the ink on press…and more importantly when. Their knowledge of underbasing inks is crucial to your success. If you have a crack staff, they should be the ones determining mesh counts and record their choices in your system so that your work order can be built with repeatable results. Start with standard choices, such as what mesh to use for an underbase screen, and build the knowledge from there.
As t-shirt printing is such a specialized industry, hiring an art staff that has this knowledge can be difficult. Finding creative and talented people is easier; which is why so many shops have to “grow their own” and educate their art staff with on the job training. Get the art staff away from their computer screens and out into the shop. Have them hang around, take notes on their jobs, approve all their work…maybe even help a print crew set up and run a job or two. Creative people will make decisions on their work on an unconscious and gut level based on what they think will add to the work. If you combine that will the practical knowledge of what will be able to be achieved on press, your print quality will be greatly increased and will lead to some stand-out work later.
Ink – Everybody has their favorite ink manufacturer. I’m not going to get into that debate on this blog, but let’s discuss how ink is used instead. Regardless of who makes the ink in your shop, it is manufactured to be handled and cured in a certain manner. Are you using yours correctly? How often are you checking to see if your dryer temperatures are correct so that you know you are curing your ink correctly? The most common ink failure is undercuring.
Different types of ink have different dryer temperature needs. Are you adjusting accordingly? For example, one of the biggest problems these days is trying to control dye migration on performance fabrics. Shops will change over to use a performance ink, but fail to adjust their dryer temperature…and maybe even flash the shirt one or two times during the print run too. The dye migration still happens and they blame the ink for their white ink still turning pink on red shirts. It isn’t the ink folks. Make sure you read and understand the specific instructions for the ink you are using in your shop.
Controlling variables is the key. At the end of the day, the standards you set in your shop will go a long way to determine your printing production outcome. Minor details, such as the choices the art staff makes, the cleanliness of the screen room, or the mesh selection…can go a long way to affect your print outcome. These may not be outwardly noticeable connections on your shop floor when you have a problem on press with a big deadline due. All of the “big picture” challenges need to be addressed and corrected in a proactive manner. Here’s where the leadership of your production staff should come into play. If they don’t address the situations, why should your print staff? Want to improve your print quality? Connect all the dots in the shop and see if you get better results.