There is absolutely no difference in sourcing these items: both are freely available at places like Bunnings. As I pointed out, or meant to point out, the difference is that bleach will inevitably leave more toxic residue in a relatively porous medium like limestone, and it can be difficult to ensure that this toxic residue is completely removed. There is no such toxic residue with hydrochloric acid (spirit of salts for those who prefer kitchen names) as it simply takes part in a neutralisation reaction with the limestone, and reaction products are easily eluted. Any slight residue would simply add minutely to Gh.
Syd.
