Festival of Archaeology 2017

Conservation of Artefacts from the wreck of the London

I am pleased to welcome this month’s guest blogger Eric Nordgren of Historic England, who tells us more about conservation of artefacts excavated from a maritime context.

Eric at work in the lab
Eric at work in the lab. © Historic England

 

I have been working with Historic England as a conservation project assistant since November 2016. My main role is to carry out remedial and investigative conservation on artefacts lifted from the London protected wreck. The London was a Royal Navy warship that sank in the Thames Estuary following an explosion in 1665. A program of work to better understand this protected shipwreck has been under way since 2014, resulting in surface recovery of exposed objects and in two seasons of underwater excavation and recovery of hundreds of artefacts made of wood, leather, rope, ceramic, glass, iron, copper and lead. The London: Excavation of material at risk project is a collaboration between Historic England, the protected wreck licensee, Cotswold Archaeology, and Southend Museum Services, where the artefacts and site archive will be deposited.

The process of conserving marine archaeological material can often involve quite a bit of time and repetition: consider that 150 Apostle musket cartridge bottles have been recovered from the London, from complete examples with cap, to some that consist of just a few broken fragments. Each one has to be photographed, assessed, repackaged in soft nylon netting, wet cleaned to remove mud from the sea bottom, desalinated, treated with polyethylene glycol and freeze dried. I’ve just finished the wet cleaning stage which took 4 workdays!

At top of image, label naming the artefact with text '6901: The London 3527: wood'. Centre of image, wooden bottle, with stopper to left, body of bottle to right, underneath this is a scale marked off in centimetres.
‘Apostle’ musket cartridge bottles. © Historic England
Jumble of black bottles, all with individually numbered white labels.
Some of the 150 bottles after wet cleaning. © Historic England

It’s not just the Apostle cartridges, all the artefacts from the London have to go through similar stages.  The water in all 158 boxes of artefacts has to be changed every month in order to remove salt from the marine environment in a process called desalination. Both organic (wood, leather) and inorganic (ceramics, glass, metal) materials can be damaged if allowed to dry out while they still contain soluble salts such as sodium chloride. Artefacts are soaked in baths of distilled water which allows salts to diffuse out, allowing them to be safely dried. Desalination isn’t difficult, but it does take some time and requires knowledge of the drying behaviour of a wide variety of materials.

Though some stages of marine conservation are repetitive, there are lots of interesting moments as well. One of the most exciting things about archaeological conservation is finding out more about the artefacts during the process and especially discovering clues about who made them and the technology they used. This process is called ‘investigative conservation’ and uses a variety of tools and techniques such as microscopy, X-radiography and digital imaging.

Here is one example discovered during digital x-radiography of a pewter spoon:

Bowl of a spoon, darkened with age and contact with water, against a plain grey background.
Pewter spoon from the wreck of the London. © Historic England
Spoon seen in x ray as white against a black background, with red ring around the letters BA on the spoon. At top of image above the spoon is the Historic England logo.
Digital x-ray of the same pewter spoon from the London. Computed radiography revealed a touchmark of the letters ‘B A’. © Historic England

 

The letters ‘BA’ can be seen in the x-ray, just above the point where the handle meets the bowl of the spoon. Marks in this area are called ‘touch marks’ and can tell us where and when the spoon was made and who made it. Some marks on pewter made in London or Edinburgh can be identified by records on ‘touch plates’ kept by the Worshipful Company of Pewterers, but marks from the period of the London are difficult as many records from the Pewterers were destroyed in the Great Fire of London in 1666, just a year after the ship sank.  Still, it may be possible to identify who made the spoon based on comparison with other examples. We are hoping to find out more about who ‘BA’ refers to.

Another type of mark was found on a leather strap during wet cleaning. A stamped letter (or letters) can be seen in this photo taken with raking light illumination:

Horizontal strip of dark leather against a white background. Just off-centre to the right of the strip is a stamped mark resembling a letter P.
Leather strap from the London, showing stamped mark. Could it be from the leather worker or the artefact’s owner? © Historic England

Markings like this can be added by the leatherworker who made the strap, or might indicate its function or the sailor who used it on board the ship. We will pass this information on to the experts studying leather artefacts from the London.

