A new class of polymeric glasses belonging to the B-O-F system has been synthesized by reaction between B2O3 and BF3 gas in a sealed silica tube being in a temperature gradient condition. The glass formation mechanism which involves a vapor phase transport indicates that the F concentration in the glass varies with the deposit temperature. The glass transition temperatures Tg are in the range -15 to 120 degrees C and depend on the F/B ratio. A foaming phenomenon, due to BF3 bubbles nucleation, is observed when the "BOF" glasses are maintained above Tg.