The Science Behind the Restoration of a Painting

Restorer working on antique outdoor chapel fresco in Italy: Painting restoring of religious art.

The history of art restoration is one that spans centuries, driven by the mission to ensure famous works of art remain accessible. Michelangelo’s iconic Sistine Chapel frescoes were first restored as early as the 16th century due to water damage, and since, advances in technology have led to the development of increasingly safe and effective approaches to preserving and repairing a range of works. Art restoration is intended to preserve the integrity (and thus, value) of an original work of art. Many in need of repair, however, date back centuries, and the inevitable decay from time and climatic conditions can have a significant impact on their current value in the art market.

Regardless, art restoration has become increasingly important as museums and civic authorities work tirelessly to clean and protect cultural collections. The Metropolitan Museum of Art, the Museum of Modern Art, and The Getty each have a full-time scientist on staff devoted to developing custom conservation plans. Whether damaged accidentally, willfully, or inevitably through time, art restoration continues to evolve, and the techniques used to preserve paintings and address condition issues are constantly evolving to maintain the historical significance of the world’s most influential works.

What is Art Restoration and Conservation?

side by side painting to depict art restoration.

Painting damaged by a fire, before and after restoration. Image via Oliver Brothers.

Art restoration is any attempt to preserve and repair architecture, paintings, drawings, sculptures, or other objects of fine and decorative art whose condition has been negatively altered. While art restoration and conservation techniques go hand-in-hand, their definitions are slightly different. Art restoration denotes the repair or renovation of works that have already sustained decay with the attempt to restore a work to its original, undamaged appearance, while conservation refers to the maintenance and preservation to safeguard against future damage and deterioration.

There are many reasons as to why a painting might need to be repaired. In 2015, for example, a twelve-year-old boy lost his footing and accidentally punched a hole in a $1.5 million Paolo Porpora Baroque-style oil painting titled “Flowers.” Additionally, “The Night Watch,” a famous work by Rembrandt van Rijn on view at the Rijksmuseum in Amsterdam, has been intentionally vandalized three times. Other works, like “The Resurrection” (1465) and “The Last Supper” (1546), were made in a type of paint that was ephemeral in nature, or they were exposed to climatic conditions that accelerated the decline of their condition.

The Evolution of Art Restoration

woman holding paintbrushes.

In the early 19th century, it was commonplace to attempt to restore Old Master paintings. Techniques at the time, however, were far from scientifically precise and proved to be more severe than conservators intended. Manuals suggested covering entire paintings in wood-ash, then wiping it off with water, which formed an extremely alkaline substance that was harmful to the painting. By the late 19th century to the early 20th century, there was a growing movement to combine the disciplines of art and science, a movement which drastically improved methods of art restoration and general understanding of techniques.

The period between 1925 and 1975 was particularly important in expanding the field of art conservation: museums established dedicated departments and analytical laboratories and art technical journals were created. By the late 1920s, a group of scientists, art historians, and restorers were assembled by the Fogg Art Museum in Cambridge. Edward W. Forbes, art historian and museum director from 1909 to 1944, proved to be a pivotal figure in the development of the principles of art restoration at this time. He encouraged technical investigations and X radiography, an imaging technique using x-rays, gamma rays, or similar radiation to view the internal composition of an object or work of art.

Two other significant “Fogg founding fathers” included Rutherford John Gettens and George L. Stout. Gettens was the first chemist in the United States to be permanently employed by an art museum, and Stout became the founder and first editor of Technical Studies, the first journal dedicated to conservation-related research in 1932. Together, the two authored Painting Materials: A Short Encyclopedia, which was immediately recognized as an essential resource for artists and art professionals concerned with preserving art. It remains regularly cited to this day.

Gettens and Stout also helped launch the Foundation of the American Institute for Conservation (FAIC), which supports conservation education, research, and outreach activities. By the early 1950s, the members of the original Fogg team of conservators dispersed, many of whom founded their own technical laboratories. Throughout the mid-20th century, major professional societies and training programs also emerged, including the International Institute for Conservation of Historic and Artistic Works (IIC) and the American Institute for Conservation (AIC) in 1972.

From 1975 forward, methods of analysis have become far more sophisticated than just X radiography or examination of a work through ultraviolet light. The number of conservation scientists and scientific research laboratories has grown, and conservation methods have been improved as an explosion of information has become readily available.

The Process of Restoring a Painting

Human hand cleaning an ancient canvas in his studio.

There is no “one size fits all” approach to painting restoration, as each work has to be carefully examined to determine which process and techniques will be best suited for the piece. Trained art historians, chemists, and materials scientists combine extensive areas of knowledge to assess original areas of a work and determine the least invasive solution for repairing loss.

