Your client’s digital graphic illustration looks great when it comes off the printer. But your client expects that vibrant image to look good months or even years later. To ensure happy customers, you want assurance that ink suppliers have tested their inks’ durability.
Tests may be conducted in-house and at independent laboratories. Ink manufacturers follow guidelines of the American Association of Textile Chemists and Colorists and International Organization for Standardization. Primarily, they test for color fastness in terms of light, washing and rubbing.
As an example, 3M does most of its testing in-house, but also uses the services of Atlas Material Testing Technology of Chicago, Ill., which operates natural weathering test sites around the world (in the United States, mostly in sunny Arizona and Florida). 3M chemist Richard Severance says color panels at natural weathering test sites are checked every six months for several years.
But you and your client can’t wait five years to see if the latest ink for an outdoor banner holds up. Nor can ink manufacturers. So they turn to accelerated weatherometers.
Severance says 3M’s accelerator exposes samples to heat, light and water and that “poor materials can fail within two to three days.” The amount of time they spend in the machines varies.
“Things that maybe would last two to three years outdoors we probably need to go into the thousands of hours, and we do that routinely,” Severance says. “If it’s early in the program and the nature of what’s being tested is just formulation development, I would probably only do the accelerated test and weed out the weak ones. Then at a point where I have two or three good candidates, I submit them for accelerated and natural weathering.”
There’s a reason for artificial weather testing besides the time issue: consistency. “If you put something outside to fade, it may be in North Carolina, Arizona and Maine. In North Carolina, it may fade in three months; in Arizona, in one month; and in Maine, in two years,” says David Clark, U.S. business development manager for Huntsman Textile Effects. Huntsman uses an Atlas fadeometer, equipped with a xenon bulb that glows brighter than the sun. “No matter where you run that test in the world, the result will be the same,” Clark says. “We do our own testing in-house on a day-to-day basis. Before going to market, we have an independent lab certify the results.”
While it depends on the application, Severance says, 3M’s testing could include abrasion resistance, overcoat adhesion, tensile testing to see how well the printed sample stretches without cracking, and oven tests to see how well the product holds up in heating and cooling.
“Inks tend to be evolutionary, and every generation builds on the last, so they’re typically not totally new,” he says. “But there’s almost always some aspect that’s different every time we get a program going, because of things we have learned.”