Analytical Technique for Measuring Transmission of Light Through Milk Carton Materials

Light transmissions through milk carton paperboards, milk cartons, and blow-molded polyethylene containers were measured in the 350 to 800 nm region using a Cary 17D spectrophotometer equipped with a scattered transmission accessory. The paperboards had S-shaped transmission curves and were nearly opaque to wavelengths below 400 nm. Transmission at 800 nm averaged 5-3/4, 5-1/2, 4-1/2, 3, and 3% for the Eco Pak™, half-pint, quart, half-gallon, and gallon carton paperboards, respectively. Depending on wall thickness and wavelength of incident light, polyethylene containers had from 50 to 70% transmission. The effectiveness of different colored inks in reducing light transmission was compared using printed and unprinted areas of the paperboard cartons. Yellow, orange, gold, red, brown, and black inks opacified half-gallon cartons to wavelengths below 500 nm. Light transmission was reduced throughout the visible region by black, brown, and blue inks.