Abstract: The invention relates to a method of heat processing particles of glass. A first current of a mixture of a combustible gas and a gas capable of oxidizing the combustible gas is introduced into a substantially cylindrical chamber from its lower end. The combustible gas is ignited to form a flame in which the gases have a speed of less than 10 m/s. The resulting flame creates a heat processing zone in the chamber. A quenching zone is provided by a second current of gas introduced into the chamber adjacent the chamber side wall such that it swirls around the flame. Particles of glass are then introduced at the lower end of the chamber and these particles contact the flame in the heat processing zone and are then directed to the quenching zone where they are hardened and from which they are collected.