Direct to Garment Printing

Direct to Garment Printing

What is Direct to Garment Printing?

(DTG) is a process of printing on textiles using specialized aqueous ink jet technology. DTG printers typically have a platen designed to hold the garment in a fixed position, and the printer inks are jetted or sprayed onto the textile by the print head. DTG typically requires that the garment be pre-treated with a PTM or pre-treatment machine, allowing for the following:

• Stronger bond between garment fibers and the pigmented inks
• Lay down loose fibers to provide a smoother substrate
• Chemically reacts with the inks to promote drying and curing

Since this is a digital process, the print is sharper and has a higher resolution, or DPI, than traditional printing methods such as screen printing. However, unlike screen printing, there is no long setup or clean-up process, and DTG has the ability to print just one single shirt for minimal cost.

Printing Process

DTG printers use aqueous textile inks (water-based chemistry) that require a unique curing process. Since D2 inks are water-based, they work best for printing on natural fibers such as cotton, bamboo, hemp, and linen. In addition, pre-treatment is typically applied to the garment before printing. The pre-treatment is heat-pressed into the custom t-shirt causing the fibers of the shirt to lay down. The pre-treatment also allows the water-based inks to bond more fully to the garment. This is especially important when using white ink on dark garments.

Once the custom garment -for instance a t-shirt- has been properly pre-treated, the shirt (or garment) is then positioned onto a platen system designed to hold the shirt in place. The shirt is then digitally printed according to the design in the printer queue.

What is Pretreatment?

Pretreatment is a liquid solution used by Direct-to-Garment printers to allow the printing and washability of white ink, or full color images on a variety of colored shirts, most commonly black shirts.

The concept is simple. Just as drywall is primed with primer before painting, this primer allows the colored paint stay on top of the drywall and not soak in. If the paint soaks into the drywall, the color  selected will be muted and off color.

The same is true with pretreating any DTG shirt. The pretreatment acts just like the primer in the drywall example.  It allows the white ink printed through the DTG printer to adhere to and sit on top of the shirt. If the white ink soaked into the shirt, it wouldn't be white – more of a grey, and not give a smooth surface for the CMYK inks to print on, resulting in a really bad looking, unsellable shirt.

Pretreatment also reacts with the white ink. This reaction is similar to when a screen printer uses a “flash” unit to semi-cure the plastisol ink so the next colors printed on top don't smear or mix together (a result of printing wet-on-wet). The pretreatment “flashes” the white ink causing it to change properties and become more or less a semi-solid surface so when you print CMYK on top of the white ink, it doesn't mix and look muddy.

Pretreatment is the cornerstone of direct to garment printing. It is the foundation of your garment. A proper application of pretreatment will help yield better results for any white ink direct to garment printer.

Pretreatment is an aqueous solution, usually milky or clear in color, and designed to help the white ink sit on top of the shirt. Though it will not necessarily cause a reaction if you touch it, it is recommended to wear protective gloves, a respirator and other protective clothing just in case.