Sometimes we find unknown or unexpected materials on artefacts during conservation, and need to investigate them further to get a better idea of what they are made of and why they are there. I noticed a yellow material with a tar-like odour inside the layers of a leather shoe from the London. Using a technique called Fourier-Transform Infra-Red spectroscopy (FT-IR for short) I was able to determine that it was indeed an organic material with chemical bonding similar to natural resins. This material may have been applied during the shoe’s construction as an adhesive or a sealant.

Two shoe soles one below the other, against a white background, and a centimetre scale rule underneath. Annotated on the lower sole where unknown tar-like materials have been seen.
leather shoe fragment from the London, with location of unknown material. © Historic England
Graph marked in units of 5 from 50 to 98 on the vertical axis, and 4000 backwards to 650 on the lower axis, showing significant spike between the 3000 to 2000 mark.
Transmittance spectrum produced during FT-IR analysis of the shoe sole. © Historic England.

Conservation work on material from the London is quite rewarding as we have a chance to progress artefacts from post excavation though conservation treatment, learning more through investigative conservation along the way and preparing them for storage and display at Southend Museum.

Find out more about the London by following #LondonWreck1665

Many thanks to Eric for his fascinating blog. The thing that caught my attention particularly was the stamped leather – that such detail has survived 350 years of immersion in a hostile environment and can be recovered by archaeology is amazing.

For more on conservation of artefacts from the wreck of the London, please also have a look at an earlier post from 2015.

 

No.83: The London, No.3: A Conservator’s Tool Kit

This week Angela Middleton, Archaeological Conservator at Historic England, is my guest blogger, explaining the tools of her trade in conserving some of the objects recovered from the London.

A conservator’s tool kit: air brush, hammer and chisel

As a conservator you may spend many hours peering down a microscope, using a scalpel and slowly removing layers and years of dirt or corrosion: a painstakingly slow process; just like watching paint dry or grass grow. Progress can be hard to measure and to the untrained eye is often barely noticeable.

So why bother, you may ask?

During conservation, the conservator and the object go through a couple of stages. You normally start off with an assessment, where the condition of the object is evaluated, allowing a picture of the artefact’s composition, construction and state of preservation to emerge. Following that you devise a treatment according to the artefact’s condition and its purpose.

The ultimate goal is always to stabilise the object, preserve it for the future and to understand it: and by doing this a conservator also helps others to understand and appreciate it. This is often difficult when the surface is obscured by corrosion products or discoloured due to centuries of being buried. Removing these obscuring and distracting layers will help to reveal the object.

Lately I have been working on artefacts from the London, a shipwreck which sank off Southend-on-Sea in 1665. After their initial assessment (see Heritage Calling: Looking Inside) and a lengthy programme of desalination* (remember this is like watching paint dry…), artefacts can be actively conserved, without obscuring fine surface details or allowing layers of dirt to be consolidated onto the surface.

So this is where the pressure washer comes in. I have been using an air-brush system to clean off loose surface dirt on some of the leather from the London. It works just like a conventional pressure washer, albeit on a smaller scale, with the advantage of being able to regulate the pressure down and work with a really small outlet, enabling you to focus on small areas.

The example shown below is a leather sole from one of the many shoe finds. It is contaminated with iron compounds, which are commonly found in the burial environment (iron compounds originate from naturally occurring minerals or from corroding artefacts in the vicinity). They settle on the leather surface and do not only obscure fine surface details but also discolour the artefact. If not using an air-brush system, I would be cleaning them with sponges, which can sometimes be too harsh on sensitive surfaces such as leather, which can be easily marked and damaged. The air-brush is a much more gentle method of cleaning.

leather sole
Left to right: Leather sole 3141 before cleaning; during cleaning with top half cleaned; fully cleaned.

Here is the mini pressure washer in action:

However, sometimes ‘gentle’ is just not good enough, especially for maritime finds. They often become covered in huge and unsightly concretions. A concretion is formed when a corroding iron object interacts with the surrounding environment, encapsulating marine organisms, surrounding sediments, corrosion products and even other artefacts in a lump. In most cases the artefact cannot be recognised at all. In order to stabilise and understand the object, these concretions have to be removed. And yes, as the name suggests: they can be as hard as concrete. There is little choice but to use a hammer and a chisel to remove them: tools you don’t often find used by an archaeological conservator.

