Learn how the steps you take in prepress, printing, and drying influence print longevity.
By Rick Davis
If you want to achieve success in the garment-printing industry, you must know how to give customers what they want in a productive and cost-effective manner. A client of mine recently brought me a job that involved a three-color print on the garment's front and a single-color print on the back. For the back print, the customer requested an athletic-like ink film to enhance the longevity of the print. This is a situation you've more than likely encountered several times: The customer is under the misconception that ink-film thickness determines the longevity of the print.
Typically, when ordering screen-printed T-shirts, customers want prints with a soft hand, which means they actually need a thinner ink film. A really thick ink film and a bullet-proof print are usually not a priority when it comes to conventional garment graphics. Educating the customers about the relationship between ink-film thickness and print durability will help you steer them to the best solution. But you also need to understand how to produce the ink-film thickness that the print requires, whether it's a standard garment graphic or one designed for use in athletic activities.
Our industry has no bible to dictate the proper printing parameters for every situation. That means we have to determine what works best for us on a case-by-case basis. Sometimes all we can do is make our best guess and hope everything works out. This can be a true challenge for novices who are trying to work through the learning curve of discovering how each part of the workflow can influence the finished product.
Each choice we make in the screen-printing process has an impact on the products. Mesh selection, ink characteristics, squeegees, and your printing habits all play a role in the quality of the end results. In most cases, a printer may opt to use 110- to 125-thread/in. mesh to ensure good coverage and produce a thicker ink film to meet a customer's demands. This thread count will work when printing light-colored inks onto a dark garment. But in my situation, the job involved printing a navy-blue ink onto a white and heather-gray garment. I was able to print the image with a 200-thread/in. mesh and double stroke the print to achieve the desired result. I laid down a good, solid ink film without needlessly wasting or caking on the ink. I could have achieved the same results by using any mesh in the 180- to 225-thread/in. range.
I live by the concept of quality in/quality out in my shop. That means that by bringing a well-made screen from prepress to production, I can more easily set up my press to properly accommodate the job. The conditions under which we print impact the final product, so if we make quality and process control a priority, we can fine tune our processes and efficiency to better please our customers.
In my situation, retensionable screens helped me meet the customer's requirements and maintain control over the actual amount of ink being deposited onto the shirt. Retensionables make it possible to maintain higher tensions, which allows for easier printing (especially on manual presses). In addition, higher tensions make it possible to use a finer mesh count as opposed to one twice as coarse. I printed the job with minimal off-contactabout 1⁄16 in. Reducing off-contact made the printing process much easier because the mesh had to travel a shorter distance to meet the surface of the garment.
Printing with high-tension screens requires care. It's easy to apply a lot of force to transfer the ink through the mesh. Some printers also feel the need to increase off-contact in order to achieve a clean snap-off. Printing with greater force often passes the ink into and through the substrate instead of depositing it onto the substrate's surface. The end result is a thick, heavy ink film that requires a greater amount of time in the oven to achieve the proper cure rate. This practice also is notorious for wasting lots of ink.
Garment screen printers who decorate athletic apparel might use a mesh as coarse as 86 threads/in. in order to deliver the ink coverage and bulk that many athletic-garment buyers want to see. The greatest issue with printing the thicker ink films associated with athletic applications is ensuring that the entire ink deposit is properly cured. This can be especially challenging for smaller shops that use smaller infrared dryers (as opposed to larger shops that typically use gas-fired units).
The most critical aspect to keep in mind is that the thicker the ink film, the greater the amount of timenot necessarily heatthat is required to properly cure the entire ink deposit. With standard plastisols, this means the printed ink film must reach 320 °F from the surface of the ink film to the point where the ink film comes in contact with the substrate. Anything less will simply result in an under-cured ink film that lacks durability and washability. This is one reason why it's beneficial to use a screen with high mesh tension and fine mesh count to help control ink deposition.
The greatest mistake that printers make when working with thicker ink films is forgetting to set up their dryers to properly meet the requirements of the print. Some printers will increase the dryer temperature in an effort to properly cure the thicker ink films, but they neglect to consider the fact that the greater volume of ink requires a greater amount of time in the oven to properly cure. The end result here can be an ink film that is over-curedre-melted by exposure to temperatures that exceed 360 °Fon the surface and under-cured at the base of the ink film, which happens when that part of the ink deposit fails to reach a minimum of 320 °F. Again, print durability and washability suffer.
Smaller shops that use infrared dryers need to slow the belt speed to increase time that the printed garment remains in the heating chamber. Even though printers use thermocouples, non-contact pyrometers, and heat-sensitive tapes to measure curing temperatures, I still recommend wash testing to ensure that the ink film is properly cured.
When it comes to productivity, I firmly believe that less is more. The suggestions I've made here will allow you to print a thinner ink film and still achieve the print durability that a customer may desire. Meeting the customer's requirements for a thicker ink film does not mean you have to lay down what amounts to an actual athletic print. The parameters I mentioned also allow for faster printing strokes and smoother ink deposits than those attainable when coarse meshes are used.
It's not uncommon for customers to know what they want without knowing what they need. You need to be creative in order to achieve the result the customer desires while meeting the productivity and profitability needs of your screen-printing business.
Did you enjoy this article? Click here to subscribe to the magazine.