We left off in our last post having explained the research and assessment that precedes any conservation treatment. Using Echo as our object of study, we examined questions that arise after looking closely at a painting. Let’s delve into one such question. When Pollock painted this and similar works in 1951, many critics referred to them as Pollock’s “black and white” paintings. Echo‘s canvas was certainly never pure white to begin with, but it has discolored over time and today might more accurately be described as a straw yellow. This discoloration is due to characteristic degradation processes.
Exposure to the atmosphere, heat, and light typically causes yellowing of natural fibers. Similarly aged textiles are commonplace in our lives outside the museum: a grandmother’s wedding dress or an heirloom tablecloth. So some mark of age in the canvas of a 60-year-old painting is expected.
In Echo’s case, however, the yellowing is uneven—the top of the canvas more discolored than the bottom—and this gradation of discoloration draws attention, disrupting the original composition. Documenting our findings using written reports and photography, like the images above, is a core practice in conservation. The initial images taken before a painting undergoes treatment, aptly called “BTs” (Before Treatment), are composed under consistent conditions and embedded with metadata to record that information.
Standardization of our photodocumentation process produces images that can be relied upon to be an objective measure of the state of a work of art. As a simple image search for Echo illustrates, varied lenses and lighting can not-so-subtly alter the look of a painting. It’s difficult to isolate a single event or factor responsible for the accelerated discoloration at the top of Echo, but it seems likely that the top, always closest to ceiling lighting fixtures, has been exposed to a greater intensity of light and heat than has the rest of the painting. Moving forward, we’re exploring the nature of this discoloration and developing a controlled, effective way to mitigate future degradation. In the near term, though, our first objective for Echo was to remove any loosely bound dirt and grime and, after testing a variety of methods, we chose to use a combination of dusting brushes followed by soft rubber sponges.
We then addressed the problem of Echo’s uneven discoloration. For this step, we consulted paper and textile conservators—they know their cellulose!—as well as paintings conservators who have worked with similarly discolored canvases. Again, we tested small areas to determine what materials and methods might most gently produce our desired result. We found that a small amount of moisture, first applied to the canvas then blotted away, removed the discolored degradation products in an easily controllable way. By applying this method over the top quarter or so of the canvas, we were able to produce a more consistent overall tone. Now that we’ve reduced Echo’s discoloration disparity, we’ll look toward ways of preventing future uneven yellowing of the canvas and slowing its inevitable degradation.