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Fossil preparation: How do we get specimens ready for display?
Excavating a fossil is only the beginning. It takes time, endless patience and skill to transform it into a museum-worthy exhibit.
The fossils you see on display in museums and those in research collections studied by scientists didn’t start out as pristine, clean specimens. It can take hours, months and even years to properly prepare a fossil.
Most of this work is done by fossil preparators - experts in the tools and techniques needed to release specimens from the rock they’ve spent millions of years encased in.
What does a fossil preparator do?
When palaeontologists find a fossil in the field, often it’s trapped in rock. Fossils can be quite fragile. To get them back to the lab without breaking them, fossil hunters will usually dig down around the fossil and extract the block of rock it’s embedded in, supporting it all in a plaster jacket.
A fossil preparator’s job is to carefully remove that jacket and rock, which is known as matrix, using the tools and techniques they think are most appropriate. It’s not just about making fossils pretty for display. By removing matrix, fossil preparators are key to revealing crucial information about prehistoric life.
The first person employed by the Natural History Museum as a professional fossil preparator was Caleb Barlow. He was hired by Sir Richard Owen in 1874, just a year after work had begun on our main building in South Kensington.
The Geology Department’s junior staff in 1900. Fossil preparator Caleb Barlow sits in the front row, second from the right.
Until 1921, our fossil preparators were known as masons, as they often had backgrounds in stone masonry. Over time the skills needed for the role expanded and fossil preparators were expected to understand areas including geology, palaeontology, conservation and materials science.
‘You need to know a bit of anatomy and chemistry because you work with acids as well,’ explained our fossil preparator Kieran Miles during our Hidden Treasures livestream. He also noted that the role involves more than just removing matrix.
‘There are other things I’ll be doing too. I’ll be doing repairs, restoration, filling cracks, stabilising any fragile bits and coming up with storage solutions as well,’ he says.
Our fossil preparation lab in 1934.
Fossil preparation tools
Fossil preparators have a variety of tools and techniques in their arsenal. Arthur Rixon, a fossil preparator who worked for us from 1933 to 1971, noted in his 1976 handbook that a preparator is ‘a living contradiction of the old adage, for he must be a jack of all trades in order to be master of his own’.
Their methods can be divided into two main categories - mechanical and chemical.
Mechanical preparation
Mechanical preparation involves using physical force to remove matrix from around a fossil.
Our early fossil preparators exclusively used hand tools such as hammers, chisels and awls. They had to work very slowly and carefully, especially as the shock of a tap with a hammer could be enough to damage a fossil.
Louis Parsons joined us in 1908 at the age of 19 and worked here for 46 years. He had one of the most illustrious careers of our early preparators, having worked on Archaeopteryx and the Piltdown Man, among many other specimens. He’s pictured here using a hammer and chisel on his greatest challenge in dinosaur preparation - the massive ankylosaur Scolosaurus.
Preparators still use hammers and chisels, but now have a variety of more modern equipment too, including pneumatic tools called air scribes. We got our first air scribe sometime after 1911 when our building was first connected to electricity.
These tools are like mini jackhammers that you hold in your hand like a pen.
‘When you switch it on and connect it to compressed air, the tip, which is made of tungsten carbide - so it’s harder than most rocks - will vibrate up and down thousands of times a second. I can use it to chisel away at really hard rock,’ Kieran explains. ‘It’s one of the most useful tools in the kit.’
A fossil preparator using an air scribe to remove rock from around a Baryonyx bone.
Air scribes have different tips for different jobs. For example, Kieran might use a chunky, chisel-like head for hard rock and a finer tip for more delicate rock.
Then there’s the air abrasion tool, which is like a mini sandblaster. Powder, such as aluminium oxide or sodium bicarbonate, blasts through the nozzle and is used to jet away matrix. Different abrasive powders have different uses, with the hardness, shape and size of the particles having different effects on rock. This technique can reveal fine detail that others can’t.
‘If they’re very tiny things, I might be working under a microscope with a pin vice,’ says Kieran. ‘I’ll be literally scratching away, grain by grain.’
‘Manual dexterity is one of the top things you need to be a fossil preparator. That and a lot of patience.’
Mark Graham, who was our fossil preparator until late 2021, uses a microscope to help him see to remove tiny grains of rock from a crinoid fossil found in a Jurassic seabed in the Cotswolds.
Any of these techniques could damage a fossil if they’re not used carefully, which is what makes a preparator’s knowledge and experience so important, but it can still be a nerve-racking job.
‘The preparator is probably the most likely person to damage the specimen,’ explains Kieran. ‘My tools, they might vibrate. They might put huge forces through the specimen.’
‘But it’s something that might even be a good thing at times. If the specimen breaks, it might reveal more information. It may also allow a preparator to remove previously inaccessible areas of matrix.’
Where possible, any unintended damage is repaired using materials that are reversible so that if the pieces need taking apart again, any adhesive can be easily dissolved.
Judy Goodall, one of our former fossil preparators, using a vibro-tool engraver to prepare a specimen in 1969.
