The colander is installed on a cooking container, for example, a pot, a cauldron or a frying pan.
When the liquid boils, an air-bubble flow is formed, which raises the foam and goes up through the holes in the perforated bottom, which will separate the liquid from the foam. The boiling liquid when passing through the holes loses its power due to burst bubbles and sinks, which gives a positive effect for collecting foam and slag.