First I washed it out, hand-lathering with some soapy water to remove all the grime and dust and also to see if there are any hairs coming loose. Then rinse it thoroughly with warm running water. The sterilization, or better disinfection, was done with the Sally's brand of Barbicide, very diluted (4 oz/gal - according to their recommendations for barber tools) for some ten minutes. Again rinse out very well and then hand-lathered with a nice soap 3x times, followed by very good rinsing and drying for two days. No hairs came out and the knot is quite nice for such an old brush.