On Tue, 10 Aug 2010 00:17:52 -0700 (PDT), Jim K
wrote:

If these are old bricks it sounds a great way to ruin them. Cement can
be removed with HCl, and dirt with a long water soak.

indeed, tis the (more) weatherproof outer surface that is the most
important thing about old bricks....


Thanks Tim, Andy, Tabby, Jim,

It's the brickwork sides of an opened-out fireplace in a 200 year old
building. It's coated with soot tar and a semi hard, fibrous material
which I suspect is built-up layers of some combustion residue turned
grey/white. In some places it comes off in slabs, other patches are
more recalcitrant and so I'm looking for the scraper or the slow brush
powertool. Point taken on brick surface, reminds me of looking after
our teeth enamel.

I want to see if the exposed brick can be made cosmetically pleasing.
Otherwise I'll panel the sides with Promat fire boards!