On Jul 11, 11:25*am, Red Green wrote:
Often when I take apart OLD plastic drain piping under sinks I find some
really sticky brown material on the threads. Usually I see it on black ABS
pipe. Apparently put on by plumbers long ago. Stuff is so goopy/sticky I
assume not only did it seal threads but also keep from working loose. Very
difficult to remove.

Anyone know what it is or if it's still used?

Sounds like Permatex #3 Aviation Grade sealant. Still a staple in many
A & E and car mechanics toolboxes. Treasured by Chevy motor builders
for those wretched intake manifold gaskets and the Mopar guys for
water pump gaskets. Personally, I like it for all manner of thread
sealing. Disassembly is helped by a bit of heat, and the sealant is
soluble in alcohol. Great stuff for assembly of Lycoming and VW air
cooled engine case halves, too. The product has been around since
before WW II I am told.

Joe