An Investigation into the Suitability and Stability of a New Pigmented Wax-Resin Formulation for Infilling and Reintegration of Losses in Paintings

A new Pigmented Wax-Resin (PWR) formulation for infilling and reintegration of losses in paintings is introduced and tested for its suitability and stability. It consists of a mixture of Cosmoloid H80 microcrystalline wax and Regalrez 1126 hydrogenated hydrocarbon resin with dry pigments and/or fillers. Unlike other PWR formulations, including those sold by Gamblin Conservation Colors, it does not contain beeswax. Beeswax is reported to develop bloom and to corrode copper supports. The authors share methodologies and techniques used to characterize and assess the suitability of the new formulation in terms of its physical and optical properties, and to assess its stability to fluctuating relative humidity and temperature, particularly high temperatures. The new formulation was evaluated for its workability, opacity, and flexibility and for its compatibility with a selection of varnish coatings and inpainting media. Results showed that 1.5 parts of Cosmoloid H80 to 1 part of Regalrez 1126 (by weight), mixed with pigments and/or fillers, is a viable alternative to other infilling and inpainting media. It has good optical and working properties, a suitable degree of hardness, and remains stable during fluctuations in relative humidity and temperature, as well as to temperatures as high as 70°C.