Methods and systems for de-stabilizing foam produced in submerged combustion melters. A molten mass of glass and bubbles is flowed into an apparatus downstream of a submerged combustion melter. The downstream apparatus includes a floor, a roof and a wall connecting the floor and roof, but is devoid of submerged combustion burners and other components that would increase turbulence of the molten mass. The molten mass has foam on at least a portion of a top surface of the molten mass. Certain methods include imposing a de-stabilizing force directly to the foam or to the molten mass and foam, where the de-stabilizing force may be a vibratory force, an acoustic wave force, a particulate-based force, or a non-particulate-based mechanical force. Systems for carrying out the methods are described.