Paperboard Substrate Lightfastness Criteria under Accelerated LED Exposure
Substrate lightfastness under retail LED fixtures depends on optical brightener stability, requiring specific 450 nm test criteria to prevent retail chargebacks.
Lightfastness Bench Testing
Meaning
Laboratory simulations of light-induced fading provide a controlled method for predicting how materials will respond to long-term exposure in a retail or outdoor setting. Through lightfastness bench testing, technicians expose samples to high intensity xenon or fluorescent light to accelerate the aging process. This method allows for the evaluation of inks and substrates in weeks rather than months.
The procedure ensures that packaging remains visually acceptable throughout its intended shelf life.
Simulated Environment
Testing chambers control the variables of temperature and light intensity to mimic the specific conditions of a distribution channel. A standard lightfastness bench testing setup uses filters to remove wavelengths that the product would not encounter in its real-world application. For example, a package intended for indoor retail use will be tested under glass-filtered light to remove shortwave uv.
This precision prevents over-engineering the material while ensuring sufficient protection against the actual threats it will face.
Outcome Measurement
Evaluation of the test samples involves comparing the exposed area to an unexposed control using a spectrophotometer or a gray scale. During lightfastness bench testing, the delta E value represents the total color change, providing a numerical figure for the degree of fading. A low value indicates high stability, while a high value suggests that the pigments or substrate are susceptible to light damage.
This data allows for the comparison of different ink formulations before a full production run begins.
Contractual Validation
Performance data from these tests often serves as the basis for product guarantees and supplier selection. If a material fails lightfastness bench testing, the manufacturer must reformulate or choose a more stable alternative to avoid future claims.