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Home , Embalming, Mummy, Natron

Archaelogical analysis mania Mummified remains from and beyond hold chemical information about the daily lives of ancient civilisations. Emma Davies reports

Egyptian have been late Ptolemaic (c.200–30BC) and repellent materials to seal and protect prodded, poked, and pondered over In short Roman (30BC–c.AD400) periods and it, and wrapped. In later periods, by generations of archaeologists,  Mummified remains in stopping altogether when Islam was some embalmers sealed the eyes, ears, scientists, and historians. The Egypt and elsewhere have introduced in the seventh century AD. nose and abdominal incision with Victorians had a nasty habit of fascinated archaeologists The mummification process beeswax or bitumen. unwrapping and dissecting them, and and chemists for involved stripping the body of its The mummification balms were mummies are now routinely scanned centuries internal organs – except the heart – generally based on relatively cheap, by medics hunting for cause of  Chemical analysis can and drying it using natron, a naturally readily available fat and plant and analysed by chemists eager to find reveal the origins of some occurring salt containing oils, with more expensive – often out more about chemicals. embalming ingredients , sodium , imported – perfumes, wood oils, The ancient Egyptians desperately  Antibacterial and and . spices and or pitches added for wanted to be spoken of after their antifungal terpenoids and Generally speaking, the dried body their special symbolic and preserving death, says Stephen Buckley, mummy phenols in resins and would have been stuffed with properties. The plant and animal expert and chemist at the University pitches helped protect cloth and bags of various substances, oils are not only hydrophobic but of York, UK. ‘In a sense, chemistry is and preserve mummies including natron, -soaked would have polymerised to produce a bringing them back to life.’  Chemical evidence bandages and sawdust. It would then network capable of protecting fragile The ancient Egyptians used suggests ingredients have been coated with viscous, water- tissues and wrappings from microbial materials that were very much part were imported, giving attack. Meanwhile, modern chemical of daily life for mummification. By insight into early trade analysis tells us that the the protective revealing the tricks of the embalmer’s wood pitches, resins and oils would trade, chemistry is uncovering the have contained disinfectant phenolic everyday lives of the Egyptians. compounds, and molecules good Significantly, chemical analysis of at inhibiting microbial and fungal mummies shows how embalmers growth called terpenes. used a host of highly effective Terpenes and related terpenoids antimicrobial and antifungal are a family of molecules based on materials to preserve the bodies and isoprene (2-methyl-1,3-butadiene). provide safe transport to the . They are mainly made by plants and are classified by the number Mummy methods of isoprene units they contain. Research to date shows that Egyptian 10-carbon monoterpenes and mummification was carried out in paintings indicate monoterpenoids are made up of the Old Kingdom (2649–2152BC) the rituals and exotic two isoprene units, 15-carbon and through the Late period ingredients used in sesquiterpenes three units, and

PHILIPPE PLAILLY / EURELIOS / SCIENCE PHOTO LIBRARY LIBRARY PHOTO SCIENCE / EURELIOS / PLAILLY PHILIPPE (712–332BC), declining during the Egyptian mummification 20-carbon diterpenes four units. 48 | Chemistry World | February 2011 www.chemistryworld.org TOM MCHUGH / SCIENCE PHOTO LIBRARY LIBRARY PHOTO SCIENCE / MCHUGH TOM

