A further stage of analysis will involve the identification of individual pigment particles perhaps using a polarising, or a scanning electron microscope. This will often provide information on the age, finish and purpose of a particular layer.
The presence of chrome yellow will usually indicate that a decorative scheme could not have been applied before ca.1820, for example. Other useful datum points are suggested by the first occurrence of emerald green (1814+), lithopone (1870s+) and titanium (1920s+).
A combination of documentary and pigment analysis can often enable the identification of the scheme that was visible at any particular period in time. This might be the years during which a notable individual lived in the house, or even when a specific event took place there.
The interpretation of such analysis can only be done by someone who has made a study of the house-painter’s methods and materials.