I'm trying to determine whether it was not mixed properly, left on to long or not rinsed off enough.
ma0641
Sep 3, 2010, 07:31 PM
If the acid was too strong or left on too long, it will whiten the bluestone. It can come from the mortar used. Even though bluestone is a variety of sandstone, impurities, limestone or marble as a metamorphic intrusion will react with muriatic(Hydrochloric) acid.