Flip-flops and nail polish that changes color when exposed to sunlight has long been a fun fad,  but now that trend also extends to screen print ink, allowing screen printers to create garments, tote bags and other items that change color when exposed to the sun. Solar Active International has created a series of screen-print inks using a proprietary process that makes the inks appear colorless until they are exposed to UV rays. While the prints don't need to be exposed to full sunlight, they do need to be exposed to UV rays for the color change formulation to work properly.  

Solar Active screen-print inks are phthalate-free plastisol base and environmentally friendly. The formulation that allows for the color change has been perfected over a number of years, and formulas are periodically adjusted to meet current environmental standards. The ink has a long shelf life as long as it is stored in a cool environment. Take care to ensure that ink being stored is never exposed to direct sun or UV rays. Solar Active inks can be stored for years as long as they’re stored in closed containers and out of the direct light of the sun.

In addition to the 26 colors currently available, Solar Active is working to develop deeper, richer colors based on PMS numbers. Currently the firm has added Green PMS 5743, a dark green for shading and trees and PMS 5255 which turns to a deep blue purple when exposed to the sun. While these color changing inks look virtually colorless when not exposed to UV rays, exposure to sunlight turns subdued designs into a riot of color. Solar Active inks are pure colors, not blends, so the formulation and the color match stay consistent batch after batch. Solar Active inks are also available in four-color process inks.

When creating designs for use with Solar Active inks, keep in mind that the design will appear one way under normal room light and another when exposed to UV rays or sunlight. Shirts can be screen printed with a design that looks simple but reveals hidden details when the garment and design are worn out into the sun. Creating designs with intricate elements that only appear when the design is exposed to UV rays allows for a garment to have two looks, one simpler look for indoors and a more colorful look when in the sun. 

Shirts printed with Solar Active inks can be washed repeatedly and will last for at least the season they're intended for. Air drying rather than drying in a dryer is recommended, making sure to hang the printed garment to dry in an area that is out of the direct sun. Solar Active screen-printing inks are available in a variety of colors and can be mixed together to create even more colors. Inks are shipped ready to be used, so no additional mixing is necessary. These color changing inks are printed and cured using the same methods as would be used with any plastisol screen-printing ink.  

Online Resource: Screen Printing with Solar Active Screen-Print Ink
So how do Solar Active screen-printing inks really work?  In a video tutorial, the company shows how the ink works by first applying the ink away from direct sunlight and then taking it out in the sun to demonstrate the color change effects. Watch the video below.