Cabosil is the trade name for Fumed Silica, a 'universal thickener'. It is an extremely fine white powdery substance (under some lighting and film stocks, it can show with a slight blue tint). It can be used to thicken Resins, Adhesives, Silicones, and basically any other liquid substance. It is technically nontoxic, but as with all particulate substances, it is dangerous if inhaled. Also it is naturally hygroscopic, physically hard as glass, and under a microscope, sharp. These properties cause it to be irritating to the skin while in it's dry form.