Agglomerated flux

Agglomerated flux consists of individual grains held together by a binder. The grains are porous and attract moisture like a sponge. If you weld with wet flux, you get hydrogen into the weld pool, and that causes cracks. So you have to dry the flux properly before use, otherwise you'll have trouble. Store the flux dry and warm, preferably in a sealed container. Before welding, put it in the drying oven to remove moisture. If the flux clumps or doesn't flow anymore, it was damp or has slag residue in it. After welding, sweep away the old flux and don't mix it with fresh, otherwise the weld quality suffers.