The sole report of glycerin-water viscosities at high shear rates, by Ram,
has so far been interpreted as evidence of shear thinning. Two alternative
interpretations, both of which invoke experimental artifacts, have now been
explored. One of these, viscous dissipation, qualitatively explains the pr
ogressive fall in the viscosity of glycerin-water as the shear rate is ramp
ed-up beyond 60 000 s(-1) to 90 000 s(-1). New measurements with parallel d
isks separated by a narrow gap indicate that the viscosity of 60 wt % glyce
rin in water is constant up to 90 000 s(-1).