Forms durable coating for repair of damage to muffler insulation. Fills cracks and voids in sagger trays and heating chamber of furnace. Does not reduce heat flow. Reduces greening of porcelain by blocking the release of silver vapors from contaminated furnace surfaces. Tougher than original muffler surfaces. High-visibility color ensures accurate applications of Green Guard. Green color is noncontaminating and turns permanently white when fired. Especially useful with the new, lightweight furnaces and muffles.