Hi,
we were recently asked to clean some stone walls in a pub/restaurant which did not want to close for the work, I found a product on the t'internet called rem-scale, we diluteded as advised, put floor protection down and applied to the walls, left it for 20 mins then rinsed off. the effect was not brilliant so we repeated the process and used a wire brush to the worst areas.
TBH I was not that pleased with the results, i called the manager the following morning and explained that we had done our best , but it just wasn,t coming clean, He thought I was mad, he was hopping with joy. I drove down there, and it looked like a new build. The product is not the nicest, full PPE etc, but great results.
Regards
MCM