Rheology and density of glucose syrup and honey: Determining their suitability for usage in analogue and fluid dynamic models of geological processes

Analogue models of lithospheric deformation and fluid dynamic models of mantle flow mostly use some kind of syrup such as honey or glucose syrup to simulate the low-viscosity sub-lithospheric mantle. This paper describes detailed rheological tests and density measurements of three brands of glucose syrup and three brands of honey. Additional tests have been done for one brand of glucose syrup that was diluted with water to various degrees (2%, 5% and 10% by weight). The rheological tests have been done to test the effect of shear strain, shear rate and temperature on the dynamic viscosity of the syrup. The results show that the viscosity of all glucose syrups and honeys is independent of shear strain (i.e. no strain hardening or softening). The viscosity of the glucose syrups is independent of shear rate ( γ ˙ ) , i.e. linear-viscous or Newtonian, in the range γ ˙ = 10 − 4 – 10 0 s − 1 with stress exponents that are almost identical to one (n = 0.995–1.004). All the honeys show a very weak, but consistent, decrease in viscosity with increasing shear rate of 7–14% from 10−3 to 100 s−1 and have stress exponents more distinct from one (n = 1.007–1.026). All syrups have a viscosity that is strongly dependent on temperature in the range 0–50 °C, where viscosity decreases with increasing temperature. Such decrease can be fitted with exponential and Arrhenius functions, with the latter giving the best results. Furthermore, the viscosity of glucose syrup decreases approximately exponentially with increasing water content. Oscillation tests indicate that the rheology of all the syrups is entirely dominated by viscous behaviour and not by elastic behaviour at frequencies of 10−3–102 Hz. Finally, the density investigations show that the density of glucose syrup and honey decreases approximately linearly with increasing temperature in the range 10–70 °C, with coefficients of thermal volumetric expansion at 20 °C of 3.89–3.95 × 10−4 °C−1 and 4.57–4.81 × 10−4 °C−1 for glucose syrup and honey, respectively. The new results demonstrate that glucose syrups and (to a lesser degree) honeys are well suited for usage in analogue and fluid dynamic experiments to represent linear-viscous strain independent and shear rate independent rheologies to model geological processes. Glucose syrups have the added advantage of being more transparent than honeys, allowing for accurately resolving and quantifying flow patterns in the fluid during a model run.