For over 70 years, Libbey's proven commitment to quality has backed by our guarantee, "a new glass if the rim of a Safedge® glass chips." If the rim of any glass covered by the Safedge® guarantee chips, Libbey will replace or refund the price of the glass when it is returned to the dealer/distributor from whom it was originally purchased. Of course, this guarantee does not cover breakage. Heat-Treated Glassware. Libbey's heat-treated tumblers and stemware are created through a special heating and rapid cooling process after the glass is formed. This secondary process on "blown" glassware is performed only on the upper portion of the glass where most abuse occurs. Libbey's heat-treated glassware offers increased resistance to thermal and mechanical shock and is recommended for fast service cycle operations.