Investigating Shellac: Documenting the Process, Defining the Product. : A study on the processing methods of Shellac, and the analysis of selected physical and chemical characteristics.

Abstract

This thesis examines shellac, a natural animal-produced resin and wax mixture, in relation to the conservation of furniture and objects of cultural heritage. As demands for shellac have changed with time, so have its processing methods. The thesis aims to determine whether these differences result in physical or chemical variations, and uses FTIR to investigate whether they can be identified using analytical analysis. Utilized methods include literature searches, fieldwork in India, a survey, FTIR and GC-MS analysis, as well as specifically devised experiments.

Part 1 of the thesis presents the history and entomology of the crop, and documents the traditional and modern processing techniques of the product. Part 2 offers a review of FTIR as a method of analysis, identifying GC-MS as a secondary method. FTIR is used to investigate whether or not different processing methods are detectable by examining the resulting spectra. The chemistry of Lac is explored, and 10 shellac samples are analyzed with FTIR, identifying the process of polymerization by esterification, and monitoring it during various stages of ageing and curing. Additionally, experiments are conducted to test the gloss, color and adhesion of shellac during various stages of polymerization, and whether there are any patterns due to processing techniques.

The results show that although certain relations can be identified, FTIR is not capable of differentiating between shellac processed by varying methods. The esterification of shellac is identified and monitored. The findings are related to the practical implications and uses for conservators. Further, the thesis divulges the failure of GC-MS testing, and concludes that further research is necessary to quantify the components of shellac processed by traditional and modern methods.