I really enjoy your demonstration vids.. The citric acid tip was a game changer for me. It's a bit out there but have you ever 'antiqued' or 'oxidised' a spelter lamp? I'd really like to know how to get that aged jet black finish without waiting 100 years, Have managed to assemble a matching pair of Victorian English Hink's urn style lamps but one is coloured like dull steel due to a previous custodians cleaning. The other looks as it should (like ancient bronze). Early research has found plenty of antiquing agents for ferrous alloys but nothing for lead and/or zinc.
I use Liver of Sulfur on brass to give it an old finish. I polish the brass to high polish then dip it hot water with liver of sulpher and scrub with green scrub or steel wool. Then dunk it in baking soda and water to neutralize, dry, then lacquer to keep the finish. Spelter is different . I would try a gun blueing agent as an experiment. Just a guess . Cheers