Chemical preparation
In some cases, a fossil preparator can exploit a chemical difference between a fossil and its surrounding rock and use dilute acid to dissolve the matrix. Which chemicals are used depends on the composition of the rock the fossil is embedded in.
Chemical preparation is a potential option for delicate fossils that could be damaged by mechanical preparation methods and for those where it’s necessary to remove all of the rock from around a specimen.
While it has its benefits, it can also be a hazardous and time-consuming technique, as the fossil needs to be rinsed regularly and coated to protect it through each treatment. Rinsing thoroughly is vital, as any chemical remaining on or in the fossil could eat away at it over time.
In this episode of Hidden Treasures, Kieran gives us a peek at a day in his life as our fossil preparator.
Skill, science and art
Preparing fossils is a mixture of skill, science and art.
By knowing how and when to use certain tools and techniques, fossil preparators make vital contributions to science, revealing information that might have been hidden for millions of years. The hours they spend on a fossil means they’re sometimes the first to spot unusual features.
Science and art are often thought of as opposites, but fossil preparation does involve creativity. Whether that be in coming up with unique storage solutions, bending traditional techniques to work for a particular specimen or applying aesthetic touch ups to a fossil while keeping it scientifically accurate.
In 2006, Scott Moore-Fay, our fossil preparator from 2004 to 2010, worked on the restoration of a Rhomaleosaurus skull belonging to the National Museum of Ireland.
Our cast of Rhomaleosaurus on display in our Fossil Marine Reptile Gallery. This seven-metre-long plesiosaur lived during the early Jurassic Period. The skeleton this cast was based on was discovered on the Yorkshire coast in 1848.
The specimen needed work to repair and prevent future damage. Researchers also needed more matrix removed so they could study hidden parts of the skull.
In Victorian times, when the skull was found, the beauty of a specimen was highly valued and fossils had to fit an aesthetic ideal to be displayed or sold. Past preparators had used fillers, wax and animal glues to try to stop the Rhomaleosaurus falling apart. Plaster, cement and paint had also been used to mount it, hiding details and making it more of a piece of art than a natural object.
Using modern techniques, old material was removed, breaks were fixed and a new protective jacket was made to keep the specimen safe for the foreseeable future. The work took Scott 18 months.
Aesthetics are still considered when preparing specimens for display, but they’re always second to scientific accuracy. Take our Mantellisaurus on display in Hintze Hall for example. It’s 80-90% real bone and one of the most complete dinosaur skeletons ever found in the UK.
Mantellisaurus was a plant-eating dinosaur that lived during the Cretaceous Period. The specimen in Hintze Hall was discovered in 1914 on the Isle of Wight. Its head is actually a cast based on two partial specimens.
The skull on display is actually a cast. This dinosaur’s real skull is in our collection, but it’s in pieces as the sutures where the skull joins together have broken apart. It’s never been put back together and is more scientifically valuable as it is.
Mantellisaurus used to be on display in our Dinosaurs Gallery. Suspended high up, it was tricky to get a good look at. Its skull cast and the metal frame supporting its bones known as armature had been painted black. But when Mantellisaurus became a star specimen in Hintze Hall in 2017, it needed some aesthetic improvements. Mark Graham, our fossil preparator at the time, repainted the cast and armature a marmite colour to almost match the dinosaur’s real bones.
Like Rhomaleosaurus, during the conservation of Mantellisaurus, the specimen was found to have been subject to out-of-date fossil preparation techniques. Its fragile ribs had been covered by a canvas-like material and coloured to match the bone and part of its pelvis known as the ischium had been plastered onto its mount.
Two of our former fossil preparators Mornington John Meade (left) and Pat Hammond (right) working on an Edmontosaurus specimen in 1949.
There’s now a fine balance on the artistic side of fossil preparation. Dinosaurs on display are still valuable to researchers, so it’s important that it’s clear where conservation has taken place. For example, today, a fossil preparator might paint over conserved areas, such as repairs, but would never paint over fossil bone.
How do you become a fossil preparator?
Fossil preparation is a niche profession that can be a little tricky to get into. You need to understand a range of areas, from geology to conservation, as well as be able to pick up and master all of the skills and tools you’ll use.
This isn’t an academic research role, so a higher-level qualification such as a PhD isn’t strictly necessary. Kieran, for example, got the foundation he needed for the role from his undergraduate degree in palaeontology.
Fossil preparation can take hours of painstaking work, sometimes involving removing rock grain by grain to reveal a specimen.
Currently, there’s no professional qualification that covers all the things you’ll need to know. Kieran suggests that one potential route in is through volunteering.
‘If you know of a local museum or place that has fossils and needs them prepared, find out if they’ve got a volunteer programme. Find out if you can get some experience in the lab, because it’s such a hands-on, practical job, you can only learn by doing it,’ he advises.
While for some being a fossil preparator is the best job in the world, for others the amount of patience, skill and knowledge needed may mean it’s just not for them. Volunteering is a really good way to test the water.
If fossil preparation isn’t for you why not think about palaeontology? Find out how to become a palaeontologist.
