Characterization of Scale Formed on the Surfaces of Toilet Bowls

Repeated use of a toilet results in the build‐up of a deposit derived from urine and hard water on the surface of the toilet bowl. The hardened mineral scale is difficult to clean completely, especially in the case of deposits under the rim. A number of studies have focused on kidney stones, which are also caused by urine in the urinary tract; little attention, however, has been paid to the detailed composition and structure of the toilet scale. To develop powerful products for removing the toilet scale effectively instead of relying on acid‐cleaning and scrubbing, the composition and the accumulation mechanism of the scale must be clarified. Scale samples collected from the bowl surface were characterized by IR, XRF, XRD, ICP–AES, SEM–EDS and HPLC techniques and found to consist mainly of calcium phosphates, struvite, calcium carbonate, uric acid and proteins. After acid treatment of the scale, a film‐like structure of protein, produced as a result of the metabolism of bacteria and mold, was left behind. The scale had composite structures that were composed of the inorganic minerals and the organic materials listed above. This structure might be critical to making the scale resistant to removal by acid‐containing cleaners.