Ink drying methods for screen printing can be broken down into four types, dictated by the type of ink used. It is important to understand the difference between "drying" and "curing," however. After printing, ink may become dry to the touch, but must achieve full internal curing to obtain durability. Specific instructions and proper methods regarding drying and curing can be found on the ink package, or by contacting the ink manufacturer.
The air-dry method is used for inks containing evaporative chemicals such as water or solvents. After printing, the items are racked or hung to prevent ink smudging, and the ink is allowed to air-dry. In high-volume commercial applications, items may be placed in forced-air conveyor dryers to speed the drying process. Hobbyists and smaller commercial shops sometimes use ordinary fans to increase air movement around printed items to cut down on drying time. Full cure is achieved after a specific length of air-exposure time.
Heated Air Method
Heated air is required to fully cure some air-dry inks. Used primarily for professional textile printing with water-based inks, items are sent through a heated air conveyor dryer after printing. Although water-based textile ink may be dry to the touch after exposure to room-temperature air, the addition of heated air is required to ensure that the inks will not fade or wash-out during laundering. Heated air is sometimes used for some air-dry inks to speed the drying and curing process more quickly and efficiently than exposure to room temperature air.
Infrared Heat Method
Infrared heat is used primarily for drying and curing PVC resin, or plastisol, inks used in the printing of wearable goods. The infrared heat penetrates the ink and fuses the PVC resins and other ingredients. Directly after printing, garments are placed in a conveyor dryer containing infrared heat panels. Small stationary infrared heaters, called "flash dryers," are sometimes used by hobbyists and small commercial shops to cure plastisol ink. Infrared heat is also used to dry and cure epoxy-based inks and other specialty ink formulations for the printing of metal, glassware and ceramics.
Ultra-Violet Light Method
Ultra-violet light is used in commercial applications for drying and curing ultra-violet inks in the printing of paper and some plastics. After printing, items are placed in special conveyor dryers with internal high-intensity ultra-violet light sources which dry and cure the ink. UV inks will not dry or cure with any other drying method, and are the only inks that require the use of the ultra-violet drying method.
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