Comments on "Viscosity of high crystal content melts: dependence on   solid fraction"
  Here we propose a simple modification of the parameterisation presented in Costa (2005) [Viscosity of high crystal content melts: dependence on solid fraction, Geophys. Res. Lett., 32, 2005] which improves all the main positive features of it, yet at the same time, does not show a plateau region as the solid fraction tends to 1, generally increases the performance of the model, and exactly recovers the classical well established relationships valid for small fractions. 
A. Costa