White Patches

White patches on level one columns

Irregular white patches are observed on various parts of the columns. Substrates are damaged by weathering within months or years where carbon dioxide and water vapour from the atmosphere may diffuse into the surface, resulting in failure of TiO₂ coating³⁶. Due to long term exposure to rain, rain water and condensation within the wall may be able dissolve the lime from cement. This reaction, involving carbon dioxide, will result in a deposit of insoluble calcium carbonate as the water evaporates off the surface of the columns will then result in the white patches column.