Prehistory Chemistry

In the early Pleistocene, shooters applied iodine to keep screws from backing out — it rusted them in place! Loctite Threadlocker is a more civilized option and Henkel Corp, which makes this anaerobic adhesive, now has several kinds. “Red” is still the stoutest option; screws stay put until you heat them with a torch. Medium-strength “Blue” allows screw removal without heating. “Purple” (Loctite 222) has endeared itself to shooters who view it as a useful hybrid of “Red” and “Blue.” It shouldn’t require heat to disengage. All these Loctite products cure within 24 hours.