This is a series of tinners at work. It's like magic: one moment there is this well-worked but dull copper vessel, than some salt is thrown on it, and a bit later some tin is pressed against the heated sides. There is a lot of rubbing with cloth and smoke, and all of a sudden the vessels seems transformed into silver.
I suppose vessels are tinned because copper green is not really good for one's health. Although I recently read that in India one has found that water, kept in copper vessels, will remain drinkable and free of bacteria, well after ordinary water would have gone bad (it must remain in it for at least two days, and even then: don't try this at home. The article was in a New Scientist of March or April 2005).