Methods of Controlling and Minimising Scale (Evaporators) 1. Use low-pressure evaporation plant, that is, operating at temperature below 80C a so that calcium carbonate scale predominates- that is a soft scale which is easily removed and not such a poor conductor of heat as other scales. 2. Use magnetic treatment: a unit consisting of permanent magnets, preceded by a filter, is installed in the evaporator feed line. The water passes through a strong magnetic field which alters the charge on the salts so that amalgamation of the salt crystals, formed during precipitation in the evaporator, is prevented and the salt then goes out with the brine.