Metal rich hot dross should be cooled quickly to avoid metal loss.
When hot dross is removed from the furnace it comes into contact with ambient air and an exothermic reaction is generated within a few minutes.
Hot dross left in the open air looses between 15 – 20 % of metal. To avoid such metal loss there are two techniques:
Either enclose the dross in an air free chamber; however cooling time can be very long and so a large number of ‘chambers’ is required.
OR use a cooling press fitted with a single or twin press head the dross is cooled quickly.
Hot dross is skimmed from the furnace into special pots. The pots are placed under the hydraulic press and pressed for several minutes. A metallic skin forms on the surface of the dross so preventing air ingress and avoiding any reaction.