The Static Master with an active cartridge works well for me. The cartridge contains a low level radioactive isotope that emits gamma radiation that ionizes the layer of air next to the negative, dissipating any static electric charge. Static charges can make dust particles cling to the negative, and make it a magnet for any that may be floating around or hiding in the enlarger head. Static charges can be generated by simply removing negatives from a sleeve, brushing, or even blowing a stream of canned air across the surface. Although the idea of using something that emits radiation sounds a little frightening, it's perfectly safe unless you swallow it!