The example below is a concretion containing a multitude of artefacts. Visible at the top was a copper alloy artefact, half embedded in the concretion. A conservator would normally take an X-ray to visualise the embedded artefact(s). However, the concretions are often so dense that X-radiography is of limited use. So in this case I used the shape of the object partly showing at the top to guide me and started chiselling the concretion away. Once again it was a slow process, but totally worth it. What I managed to reveal and finally remove from the concretion was a pair of callipers: the only one from the wreck so far and in near perfect condition. Callipers were used to check the diameter of shot. By also knowing the material and the density the weight can be calculated. In our example it looks like the diameter is engraved on one side of the scale and the weight on the opposing side. The anaerobic conditions on the seabed and inside the concretion have preserved the markings on the calliper and it showes very little corrosion.

Left to right: Concretion as found, the callipers are visible at the top; callipers after being removed from the concretion.
Left to right: Concretion as found, the callipers are visible at the top; callipers after being removed from the concretion.
Detail of the markings on the callipers
Detail of the markings on the callipers

The other example is an iron cannonball which was also covered in concretion. It was important to remove it, not only to reveal the true size of the artefact, but also to reduce treatment times. The thick layer of concretion forms a barrier and will hinder passage of water during desalination.

After the concretion had been removed the cannonball diameter could be determined as roughly 15cm, making it a 30-pounder, suitable for a demi-cannon.

cannonball
From left to right: Cannonball before removal of concretion; during removal of concretion; after removal.

Each conservation task requires a specific set of tools, depending on the job in hand and the nature of the artefact. The gadgets an archaeological conservator uses are very different to what a paintings or textile conservator would use. However, the similarity is that each conservator strives to preserve the object and enable others to study and enjoy it.

 *Desalination: During burial salts from the burial environment accumulate inside artefacts. If such an artefact is simply dried, salt crystals will form, which expand in volume on drying, which can cause surface layers of the artefacts to flake off, or the whole artefact can actually fall apart. Also salts are hygroscopic, which means they attract moisture from the air. This moisture can cause further corrosion. This is especially true for metal artefacts.

During desalination artefacts are immersed in tap water, and then in de-ionised water, to remove water-soluble salts. This is achieved by regularly changing the water and measuring the chloride level or the conductivity of the storage solution. Once these readings remain sufficiently low, the artefact is considered desalinated and can be treated as in the case of wood or leather, or can be dried as in the case of glass or ceramics.

To catch up with previous posts on the London, here is a post commemorating the anniversary of her loss in March 1665 and another on recent archaeological work.

No.77 The London wreck today

2015: Telling the story of the London today

A CGI reconstruction of the wreck of a wooden vessel lying on her side with holes blown in her structure.
A CGI reconstruction of the London wreck on the seabed. © Touch Productions

The ordnance, so crucial to the story of the lost London, as described in the previous post, and the salvage of the vessel in the aftermath, is also the theme of her more recent story. A gun was found on the site in 1962, and further investigation of the site in 1985 concluded that its iron content was too great to indicate a 17th century vessel (because the ordnance aboard the London was believed to be predominantly brass). Archaeological investigation in 2006, before dredging for the London Gateway project began, identified two discrete sites close to one another. In 2007 two bronze cannon said to be from the site were reported to the Receiver of Wreck, suggesting a threat sufficient to trigger an assessment of the site’s national importance as a candidate for designation under the Protection of Wrecks Act, which was achieved in 2008.

Local volunteers, under the site Licensee Steve Ellis, began monitoring the site in 2010. The Thames Estuary is a challenging environment for divers and for the wreck itself, which is also under threat from natural forces: the sediment mobility in the area and the effects of climate change, in which warm-water organisms have migrated northward with the potential to impact on wooden wrecks such as the London, leading to a noticeable loss of artefacts from the site.

Steve illustrates another major challenge facing archaeologists on the site, at the edge of a busy shipping channel:

A huge container ship dwarfs the dive vessel as it passes close by.
A large container ship passes close to the dive vessel near the London site. © Steve Ellis

These environmental threats in turn triggered a programme of finds recovery, with a very successful season in 2014 involving a collaboration between English Heritage, Cotswold Archaeology, Licensee divers, Southend Museums, and local volunteers, who sorted the recovered finds. Over 70 items were recovered, 41 by Cotswold Archaeology and 35 by the Licensees, a time capsule of life aboard a 17th century vessel, including bottles and personal items such as clay pipes and shoes.

