Scale deposition on the heat transfer surfaces from water containing dissolved salts considerably reduces fuel economy and performance of heat transfer equipment. This problem is more serious during nucleate boiling due to the mechanisms of bubble formation and detachment. Using a precision pool boiling test apparatus, the effects of heat flux and calcium sulfate concentration on heat transfer coefficient and formation and growth of deposits are investigated. The transient change in heat transfer is closely related to wick boiling, and the associated changes in bubble departure diameter and bubble site density. A physically sound prediction model was developed for the prediction of heat transfer coefficients as a function of time during deposition processes. Based on comparison with experimental data over a wide range of foulant concentrations and heat fluxes, the model is considered to be sufficiently accurate for practical application.