Spray nozzle and method for dusting freshly printed products

A powder duster spray nozzle system for dusting a freshly printed product via connection to a tube supplying a powder-air mixture, the printed product being transported beneath the spray nozzle system in a transport direction, the spray nozzle system comprising:

• a spray nozzle, said spray nozzle having means defining a distribution chamber and at least two nozzle channels which fan-off from said distribution chamber, wherein, transverse to the transport direction of the product, an opening angle α between outer-most nozzle channels is between 8° and 15° and, in the transport direction of the product, each nozzle channel has an opening angle of 0° and a length which is four to eight times a diameter of its largest cross sectional dimension, thereby producing a line-shaped powder curtain of small width;
• means for connecting said spray nozzle to the tube;
• and means for holding said spray nozzle at a defined separation from the product, wherein said defined separation is selected and each nozzle channel is structured and dimensioned such that jets of powder and air emanating from adjacent channels slightly contact each other but do not overlap when they impinge on the product.