[TalnSG]

Ideally, an antique of any kind should never be cleaned (except professionally) if its value is to be retained. But since it is more valuable to you when it is useable, here is how to clean it.

Basically, do not use anything more than boiling water, if at all possible.
If rust is discoloring the boiling water (making it rusty looking), repeated brief steeping with fresh boiling will water will clear it. If the discoloration of the boiling water looks more like weak tea, that is good and just go ahead and use it.

If the rust is flaking off, scour it with a soft cotton cloth and hot water it it no longer flakes.

DO NOT use soap or any sort of cleanser..... not even the stuff designed for coffee pots.

Unless you are sure of the provenance of this pot, though, a professional lead testing might be a good idea before using it on a regular basis. Many older, especially antique clays contain it. However, the best pots have little or none in them.