Photos: Visitors of different age groups examining the object’s perception. (Photo cred: Amalia Siatou)
How do visitors perceive the appearance of silver museum objects?
When exposed to the atmosphere silver interacts with sulfur creating a uniform and stable layer of corrosion called tarnish. Tarnishing is a slow process that creates alterations to the color appearance of the object, ranging from a yellowish layer and extending to dark colors. Cleaning silver is usually performed for the improvement of the aesthetic appearance of the object and involves the removal, full or partial, of the tarnish layer. During the cleaning process, both monitoring and the extent of cleaning are determined based on visual observations/examination. Equally, when monitoring the condition over time of an object, i.e. to examine its stability in the museum environment, this evaluation is also commonly performed by visual documentation.
However, there are limitations between what eyes can see and what instruments can measure and this plays an important role in the preservation of Cultural Heritage. On the one hand, even a minor change in the appearance can be the sign for a chemical alteration of the surface leading to a change of the object’s condition. On the other, the inability of the human eye to detect minor changes on the surface of an object can affect the decision of the cleaning level during conservation.
In an effort to examine these limitations, while trying to create a correlation between human perception and physical measurements, CHANGE PhD fellow Amalia Siatou conducted a psycho-visual survey aiming to collect people’s perceptions on the surface appearance of silver.
What is the texture and color of silver? What kind of finishing is preferred for the luxury objects of the past centuries? Do you think the displayed objects are adequately cleaned?
These where the main questions that the psycho-visual examination was inquiring.
138 people, of different age groups, participated in this survey that took place in the Museum of Fine Arts in Dijon. Visitors were asked to evaluate the appearance of a series of selected objects in correlation to artificially tarnished coupons.
Coupons (metal plates) with different textures (matte, satin, mirror) were artificially corroded to represent different degrees of silver tarnish, demonstrating different surface colors. These coupons were then placed next to real objects of the collection of the Museum of Fine Arts.
By comparing the surface of the coupons to those of the objects we are trying to document the human perception on the visual appearance of silver surfaces.
To quantify and classify the visual appearance of silver colorimetric measurements were performed and will be compared with the results of this psycho-visual survey.
This survey aims to shed light to the ongoing project of ESR 15 Amalia Siatou and the effort to detect, characterize and quantify the perception or the change of the appearance, visual or not, of challenging museum objects. The results of the survey are currently under statistical evaluation and will soon be published. Preliminary results show the difficulty in separating textural from color perception on high reflective area, especially in when surface defects like scratches and tarnishing are present. However, regardless of the surface appearance, the majority of visitors accepts their display in a museum without expecting a high lustrous surface.
This project was conducted under the CHANGE program, in collaboration between the Direction des Musées-Mairie de Dijon and Haute-Ecole Arc Conservation-Restauration (HE-Arc CR), Haute Ecole Spécialisée de Suisse Occidentale, Neuchâtel, Switzerland as well as the laboratory of Imagerie et Vision Artificiel (ImViA), Université de Bourgogne-Franche-Comté, Dijon, France.