Initial Analysis

First, the painting undergoes initial assessment. Conservation associates should be well educated on the style and period of the work they’re evaluating, as this knowledge will help determine painting techniques, materials available to artists during the time, and pigments and fabrics that were commonly used. X-rays also reveal how the work was composed, which allows the conservator to formulate an outline of the painting or work based on differing absorption of paint.

Assessing Loss of Paint

Next, infrared imaging is used to view the original drawings and losses of paint underneath the surface of a painting. Recently, technological advancements in art restoration have included cameras with fixed wavelengths. Because different pigments and materials reflect or absorb various wavelengths differently, these devices can help distinguish them. They allow conservators to pinpoint carbon-based drawings, for example, using distinctive wavelengths at about 1,700 nanometers. This is part of a larger movement aimed to eliminate previously destructive techniques and help identify varnish layers.

Girl measuring for renovation an ancient fresco.

Removing Discolored Varnish

Once an accurate picture of the original painting is in place, the next step is to find the appropriate solvent mixture to remove discolored varnish layers, if applicable. The development of spectroscopy—a technique used to observe vibrational, rotational, and other low-frequency modes in a system—has since made it easier to determine the exact composition and characterization of varnishes.

Repairing the Painting

After the identity of the varnish is determined and outer layers are removed, it can be repaired. An example of one way this may be done in modern practice is as follows: An intermediate coat of varnish is applied to the original painting to physically separate the new paint from the old, and ensure that any future restorations can be done without affecting the work’s original layers. This allows for stylistic fluctuations, which are common in art conservation. The conservator will carefully inpaint damaged areas using dry pigment mixed with synthetic non-yellowing solvents to ensure that a professionally restored work will rarely need further conservation.

What Does it Cost?

The cost of restoring art varies greatly depending on a piece’s condition, the extent of its damage, and the size of the work. Museums with dedicated departments have access to sophisticated (and costly) technology such as x-ray machines, which can cost hundreds of thousands of dollars. Independent conservators usually send samples to labs for scientific analysis.

According to Nicholas Dorman, Chief Conservator at the Seattle Art Museum, “In the public realm, conservators will have an hourly rate, and a conservation treatment will either be charged according to that rate or a total project cost.” Projects can include anything from cleanings to more involved restorations, which can cost thousands of dollars. When dealing with more expensive paintings, insurance policies often cover treatments, as was the case for the high-profile restoration of the Paolo Porpora painting.

One of the most significant costs in restoration is that of time, experience, and training. It is a relatively labor-intensive skill and can often take weeks to months to finish a project. Experts often recommend against restoring a painting worth less than $700 because the cost to restore it can exceed the value of the painting.

How Does Restoration Impact Value?

Anthony van Dyck, “Portrait of Olivia Boteler Porter,” 1630–1640. Image via Wikimedia Commons.

One of the main objectives of art restoration is to preserve the inherent value of a work of art. For the art collector, paintings with damage such as discoloration, dullness, yellowing, and other aesthetic imperfections are valued much less than those in good condition. Scott Zema, an appraiser at Ark Limited Appraisals in Seattle explains, “Restoration is a huge part of value determination. If restored correctly, there is no loss in value. But you have to look at the quality of conservation and the amount of damage; it all comes into play in [affecting] the value.” He explains further that as long as the damage does not materially affect the original work, conservators can restore the painting without decreasing the value.

The Future of Art Restoration

The survival of vivid colors used in Renaissance art is due in large part to the chemical stability of inorganic pigments. Organic dyes and acrylic-based paints that were in heavy use in the 20th century will likely fade and their plastic binder may depolymerize, which can cause the surface of the work to become powdery. Modern conservators work to improve methods and proactively slow fading. Recent themes in discussion at industry conferences have included improving methods, as well as the fields of nanotechnology and artificial intelligence, and how they can be applied. As science is more routinely integrated in the realm of art conservation, techniques and methods will only continue to advance.

As iconic works of art continue to age, art restoration remains a vital tool to ensuring the availability and longevity of a painting. The practice is something that interests art enthusiasts and collectors, as the value of these works greatly depends on their conditions. So intriguing is the process, that the Rijksmuseum museum in the Netherlands plans to make the restoration of Rembrandt’s famous work “The Night Watch,” available to the public in July 2019. Patrons will be able to see the process both on-site at the museum and online, witnessing firsthand how modern art restoration allows for paintings from Old Masters to remain true to their original form.

Sources: Yale Scientific | Scientific American | Smithsonian | Encyclopedia Britannica | Art Business News | Art Care | Van Witt