I had pretty bad calcium buildup around the tile that goes around my pool. I scrape the calcium off and then used muriatic acid to get the remaining residue in that seem to work pretty well until the tile dried. It appears I almost have a chalk line on the tile. I scrubbed it down with muriatic acid several times and after rinsing when it dries it still looks like a faint chalk line running across the tile. I don’t know how to get this off. Does anyone know what it is and what the solution is? I’ve also tried using the pumice stone. It’s almost like white chalk.