This document specifies a method of extracting, for analysis, acid soluble contaminants from a surface by use of flexible cells in the form of adhesive patches or sleeves which can be attached to any surface, regardless of its shape (flat or curved) and its orientation (facing in any direction, including downwards). The described method is suitable for use in the field to determine the presence of acid soluble contaminants before painting or a similar treatment. This document does not cover the subsequent analysis of the contaminants that have been dissolved off. Methods of analysis suitable for field use are described in other parts of ISO 8502 such as ISO 8502-5. This document is similar in procedure to, but not equal to, ISO 8502-6. The main difference is the solvent used and the subsequent analysis that can be performed on the extraction solution.