The present inventions relates to An ink-jet printer for printing on an edible substrate, the printer comprising a guide roller for guiding the substrate through the printer and a print head for printing on the substrate, the print head being mounted adjacent the guide roller so as to be movable in a reciprocating manner substantially parallel to the guide roller characterized in that the print head mounts a roller cleaning apparatus which engages the guide roller as the print head reciprocates. This prevents a build-up of residue from the edible substrate on the guide rollers, thus providing improved performance and reliability. A method of operating the printer in conjunction with a user terminal is also disclosed.