Large-scale buoyant low stretch stagnation point di4usion 6ames over a solid fuel (polymethylmethacrylate) were studied for a range of aerodynamic stretch rates of 2+12 s ุ1 which are of the same order as spacecraft ventilationinduced stretch in a microgravity environment. An extensive layer of polymer material above the glass transition temperature was observed. Unique phenomena associated with this extensive glass layer included substantial swelling of the burning surface, in-depth bubble formation, and migration and/or elongation of the bubbles normal to the hot surface. The bubble layer acted to insulate the polymer surface by reducing the e4ective conductivity of the solid. The reduced in-depth conduction stabilized the 6ame for longer than expected from theory neglecting the bubble layer. While buoyancy acts to move the bubbles deeper into the molten polymer, thermocapillary forces and surface regression both act to bring the bubbles to the burning surface. Bubble layers may thus be very important in low gravity (low stretch) burning materials. As bubbles reached the burning surface, monomer fuel vapours jetted from the surface, enhancing burning by entraining ambient air 6ow. Popping of these bubbles at the surface can expel burning droplets of the molten material, which may increase the 5re propagation hazards at low stretch rates.