Sublimating T-Shirts?

John Barker has been steeped in the digital printing and imaging world for over six years. Since 2005, he has headed up the acclaimed sublimation educational series Project Sublimation. To catch Barker at a workshop or trade show in your area, visit projectsublimation.com or email info@projectsublimation.com.

The digital decorator who employs dye-sublimation in his or her line-up of embellishment technologies knows that the specialty shirts required for sublimation (eg: 100 percent polyester or garments with a polyester shell) are not cost comparable to the 100 percent cotton or poly/cotton blends often used in other technologies such as screen printing. In other words, these are not one-dollar T-shirts. Ruining a sublimation-friendly shirt hurts more, especially if you’re decorating one of the new performance-apparel products designed to wick moisture from the body. To avoid costly mistakes, there are a number of troubleshooting techniques as well as tips and tricks to employ when decorating a sublimatable garment.

Before pressing

When you’ve been using sublimation inks regularly, you start to get a feel for color even before pressing. Sublimation inks are activated with heat and pressure, so the image tends to brighten as it gasses off of the page. First and foremost—before decorating a shirt for a customer—it is imperative that you print and press a representative palette of RGB colors onto a shirt using your chosen sublimation inks. Sublimation is dependent on designing the image with the final product in mind. You will not know how the colors will look on that shirt until after pressing.

Hence, the color palette. If you print out a palette of RGB colors and press it onto a shirt, you will be able to choose specific RGB colors when designing the garment graphic based on what they look like post-pressing. Think of this T-shirt as you would a Pantone book. Remember to design and print in RGB mode when using sublimation (despite the fact that you’re outputting to CMYK).

You don’t necessarily have to print and press the palette only onto a T-shirt; you can get away with doing so on a cut piece of 100 percent polyester fabric, too. What is important to remember is that your sublimation colors will look different based on the color of the substrate. If you’re only decorating white shirts, a standard RGB palette on a white shirt or swatch of fabric will suffice. However, if you’re branching out into other colors available (some suppliers now offer over 15 colors that will take sublimation), it is recommended that you press a palette onto a shirt or cut piece of each particular color in order to see what your final, decorated colors will look like. The reason for this is simple: Sublimation inks are dyes, not pigments. Therefore, the color of the substrate affects the range of reproducible colors. On many of the lighter, pastel colors, you can reproduce about 70 percent of the available color gamut. 

Before decorating a five- or six-dollar (or more!) shirt with a permanent, sublimated image, I often will print out a smaller version of the graphic and press it onto a swatch of fabric. It costs very little in ink and paper, and often you can catch color mistakes ahead of time by doing so. If you’re not satisfied with the color you see on the small version, you can then go into your graphic, change the RGB value based on your palette T-shirt, and re-print. Industry suppliers offer shirt swatches you can either practice on or hand out as samples. You can also visit your local fabric shop or Wal-Mart to purchase bulk, 100 percent polyester fabric which you can cut into small swatches.

Pressing a shirt

When decorating a sublimation-friendly shirt, there are variables you can manipulate to achieve a quality image on the final product with which both you and your customer will be satisfied. Depending on the manufacturer, you may have different temperature settings and dwell times. With certain shirts, pressing the image for 35 to 45 seconds at 400°F is recommended. With others, the temperature should be dropped to a range between 385 and 390 with a dwell time of 55 seconds. The point is, you can play with temperature and dwell to elicit a desired result.

Here are three common trouble spots to watch out for when pressing:

1) The colors look wrong on the decorated shirt—First of all, let’s assume that you’ve installed the proper color profiles for your ink and printer, and that you’ve set up your software and drivers as recommended by the ink manufacturer based on its product. If you’ve printed and pressed an RGB palette on a shirt (as discussed above), this prevents a lot of color surprises. All things being equal, if you plug in the RGB value of the color you see on your T-shirt palette, you’ll get the same color when you print your customer’s T-shirt graphic. For example, if you pressed the T-shirt palette at 390° for 55 seconds at medium pressure, when you press the same RGB value using the same temperature, dwell time and pressure, you’ll get the same results. There is much to learn about color management, and it is recommended you attend a hands-on educational event either through a trade show, your distributor or an independent workshop series.

In addition to working with colors in your Corel or Adobe software, heat-press temperature is a critical factor. When trying to recreate palette colors, it is imperative that your thermostat on the press is accurate. Investing in an infrared temperature gun can help ensure that your press temperature is accurate. If your temperature is wrong, you’ll get mixed results on your end product.

Also, make sure that you’re designing the shirt based on how the colors look on the final product (eg: your palette T-shirt) and not based on what you’re looking at on the screen. When the inks gas under heat and pressure, they change. Not only do they brighten, but there is a spectrum shift, too. Even calibrating your monitor will not give you a completely accurate representation of the final product. For example, I don’t worry that my burnt orange looks pinkish on my computer monitor; I know that when I output to my CMYK printer and transfer the image under heat and pressure, the color will migrate to my desired burnt orange.

2) You see press lines from your heat press and the transfer page—This is a common occurrence when pressing sublimatable T-shirts, and is a direct result of the fabric. Polyester is a type of plastic and, when subjecting a plastic to 400° of heat, it can soften the fabric. You may see the shape of a square matching the size and shape of the heating platen on your press, as well as a square matching the shape and size of the transfer paper. The good news, based on feedback from many digital decorators, is that the benefits of a sublimated shirt (full-color, photo-quality, permanent image with no hand) usually far outweigh the occasional press lines, and customers rarely complain. That being said, there are ways to avoid press lines:

  • reduce the temperature slightly while increasing dwell time;
  • bevel the edge of your heat press pad (45 degrees); this dramatically reduces press lines caused by the edges of your platen;
  • use a larger size transfer paper (if your printer model allows for it) so that the edges drape well beyond the image;
  • purchase foam pads to be placed under the T-shirt to slightly elevate the shirt and diffuse the lines from the platen and transfer paper;
  • immediately upon removing the transfer from the pressed shirt, while the shirt is still hot, pull the sides of the shirt away from each other to diffuse the lines.

3) The image looks blurry after pressing—If the graphic looks good coming off the printer, but winds up a blurry or mottled on the shirt, a couple of things may be happening. First, make sure your temperature, pressure and dwell times are consistent. If you dwell too long when transferring a sublimation image, the inks can continue to migrate across the fabric, leading to a blurred image; this can shift colors, too. Not using the proper pressure can also lead to image quality issues. Medium pressure is best: not too hard to close the press, and not too easy. If you’re using a manual press and you have to stand on it to close, you’re using too much pressure. With a pneumatic press (depending on the model), 30 to 40 psi is usually enough.

In the end, the more you use a technology, the better you get at that technology whether it is embroidery, screen printing or sublimation. It becomes second nature. Practice might not necessarily make perfect (even seasoned sublimators make mistakes), but it can help you prevent costly mistakes when decorating garments using dye sublimation.