Lime repointing
Failed and cement-rich joints are raked out by hand and repointed in a lime mortar matched to the original. The wall is left breathable, so moisture leaves through the joint rather than the stone.
Most of the failed pointing we see is a hard cement repair from the last fifty years. Taking it out without damaging the stone is slow, careful work, and matching the new lime to the original mortar in colour, texture and strength is what makes the repair disappear.