Peetal, the brass alloy our vessels are made from, conducts heat beautifully. It also reacts with anything acidic sitting in it overnight. Kalai solves that. Molten tin is flowed across the cooking surface, leaving a thin silver lining that stands between the food and the metal.
The lining is not a coating in the nonstick sense. Nothing is sprayed on. It is metal bonded to metal, applied hot by hand, and it behaves like part of the vessel because it is one.
A fresh lining looks bright silver. With use it dulls to soft grey and picks up faint marks where spoons rest and curries sit longest. That is the lining working, not failing.
When bare patches of the yellowish base metal start showing through across most of the cooking surface, the lining has done its years and the piece goes back for a re-tin. That cycle, use and renew rather than discard, is the whole idea behind how these pots are built.
Freshly tinned interior of a peetal vessel showing its silver kalai lining.
