Can you remove cement off facing bricks

[Richard]

Hi, another problem for you guys to advise on if you would be so kind!

Last year whilst building the extension, my beautiful old outhouse, constructed of 1860's kent red bricks, was splattered by the morons who pumped cement into the foundations. Their pipe blocked and apparently it went everywhere. They managed to clean most of it up before I returned, but there was a significant amount stuck to the outside of the bricks that was rock hard before I had a chance to do anything. I dont suppose anyone knows of an effective method to remove this foundation mix without totally destroying the bricks. The stuff on the lime mortar can be removed as it crumbles easily, but I'm stuck for the bricks themselves. Any help gratefully received.

Thanks.

[Lobster]

Brick acid (obtainable from any builder's merchant or B&Q) would almost certainly do it, but the problem will be that it will also make short work of the mortar between the bricks, so would need applying v-e-r-y carefully to avoid having to repoint the outhouse...

David

[Phil L]

brick acid will remove cement *stains*, it won't remove dried concrete.

The ony thing you can do in these cases is remove each splatter manually, IE with a scraper, or if needs be, a small hammer, such as a pin hammer, laborious but sadly, the only real alternative to what you have now.

[The Natural Philosopher]

Brick acid.

[The Natural Philosopher]

Nope, it works very well, there being usually only a few mm on the surface, and a few inches in the gaps..being eaten at similar rtes..it takes a LOT to completely screw a mortar joint.

paint on, and wire brush.

Then pressure wash or hose the whole thing down.

[The Natural Philosopher]

It will. In time. I have 'concrete proof' harhar.

It turns just about any portland or lime based cement into a soluble chloride salt. The rest - the ballast and the sand - washes away.

Obviously chip of big bits, but for a bit of fun, make a bowl shaped bit of mortar, and put in brick acid..it may take several goes and esevarl liters, but it will all dissolve in time.

[Andrew Gabriel]

Never use a wire brush on facing brickwork. Depending on the relative hardness, it either wrecks the faces, or they are stained with the metal from the wire.

Don't pressure wash a lime mortar wall.

[The Natural Philosopher]

Oh dear. I must have been exrtremely lucky then.

Oh. I forgot. One decent thunderstorm and a lime mortar wall comes crashing down.

I think that's probably what happened to Rome.

[Richard]

Thats what i was concerned about - the bricks are very soft! Thanks for al the useful replies btw

[The Natural Philosopher]

In that case te acid will penetrate a little and get behind the concrete spalatters, which can just be hosed off.

I've got a chimney breast made of very soft reclaimed tudor bricks and

50:50 lime cement mortar.All cleaned with brick acid.

[Richard]

That reminds me that I've also got some bricks to clean which have been marked by lime mortar dust when the builders cut the joint for the new lead flashing on my extension to be slotted in. Is there anything I should know about brick acid and lead or slates, both being in danger of getting splashed. Will they get marked?? Thanks for the help.

[The Natural Philosopher]

Lead will suffer BADLY from acid, but bricks and slates can be soaked too your hearts content.

In practice if you can keep your acid confined to the cement, it gets neutralised by that. So you can use it oversensitive surfaces, as long as it hits the cement faster than the substrate. As soon as possible wash it off with water - lots of it.

[Richard]

Many thanks for the help! I'll be careful..