Heavy black coating on old stone wall - lead?

AdrianC

We're stripping a load of modern plastic paint off an old stone house wall, in order to paint with proper old-school breathable stuff - and we've come across a really heavy-duty layer, almost a primer on the stone itself. It's VERY tough - a wire brush in an angle grinder's not touching it without dedication, nor is paint stripper.

Anybody heard of some kind of a lead primer, maybe some kind of weatherproofing? It's behind umpteen layers of paint, so it's clearly been there a looooong while.

FreeBear

More likely a bitumastic paint - Nasty stuff to get off. You could try warming it with a blowtorch to soften it and then use a scraper, but even then, you'll not get all of it off.

You may need to get a specialist in with a portable grit blasting rig. There are some blasting media that can be used that won't cause too much damage to the stonework. Dry ice and walnut shell springs to mind.

neilmcl

Agree with the above, sounds like bitumen to me.

Jonesya

You can buy lead paint testing kits to check for presence of lead if you're unsure, if the house is old they might be useful for checking old woodwork which will probably have been painted with lead paints at some point.

AdrianC

Bitumen crossed my mind - but it's very, very thin.

The local builder's merchant don't do lead testing kits... so there's one coming from online.

Woodwork's pretty much all been replaced - and not painted well, so the bigger problem is the (relatively recent) old paint just peeling off!

<sigh>
Houses. Who'd have 'em?