[Richard Farrant]

When I worked in army workshops, a lot of parts for the older vehicles were like this, especially shell bearings, pistons and ball bearings, here we had a water tank with an element in it and a basket like a chip fryer, the preservative floats to the top and you can skim it off.

I had a brand new diff/ crown wheel and pinion assembly for a WW2 Humber once, and did not have the benefit of a hot tank nor a steam cleaner, had to resort to stripping the whole thing out. Another time I dismantled a gearbox from a wartime armoured car and there was still traces of the preservative in the box, but the bearings were worn out due to the balls being gummed up and skidding in the races.