ISO 4628-1-2016 "Assessment of the number and size of defects and the intensity of uniform change in Appearance in Paints and varnish coatings, Part 1: General principles and assessment system" is one of the standards published by the international standards organization (ISO), which is applicable to the assessment of various types of defects and uniform changes in Appearance caused by coating aging, such as yellowing. This standard first defines an assessment system for the number and size of defects, and outlines the general principles of the overall assessment system. This system is particularly aimed at defects caused by aging and weathering, including assessment methods such as blistering, rusting, cracking, flaking, chalking, etc. The Miscellaneous section of ISO 4628 provides a detailed assessment methodology for specific defect types, as well as a general framework for assessing non-covered defects. ISO 4628-1-2016 standards are designed to provide a comprehensive and consistent assessment system for the monitoring and assessment of coating quality, helping to ensure the mass and durability of coating products.