VISCOMETRIC REMINISCENCE Available to Purchase

If one consults an up‐to‐date list of approximate tests issued by a wholesale lubricating oil concern the following kind of item will be encountered : “150 Solv. Neut. Redwood viscosity at 70°F. 310″, at 140°F. 66″”. The grade number refers to a Saybolt reading and the viscosities are in Redwood seconds. But this is 19G2 and we are well in the kinematic era. Yet reference to empirical viscosity units is by no means uncommon. Brooding on this prompted the author to recall something of efflux viscometers, the transition to the capillary instrument and the persistance of an earlier tradition.