Firstly, fill the iron tank to MAX with water.
Set the thermostat control to Max and the steam control on DRY and switch on.
Place the iron on its heel and leave to heat up for around 5 minutes.
Unplug the iron then hold your iron horizontally above the sink.
Remove the anti-scale valve (or set the control to self-clean/autoclean depending on the model). Steam, water and scale deposits will leave the steam chamber through the steam holes and the iron will be clean.
At the end of the operation, push the anti-calc valve back into position. When your iron is cold, you will also be able to use your vacuum to gently suction limescale and dirt that may have clogged the holes in the soleplate.