Advice for removing stubborn cement render on stone wall

[Graeme1983]

Does anyone have advice for removing stubborn cement from a mixture of stone, old brick and earth brick(cob) walls?

Using mostly a miner's pick Ive been able to gently remove about 95% of the cement and paint from the wall which came off in nice dry chunks.

All thats left(mostly where the damp patches were) are patches of a white powdery thick amount of cement(efforvesence?) It doesnt really come away much using hand tools like chisel and hammer Im thinking maybe an electric sander or grinder but Im wary of damaging the material.

Also in some places under that cement a really solid grey substance that only comes off with loads of elbow grease which damaged a brick.


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[joe-90]

Have you tried an acid brick cleaner?

 

[Graeme1983]

No I read about that but dont fancy it. Im a self builder not a pro and its a bit dangerous to be messing about with. I dont want to end up like Simon Weston. Also how would it react with damp earth brick?

I got most of it off with a little cross pein hammer, many small taps and used the sharp end a bit, it was hard going but did little damage. Would be good if someone knows any quicker tricks as Ive another two and a half rooms like this and the outside.