The wide choice of materials East, which corresponds roughly to Identifying materials garden. She heats woods at 500°C in available to Egyptian embalmers today’s Middle East. Nevertheless used in embalming can the absence of oxygen and compares gives today’s archaeological chemists they were widely used by embalmers give insight into trade the resulting mixtures with those a tough task in their chemical hunt. from the Old Kingdom onwards routes and daily life found in mummies. ‘You have to look at just about and their general biomarkers are The Pisa team used GC-MS everything,’ says Buckley. often relatively easy to spot. Their to analyse Egyptian embalming The best way to do this is to use gas diterpenoid ‘resin acids’ make materials held at the Natural chromatography–mass spectrometry excellent biomarkers. For example, History Museum of the University (GC–MS) to look for biomarkers – the conifer biomarker dehydroabietic of Florence, , and compared stable molecules either present in acid can survive for millennia and is the results with the modern pitch original materials or, more usually, frequently found in mummy samples. data. Polycyclic terpenes and acidic formed through ageing processes. But narrowing down to conifer diterpenes led them to conclude ‘Looking for biomarkers is tough, species using these mono- and that balms consisted but some do survive and relate sesquiterpene biomarkers is no mean mainly of ‘pine pitch’. They also found to the chemistry of the original feat. Unfortunately the compounds sesquiterpenoids and phenols which compounds,’ says Buckley. Over the are volatile and readily change with are highly likely to have come from years, researchers have built up a age. ‘In many cases you can only cedar oil but remain cautious in their large database of biomarkers, many of conclude that you have, say, a conifer analysis because of the compounds’ which come from analysing materials resin, not which kind of pine or volatile nature.1 that have been artificially aged under whether you have pine or cedar,’ says strictly controlled lab conditions. At Francesca Modugno, a member of the Smoke signals London’s , scientists Chemical science for the safeguard Many sources suggest that cedar routinely age materials and scour for of cultural heritage group at the pitches were used for mummification biomarkers but also work on naturally University of Pisa, Italy, led by Maria and ancient texts by the Roman aged plant materials, such as those Perla Colombini. ‘Looking for scholar Pliny and Greek historian held in 19th century collections in But that’s not to say that the Pisa biomarkers Herodotus link a wood called Kew Gardens, London, says Rebecca team isn’t working on ways to extract ‘cedrium’ to embalming. Ursula Stacey, a chemist at the museum. the species information. A reliable is tough, but Baumer at the Doerner Institute in Resins from coniferous trees way to spot a conifer species in some do survive Munich, , is certain that such as pine, cedar, or fir hold mummy resins would release valuable her team found cedar materials in a particular appeal for mummy information on ancient trade routes. and relate to unused ancient Egyptian embalming scientists. Conifers are not indigenous Jeannette Jacqueline Łucejko has the original materials from Deir el-Bahari, an to Egypt and their resins were been recreating pitch formation in Egyptian complex of mortuary probably imported from the eastern the lab using pine and cedar samples embalming temples and dating from Mediterranean or the ancient Near collected from Pisa’s botanical compounds’ about 1500BC. GC-MS analysis www.chemistryworld.org Chemistry World | February 2011 | 49 Archaelogical analysis

linking would have been great for the embalmers but not so good for today’s archaeological chemists, hiding the guaiacol from chemical detection.

Bit of bitumen York’s Buckley did his PhD on Egyptian mummies with Richard Evershed at the University of Bristol, UK. This team was one of the first to study dated Egyptian mummies with authenticated provenance (from 1900BC to AD395) using modern chemical techniques, a little over a decade ago. One of the substances they looked for was beeswax, introduced long after conifer resins, and characterised by alkanes, wax esters and hydroxy wax esters. The black resinous coating of one Ptolemaic mummy the team analysed turned out to be revealed the presence of phenols and which binds tightly to hydroxyapatite Terpenoid biomarkers 87 per cent beeswax, mixed with a sesquiterpenoids and, importantly, in bones and can apparently survive like dehydroabietic acid small amount of resin from trees in a compound found in wood smoke for thousands of years, provided from conifer trees and the pistachio (pistacia) family. called guaiacol. there is no microbial attack. Baumer’s phenols like guaiacol from Buckley and Evershed’s research2 Baumer and her team attributed team coated pigs’ ribs in guaiacol cedar oil can give clues to suggested that ancient Egyptian the guaiacol to a tar oil produced and measured alkaline phosphatase embalming ingredients embalmers used a far wider variety from cedar wood, known to be rich levels, which turned out to be seven of materials than had previously in the compound. The embalming times higher than in untreated bones. been thought. At one time, bitumen material would have had ‘powerful The guaiacol had apparently had a was considered to have been the bactericidal and fungicidal activity,’ ‘sealing effect’, trapping high levels main embalming ingredient, largely the researchers say. of alkaline phosphatase in the bone. Not all mummies are because of the amorphous black To show just how effective cedar Guaiacol and its derivatives would Egyptian. There are appearance of many mummies. would have been for embalming, also have cross-linked with keratin, mummified remains all ‘Their appearance brings to mind Baumer and her team measured levels the structural protein in skin, to over the world, including bitumen but it is not necessarily of the enzyme alkaline phosphatase, give a rigid structure. Such cross- in and Yemen the case,’ says Stacey. ‘Sometimes

50 | Chemistry World | February 2011 www.chemistryworld.org the discolouration is because of embalming process was symbolic. oxidation and ageing and sometimes For instance he identified insect wax it is conifer pitch and resin.’ on the limbs of one South American Buckley had the opportunity to mummy dated to AD1100 whose analyse a shiny, black ‘Early Kingdom’ head was coated with a plant wax. ‘In mummy in Bristol Museum, which South American mythology, many- was labelled as being coated in limbed creatures are part of the world bitumen. When he took the sample of deities, including -headed back to the lab he was surprised scorpions and spiders,’ says Buckley. to discover that the predominant Buckley’s work on South American

