Colour measurements on patinas and coatings systems for outdoor bronze monuments

Colour measurements have been performed on outdoor bronze patinas and protective coating systems with a portable spectrophotometer. Colour difference reduction upon patinas cleaning on a monument is monitored. Colour differences upon natural weathering measured on coatings applied to bronze coupons show they are mainly due to the decrease in lightness L*. Application of colour measurement in support to outdoor bronze monument conservation is discussed.