All direct-to-garment printers use a water base ink system and special treatment is required when printing dark shirts. The rule is: When you print white ink, you must pretreat the shirt first. Without pretreat solution on the shirt, the white and color inks will simply disappear into the fabric after printing.
White shirts need no pretreatment, plus ash grey and some pastel shirts may not need pretreatment either. We say “may not” because the translucent CMYK inks can take on the color of the shirt being printed. (A blue ball printed on a yellow shirt may appear green.) So, if the image is not impacted by some color shift, no white underbase with pretreatment is required. If you need to match colors exactly, then pretreatment and white ink even on pastel colors may be necessary.
There are special pretreats available for light shirts, even when you are printing CMYK only without white ink. These pretreats will aid in a brighter image and better wash-ability, but are not required for a salable finished product. Use of this light shirt pretreatment is simply a personal preference choice on the part of the operator.
Pretreatment is best applied by either a hand held power paint sprayer, or by using an automatic pretreat machine. The choice between the two is usually budget related.
If you pretreat with a hand held power sprayer, you must accomplish this task in a separate room from your printer. You need to protect the print head from any pretreatment spray floating in the air. Hand pretreating will do the job with a little practice, but can be messy and inconsistent. Most operators who hand spray pretreatment tend to lay down too much pretreat solution on the shirt.
Pretreat application using a “fully enclosed” automatic sprayer can be done in the same room with your direct-to-garment printer. This is the most consistent, cleanest method of pretreating your garments. Using a pretreat machine will help to remove the “pretreating variable” out of the formula to a high quality final image.
Shirts can then be either heat pressed dry immediately after pretreatment is applied, or can be hung to air dry. If you air dry, press the shirt for about five seconds before printing to flatten the fibers of the shirt for ideal image. Most operators will pretreat large quantities of shirts to have in stock. You can pretreat your shirts even months ahead of production with perfect results.