Saw a crew in Wilmington laying brick over old block and the bond lines were dead on
I was in Wilmington, NC for my niece's graduation this past weekend and walked past a crew working on a storefront on Front Street. They were going right over the old block with a full bed of mortar and their bond lines stayed dead level across the whole 20 foot wall, no string line slop anywhere. How do you all handle going over old block, do you scuff it up first or just butter it heavy and trust the mud?
Read a piece a while back from an old mason out of Charleston who swore by scuffing the face of old block with a grinder or a wire wheel before laying over it. His point was that old block gets a glaze on it from years of rain and dirt, and mortar needs something to grab onto. Buttering it heavy can work but you are really just hoping the mud sticks. The crew you saw probably did some prep you did not notice, maybe acid wash or a good scrub. Bond lines staying true over 20 feet means their base was solid too, not just the mud. Anyone can get lucky for a few courses, holding it that long takes real setup.