I'm not a specialist on textiles but here they were bleaching and washing the spun cotton strings before dying them.

This man tried to get the last drop of water out of the strings after they were rinsed with clear water to get the chemicals from bleaching out.

All those companies are in the poor area of Sellur just across the Vangai river, the place where the real Ochappan lives with his family.
Mostly they make towels here and companies are modernising with automatic machines, second handed from the West, making a lot of dust and noise.