Hi Glenn,
No I finished up with plaster, but the main part is steel scraps found here and there and chopped into pieces, melted together with 7 kg of lead. But the top surface was not very nice so I finished and filled up the rest with plaster.
Before plaster, it was pretty ugly like on this photo :
http://www.labellenote.fr/file/Metal...eur/Bol_06.jpg

The bowl is very heavy, I think it must be ~12 kg for 20cm diameter.
It provides plenty of inertia, that's what I wanted.