Instant Gasket, Threadlock, Liquid PTFE - which to use when?

[mike]

I found this gas fitting (pic link below) while I was ripping out some old pipework which seems to have been sealed with something that sets hard and is permanent but without the thread being driven fully home, so you can get the fitting at the right angle.

at Toolstation's website, I've found Instant Gasket, Threadlock and Liquid PTFE.

anyone tell me which one has likely been used here for a permanent solid joint (and what the other two would be used for)?

Thanks in advance.

[john]

>>> Can anyone tell me which one has likely been used here for a permanent

The angle fitting looks like a standard 1/4" taper B.S.P. (other bit is a 'nipple') and sealant is optional to the mechanical assembly aspects. The red stuff ISTR as "Stag". Used buckets of the stuff on gas and instrumentation piping. Needed dry, clean surfaces, was horrible to paint on, it stunk and dissembly was a pain-in-the-bum. PTFE thread tape when it turned up on the market was a true revalation. Stag was dumped within weeks. The fillers you show all look like very pricey cyano type adhesives. I'd be inclined just to use cheap PTFE thread tape