On Oct 13, 12:16*pm, "John Grabowski" wrote:
What is the technical term for the putty that electricians use to seal
around service cables where they enter meter boxes, or pass through
walls?

*Duct Seal

It's Duct Seal, or as manufacturers call it, thumbgrade.

We use it only to seal conduits going into hazardous areas. It will
prevent a dust explosion from propagating through conduit, at least in
theory.

They sell it in all the big box home improvement stores, BUT the
actual purchasers are a very specialized group.

The only people who buy much duct seal are airgun shooters. Duct Seal
makes an ideal pellet trap, just fill a flat box with it. It absorbs
a pellet silently and traps all lead dust. Every once in a while (few
thousand rounds) you dig out the pellets and smooth out the duct seal
again.

Long ago I talked with an old timer at Johns-Mansville or whatever
they were at the time who used to make the stuff. It's basically
calcium oxide and grease, made in a big pug mixer in batches of about
1000 pounds at a time. Of course he wouldn't tell me the real
recipe.