A largely intact black leather latchet shoe viewed from above, next to an i
A well-preserved latchet shoe recovered from the wreck of the London. © Steve Ellis

Dan Pascoe, one of the site archaeologists, resumes the story with an account of recent archaeological activity concentrating on the guns:

‘The excavation thus far has revealed tantalizing clues towards determining which part of the ship survives on the seabed at site 2. The discovery of an intact gun carriage with the trucks situated against the remains of a deck, suggest the survival of parts of the gundeck. Directly either side of the carriage cheeks were the associated gun tackle, furniture and even gunner’s implements. The deck and carriage are situated on the vertical rather than horizontal, identifying that the remains of this part of the ship are on its side. Full excavation and recovery of the carriage this season will hopefully reveal the side of the hull and gun port.

South of the deck line, which would be below the gundeck, the excavation has uncovered  numerous cut logs of fired wood, galley tiles and bricks. In large ships, like the London, built prior to the mid-1660s, the cook room was found on a partial deck or platform within the forward part of the hold. Also found have been sections of partition planking, probably related to the internal structures of the ship, such has cabins and storerooms. The litter of hundreds of musket and pistol shot points to a possible location near the gunner’s storeroom. The present thinking is that site 2 is part of the bow from at least the gundeck down to hold, which includes the remains of a partial deck or platform. The excavation continues this spring and will hopefully be able to confirm the team’s initial thoughts and theories.’

The remains of a wooden gun carriage truck in poor visibility in the Thames
Gun carriage truck in situ in the Thames, which also illustrates the challenges of working in limited visibility. © Steve Ellis

Steve Ellis, the site’s Licensee, says:

‘It has been a fantastic experience working on such a fascinating wreck site, especially the discoveries we have come across to help us all understand more about life aboard a 17th century British naval ship. This would not have been possible if it wasn’t for the full support that we had from English Heritage, seeing that we are only amateur archaeologists.’

A photographic exhibition documenting the finds opens later this month at the Beecroft Art Gallery, Southend-on-Sea, Essex; underwater investigations are due to resume in summer 2015 and can be followed via the Twitter hashtag #LondonWreck1665.

With many thanks to Dan and Steve, who have contributed so much to this post.

No. 76: The London Blows Up, 7 March 1665

To commemorate the 350th anniversary of the loss of the warship London in the Thames Estuary on 7 March 1665, I would like to take a look at the London in 1665 and in 2015, in a two-part blog. In this first part we look at the story of the wreck event in the words of those who were there at the time, and in the next part on Monday we will hear from those working on the London today.

1665

Pen and ink ship portrait of the hull of the London in broadside view, with flag at her stern.
The London, circa 1660, Willem van de Velde, © National Maritime Museum, Greenwich, London. Van de Velde was a Dutch marine artist and specialist in ship portraits, and played a role in documenting the battles of the Anglo-Dutch wars.

The London was a stalwart of the Commonwealth Navy, built in 1656 under Cromwell, but had also been part of the fleet accompanying Charles II on his return from exile in the Netherlands in 1660. On 7th March 1665, the London was bound from Chatham Dockyard to the Hope Reach in the Thames, a key location at a tense time, since war had just been declared between Charles II’s England and the United Provinces of the Netherlands on the 4th. The national mood was sombre, and it was also a cold day: thirty miles north, Ralph Josselin, vicar of Earls Colne in Essex, noted that his water pump had frozen that day. (1) Undoubtedly what happened next would have made headlines had there been such a thing as newspapers in England, but the first edition of the London Gazette would not come out until 7th November 1665. However, as Josselin’s journal shows, this was a time of assiduous diary-writing and administrative record-keeping, which allows us a window into the past.

Between Chatham and the Hope Reach lies the Nore: as so often, a safe deep-water anchorage, which was, and remained, a traditional assembly point for battle fleets and convoys up to and including the Second World War, lay next to a hazard, the notorious Nore sandbank. Yet it was not the Nore that was to claim the London.

