The toner image is permanently fixed to the paper using either a heat and pressure mechanism (hot roll fuser) or a radiant fusing technology (oven fuser) to melt and bond the toner particles into the medium (usually paper) being printed. There also used to be available "offline" vapor fusers. These were trays covered in cotton gauze sprinkled with a volatile liquid, such as ether. When the transferred image was brought into proximity with the vapor from the evaporating liquid, the result was a perfectly fixed copy without any of the distortion or toner migration which can occur with the other methods. This method is no longer used due to emissions of fumes.