Amazing shampoo!! I don't know why the friend who gave a low rating did so, but I have the best impressions. Besides the fact that it cleaned waterspots for FUN, it also restored the hydrophobicity from wax that I had applied and I thought had disappeared months ago! Check out the video below:
https://youtu.be/OeMQQKn8b1M?si=hIMiLv0lYyIopj00

I was using the very good but quite expensive Labocosmetica Purifica, which is top. Due to the price and ease of use on the bathtub, I decided to try the rs. The smell is unpleasant, like a bathroom detergent, but okay. I noticed that it doesn't "unclog" the ceramic and reactivate hydrophobicity like the untouchable purifica, but for some reason it seems to weaken it and the hydrophobicity decreased. I did a top-up with wash n coat shampoo and it worked well. I won't use it again, maybe I'll use it on a car to remove waterspots and salts in the future, but I won't risk it on ceramic again.