Fitting loose then a parallel thread was used which required a fibre washer or shoulder.
I don't recall two types of PTFE years ago 112??...over the last 20 odd years the PTFE has got thinner and thinner so they decided to manufacture a thicker tape for gas....fook me it's the same thickness we used 30 odd years ago on gas and water..
Do you remember using two types of PTFE tape years ago?..cos I don't..
Gas tape is a one wrap jobbie , normal tape then wrap a good few turns...
I use locktite now but used PTFE for years..
Only saying what i found steel and it wasnt parallel threads , same as some people used ptfe then coated it with paste , fek knows why but Watson house sent a bullitine out around 30 years ago saying all 3 reacted with each other causing tape to disintegrate
Steel i remember as an apprentice doing industrial meters and two inch pipe in the workshop . Tested up and it was pishing out . thought how the fek i cant tighten it any more then i smelt it one of mates had mixed my paste with barrier cream . They were all pishing themselves laughin at me getting bubbles at every joint