KLAUS GULDBRANDSEN / SCIENCE PHOTO LIBRARY LIBRARY PHOTO SCIENCE / GULDBRANDSEN KLAUS ingredient was paraffin wax. Rifling mummies also hints at wider trade through museum records revealed links with the rest of the world than that museum staff had indeed coated previously thought. He hopes to the mummy in paraffin wax. ‘The publish the results this year but until mummy had been in a light box for then remains tight-lipped. decades and had turned completely Buckley has also worked on black and very shiny with oxidation,’ mummy materials from Yemen from recalls Buckley. around 700 to 400BC. Getting access Stacey had a similar experience at to the mummies proved difficult to the British Museum when analysing say the least, with local tribal disputes samples from the ‘Granville mummy’, and challenging topography. ‘It was a famously unwrapped and dissected very interesting experience,’ he says. by Augustus Granville during the Until recently, Yemeni mummies peak of mummy mania in 1821. were thought to have been extremely Granville had deduced that ‘the body also found evidence for ‘ancient hair Black coatings on a basic. Proposed preservatives include must have been plunged into a vessel styling products’, suggesting that the mummy might be bitumen the hygroscopic plant el-Raa, which containing a liquefied mixture of wax hair was treated separately to the rest used in embalming, but could have been used as a desiccant. and bitumen and kept there for some of the body to maintain the deceased’s could just be oxidised Buckley and the rest of the York and hours or days, over a gentle fire.’ hair style. In work with York-based paraffin wax applied by Yemeni team used GC-MS to study Stacey was able to throw out this Egyptologist and ancient hair expert museum staff samples from four Yemeni mummies theory using GC-MS, finding no Joann Fletcher, Buckley has seen and found animal fat, most likely from evidence for beeswax or bitumen something similar in a mummy a camel, plant wax, a gum or sugar but instead finding degradation dating from around 500BC, where and aromatic acids hinting at a plant products from conifer resin acids. elaborately curled hair had been fixed extract, possibly a resin similar to the Indeed, pimaric acid had survived in place with beeswax, absent from highly perfumed storax extracted from the original resin. But bitumen the embalming recipe. from the bark of Styrax trees. Buckley was commonly used in later is confident that a ‘complex recipe’ mummification and Buckley and Museum trip was used to embalm the Yemeni Evershed even found it in Pharaonic Most of the European work on mummies. ‘What is really quite mummies of pets, embalmed as mummies has to be done on museum interesting to me is that the materials painstakingly as . exhibits since Egypt has banned they were using were chosen to Colombini’s Pisa team worked removal of samples from the country identify them with Sheba,’ he says. on ‘Merneith’s mummy’ from the in all but exceptional circumstances. The location of the famous kingdom seventh century BC, finding pistacia Working on exhibits brings a whole Beeswax was a common of Sheba is disputed, but many resin, vegetable oil, beeswax and set of chemical challenges. Not only embalming ingredient, scholars suggest it was in Yemen. bitumen. They identified terpenoids do researchers have to consider the and could even be used to that had clearly come from a thermal original archaeological environment fix a mummy’s hairstyle Pure chemistry treatment, backing the theory that a but they also have to factor in museum Buckley sometimes gets frustrated hot fluid was used for embalming in handling and storage conditions. ‘It’s with what he sees as the snobbery of the Late period. Heating the mixture very challenging material but that’s some chemists ‘who think that doing allowed it to be poured into the body, part of the attraction,’ says Stacey. chemistry and archaeology is a bit giving brown degraded compounds And there is still much research to frivolous’. ‘Not only is it justified in which would have given the mummy be done on museum samples, such itself but by having unusual mixtures her black appearance when combined as analysis of carbon isotope ratios, put together and then processed with bitumen. says Pisa’s Modugno. ‘There is a also you’re actually finding molecules that Meanwhile, Natalie McCreesh a lot of work to be done to understand are quite rare, telling us something from the University of Manchester’s which products were used in non- interesting about chemistry in its KNH Centre for Biomedical Mediterranean areas,’ he adds. purest sense,’ he counters. has used a technique Buckley has already started called micro-scale sealed vessel projects far from Egypt. As part Emma Davies is a freelance science GC-MS to detect bitumen in ancient of a York team, he has worked on writer based in Bishop’s Stortford, UK Egyptian samples from Manchester mummies from Peru, claiming to have Museum and the British Museum. found the first conclusive scientific References The pyrolysis thermally breaks down evidence of embalming practices 1 This research is not yet published and the there in 2007. ‘What they were doing researchers would like to thank J Moggi, samples, requiring no wet chemistry M Zavattaro and S Boccone from the Natural and less than 1mg of sample. All of was actually quite a complicated History Museum, University of Florence, Italy, the samples that she analysed, from procedure,’ he says. for providing archaeological samples the Third intermediate period to the As with , Buckley 2 S A Buckley and R P Evershed, Nature, 2001, Late period, contained bitumen. She thinks that much of the Peruvian 413, 837 THINKSTOCK

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