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Create the perfect printing canvas

Smooth Operator

Brian Walker started in the screen printing industry in the mid-1980s while still in high school and has since been involved extensively with the direct-to-garment printing market. Currently, he is the CEO and owner of RTP Apparel and Image Armor. RTP Apparel provides pretreated T-shirts to the DTG industry. Image Armor is a DTG solutions provider that manufactures inks and pretreatments.

In general, most people don’t think much about the shirts on which they are printing, let alone about how those canvases should be properly prepared for printing white ink with a direct-to-substrate/garment printer. But the shirt itself is a huge factor in the quality of the final print.

This is a microscopic picture of a shirt that had pre-treatment applied but was allowed to air dry. Notice the fi bers still tend to stand up off of the weave of the garment, making the shirt a little more “fuzzy” and giving a rougher print surface. This would be similar to using regular copy paper in our photo example. Here, the same shirt was pre-treated with the same method (using a pre-treat machine) with the same settings and solution, but a regular clamshell heat press was used to cure the pre-treatment. Notice the fibers are more compressed and lay down much better than the airdried shirt.

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The variable that changed in the example at left was that the shirt was cured with a pneumatic heat press set to 80 psi. The additional pressure helped to really compress the printing surface area and provide a better result than both the air-dry method and use of the standard clamshell heat press.

For a parallel, think about printing pictures on a home computer with inkjet printer. The prints will look good on regular copy paper, but it is not the same result one would get by printing the image on glossy photo paper. The reason the print on photo paper looks so much better is because it has a much smoother surface that allows for sharper dot patterns. The same applies to our garment printing machines and the T-shirts we use.

A great shirt with a tight weave and little fibrillation (with few loose or stray fibers) makes a better printing surface. Remember that the better the starting canvas, the better the final print. Of course, great artwork and knowing how to get the machine to print optimally for the job at hand will also achieve better-looking finished garments. However, there is an overlooked aspect of the entire process that can easily give finished prints that higher-quality edge.

The cure

It is no secret that the pre-treat process is essential to digital direct (D2) printing. It’s imperative that users achieve as good and consistent application of pre-treatment as is possible in order to get the ink to “stick.” Applying the proper amount of pre-treatment fluid to the shirt in as consistent a manner as possible will also lend to a much better final print.

Most often, this consistency is achieved via an automated pre-treatment machine. Though many people still apply pre-treatment by hand, this is another often overlooked area where an uneven application of pre-treatment, too much or too little, will affect the final print.

Given all of the above factors are in place, the next variable is how the pre-treatment is set or cured. There have been two main methods adopted in the garment decorating industry—one is to let the pre-treat air dry and the other is to use a heat press to dry the solution. Let’s take a look at the differences between the two.

The air-dry method can work. However, problems come into play where production volume is concerned. There are also other factors to consider—dedicating area in which to hang and dry the shirts while the water content in the pre-treatment evaporates, for an example.

Utilizing a heat press, on the other hand, immediately compresses the garment with pressure and heat to evaporate the moisture more quickly. It provides a better result, as applying heat and pressure to the pre-treatment is, in essence, “curing” the shirt. This causes the fibers to be compressed down flat. And, as the water from the pre-treatment evaporates, it leaves the polymers in much closer contact with the shirt fibers that are being compressed. The result is that the pre-treatment actually holds the fibers down, “trapping” them closer to the shirt and providing a much smoother surface.

1. Air-dry cure of pretreatment;
2. Regular clamshell heat press;
3. Pneumatic heat press:

Three shirts were printed with the same exact image (the larger text is a 16-point font while the smaller text is 8-points) and cured on a manual heat press with slight to medium pressure. The results are seen here. Additionally, the air-dried shirt did not have nearly the optical brightness as that which was pressed with the pneumatic heat press.

Beyond the merits of heat pressing pre-treated garments for quality prints, the other factor at play is what type of heat press will provide the best results—a manual clamshell style or pneumatic (automatic) press.

Scott Trammell of Dennison T-Shirt Graphics in New Philadelphia, Ohio runs a retail screen printing, embroidery and direct-to-garment printing shop. During the first year of printing white ink, he utilized a standard clamshell heat press to cure the pre-treatment. He reports a noticeable change in making the switch from a clamshell to a pneumatic heat press: “The main difference was in the print quality. When we used the manual heat press, we could see more of the fibers sticking up through the white ink film. The pneumatic heat press decreased that issue.”

When later asked if it was worth making the switch to the pneumatic heat press, Trammel noted that it was, because the quality of prints increased and there was less operator fatigue.

Though a pneumatic heat press is considerably more expensive than a standard heat press of the same configuration, the results may be well worth the investment. It’s important to determine whether the improved quality justifies the additional expense of a new pneumatic heat press.
Those who are continually looking for ways to improve overall digital direct prints need to review the entire process. The utilization of a pneumatic heat press in the process will definitely help achieve a better overall end product, as will the selection of a good shirt on which to print the designs.