Conservation lab brings together science and art
In a light-filled laboratory, Terri White peers through the eyepiece of a microscope, adjusting the lens until the surface of a silvery spiral comes into focus.
Wearing the same protective purple gloves a doctor or dentist wears when performing a checkup, she picks up a cotton swab and smooths a watery slurry of powdered chalk across the object’s surface.
The object of White’s focus is not some precious scientific specimen. She is polishing a silver brooch, a jewelry piece designed by Alexander Calder, an American sculptor most famous for his room-sized abstract mobiles.
The room’s walls are lined with grey countertops and shelves of bottles holding chemical powders. To White’s right is a long table covered with sketches, drawings and other works made on paper, while a table in the corner supports a prone, 6-foot-tall wooden statue of Uncle Sam holding an aluminum mailbox.
This is the conservation lab at the Milwaukee Art Museum.
The museum, which reopened its doors to masked visitors June 16 and is offering free admission until Aug. 16, houses thousands of pieces of art, all of which require regular cleaning, inspection and, at times, repair.
They must be stored and displayed under conditions that minimize damage from light, humidity, chemicals and bugs. Each task requires both artistic expertise and scientific knowledge.
That’s where the museum’s conservation team comes in.
Three conservators, now working in shifts due to the COVID-19 pandemic, keep tabs on the museum’s 30,000 piece collection, doing what they can to prevent damage and making repairs when needed — like gluing flakes of red, white and blue paint back onto the Uncle Sam statue, part of the museum’s folk art collection.
“The really fun stuff is when we have the opportunity to research a particular piece of artwork,” said White, who joined the conservation lab in 1992.
The lab, tucked into the museum's ground level, is not open to the public. Likewise, if the conservation team does its job well, its efforts are hidden from visitors — even if the results are on full display in the museum's galleries.
So in a building where art and history are everywhere, what behind-thescenes role does science and research actually play?
Research project keeps silver shining
In 2005, White noticed something strange: silver objects displayed in the museum's lower levels were tarnishing more quickly than pieces on the upper floors.
The mirrored surfaces of teapots and bowls were turning a mottled black. Polishing would restore the shine, but only for so long.
“Every time I polish a piece of silver, I'm taking off a microscopic amount of metal,” said White. “That doesn't seem like a big deal.”
Unless, that is, the pieces are hundreds of years old.
Polishing silver repeatedly can expose inner layers that contain higher amounts of copper, revealing an undesirable fiery purple hue called fire scale.
“That's something that the more you polish, the worse it gets,” White said.
So instead of polishing the silver objects more frequently, White decided to figure out why some were tarnishing more quickly. She sought help from Joseph Aldstadt, a chemistry professor at the University of Wisconsin-Milwaukee.
Aldstadt used a technique called gas chromatography to discover that there were higher levels of a gas called sulfur dioxide in the museum's lower floors.
Sulfur dioxide, commonly found in vehicle exhaust, can react with silver surfaces and is one of the main contributors to silver tarnish.
A museum loading dock was located near the gallery that contained the tarnished silver pieces.
The conservation team moved the pieces to upper museum floors, farther from loading docks and streets and other sources of sulfur dioxide. With this small change, the problem was solved — the silver no longer became so tarnished.
As an added precaution, conservators installed hidden trays of charcoal under the display cases holding the silver pieces. The charcoal absorbs any sulfur dioxide that finds its way to the museum's upper levels.
Several years ago, a case containing a silver teapot, chafing dish and other silver pieces from the 16th and 17th centuries was installed using all these precautions.
“It still looks amazing,” said White. “I haven't had to do any polishing.”
Technology reveals hidden stories
Under a microscope, the museum's conservators can see an artist's unique pattern of brushstrokes or determine that the blue paint they used is made from a rock called lapis lazuli.
Sometimes there's more to a painting than what meets the eye.
When a 1906 portrait of art student Josephine Nivison by American painter Robert Henri was slated for cleaning and conservation work, a conservator noticed something strange. The brushwork and texture near Nivison's skirt didn't match the rest of the painting.
To figure out what was happening, the conservation team decided to take an X-ray of the painting, titled “The Art Student.”
“Lo and behold, the X-ray comes back and there is a second painting underneath what we can see of Joesphine Nivison upside down,” said White.
In the X-ray image, the name “Stafford” appears in the margin of the painting and an upside-down face appears in the hemline of Nivison's dress, a woman with upswept hair and a ribbon around her neck.
Unlike the pigments used to paint Nivison's dark skirt, the paint used for the signature and hidden figure's face likely contain pigments made with metals such as lead, which can absorb X-rays.
The result? The skirt disappears in the X-ray images, revealing the hidden figures.
“This is where the synergy between the curator, conservation scientist and the conservator comes together,” said White.
The piece's curator found out that the first artist to use the canvas, Stafford, was one of Henri's students at the New York School of Art.
“The theory is that, for whatever reason, he decided not to finish this painting. And maybe Robert Henri, thought, ‘Hey, a stretched canvas. I don't have to do all that work. I'll use this,' ” said White.
White appreciates that technology and scientific questioning can give these types of insights into a work of art.
“It gives a little glimpse into this really creative atmosphere that must have been happening in the school,” said White. “It's not really just about the technical studies . ... It contributes to our understanding of the art world.”