A study of the effect of the biscuit beetle (stegobium paniceum) on different compositions of 'colla pasta'

Abstract

Canvas paintings having a weakened support are generally treated by a conservation intervention called lining. This involves the adherence of a new canvas to the back of the painting. Until some years ago, the primary lining methods adopted in Malta were the Florentine and Roman 'calla pasta' (glue-paste) techniques, using an adhesive mainly composed of flour and animal glue. However, the glue-paste is susceptible to Biscuit beetle (Stegobium paniceum) infestations which may cause extensive damage to a painting. The development of lining adhesives and the various ingredients added to the glue-paste by Maltese restorers is explained. The deterioration caused by Biscuit beetles, in Malta and abroad, is examined through documented case-studies and surveys. Painted fragments lined with different compositions of glue-pastes, based on the Florentine and Roman techniques, were produced. Experimentation involved placing Biscuit beetles on the lined samples for five weeks whilst observing their effects and analysing the adhesives. The results obtained showed that the Biscuit beetles did not eat through any of the lined samples and some of the beetles died by the end of the experiment. No evidence has yet been found that the Florentine glue-paste technique has ever been infested with Biscuit beetles in Malta. However, case studies show multiple infestations on the Roman glue-paste technique. This study aims to create awareness of the damage that may be caused by a glue-paste lining and can also serve as a basis for further investigations in order to gain additional knowledge to address this deterioration problem. Notwithstanding, it is recommended that the Roman glue-paste technique is avoided unless the painting is safeguarded by stable climatic conditions and monitored regularly.