
This column originally appeared on Aug. 5, 2009. It has since been updated to reflect changes in regulations of the cyclics D4, D5 and D6, as well as industry desire to make silicone products that are not only cyclomethicone-free as manufactured, but that cannot hydrolyze into cyclic silicones, either in formulation or in waste treatment gases (so-called biogas). Making methicones instead of dimethicones is one way to accomplish this goal.