cleaning mortar off stone

[buildergirl]

how do i clean mortar off stone? i have taken down a wall which was blocking an old doorway. where the stone had been put in there is mortar on the stone which i cannot get off without chipping big holes in the stone. is there something that dissolves old mortar or am i being optimistic?

[powelly]

use brick acid you can get it from focus/b&q that will sort it no probs