The symphony of red : investigation of red stained plaster in Hakka vernacular architecture in Hong Kong

Abstract

Red stained plaster panels are common decorative elements in Hakka vernacular buildings in Hong Kong and China. Given variations of the colors and conditions observed on these panels as well as the purposes for applying such decorations identified in different sites, it is worth studying the differences in their compositions and investigating how they respond to geographical differences or the traditional recipes written in classical literature. The stained plaster panels of two Hakka mansions, Sik Lo and Pun Uk in Yuen Long, Hong Kong, are investigated and analyzed in detail. Samples were predominantly investigated with a stereomicroscope; some selected samples were also analyzed with Scanning Electron Microscopy (SEM) and Scanning Electron Microscopy - Energy Dispersive X-Ray Spectroscopy (SEM-EDX). According to historical government documents, the stained plastering technique is composed of two layers, a stained plaster layer (lime, aggregates, fibres and pigments) and a red lime wash layer (lime, pigments, alum and sticky rice soup). The standard pigment is natural red iron oxide pigment, while there are local variations found, including vermillion and brick powder. The amount of pigment added is dependent on the status of the building. The result of the analyses reveals that the pigments used for the stained plaster panels for both the sites have varying grain sizes as identified under a stereomicroscope, and with high percentages of iron, aluminium and silicon identified in SEM-EDX spectrum. The result indicates that the pigment used is possibly natural red ochre, which follows the traditional recipe. In contrast with the imperial recipes, the limewash layer is only identified in Pun Uk, giving a possible indication that the layer may not be a prominent feature for the stained plaster panels in Hakka vernacular architecture. However, the additives used in the limewash layer are not identified, leaving future possibilities for research.