Analytical chemistry a secret weapon in the conservation of museum objects

At Conservation, located in the cool white underbelly of the Melbourne Museum, object conservator Charlotte Walker prepares a psychedelic Jenny Bannister jacket ready for display in the Melbourne Story gallery.

The sleeveless tunic – made by the nationally significant designer when she was just 14 and attending Red Cliffs Secondary School in Victoria – is laid out face down on a white bench.

The influence of David Bowie’s Ziggy Stardust is evident in the design, which is accented with strong hand-cut red, green and pink stars applied to a black, purple and red background.

The garment has already spent two weeks in the freezer – at minus 20 degrees – to kill any pests, such as carpet beetles or canvas clothing moths.

Next, Walker will lean on the museum’s secret weapon — analytical chemist and materials scientist Dr. Rosemary Goodall — to learn more about the jacket’s material composition.

Both Walker and Goodall are based at Museums Victoria Research Institute, where Goodall’s scientific techniques help preserve items in the museum’s extensive archive.

Today, most museums and galleries employ scientists in similar roles, and there are even specialist courses in conservation science. This is testimony to the usefulness of science in informing the management of museum collections.

Goodall’s analysis informs everything from preservation and storage to repairs and display, as well as safe handling protocols.

“Because you start with a very large natural science collection, which is sometimes 150 years old. And they really liked putting arsenic and mercury on these things 150 years ago. We take care of this heritage. And so it’s very important to manage all of these things properly,” Goodall points out.

His work relies on three main elements of high-tech kit and analytical techniques.

The first, a handheld X-ray fluorescence spectrometer, looks like a small radar gun. “It’s point and shoot,” Goodall says.

The instrument identifies the elements present, vital information for identifying hazards and heavy metals, things like lead paint or mercury.

“You shoot an X-ray beam at the material. It excites the atoms and electrons inside […] and when the electrons fall to fill the gaps, they emit fluorescence which is what we measure,” she explains. These emissions are unique for each element, allowing Goodall to determine which are present.

The next tool in this analytical chemist’s toolbox is a Fourier Transform Infrared (FTIR) spectrometer. This device is small and mobile, which eliminates the need to carry bulky and heavy museum objects from their storage.

The FTIR spectrometer uses infrared radiation to illuminate the chemical composition of an object, this time molecules rather than simple elements.

Goodall says that a beam of infrared radiation from the FTIR spectrometer excites molecules inside an object, say a textile, and the radiation vibrates those molecules into different motions like rocking or bending.

The result is a unique fingerprint with bands at known wavelengths, which Goodall likens to his “enormous library of 20,000 spectra”.

“I can make a spectrum of a textile, go look in the library and come back and say, ‘well, that looks like an acetate fabric’ or ‘that looks like a nylon fabric,'” she says.

For Walker, whose job it is to preserve, conserve and display the vast array of objects in the museum’s collection – from automobiles to teacups to historic dresses – the information provides crucial information.

“As conservators, we study how materials are made, how they degrade, and how to try to keep them from degrading,” she says.

Knowing what something is made of is a “big help” in determining storage and display conditions, things like lighting, humidity, temperature and safety, she says.

“For example, if something is identified as wool, we know it will be very susceptible to pest attack, potentially sensitive to changes in humidity, potentially sensitive to light. So we can put strategies in place to prevent these degradation processes from happening, or to try to slow down these degradation processes,” says Walker.

Another example, when silk is “weighted down” – a process of adding salts to make the fabric heavier – the material is more likely to degrade.

Material composition can also add to an item’s story. Metals and synthetics can be dated based on knowledge of when certain manufacturing processes were developed.

Walker says that before Goodall and his analytical tools came along, there were other methods of identification — looking at materials under a microscope or testing with chemicals.

But the new technology provides information faster and does not damage objects.

The museum is currently working with the University of Melbourne on research analyzing different plastics within its collection – what types exist, and how and when different plastics begin to break down.

“Some of the old projectors and tape recorders, you can get up to ten different plastics on those things. There’s the plastic casing, the buttons, the reels, they can all be different plastics,” Goodall says.

Some plastics are very unstable, crumble and break down quickly. Exposing them can speed up this process. It’s a challenge for museum conservators whose goal is to preserve the collection on behalf of the people of Victoria and share it with the public through exhibitions.

This is essential for textiles, especially the archives of Jenny Bannister who likes to use plastic in her designs.

“We have one of her dresses where I analyzed 24 different plastic objects – that wasn’t all – and I probably identified about six or seven plastics,” Goodall says.

This sometimes poses a dilemma for restaurateurs.

After discovering a cardigan with buttons made of cellulose nitrate, a material that can damage wool as it degrades, restorers added tiny shields behind each button to better preserve the garment.

Another, more delicate example is a turban hat with faux pearls. These are also cellulose nitrate and degrade, a process that causes the copper metal fibers of the cap to turn green. Yet here, unlike the cardigan, it is difficult to separate the materials without harming the integrity of the article.

According to Walker, in these cases, the analysis of the materials fuels a discussion involving several people – curators, conservators, collections managers and Goodall.

“It’s not a decision that would be made by one person. [… ] we discuss these things together and determine what will be the best option for this object. And it could also determine whether or not it is suitable to be displayed in the future. Or if we decide to digitize it and put it on the website and accept that it will not be displayed in the future because it is in such poor condition.

Goodall’s third technique is called micro-fading.

“It’s supposed to be a really quick way to tell if something is going to fade as it passes under exposed lights,” she says.

Here, she shines a tiny – 300 micron – but intense beam of light onto a fabric and measures any color changes for ten minutes. The results are compared to the “Blue Wool Standard”, an internationally used measure of fabric fading (on a scale of 1 to 8) used by the fashion industry and in the development of washing powders.

“Blue wool fades very quickly. It goes up to eight which barely fades. If something fades the same or worse than level one, we wouldn’t expose it for very long, we might not expose it at all,” Goodall says.

When Bannister’s colorful jacket is on display, it will be illuminated with gallery lighting specially designed to display the textiles.

After testing all the different materials and colors, the micro fading revealed that special care was needed with the green fabric, which is primarily used on the shoulders. It was more likely to fade under the light, Walker says.

It illustrates how materials science informs the work of conservators to better understand, preserve and prepare museum objects for display.

“The lighting in the existing window is top notch. So we’ll be in discussion with the Tech Ops team to see if we can light it from below instead, which will just allow us to keep that gorgeous coat on display for a bit longer.