"Iran nomadic dairy: How do the Sangesari nomads make curd and butter?

The Sangesari nomads use the skin of a cow known as Tilem to produce dough and butter from the yoqurt. The dough is then boiled and put in a certain type of fabric to draw out the water. Afterwards, until Qareqorout happens, the water would be brought to a boil. and the curd is the substance that is still contained within the fabric.
As you can see in the video, the Golbahar family was using an outdated and worn-out Tilem, thus in the middle of the operation, they had to swap it out with a sizable green plastic containter.