Meaning
Permanent color loss occurs when the underlying material of a product is degraded by exposure to light. Retailers observe substrate photofading when the paper or plastic behind a printed image turns yellow or brittle. This process can happen even if the inks themselves are lightfast.
It results in a loss of visual appeal that can make merchandise look old or damaged.
Material Discoloration
Solar radiation breaks down the lignin and other fibers within the structure of the paper. As substrate photofading progresses, the surface of the material often becomes more porous and absorbs more moisture. This change in the physical properties can lead to curling or warping of the packaging.
Coatings are often applied to the surface to block the wavelengths that cause this damage. Recycled paperboard requires careful assessment of the chemical stability of its fibers. Testing in environmental chambers allows for the prediction of this behavior before the material is selected for a production run.
Exposure Mechanism
High energy photons penetrate the surface and disrupt the chemical bonds that give the material its color. During substrate photofading, the rate of change depends on the intensity of the light and the duration of the exposure. Indoor environments with fluorescent lighting can still cause a measurable shift over several months.
Heat from the light source often accelerates the chemical reactions.
Value Loss
Deterioration of the packaging often forces a retailer to discount the price of the goods to move them quickly. Using materials that resist substrate photofading is a standard requirement for products with a long shelf life.
