The situation becomes somewhat confused as the term viscosity is sometimes used for solid materials, for example Maxwell materials, to describe the relationship between stress and the rate of change of strain, rather than rate of shear. Viscosity may be an appropriate characteristic for solids in a plastic regime. This distinction can become muddled if measurements are continued over long time periods, such as the Pitch drop experiment. Even if solids flow at higher stresses, they are characterized by their low-stress behavior. However, others argue that solids are, in general, elastic for small stresses while fluids are not. This distortion is more likely the result of the glass making process rather than the viscosity of glass. This position is often adopted by supporters of the widely held misconception that glass flow can be observed in old buildings. This has led some to the view that solids are simply liquids with a very high viscosity, typically greater than 10 12 Pa On the basis that all solids such as granite flow to a small extent in response to small shear stress, some researchers have contended that substances known as amorphous solids, such as glass and many polymers, may be considered to have viscosity. * These materials are highly non-Newtonian. Some dynamic viscosities of Newtonian fluids are listed below:įluids with variable compositions, such as honey, can have a wide range of viscosities. Peanut butter is a semi-solid and can therefore hold peaks.
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