This International Standard specifies methods of determining the partial acid value (method A) and the total acid value (method B) of polyester resins and binders for paints and varnishes. It is not applicable to phenolic resins. It is intended to provide quality-control data for the acceptance or rejection of such products in accordance with the terms of a specification, as well as to be used in research and development to monitor the completion of the polycondensation reaction.