Methods to Measure Viscosity of Tiny Volumes of Oil With Blotter Paper

Abstract

This article describes a method for measuring the viscosity of oils that behave as Newtonian at low shear rates, by using only 80 μl of oil. This method is particularly useful when only such small quantities of oil are available—for example, when oil is extracted from grease taken from bearings. The method consists in placing an oil drop on blotter paper where an oil stain will grow in time. The rate of growth is then a measure of viscosity. Master curves were generated expressing the relation between viscosity and oil stain growth, both at a given time and as a function of time, each with its own accuracy. The viscosity measurements with this method were compared with those obtained in a conventional viscometer using poly-alpha-olefin (PAO), ester, and mineral oils.

Keywords:

• Lubricating oil
• viscosity
• blotter paper
• viscometry
• capillary flow
• grease

Acknowledgements

We thank SKF for the permission to publish this paper and Dr. Dirk van den Ende for valuable input.

Disclosure Statement

No potential conflict of interest was reported by the author(s).