Analytical pyrolysis applied to the characterisation and identification of Asian lacquers in cultural heritage samples – A review

In the past 30 years the study of the composition and chemistry of Asian lacquers has reached a high level of interest among scientists and conservators. As a result, analytical strategies have been developed to characterise and identify these materials in complex samples, sometimes thousands of years old. Asian lacquers are mainly composed of polymerised alkylcatechols and they are often applied in mixtures with several other organic and inorganic materials, such as oils, plant gums, mineral pigments, organic additives, etc. The polymeric nature of Asian lacquers limits the scientific approaches that can be used to investigate them. Technological progress and an increase in popularity of analytical pyrolysis (Py) have run parallel to the advancement of research in the field of Asian lacquer identification. With the ability to distinguish the different types of lacquers and to identify most of the other materials mixed with them, pyrolysis coupled to gas chromatography and mass spectrometry (Py-GC/MS) is the most effective technique in this type of investigation. Several research groups have optimised analytical conditions, derivatisation steps and data treatment to create reliable protocols with wide applicability. The information related to the development of such protocols is summarised in this review, together with some critical comparisons and suggestions on future perspectives in this research field.