In many ways, the pre-treating step is the most important step of Direct-to-Garment (DTG) printing. Pre-treat is a solution of distilled water and glue. It is applied to a garment and then heat cured to remove the moisture. This yields a printable surface. Properly pre-treating a garment will ensure a quality print that will be durable and have excellent washability.
There are two ways in which to pre-treat a garment for a DTG printer. It may be done either by hand or with an automatic pre-treat spraying machine. Since pre-treat must be laid evenly over the garment, an automatic spraying machine will produce the most consistent results. However, with practice, spraying by hand will work just fine if an automatic sprayer is out of your price range.
The amount of pre-treat needed to ensure a high quality print is dependent on the weight and color of the garment being printed. Lighter garments require less pre-treat. Conversely, more pre-treat is required for darker garments. This is because darker colors are more likely to show through the ink in a design, so more pretreat will ensure that the design is opaque enough to cover the shirt’s color. There are also different types of pre-treat that allow you to print colors on white garments and to print onto polyester garments or blends. It is very important to know which type of pre-treat is needed, and how much, for each type of garment and color to ensure the highest quality finished product.
Once the pre-treat has been sprayed onto the garment, the garment must be cured using a heat press. A pre-treated garment is cured with 60-80 pounds of pressure for around 35 seconds at 355 degrees using a heat press. The temperature of the press is crucial, but is determined based on the type of pre-treat being used. This step is vital for the durability of the print as any remaining moisture can interfere with the ink’s ability to adhere to the garment.
As with any part of the printing process, there are several common hiccups associated with the pre-treating process. One is staining. Staining is typically caused by impure water used in the manufacturing process of the garment itself. Garments are manufactured all over the world and the water used in dying the product is not always the same quality. Another common issue is scorching the garment. Scorching happens when a burn mark is left from the heat press. Certain garments are not able to handle the time, temperature, and pressure necessary to create a proper, printable surface. Speaking of pressure, it is also possible for the heat press to leave a permanent box on the garment. It is important to do a lot of test printing onto different brands and types of garments to see what works best. Some brands simply pretreat and print better than others due to where the garments were manufactured. However, with a little research and practice most of these issues can be avoided.
Preparing the artwork for DTG printing primarily revolves around determining how much white and color ink will be necessary to print the design. Like pre-treat, the amount of ink needed to print the design is determined based on the weight and color of the garment being printed. The white underbase ink layer acts as the primer for the CMYK colors. In many ways it is very similar to painting a wall, when it comes to laying down a solid base coat in order for the paint to cover the wall properly. The CMYK settings revolve around setting the contrast, saturation, and amount of print coats that are necessary to print the design. Sometimes color may need to be printed twice to achieve the desired look. However, sending color multiple times will produce darker colors. So, if only one color needs an extra layer of ink, then delete the other colors first before sending the artwork to the printer again.
The print operator must make sure that the garments are clear of any fibers, fuzz, or other debris prior to loading them. Any debris under the garment could lead to ink being dragged or printed in an area where there should be no ink. Also, there are all kinds of different platens now, from standard 14x16 to youth to shoes. Be sure to familiarize yourself with the use of whatever platens you will need. Once the platen has been cleared, garment is threaded onto it, if possible. It is very important that garments are threaded onto the platen. If the printer simply lays the entire garment on top of the platen, then the print surface is less stable and the ink can bleed through the front of the garment and onto the back.
With the garment on the platen, it is time to align it. This step is critical because once printing begins, there is no way to reclaim the garment if it is ruined due to design placement. The print surface should be lined up properly and fully covered in pretreat. Often, platens will have grids printed on them to help with the alignment process. With the garment in place on the platen, it is time to send the artwork to the printer. Once the artwork has been sent, the print can be initiated.
The printer first lays down a base coat of white ink. Then, a second coat of highlight white is laid down. The amount of white necessary to print the artwork is determined by the type of product and color being printed. The printer will then lay down color (unless printing on a white shirt, in which case only color needs to be printed). Before removing the garment from the printer, the print operator will double check the print quality and make adjustments if needed. Once satisfied with the print quality, the print operator will carefully remove the garment from the platen. The ink does not dry on its own. So, if the shirt curls or puckers up when removing the garment, then it can stain parts of it outside the print area permanently.
DTG printed garments are typically cured using either a conveyor dryer or a heat press. Conveyor dryers used to cured DTG ink are not like most screen print dryers. Conveyor dryers require air to flow through the heating chamber so that the water-based ink is completely absorbed into the fabric. A heat press is a better solution for smaller shops for a few reasons. Conveyor dryers take up a lot of space, are expensive to power, take much longer to cure the garment, and can only serve one purpose, curing DTG prints. A heat press can cure the garment much quicker since it uses pressure (unlike a conveyor dryer), costs much less, and is already a necessary piece of equipment for curing the pretreat.
A DTG print is cured using a heat press by threading the garment onto the platen if possible. The garment should sit under the heating element of the press to allow the design to be flash-dried for a few seconds, so that the ink is dry to the touch before being pressed. Most garments are then covered with parchment paper (to prevent ink from contacting the heating element directly) and cured at around 350 degrees for approximately 30 seconds, but those numbers can differ based on the manufacturer of the ink. Once cured, the garment is finished and ready for sale! It is highly recommended to include wash care instructions with DTG products to ensure the print maintains the highest possible quality (washed in cold water and inside out).
Taking good care of your DTG printer is essential to maintaining consistent quality. There are likely both daily and weekly maintenance procedures that must be performed in order to ensure that your DTG printer prints beautifully every time, and that it does not break down. In the event that your printer does break down, it is crucial to have a local contact that can repair or at least diagnose the issue. Finally, DTG printers work best when they are frequently in-use. Most DTG printers can run day and night, and actually use little power. Letting a DTG printer sit for an extended period can lead to a whole host of complications, so do your best to avoid long periods of stagnation between prints. If you have to go for a while between prints, then at least fire up your printer every week or two to perform a few test prints.
