What to use to make a mold?

On 24 Mar, 23:05, AK wrote:

Ian, I create a mold first then I pour lead into the mold. Later I
break the mold up and I use fiberglass to cover the lead so it is
trapped and I am not exposed to lead dust.

I don't think you need worry about lead dust. I used to fly a Club
Libelle (not a Libelle owned by a club) which had a 1/4" sheet of lead
under the pilot's seat - if that's the sort of thing you need then why
not glue a thin layer of energy absorbing foam to each side and make
yourself a very heavy cushion?

Ian