Method for heat treatment of mixed media sheets

A method for heat treatment of mixed media sheets having different heat capacities in an image reproduction apparatus, the image reproduction apparatus having an image forming station, a heat treatment station, a conveying path for conveying the sheets one by one through the image forming station and the heat treatment station, and a duplex loop for looping sheets back from the heat treatment station to the image forming station by means of a sheet reversing mechanism for reversing the orientation in which the sheets are fed back to the image forming station,

• the method comprising a step of pre-heating a sheet before an image is formed thereon in the image forming station,
• wherein the step of pre-heating comprises the sub-steps of:
• passing the sheet through the image forming station while the image forming station is idle, so that no image is formed on the sheet;
• passing the sheet through the heat treatment station for pre-heating;
• and
• looping the sheet back to the image forming station.