Sturdy Tub

Sources

A Sturdy Tub requires the Flax Processing skill. It is an improvement to a Basic Tub but still can crumble unlike the Marble Tub.

A Sturdy Tub is the intermediary tub and has the following uses:

Rot 20 Dung in 20 water to create 4 Saltpeter (20 teppy minutes).
Rot Flax into Rotten Flax.
Produce Sulfur from Sulphurous Water (1 sulfur produced every 1 teppy minute, 20 mins for 20 sulfur)
Steep Clay in Canvas with 10 Clay and 20 Water in Jugs to create Clay-Steeped Canvas in 3 minutes.
Steep Clay in Wool Cloth with 10 Clay and 20 Water in Jugs to create Clay-Steeped Wool Cloth in 4 minutes.

A Sturdy Tub can hold 100 Dung and 20 Water or Sulphurous Water. You can add more water at any time to continue a process.

After some number of uses, the tub will crumble to dust (no resources returned).

The Marble Tub is the next step up in quality.

This tub is more robust than the Basic Tub and about the same cost - build this one.
Always better to rot flax in a river/lake rather than a tub as the river/lake doesn't break.
If the tub is near the end of its lifetime, salvage it to recover some materials rather than letting them go to dust.
- If built and used in banks, one or two of the bank will wear out first giving warning that now is the time to salvage/rebuild.
If you can afford it, the Marble Tub is considerably longer lasting (that is to say, the Marble tub doesn't crumble at all).