Adapting and evolving the traditional technique of egg tempera retouching at the Hamilton Kerr Institute

This paper discusses the traditional retouching method of egg tempera, which, amongst other retouching techniques, remains a practised and taught method at the Hamilton Kerr Institute (HKI), University of Cambridge, UK. Since its introduction to Britain, the method has evolved and adapted, most recently owing to the absence of MS2A resin. Laropal A81 has been used as the replacement isolating varnish. However, the physical properties and handling differ from MS2A. The typical diluent used at the HKI for Laropal A81 varnish is a 50:50 mixture of Shellsol A100 and Shellsol D40, however, when used as the isolating resin over an area of retouching this mixture could disrupt lower tempera layers. To remedy this, the diluent was changed to cyclococtane, an aliphatic hydrocarbon. Cyclooctane benefits from being less toxic compared to the aromatic hydrocarbon Shellsol A100 and can be manipulated more on the surface before the activation of lower Laropal A81 layers becomes problematic.   Laropal A81 solubilized in cyclooctane was successfully used as the isolating resin for egg tempera retouching and offers promise for a variety of varnishing scenarios and retouching. This paper demonstrates this adapted method of egg tempera retouching through a case study of a 16th-century panel painting with large losses perfectly suited to this method.