Your best bet is to boil a
75/25 solution of water and white vinegar in your vessel for a few minutes. Use
a non-metallic scrub pad to work off any residue. A paste of baking soda and
water works well, too.
It's best not to put it in the dishwasher, as the
FluxRing could get damaged. Definitely do not use powdered detergent, which may
contain lye and will damage the vessel's surface.