In DTG printing, crystallization refers to a specific type of issue that can occur when drying pretreatment. Unlike other stains that discolor the fabric itself, crystallization appears to be on top of the shirt and looks like table salt is sitting on it. These crystals don’t fade over time or come out in the wash. Garments that suffer from crystallization are functionally ruined, so prevention is the best option.
Crystallization is caused when the water in pretreatment evaporates and becomes trapped on a heat press. All methods of preventing the formation of these crystals involve some way of allowing this moisture to escape. Anything that increases the amount of water stuck between the shirt and the press will increase the odds of seeing crystals form. For example, tighter knit shirts are typically considered higher quality, but tend to hold more moisture and are more likely to suffer from crystallization.
The easiest way of releasing water is to adjust the settings on your heat press. Too high of a pressure on the press will trap moisture and form crystals. A high temperature may also add to this, as the water evaporates too quickly and cannot exit before more steam forms. You should also be mindful of the type of cover sheet you use on the heat press. Teflon sheets or Teflon press covers tend to trap water and reusing these for pretreat can cause additional issues with staining and burns. FIREBIRD recommends using silicone treated parchment paper for drying pretreatment and switching to the less disposable Teflon options for lower cost ink curing.
When the easy options don’t work, you can also change the way that you dry the pretreatment. Conveyor dryers and air drying will never result in crystallization, but our favorite technique is the hover press. With this method, press the shirt lightly so that the press does not fully clamp, hovering just above the shirt for a few seconds before lifting. You will see steam escape at this step and can now continue pressing the shirt as you normally would. An alternative for presses that do not allow for hovering is to press the shirt in intervals. Rather than doing a single thirty second press, try doing two presses of fifteen seconds.
A final option is to alter the amount of water that is applied to the shirt. Too much pretreatment can cause crystallization, as well as staining and wash issues. Try laying down less pretreatment when adjusting the heat and pressure settings doesn’t resolve these problems. You should also be sure to avoid adding excess moisture when you see crystals. Some DTG users will attempt to dilute their pretreatment with water in an attempt to prevent various issues. However, all FIREBIRD pretreatments are ready to use, and further dilution may cause crystallization.