Thanks, I think I'm getting somewhere.
I had used silicone sealing grease in the military. It's sticky, inert,
and heat resistant. Later, I thought it would be just the thing for
plumbing. (It is used for plumbing at sea.)
It came to mind when my cartridge leaked. I came across the term
"plumber's grease" online and thought it must be similar. The tube of
Harvey's said it could be used in steam systems up to 350F. I thought,
"That's it!"
It worked, but in taking a second look, I found that it smells like
petroleum grease and isn't as sticky as silicone sealing grease. The
MSDS says it's general purpose lithium grease.
I've had good luck with teflon tape, but sometimes I've had to try again
because I'd applied too much for a good mechanical connection. You need
the right tape for the application. It takes two hands, and you could
end up with a bit of tape in an orifice or valve. If I applied sealing
grease to the male threads, it seems I could do it with one hand, it
wouldn't interfere mechanically, and any excess would be squeezed to the
outside, not the inside.
I've never used pipe dope because it used to harden. That could make a
joint hard to unscrew and leave the contents of a container useless.
Now I see they have non-hardening dope. I wonder how it differs from
sealing grease.