Conservators position a painting to be x-rayed

Conserving The Virgin of Valvanera–Overview of the Process

Art conservation is a field that encompasses a breadth of expertise. As we roll up our sleeves in anticipation of improvements and potential discoveries, a plan that will provide optimum preservation is essential.

Pam Skiles looks at back at Villalpando canvas
Pam Skiles, associate paintings conservator, reviews the back of the canvas and the frame of The Virgin of Valvanera.

Evaluation

An art conservator is guided by ethics, historic and technical knowledge, and science. The process is systematic and comprised of examination, research and analysis, thorough documentation, a high level of dexterity, and ongoing, collaborative decision making.

Ethically speaking, it is important for a conservator to employ practices and materials that reflect high standards and are accepted within the profession. Methodologies and materials are typically reversible. Collaboration and communication between the conservator and curator is of the utmost importance. Additional historians, conservators, and scientists may be consulted to bring broader understanding of the artist, artwork, and eventual conservation treatment.

The artwork—in this case, an oil painting on canvas stretched around a wooden strainer—is evaluated based on its material components, including the time and geographic area in which it was made, subsequent exposures and damages, and the artist's intent.

The conservator and curator discuss the nature of artistic process, condition, and damages. This dialogue addresses important historic information about the artist and artwork as well as the state of the material elements. This conversation informs the basis for analytical testing and treatment procedures that will be undertaken.

Conservation team preparing a painting for x-ray
The Denver Zoo brought over to the DAM an x-ray machine they use to x-ray large animals. Here, zoo and Denver Art Museum staffers work on x-raying The Virgin of Valvanera piece by piece.

Analysis

The conservator has a range of analytical tools at her disposal. Elaborating on historic and material knowledge, a visual assessment of the painting plays a significant role. Tools include a visible light source that, when illuminated across the surface at varying angles, will yield information regarding technique, application, and condition. (Learn more in this blog post regarding another painting conservation project.) Less visible forms of radiation such as infrared, ultraviolet, and x-ray reveal information that is otherwise invisible to the naked eye (Watch video from CBS4 of Denver Zoo and the Denver Art Museum x-raying The Virgin of Valvanera.)

Both infrared and x-ray show us what lies beneath the painted surface - or what is invisible to the naked eye. Infrared shows us artist’s preparatory drawing that may indicate changes in composition. X-ray will show us the weave of the canvas pattern, structural damages, and certain pigments such as those that are lead-based. Ultraviolet light shows us information on the surface such as varnish type and condition, physical damages, and painted restorations. These areas stand out as visually distinct from surrounding areas.

Magnification is another visual tool. High magnification with or without a polarized light helps the conservator identify fibers that make up the canvas. It can also be employed to identify pigments.

Other analytical means that help the conservator identify pigment sources include x-ray fluorescence spectrometry (XRF), high performance liquid chromatography (HPLC), and examination of cross-sections. XRF allows us to identify elemental components in a pigment such as iron (Fe) mercury (Hg), arsenic (As), lead (Pb), or cadmium (Cd). HPLC is employed to help identify organic components in a pigment such as cochineal or indigo. HPLC analysis requires that a tiny sample be removed from the painted surface – usually in an existing area of damage. Tiny cross-sections of the paint film can be sampled and under magnification and certain lighting conditions will give the conservator information about layers. In addition to paint, the cross-section may show a ground, overpainting, varnishes, and grime.

Treatment & Reporting

As the conservator undertakes the examination and analytical testing, she thoroughly documents her findings and observations in a written report. This is called a “Condition Report.” In addition, the painting is also photographed to records its condition in a “before treatment” state.

Leading up to a treatment, a conservator performs what are called, “spot tests.” Based on extensive training and experience, a paintings conservator learns a range of techniques for cleaning and varnish removal. Small areas are tested to determine the most appropriate means for cleaning. This information is also included in the condition report.

Based on the historic and visual examination, analytical techniques, and spot tests, the conservator creates what is called a “treatment proposal.” The proposal reflects aspects of the examination and outlines steps for cleaning, removing old fills, stabilizing losses, filling and inpainting, and re-varnishing. The proposal will also include materials that will be employed. Once complete, it is reviewed with the curator so that both parties are well-informed as to the methods and anticipated outcome. As treatment progresses, the curator is routinely engaged to discuss progress and new information that may be revealed. Sometimes “during treatment” photographs are taken to record the outcome of a process.

Once treatment is complete, the painting is photographed to record its state, “after treatment.” The conservator then writes the “treatment report” that articulates all processes and materials employed.

Sarah Melching is the Silber Director of Conservation at the Denver Art Museum. Sarah has been at the DAM since 2008.