'Mike' wrote:
P.S. I think you Sludge Level with a bit of board would work to a certain
degree, but not tooooooooooooooooo accurate because I feel that the board
would indeed 'sink' into the solid/sludge, but with practice I would expect
you to be able to 'feel' when it started to go into it.

Yes, getting the hang of when one had penetrated to top of the sludge
would indeed probably take practice. Hmmm, an art I never contemplated
I would wish to become proficient at! :-)

Eddy.