Each month leading manufacturers and digital print shop owners will share their know-how in our new digital printing column. This month, Oliver Luedtke from Kornit Digital explains how to pick the right garment for DTG printing

Here at Kornit we avoid calling our direct-to-garment (DTG) systems ‘T-shirt printers’, but of course 80% of what is produced on them is actually T-shirts.

In many other areas of digital printing, service providers enjoy the privilege of printing on a substrate that has been optimised for printing. For T-shirts, however, this is usually not the case. In order to enjoy a consistent print quality from your system, there are a few basic principles that we would suggest to consider.

A general challenge with most of the T-shirt brands used in direct-to-garment printing is the fact that they are manufactured far from where they are printed. The large retailers and brands have a variety of sources for their raw product, in countries such as Bangladesh, Cambodia, Turkey, China, Vietnam and elsewhere. It is not unusual for them to source their shirts from different places, and shirts can pretty drastically vary in quality between batches. The composition of yarns, dyes and finishing can vary. Sometimes mould protectors are added for the shirts to make their long way over the seas, or enzymes for obtaining the soft hand feel.

In essence, a box of T-shirts is like Forrest Gump’s famous box of chocolates: you never know what you’re going to get. However, when it comes to digital T-shirt printing, this variety of characteristics can have its consequences. For example, the absorbency rate of the shirt has a direct impact on the amount of pre-treatment that is right. The application of substances will end up between the digital ink and the shirt might impact the curing and the wash resistance. The temperature tolerance of the shirt can change, which might affect the curing process. With all other parameters being the same, the colour result might change when the T-shirt quality changes, which is bad for colour consistency, within the same job and for repeat jobs.

Here are a few suggestions for you that will help you to pick the right garment partner:

1 Start off on a small order of shirts When you are just about to start up your business, don’t order large quantities of shirts in the first place! Always try a sample batch and make sure that you can handle and process them smoothly with your workflow and your designs before you go big.

2 It is false economy to be cheap on shirts Shirts are your substrate and an important foundation for consistency, quality and reliability. Good vendors have control mechanisms and quality assurance in place for their vendors, and these cost money. Spending 30p more on a shirt might save you hundreds of pounds per production day – on time, wages, nerves, ink and corrective actions that will not be required.

3 Educate yourself and your operators Learn how variations in garment quality can impact your print result and how you need to adjust speeds, pre-treatment and colour settings to get back to the best possible quality. Many vendors offer application trainings for system operators – they might prove a valuable investment!

4 Assess the print quality and surface of your shirts after drying Before you ship your shirts to the customer, you will obviously dry them, so there is no point in judging your results after printing only.

5 Test for dye migration Some dark polyester shirts can produce ‘dye migration, which means that black, red or green dyes from the shirt can make their way through the white layer that you print on them and give the surface cloudy, coloured stains. Thus, polyester shirts for printing need to be carefully tested. Shirts with cationic dyes put you on the safe side.

6 Smooth is good The smoother the T-shirt surface and the fewer filaments it has, the better. Ringspun quality is better than open-ended.

7 Confirm your shirts’ certifications Check if the shirts have the certifications and quality seals (like Oeko-Tex, GOTS, etc) that you require and advertise to your customers.

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