Inks and fabrics work together for outdoor longevity.
By Gail Nickel-Kailing
Designers and printers produce beautiful images. While many are intended to promote a product, an event or special sale for a short time, we expect images to be beautiful for the length of time they are installed. Whether it’s days, weeks or months, the inks, fabrics, finishing and installation must work together to give them the life we expect.
With input from ink manufacturers, fabric manufacturers, printers and fabricators, this article addresses the relationship between fabric, ink and the production processes that affect fastness and adhesion, and “failures” that affect the life of the finished product.
First things first
Before you begin to put ink to fabric, a conversation must take place between you as fabricator of the finished product and your customer. Questions to consider:
- Interior or exterior? External installations will be affected by the elements, which can change the fastness of the colors and the structural integrity of the product. However, internal installations can also be affected by ultraviolet light through windows and skylights. Consider a protective layer between the source of light and the printed product, such as UV film on a window.
- How will the project be installed? Is this a flag suspended by one edge, or a banner anchored on all corners? Is this an awning or an anchored construction?
- Will the piece be sheltered or exposed to the sun?
- What is the orientation of the installation? Sunlight from the south and west will affect color fastness more than from the north and east.
- Will the project be in place during the summer or winter? In Seattle or Scottsdale? High, direct sunlight will have a strong effect on color.
Taking all of these variables into consideration will help you choose the optimal ink and fabric for the project. It will also help you with setting customer expectations.
Unless you have chosen a special product, like Glen Raven’s Sunbrella fabric or W.L. Gore’s Tenara architectural fabric, and a graphic process like applique, most outdoor projects have a fairly short life. Your customer should know that the life of the project will likely be measured in seasons or a year or two, not decades.
Different types of inks have different issues of “fastness,” such as fastness to light, heat, ozone, pressure and rubbing.
Transfer or dye sublimation inks on polyester generally have lower light fastness than selected acid dyes on nylon. The ink or dye combination that would have the longest light fastness would be direct print inks developed for use on special nylon fabrics designed for flags. These inks are set with steam.
Inks applied on the surface of the fabric such as ultraviolet- or infrared-cured inks are fused to the fabric. The heat or light turns the ink into a polymer and fuses it to the fibers. Improper curing causes images to scratch, crease or abrade. UV works best on polyester fabrics in indoor applications.
“From my experience, for digital solvent and UV printing, the best results will be achieved on fabrics that have had a top coating, generally acrylic, urethane or a combination,” advises Mike Von Wachenfeldt, Glen Raven Custom Fabrics. “It varies from fabric manufacturer to manufacturer.” The coating gives the ink something to adhere to so it doesn’t penetrate the fibers before it is completely cured.
Fiber content should be considered when choosing fabrics for external use. Cottons are not generally used outdoors. Polyester, nylon and acrylic are better choices. Acrylics are more UV-resistant and retain their strength better than polyester, with or without printing.
Selection of a fabric that will be UV-resistant will not mean that the ink is more or less lightfast, but that the underlying substrate itself will be less affected by light. Fabric treated with UV absorbers will respond to UV light differently than natural fabrics.
It may not be logical that a natural fabric would respond to light more poorly than a dyed fabric; however, a dyed fabric may have been manufactured with a dye containing a UV absorber.
A UV-protective top coating—either as a liquid or laminate—on top of the image will give the entire project longer life. Coatings may change the “hand” of the fabric and make a soft fabric stiff.
The weave of the fabric may affect light fastness and fabric strength. A tighter weave or a smoother fabric may have less fading than a coarser weave fabric. The coarser weave will present more surface area to the sun.
“If I wanted to pick a fabric that had the best fastness outdoors, I’d pick a product that’s been treated with a UV absorber; a bright fabric rather than dull, with a high denier fiber, and with a tighter/flatter weave,” advises David Clark, Huntsman Textile Effects.
While “results may vary,” your project will have a life expectancy that ranges from short to a substantial length of time. It is possible, using a complex formula developed by the American Association of Textile Chemists and Colorists (AATCC), to calculate project life expectancy with some degree of accuracy using detailed variables that include latitude, angle and intensity of the sun, amount and density of cloud cover, and elevation, among others.
The general rule is that you can expect the shortest life outdoors from dye sublimation on polyester. Direct solvent printing on an uncoated fabric, on a coated fabric, and on a coated fabric with a protective top-coat treatment will each give you a relatively longer life, in that order. For something that you anticipate will need to last years or decades, consider applique on a UV-resistant fabric.
The real key is to understand the customer’s requirements and expectations. Work closely with your ink and fabric suppliers to ensure that the two work together optimally.