limestone? what needs to be cleaned? I always had it turn black and dark green after large amounts of rain and/or humidity. For that, I just used a power washer.
I always thought Austin Stone was just the type of limestone that was found in and around the Austin area...
Maybe I am wrong.... I have the white stone that everyone seems to use to outline their flower beds. I thought it was called Austin Stone because it comes from the Austin area.
It is limestone and is found throughout most of the hill country (North of San Antonio up to about Fort Hood and areas West of that line) There are pockets of granite, sandstone and marble, but it is predominately limestone. You can power wash it but it will come back in a year or two. The coloring adds character.
As the above poster mentioned that doesn't sound any different than the limestone that prominent all throughout the hill country. Great marketing ploy though.
My house is built from very "earthy" colored stone that we were told is "Austin Stone". It looks like sandstone to me. I'm not saying the original poster's white limestone is the same thing, but rather that there seems to be some differing opinions as to what constitutes "Austin Stone".
Some guy sold me some Austin Stone the other day. It sure looked a lot like red lava rock, but he called it Austin Stone... so I decided it was worth paying a premium.
At our previous home, a line of green/black muck had built up along one corner of the limestone exterior before we installed rain gutters. This was probably about 5 years' of accumulation. It powerwashed right off, as other posters have suggested. You can rent one for the day at Home Depot (~$50, I think); or a contractor might have higher-powered machines if you want to hire someone.
To clear up what I am talking about..... the stone/rock is "white" and is cut on top and bottom. You can find it at most any landscape store.
It could be rock from the "Austin chalk" geological formation, but previous posters have probably rightfully pointed it out as a marketing scheme. Jomax/bleach works, as does the power sprayer. Careful with the Jomax, it can burn plants.