Environmental factors of viscosity and plasticity
a) Temperature affects the viscosity of a colloid. Generally, its viscosity decreases as the temperature increases. For e.g. milk becomes less viscous at high temperatures; such colloidal gels as gelatin and agar are less viscous at high temperatures than low ones.
b) The viscosity of a colloid also increases with the concentration and aggregation of dispersed particles. For e.g. cream becomes more viscous when there is an increase in the number and aggregation of fat particles in it.
c) Increased amounts of protein solids also bring amount an increase in viscosity. Thus the viscosity of custard is related to the amount of egg protein dispersed in the liquid.