Why does Turkish coffee lose its foam?

The foam forms as gas inside the coffee carries the finest particles to the surface. Grind size therefore decides everything: coffee ground as coarse as filter grind will never hold foam.

Heat is the second factor. The pot is warmed over a low flame without hurry; the foam rises before the water reaches boiling point. Stirring after that, or bringing it back to a boil, releases the gas and the foam collapses.

The method is simple: cold water, powder-fine coffee, low heat, share the foam between the cups at the first rise, then return the pot and top them up. Sugar goes in before brewing; stirred in later it ruins the foam.