Removing acid stains from clay tiles is not an everyday problem. In this case, discolouration on the clay tile floor was caused by acid from spilt apple juice in the Geislingen an der Steige local history museum. The discolouration could not be removed in previous cleaning attempts. A test cleaning with Maradin HC 43 brought the desired success. The picture clearly shows the differences: the discolouration is clearly visible in the upper area, while in the test cleaning area the tiles look bright and uniform again. The result: Maradin HC 43 is used to clean the entire floor and the customer is satisfied.