Straightening a bib tap...

Polypropylene rope (the cheap stuff), but it's not WRAS approved.

NT

Anything that's stringy and will bind the thread ... cotton, wool, etcetera

You can get PTFE cord which is better suited to that kind of thing. (You can still get hemp as well).

You can get thicker PTFE tape.

I wouldn't use materials that are likely to rot.

NT

True, but they're not going to rot because they're in Plumber's Mait and bound in the threads

I can't remember the number unfortunately, but Loctite used to do a white thread sealant for pipework - we used to use it at work where PTFE tape was banned. You used to put it on the male thread, screw it into position and allow to set. It set rock hard, although it was (just) possible to unscrew it if necessary.

SteveW

I've seen a liquid PTFE sealer in Wickes

Yes, I've seen a number of different products, I just don't know if they are the same as the Loctitie one that I knew - it was in a traditional loctite style, red bottle, with a nozzle (no brush needed) and it set solid. I am not sure whether the various options today set solid or just form a seal.

It may well be worth trying one in this sort of case.

SteveW

Mine were 'worst case' - one was correct and the other was a long way out and would have needed a shedload of something. I swapped them over and they were both almost the amount out but still too much for tape. I didn't try to adjust by a part turn but looked at the plastic washers I had and found some just the right ID. They got me to a small bit out and then some tape did the rest. Trimmed off the outer part of the washers and they're hardly noticeable now.

Coincidentally, I've recently done some bib taps & I used Fernox LS-X, which someone here recommended for this sort of thing. The trick is to patiently let it set for a while before you fiddle with it to see if it's working!