I’m a little nervous the first time I visit Kimberlee Newman in her laboratory. Not that my nerves have anything to do with Kimberlee herself. No, it’s what Kimberlee is doing in the lab that has me nervous. When she’s not working on her own research using traditional archaeological methods, Kimberlee is a lab technician here in the Earth Sciences Building at UNE, working with a device that is helping UNE researchers make waves in the world of archaeology – but which I’m worried might make waves in my cellular composition.
“Shouldn’t we be wearing lead shields or something?” I ask.
Kimberlee sets me at ease with a laugh.
“It’s not that dangerous,” she says. “You just have to be sensible, that’s all. After all, we are talking about a radiation emitting device.”
The “device” in question is sitting on the desk in front of us. It’s a PXRF machine – that’s short for Portable X-Ray Fluorescence – and it looks like a cross between toy ray gun and a hair dryer. Not that you’d want to dry your hair with it. Unless you fancy bombarding your follicles with high-energy X-rays, that is.
You also wouldn’t want to drop it. Each one of these machines is worth about $40,000 and can only be serviced by a factory certified technician. Given that the single most important component is a highly breakable vacuum tube running down the middle, it’s little wonder the carry boxes come marked “handle with care”.
By way of demonstration, Kimberlee places a test sample – a small green-grey shard of pottery – in front of the x-ray lens and presses a remote trigger. A red light comes on, telling us the machine is working. Nothing much happens for about 60 seconds. And then a rainbow of graphical data appears on the screen of a laptop computer at Kimberlee’s elbow. It’s a complete spectrographic breakdown of the elements making up the pottery shard.
“That was the easy part,” says Kimberlee, turning to the laptop. “Next comes the hard part: working out what it all means.”
From Mars to UNE
As it turns out, working out what it all means is something UNE researchers are rather good at. In fact, type “PXRF” into your Google search bar, and one of the first names you’ll see is that of UNE researcher Peter Grave. With a series of publications covering pXRF of a wide range of archaeological materials (e.g. ceramics, lithics, obsidian), Peter’s group in the Archaeomaterials Science Hub is recognised worldwide in the field of non-destructive XRF. ““Building expertise in this type of instrumentation is part of a longer term strategy to strengthen the archaeometric research environment at UNE,” says Peter.
The archaeological potential of the PXRF “ray guns” was evident at a demonstration given by the scientific equipment manufacturer Bruker in 2007. Accustomed to destructive laboratory-based techniques and long waits while he sent samples off for nuclear activation analysis, Peter was excited by the prospect of a handheld tool for non-destructive spectrographic analysis. Although x-ray fluorescence technology has been around for many decades, it wasn’t until the mid-2000s that lightweight, portable, battery-powered units became commercially available – their development propelled in no small part by the needs of NASA’s Mars Rover program. Researchers like Peter were quick to recognise that the same kinds of lightweight units that were used to analyse Martian rock samples could be invaluable to archaeologists analysing obsidian, ceramics and rock art pigments.
As the then convener of archaeology at UNE and an active field researcher with long-standing interests in Khmer and Anatolian pottery, Peter couldn’t wait to get his hands on a PXRF machine. He arranged for the University to purchase its first Bruker unit in 2008, and it wasn’t long before his research group were putting the machine through its paces out in the field, as well as collaborating with other research groups in the university.
“Field portable is a relative term”
Jillian Huntley was among the first crop of UNE research students to incorporate PXRF-based archaeometric techniques into her PhD research. She used the machine to analyse the pigments in rock art across the Sydney Basin – including the Woronora Plateau west of Wollongong – and in the Kimberley, Western Australia.
“Having a non-destructive technique for analysing the composition of rock-art pigments is fantastic,” she says. “Until now, such analysis had to be done in the laboratory after removing a small amount of pigment material from the site. We can now say to the Aboriginal custodians of a rock-art site that our study will have absolutely no impact on the art work itself. They’re over the moon about it.”
The project in Western Australia is documenting the chronology of human occupation in the North Kimberley through a study of rock art and artefacts. “I’m the project’s ochre person,” Jillian explains.
“Sources of ochre used by people often change over time, and being able to tie a particular art site to a particular source of ochre may help us trace the chronology of people’s movements and their changing relationship with the land. In Australia, ochre sources are often associated with spiritual beliefs often referred to as the Dreamtime, and so form part of a cultural landscape. It’s all beautifully complicated.”
Jillian is quick to point out, however, that the term “field portable” is relative.
“When I’m working out in the middle of the Kimberley, I’m carrying this equipment, which weighs about 25 kg, in my backpack moving in 40-degree heat at 90 per cent humidity. Just getting to the sites is a challenge. Then of course there’s the challenge of getting the PXRF instrument to the rock art itself. It’s not as though you’re always working with a nice flat surface. A lot of it is not that easy to access.”
Despite the challenges of lugging the equipment around in the bush, Jillian is happy to sing the praises of PXRF for her research.
“This technology has allowed us to conduct archaeometric analysis of artefacts where this had previously been extremely difficult – or in some cases, virtually impossible.”
Providing the context
A few years ago, “virtually impossible” would have been a good way to describe your prospects of doing archaeometric analysis on the intact pottery collection at the Freer and Sackler Galleries of South-East Asian Art at the Smithsonian Institution in Washington D.C. The collection – and many others like it around the world – had long been off-limits to archaeometric analysis due to the destructive nature of the techniques involved.
All that changed earlier this year, when Darren Mitchell, a Ph.D. student in the School of Humanities at UNE, travelled to America to conduct research on the Freer and Sackler collections using PXRF. There he was able to analyse numerous Khmer artefacts that had never before been put to archaeometric analysis – and in the process to trace the objects’ histories in a way that had never been done before.
“It is an unfortunate historical fact that many of the ceramic objects in world museum collections were the result of looting,” Mr Mitchell said. “While it is a good thing that the objects have been preserved, all too often you wind up with a group of beautiful objects sitting there without any context. As archaeologists, part of our job is to help provide that context.”
“The beauty of the techniques we are using at UNE is that museums are no longer concerned with us studying their collections or worried that artefacts may need to be taken out of the country. I can do the analysis right there in the museum. It’s an exciting development for museum curators, art historians and archaeologists alike.”
Since his US trip, Darren has spent time in the South East Asian Ceramics Museum in Bangkok, Thailand and travelled to Cambodia to participate in an archaeological excavation at the Ta Prohm temple in the Angkor Wat complex, study stoneware kiln production in and around Angkor, as well as visiting the National Museum of Cambodia in Phnom Penh.
“Besides the world-famous ruins at Angkor, the Khmer left behind many ceramic artefacts and monuments across present day Cambodia and Thailand. By taking an archaeometric approach – and with the help of PXRF technology – I have been able to compare stoneware sherds with intact artefacts held in museum collections around the world.”
Thanks to UNE’s timely embrace of PXRF technology, Darren and his fellow archaeologists at UNE are now at the forefront of archaeometric research worldwide. Which goes to show the benefit of foresight, ingenuity – and a small dose of X-ray radiation.