Print is where bag brands live, and print is where most quality complaints start. The logo that read perfectly on the approved sample fades after one summer in a shop window, bleeds in the rain, or rubs off onto a customer’s white shirt, and each of those failures traces to a different testing gap at the factory. Colorfastness testing closes those gaps, and buyers who name the right tests in the order prevent the complaints before production starts. This guide explains the three fastness families that matter for printed bags, what each test simulates, and how to write results into a specification.

Our printing floor runs digital and rotogravure lines for custom bag programs on PP woven fabrics and beyond, and the fastness discipline below complements the appearance-approval method in our specification guides. Visual color appraisal under controlled conditions follows the same logic as ASTM D1729, the standard practice for appraising color differences under controlled illumination.

Rub fastness: the everyday failure mode

Crocking, the trade’s word for color transfer by rubbing, is the fastest complaint generator on printed totes. A wet sleeve against a fresh screen print, a white shirt against a bag carried under the arm, and the print migrates. Rub tests simulate exactly this: a standardized counterface rubs the printed surface dry and wet, and the result is graded against a gray scale for staining and for color change. The pass bands belong in the order: on bags carried against clothing, dry rub at grade 4 and wet rub at grade 3 or better are common commercial requirements. Ink chemistry drives the result: prints that cure properly bond the pigment; prints rushed off an underheated dryer pass the visual check at the factory and fail the first wet shirt in the field.

Light and wash fastness: the slow failures

Light fastness predicts the bag displayed in a shop window: ultraviolet exposure fades unstable pigments over weeks, and the faded stock is unsellable even though the bags are functionally perfect. Exposure tests rate fading on blue wool or numeric scales, and bags intended for window display or outdoor use should carry a stated light-fastness rating rather than hope. Wash fastness applies to reusable bags the customer will actually launder, and it separates prints that survive twenty cycles from prints that bleed in the first cold wash. Each test family has standard methods with defined exposure and grading, spanning both destructive and non-destructive approaches, and the buyer’s job is to name the method, the cycles and the pass grade, because “colorfast” without a method is a promise with no measurement behind it.

Writing fastness into the order

Three lines in the purchase order convert fastness from hope to contract. First: “print fastness tested per named methods on each colorway, reports with shipment.” Second: “grade bands stated per test, dry rub 4, wet rub 3 minimum, or the program’s agreed values.” Third: “golden sample approved under store-equivalent lighting retained as the visual reference for disputes.” The third line matters most in practice, because fastness grades are laboratory numbers and customers judge bags in daylight; the golden sample bridges the two, and reorders are checked against it before shipment, the same golden-sample discipline applied across our QC programs alongside the stitch density specs in the same tech pack.

Our printing programs specify ink systems per fabric, cure temperatures per line speed, and fastness bands per colorway, with reports issued per shipment. Program inquiries reach the export desk with samples before bulk and fastness reports in the file.

Video: the printing line behind the logo

The clip shows custom printing in production. Ink chemistry, cure and fabric interact at this stage, and the fastness tests measure what this stage decides.

Frequently asked questions