AIC's 53rd Annual Meeting

Since joining the Canadian Conservation Institute, many of my collaborations have taken shape during hallway conversations. When asked the simple question "How do you feel?," I responded off-topic, due to my struggles as a francophone to understand English and my preoccupation with the treatment of a mismatched veneer repair on an 19th century English piano: "I want to fill with wood, but I have several issues..."

The conservation of wooden furniture and objects often requires the integration of new components due to degradation, breakage, or loss. This process becomes particularly complex when filling large areas with an alternate material. Wood is typically the compensation material of choice, but several factors can complicate the filling process, including the availability of specific wood species and the surface characteristics of colour, grain, and finish. Importantly, there is the challenge of a colour difference developing between the object and the fill after subsequent light exposure. But what is responsible for this – the original wood, the wood fill, or both? Eric Hagan, senior conservation scientist, was kind enough to ask how I was feeling one day, and that conversation led to experiments that address this question. Using customized light ageing boxes and fadeometers, we investigated the colour change response of wood to museum lighting conditions, the influence difference light sources have, and the light dose that changes color slowly enough to be acceptable. Results from our experiments showed that all freshly sanded woods, when exposed to light without UV, undergo a rapid colour change (rated Blue Wool 1 to 3) followed by a slowdown. Experiments on mahogany and purpleheart under LED, Halogen, Fluorescent, and Ceramic Metal Halide sources seem to demonstrate that light source does not have a major influence on colour change. Initially very sensitive, all woods shift to Blue Wool 5 at approximately 50 to 60 Mlxh. 

 

Thanks to these key numbers, we concluded that wood used for a fill should be chosen based on its texture and not its colour. Moreover, an object’s original wood, depending on its age, exposure, and treatment history, may remain highly sensitive to colour change; mismatches will arise over the course of a conservator’s career, requiring re-treatment of the object. Indefinitely removing and replacing adhered wood fills is not a viable option, given the potential for damaging the object. Therefore, I had to rethink my approach to matching the colour of wood fills, which led my feet down the hallway to my colleagues in paintings conservation, Marie-Hélène Nadeau and Fiona Rutka. After testing different natural and synthetic resins, we found that Orasol dyes mixed with Aquazol 200 successfully toned the sealed, light-aged wood fill, and it was easily reversible.