Abstract <p>It is believed that the solid phase particles of soil pastes interact due to coagulation contacts according to the Deryagin, Landau, Fairway, and Overback theory. This process is affected by a number of factors including temperature. Studies of a temperature effect on viscosity of pastes are known for clays. The soils and clays differ in the presence of humic substances with hydrophobic and hydrophilic bonds (together with clay minerals and other inorganic components) in the former. The hydrophobic bonds strengthen with an increasing temperature in contrast to weakening hydrophilic bonds. The aim of the work is to evaluate the temperature effect on hydrophilic–hydrophobic bonds in soil pastes, which are studied for gray forest soil and leached chernozem. The viscosity is studied in pastes, which were prepared from fresh samples dried to an air-dry state and dried-moistened soil samples. Vibration viscometry is used to evaluate the viscosity. The change in electric conductivity of soil pastes is also studied during heating. It is found as a result of experiments that the viscosity of fresh soils is higher than that of air-dried soils and soils that were dried and moistened before making the paste. This indicates different hydrophilic–hydrophobic bonds between particles in pastes of fresh soil and dried soils. The viscosity curves during heating and cooling of the samples do not coincide meaning a temperature hysteresis. The pastes from air-dried soils exhibit a non-monotonic discontinuous correlation with extreme points on the viscosity curve during cooling of pastes. A strong decrease in viscosity during cooling suggests a strong hydrophilization of the soil particle surface.</p>