There are so many different fluxes for tin and copper work, from liquids to pastes, that we wanted to put out what's worked for us and how. Please list out your experiences and preferences this trade and craft is all about oral information sharing, so it'd be great to get some of it put down for posterity.

The use of flux for soldering seams in vintage copper and tin work is necessary to make the tin move and flow. Without it, your soldering iron will just "stick" and the tin solder won't move at all, usually falling off the tin plate in pieces.

We also use sal ammoniac to clean the soldering iron after every few uses to keep it clean and the tin solder sticking to the iron as well.

I did not address the need for additional heat to make solder flow when working with copper, nor did I discuss the need for a different type of flux when working with stainless steel plate, but you will definitely want to look into using a stainless flux if you go with that type of sheet metal.

Otherwise, this is just the experiences gleaned from using different types of flux when working in the tinshop or creating copper cookware from scratch or making copper cookware tinlined.