"TCVN 6728-2010 Determination of paper and Cardboard opacity (paper backing), diffuse reflection method" is a standard in Vietnam that specifies the method of measuring paper and Cardboard opacity by diffuse reflection method. The standard applies to white and near-white paper and Cardboard, including paper and Cardboard that have been dyestuff treated or show a lot of fluorescence. Through this standard, the opacity of paper and Cardboard can be accurately assessed, providing a scientific basis for paper and Cardboard quality control, product development and related testing, and is widely used in the paper, printing and Encasement industries.