ISO 1409:2006 specifies a ring method for the determination of the surface tension of polymer dispersions and rubber latices (natural and synthetic). The method is valid for polymer dispersions and rubber latices with a viscosity less than 200 mPa·s. To achieve this, the dispersion or latex is diluted with water to a mass fraction of total solids of 40 %. If necessary, the solids content is further reduced to ensure that the viscosity is under the specified limit. The method is also suitable for prevulcanized latices and compounded materials.