chalk

Hi all, We’re going to have a stove installed this summer, and I’m prepping our fireplace ready. It’s made entirely of lime and clunch (chalk), and is extremely delicate and any substantial fixings need to be planned as the walling doesn’t hold much weight on its own (no brick or other sturdy...

Can i use white chalk to highlight repaired areas on thistle multifinish plaster without it permanently marking or damaging walls in order to remind me where i patched? I intend to Gardz & emulsion later.