ISO 21318:2007 specifies a method for the determination of the electrical conductivity of an aqueous extract obtained by extraction of an epoxy resin with water at 95 °C. The method is applicable only to epoxy resins that are in the molten state at the extraction temperature (95 °C).

The method is important for epoxy resins which are used as insulation materials for electronic devices. The electrical conductivity of the extract is used as a measure of the concentration of the ionic species in the resin.