I watch a lot of youtube videos on cleaning and restoring things. It seems folks on the other side of the planet who use many copper, brass and silver items in their kitchen have absolutely mastered the chore of removing tarnish from these items: they boil them.
There are many many ways to clean tarnish, especially from copper. Instead of a ready made product or scrubbing with vinegar and salt, I chose this method because of these heavily embossed yet very tiny molds, I didn’t want to try to lose a day trying to evenly scrub into every crack.
For this you need a cooking vessel large enough to hold whatever you are boiling, baking soda, crumpled aluminum foil and water to cover. This method is extremely popular converting silver oxide back into silver with the transfer of ions, the chemistry is the same with copper and brass, instead of wearing away the surface, it reverses the oxidation.
I probably put into too much baking soda for such a tiny pan, I’m sure a couple of tablespoons would have been fine. And I have definitely found a new use for aluminum foil used for cooking. I left it to simmer for about 15 minutes and then gave the molds a normal dish soap scrub to remove the residual baking soda. These molds are tin lined and I am not exactly sure what I will be using them for, but they at least they are very shiny.
BTW the Foil is brittle and less maleable afterward, so I am not sure how doing this IN an aluminum vessel would effect the pan – but I am anxious to see what happens when I do.