Kegs can store up to 100 potions of the same type. For every potion added, their weight increases by four fifths of a stone (up to a maximum of 100 stones). They may be dyed with a Furniture Dye Tub, which is often helpful for coloring the kegs to match the potion type inside.
The contextual menu option to entirely dump the contents of a keg so that it may be re-used has not yet been implemented.
75.0 Tinkering Under Assemblies