On Fri, 21 Mar 2008 17:38:32 -0400, clare at snyder dot ontario dot
canada wrote:

On Fri, 21 Mar 2008 14:55:13 -0600, Don Foreman
wrote:

On Fri, 21 Mar 2008 01:13:50 -0700, David Harmon
wrote:

On Thu, 20 Mar 2008 13:48:28 -0400 in rec.crafts.metalworking, clare
at snyder dot ontario dot canada wrote,
There is SOME truth to the belief.
The concrete is generally colder than a wood board, causing the
battery to cool down unevenly and the acid to stratify over time. The
"heavy" acid goes to the bottom. The "light" water goes to the top.
This apparently can cause "stratification sulphation"

Right. I was wondering if anybody who knew was going to post.
Conditions have to be right for it to occur, which is probably why
so many don't understand it.

If I pour some battery acid into a beaker, set the beaker on a cold
plate and ensure that it is not physically disturbed, do you assert
that the solution will stratify after some period of time such that
samples drawn from near the bottom will have higher specific gravity
than samples drawn from near the top?

Most definitely.

OK, perhaps I should have said lower pH or higher concentration. Even
plain water with a temperature gradient will have higher s.g. where
colder, down to 39F anyway.