Everything goes in and out of Venice on flat barges — no walls, edges, or rails to steady the contents, even when it’s expensive scientific equipment. So I sat with my hands on as many boxes as I could as we sped through the narrow canals of “The Floating City,” hoping that none of our equipment or suitcases fell into the water. Finally, we arrived at a shabby dock on the Grand Canal. We unloaded and were led through a mechanical room in a basement, down a hallway of offices, and finally to an open vault, where pieces of art are stored when they’re not on display at the Peggy Guggenheim Collection in the house-turned-museum upstairs. This room, filled with artwork from Jackson Pollock, Pablo Picasso, Salvador Dali, and many others collected by renowned American art collector Peggy Guggenheim during her lifetime would be our office and lab for the next three days.
Before my trip to Venice I had spent almost three months studying at the University of Perugia in Italy and about a year at Northwestern University as part of my doctoral work in the Department of Materials Science and Engineering. This stint abroad was part of an international collaboration to study the materials used in works by Jackson Pollock and other painters of the early 20th century. My research relies heavily on first-hand knowledge of specific paint used in works of art in order to best understand how to preserve and protect the paintings. Pollock provides a unique opportunity for research because of his use of newly introduced paints of the early 1920s, the abundance and detail of personal correspondence and information about his painting process, as well as the breadth of his work.
This trip was to investigate specific Pollock paintings that the conservator at the Peggy Guggenheim Collection noticed may not be stable. Like private detectives, we were called in to gather clues that may lead us to the source of this small-scale degradation and determine potential preventative steps. Packed on the barge with us on the Grand Canal were all the machines required for advanced study of paintings. We call it MOLAB, a mobile laboratory that travels through Europe to investigate sculptures, paintings, and other historical artifacts. Among the weaponry of the MOLAB are such diverse techniques as: X-ray florescence (XRF), which helps identify chemical elements; Raman spectroscopy, to reveal chemical compounds; Fourier transform infrared spectroscopy (FTIR), to identify all the organic molecules; and video microscopy, to inspect the surface of objects looking for fine details. Each of these techniques would tease out clues to unraveling the mystery of the materials in the Pollock paintings.
The Materials Inquisition
Our first approach with each painting was to perform XRF to search for an element first discovered and introduced in paint in the early 1920’s: titanium. A new process for iron refining developed in the early 19th century yielded a waste product that was a fine white powder: titanium dioxide. The potential for use as a white paint was immediately apparent, especially with the growing concern of poisoning from traditionally used lead paint. At once, both low-budget and high-quality paint manufacturers began using this cheap, widely available, and quality titanium dioxide white paint. However, scientists quickly discovered that the same property of titanium dioxide that today makes it good for sunscreen — absorption of dangerous UV rays — is detrimental to oil paintings. When any material absorbs energy from UV rays, that energy must go somewhere. In paint, when the titanium dioxide absorbs UV light, the energy can cause dangerous chemicals to form. These chemicals can break down the paint, leading to color change, cracking, and even flaking. Manufacturers eventually refined their process, leading to a new variation of titanium dioxide called rutile titanium dioxide. This form releases the absorbed energy differently, preventing the formation of the dangerous chemicals. However XRF cannot detect the difference between the early formulations and later. Instead, when the XRF finds that titanium is present, we must then turn to our next technique, Raman spectroscopy.
This technique uses a laser to extract information about the position and bonding of elements in particles. In our case, we use Raman to separate the early formulations of titanium dioxide with later formulations. This is a difficult process because both manufacturing methods existed at the same time as the industry slowly adapted. Anyone who has painted a room or shopped for a wedding dress knows the vast multitude of whites. Similarly, the two formulations of titanium white also appear slightly different, maybe not as different as Paper White and Pure White, but to color experts like Pollock, the decision to use one formulation over the other may have been more than simple availability. Once we have this valuable information on the formulation of titanium dioxide, we can begin to assess the stability of the painting. However, we still have only part of the story.
The next step is to find what kinds of binder, such as oil or alkyd, Pollock used in his paintings. We use FTIR to look at the chemical bonds in a layer of paint and use advanced organic chemistry to narrow down the binder. Once we gather all this information for many points in a painting, we can identify similarities throughout the painting and make informed guesses on the five or six tubes of paint (per color) Pollock used. In my case, the only color I look at is white, and I have about eight different types of white paint that existed at the time of Pollock. I rarely land on a definitive answer, only probable answers. Often, the harmful chemicals created by the titanium dioxide leave behind clues of their destruction. FTIR and an understanding of the binder help us get a sense of how much destruction has already taken place. We may also be able to separate the sources of damage in a paint, as titanium dioxide is not the only one.
The last part of our on-site research is to look visually with a microscope for more detailed signs the painting that may already be in danger. These often include yellowing of white areas, cracking, flaking, and small bumps referred to as “art acne.” Some of this is possible to see by conservators, which helps us choose the paintings to study, but the microscope can help reveal fine details that can provide valuable information. Once we gather all this information the real difficulties begin.
The Big Data Problem
Armed with gigabytes of data, I returned to Northwestern tasked with one goal: Find out what paints Pollock used and see if they are stable. In three days in Venice, I had data from more than 100 different locations on each of the seven paintings across our five techniques. I had to analyze, record, and associate each point with its location on the painting. After months of analysis, we had some guesses on the paints Pollock used. That’s when we set up a totally different kind of experiment. We created mock paintings consisting of one color all painted at the same time. Then we subjected these paintings to high temperature, humidity, bright light, UV light, or even things like cigarette smoke. This simulates anything the painting could have experienced in its lifetime, allowing us to perform invasive tests on the paint which we could never do on a multi-million-dollar painting. It turns out that “watching paint dry” can be fascinating.
Understanding the chemistry of a painting is not easy and is never exact. Unlike math or many science experiments, there is no right answer, and there are also few ways to know if you have a complete answer. Researchers like me help curators and conservators better display and preserve their priceless works of art, help historians and art historians better understand the lives and motivations of artists, and help scientists better engineer paints and materials for both artists and industrial painters. Titanium dioxide may seem like a niche area of research, but it is one of the most commonly used white pigments in the world. Many people have a hard time appreciating modern art, however, what we learn from a Pollock painting may one day help design house paint that lasts longer, prevents mold growth, or dries faster.