For decades, spring bronze was the standard for door jamb weatherstripping, until surface applied rigid weatherstripping became common. Now silicone bead weatherstripping is changing the standard again. Silicone keeps its shape better than other rubber and plastic weatherstripping materials, and it won't stiffen and crack easily in extreme temperature swings. Silicone beads are also smaller than the sometimes bulky surface types. Plus, new router-based specialty tools make it almost as easy to retrofit silicone bead as to install it in a new door frame. Tools and Materials I have used two systems professionally — one manufactured by Resource Conservation Technology (2633 North Calvert St., Baltimore, MD 21218; 410/366-1146), the other by Weatherbead Insulation Systems (47-46-46 Hepburn Dr., Indio, CA 92201; 800/966- 0159). Both companies offer a kit that