I like to use boiled kettle water to soak my brush and build lather. It seems to give me more consistent results than just using hot water from the tap. With the tap, sometimes I get good lather, other times its too thin and still other times it seems too thick and dries out too soon. I have no idea if this has anything to do with the actual temperature of the water I am using, or perhaps some of the impurities boil out in the kettle. Either way I have found for me, if I soak my brush with boiled water and use some of that water to build a lather I get consistent good results.