What does the color during cleaning say about the effectiveness?

When removing rust from natural stone, noticeable color changes can occur – especially a purple discoloration. This happens when the cleaner chemically reacts with iron particles within or on the surface of the stone. In calcareous stones like marble or travertine, metal oxides can settle deep into the pores. When a specially formulated rust remover is applied, it begins to dissolve iron compounds. The appearance of a purple color is a good sign – it indicates that the product is working actively to break down rust. This discoloration is temporary and disappears completely during rinsing. It’s not harmful, but rather a visual confirmation of effective cleaning. HMK R179 Rust Remover is designed to make this reaction visible for controlled and targeted use.

HMK R179 Rust Remover turns purple when reacting with iron particles – a sign of active rust removal.

HMK R179 Rust Remover is specially developed for removing rust from calcareous, acid-sensitive natural stones. When it comes into contact with iron and metal oxides, it reacts immediately and visibly: the affected area turns purple. This color change is a clear indicator that the product is actively breaking down rust. It also helps users monitor the treated area and reapply if needed. After 10 to 15 minutes of contact time, the residue can be rinsed off using water and an acid-free base cleaner. The purple tint disappears completely after rinsing. Thanks to this visually controlled effect, HMK R179 is ideal for both professional and private use on natural stone.