ISO 25549:2026

Fine bubble technology — Evaluation method for determining the shear viscosity of ultrafine bubble dispersions ISO 25549:2026

Publication date:   Aug 18, 2026

Scope

This document specifies a method for evaluating the shear viscosity of ultrafine bubble (UFB) dispersions.
The method is based on any of the three measurement devices, namely parallel-plate rotational shear, cone-plate rotational shear and coaxial-cylinder rotational shear. The average effective shear viscosity of the ultrafine bubble dispersion is calculated from the measured stress (or strain rate) and the strain rate (or stress) applied to the sample. There are commercially available instruments based on these measurement methods in the market. This document applies to UFB produced using different methods of production.