I have a hard, white buildup on the rock wall that makes up my sheer descent that I assumed was calcium. I got after it with some muriatic acid (after donning an outfit that looked suitable for a nuclear emergency!) and was gratified when it fizzed and bubbled like crazy. Figured my calcium diagnosis was on the money....but it didn't budge. I scrubbed with a Scotch Brite pad and a stiff brush, but no dice. Any advice?