A letter written on the 8th to Sir Joseph Williamson reported: ‘The brave ship London has blown up near the Hope’, leaving behind only her hull and stern. (2) On the same day Samuel Pepys, in his capacity as Clerk of the Acts to the Navy Board, provides us with more detail on the ‘sad newes of the London‘ in his personal diary: ‘a little a’this side the buoy of the Nower [that is, on the London side of the buoy, not the seaward side], she suddenly blew up.’ He tells us that only 24 persons were saved out of a complement of over 300, ‘the ship breaking all in pieces, with 80 pieces of brass ordinance.’ (3)

Portrait of Samuel Pepys in old age, wearing a wig and facing right against a dark background, in a gold frame.
Samuel Pepys, 1689, by Godfrey Kneller. © National Maritime Museum, Greenwich, London. Pepys was one of the key figures of the 17th century Navy and a very capable administrator. He had been asked to distribute the Articles of War to the fleet in the Hope just a few days previously.

Another letter, this time to Henry Bennet, 1st Earl of Arlington, passes on coffee-house gossip, blaming the easy availability of gunpowder ’20s a barrel cheaper than in London’ and therefore by implication suspect in provenance and quality. (4) On the 9th, John Evelyn, the other famous diarist of the period, ‘went to receive the poor creatures that were saved out of the London frigate, blown up by accident, with above 200 men,’ for he had been appointed one of the Commissioners for sick and wounded seamen by Charles II. (5) The Dutch ambassador, Michiel van Gogh, had more specific intelligence on numbers than Pepys, or perhaps more details were known by the time of his letter on 10th March: ‘The London, prepared for Vice-Admiral Lawson, was blown up while sailing up the river, and only 19 out of the crew of 351 saved.’ (6)

On the 11th Pepys recorded the results of an inspection of the wreck by Sir William Batten and Sir John Mennes: ‘out of which they say, the guns may be got, but the hull of her will be wholly lost’. (7) Those guns continued to be the focus of administrative attention for a good 30 years afterwards: recoveries made in 1679 caused some wrangling that surfaced in 1694-5, as the salvor attempted to leverage payment of a debt. (8)

What happened next? Part 2 on Monday will bring the story of the London up to date.

CGI reconstruction of the London, showing her gun decks and masts
CGI reconstruction of the London © Touch Productions

(1) Diary of Ralph Josselin, 7 March 1665

(2) Calendar of State Papers Domestic, Charles II, 1664-5, Vol.114, No.84

(3) Diary of Samuel Pepys, 8 March 1665

(4) Calendar of State Papers Domestic, Charles II, 1664-5, Vol.114, No.90

(5) Diary of John Evelyn, 9 March 1665

(6) Copy, Holland Correspondence, March 10, 1665, in Calendar of State Papers, Domestic, Charles II, 1664-5, Vol.114

(7) Diary of Samuel Pepys, 11 March 1665

(8) Calendar of Treasury Papers, Vol. 1, 1556-1696, May 17, 1694, and November 26, 1695

No.49: Mi Amigo

Radio Caroline 1999 Today, Friday 28th March, marks the 50th anniversary of Radio Caroline, originally a pirate radio station. Piracy on the high seas would not be complete without a shipwreck somewhere, in this case the vessel that became Radio Caroline South, broadcasting from the coast off Essex. This vessel was the Mi Amigo.

Seamen often say that ships have a personality of their own or that a ship is an ‘unlucky’ vessel. Mi Amigo certainly had an adventurous career, despite her origins as a workaday sailing schooner built at Kiel in 1921, operating in the Baltic region. She was commandeered by Nazi forces in 1941-3, and began her career as a radio broadcast vessel off Danish waters in 1960, before Radio Caroline.

During her years operating off the Essex coast, she exemplified the main problem facing stationary vessels. During storms they were extremely vulnerable to running on nearby hazards as they could not quickly steer themselves out of trouble, if at all, if their anchors broke. (Light vessels without motive power were particularly prone to this problem.) Mi Amigo drifted ashore at Holland Haven near Frinton in 1966, struck the Long Sand Head just off the Thames Estuary in 1975 and 1976, before eventually sinking after striking the Long Sand once more in 1980. Her mast was visible for a number of years afterwards and the wreck remains charted in the Estuary: she was recorded in English Heritage’s Modern Wrecks Project of 2010, 30 years after she was lost.

The last words broadcast from Mi Amigo were those of the DJ on duty just before midnight on 19/20 March 1980: “Due to severe weather conditions and the fact that we are shipping quite a lot of water, we’re closing down and the crew are at this stage leaving the ship.” All the crew were rescued by the Sheerness lifeboat, plus Wilson II the canary.

For a photo gallery of Mi Amigo in service and as a sunken wreck, please click here.