The Frome Hoard | Just another Portable Antiquities Scheme blogs weblog

Conservation Cleaning

To reveal important surface information (as described in the previous blog post), the coins have to be cleaned of surface dirt and corrosion products. This is done using a combination of two treatments; chemical and mechanical cleaning.

The photograph above demonstrates a typical example of the Frome coins once they have had an initial rinse in tap water and brush to remove surface dirt. The majority of coins in this photograph are covered in corrosion products rendering them illegible. These coins would first be treated chemically to reduce the majority of the corrosion products.

Chemical Cleaning

Two different chemical treatments are employed to clean the coins depending on the extent and type of corrosion present. After an initial visual assessment the conservator they will make a decision as to which chemical treatment is required. This is usually a treatment consisting of either a low percentage of formic acid, or an Alkaline solution, or both.

Chemical cleaning allows for large batches of coins to be cleaned at once, which is critical when cleaning such a large hoard. The conservator carefully monitors changes in the coins appearance and condition during chemical cleaning to ensure that the coins are not ‘over cleaned’. All coins which have been chemically cleaned are thoroughly rinsed with water to remove any traces of chemicals.

Coins in Alkaline Rochelle solution. This helps to reduce the level of blue/green copper carbonates.

Mechanical Cleaning

Mechanical cleaning is required when coins have small patches of corrosion obscuring important details. Coins with low levels of corrosion may not need chemical treatment, but will most likely require some mechanical cleaning. All coins which have been chemically cleaned require some form of mechanical cleaning.

Production line of Dremel rotary brushing.

Mechanical cleaning involves reducing corrosion products with a scalpel under magnification and brushing to remove surface corrosion product residue. The photo above shows a production line of conservators using natural fibre dental brushes, on rotary Dremels® . This allows for a greater quantity of coins to be brushed at one time, and is more efficient than brushing them by hand.

Following chemical cleaning corrosion and dirt residues remain on the coin. This coin has been brushed on one half to demonstrate the difference in legibility before and after.

Corrosion

This coin demonstrates the large red/purple crystals of cuprite on the lower half and green copper carbonate corrosion products on the upper half.

The amount of corrosion on the coins varied depending on where they were excavated from in the ceramic vessel. The diagram below shows a cross section of the vessel and the context layers as they were excavated. The annotations below describe the changes identified.

Image courtesy of Somerset Heritage Service Archaeology

Top- Layers 10-13- Coins are well preserved. Corrosion is minimal, dusty and easy to remove.

Middle- Layers 14- 17- The corrosion is very hard making the coins difficult and time consuming to clean. Coins display both green carbonates and cuprite corrosion.

Bottom- Layers 18-19- These coins respond to treatment more readily than the middle layers, however they are not as well preserved as those from the top layers.

The coins from the Frome Hoard were excavated from an agricultural site. Since its burial it is likely that the effects of a fluctuating water table have influenced how the coins have corroded. As the water level rose it caused the bottom of the pot to become more saturated than the top. The ceramic vessel in which the coins were contained would have caused any trapped water to drain slowly. The corrosion pattern noted allowed conservators to anticipate how difficult some coins may be to clean therefore influencing which treatments would be selected.

52,503 Coins: Where to start?

The Questions

Dave Crisp at the side of the trench

The quick thinking of metal detectorist David Crisp meant that the Frome hoard was not disturbed upon its initial discovery. This crucial action has allowed for a systematic study of the hoard beginning with its archaeological excavation. As the pot was excavated the ceramic sherds and coins were removed in layers. Each layer was carefully numbered and individually packaged. The British Museum received the hoard in around 60 bags, there being several bags from each layer of the pot. It was hoped that by excavating the hoard in layers it would reveal clues as to why and how the hoard was collected and deposited. These context layers formed a framework for organising the coins and retaining essential deposition information. Having reliable contextual information can help us answer questions like:

Were all the coins put in the pot at the same time? Because the latest coins, of Carausius, are in the middle of the pot this does seem to be the case.
Did the coins come from a variety of different individuals or sources? The answer seems to be yes because there are two distinct groups with coins of Carausius in them: a number of earlier Carausian coins were in the last group to be put in the hoard, at the top of the pot, while a large number of later Carausian coins were in a group in the middle of the pot.
How many different groups (smaller pots, leather bags etc) were emptied into the hoard? We hope that by analysing all the coins, by layer and bag once they have been catalogued, we will gain an insight into how many different groups of coins were in the hoard.

Forward towards some answers

The information stamped onto the coins can help answer these sorts of questions. The LEGEND is the text on a coin which names the emperor (Augustus and Caesar in Latin) ruling at the time of issue. Other titles include commander (imperator), pious (pius) and blessed (felix). Because the Frome hoard was buried towards the end of period in which there were several civil wars and many barbarian invasions, there are around 25 rulers represented over a 40 year period (AD 253 to around 290) The mintmarks on the reverse of the coin often appear in the FIELDS and the EXERGUE of the coin, giving us important information about where and when a coin was struck. In the illustration of a coin of Carausius (AD 286-93) below, the letters ‘B’ and ‘E’ are mint control letters in the field of the coin – we do not know what they stand for, but there was a large issue of coins bearing ‘B E’. The ‘MLXXI’ in the exergue stands for ‘Moneta Londiniensis’ (the mint of London), one part silver to twenty parts copper (i.e. 5% silver). The mint marks are often recorded in the format shown at the bottom right of the image. Carausius reigned from around AD 286 to 293, but we know that this coin was struck in the middle of his reign, around AD 290 and is one of the latest coins in the hoard. Carausius set up a breakaway empire in Britain and Pax (the personification of peace, as seen on this coin) was the most common reverse type used on his coinage.

A conserved coin of Carausius

After their initial rinse in 2010, the coins were further sorted into bags by emperor, still depending on the layer they were from. Funds were then raised to conserve the approximately 30,000 coins needing further conservation, from the total of 52,503 pieces in the hoard. The relative rarity of Carausius’ coins made them our first conservation priority. The next priority was the illegible coins, pieces with so much corrosion that it was not possible to identify the emperor. These made up roughly 15% of the hoard. Finally, most of the remaining coins were partially identifiable with discernible emperor types but essential information on the reverse remained obscured. Coins in this condition were third in priority for conservation cleaning and have been selected by the curators.

The coin pictured above has been conserved to a legible standard, that is, all textual information has been sufficiently revealed that our numismatist colleagues can identify them. Notice the portrait of Carausius on the obverse still has his eyes and nose covered by corrosion as these areas are not a research priority. The ‘IMP’ that precedes ‘CARAVSIVS’ remains hidden by the crystals of corrosion products. In this case, revealing the ‘IMP’ was not necessary as it is commonplace to find it preceding the name of the emperor and there is not much space for much else to fit there. However, there are instances where between the ‘IMP’ and the emperor’s name is a string of other letters that are shorthand for additional titles, such as ‘IMP C CARAVSIVS’ where the additional ‘C’ stands for ‘Caesar’. In other situations one finds ‘IMP C M CARAVSIVS’ where ‘C’ is again ‘Caesar’ and ‘M’ is for his given name ‘Mausaeus’. The presence of these additional letters implies that the coins were struck from different dies, which is important information for our investigations.

Carausius- (286-93): One of the five silver denarii from the Frome hoard after conservation, one of the finest specimens of its kind in existence

Conserving the Frome Hoard

Since the last post, the majority of coins from the Frome Hoard are still at their temporary home–The British Museum. In 2010, a huge team effort allowed for the 52,503 coins to be cleaned of mud and clay by museum conservators and sorted by Roman coin specialists. Now, two years on from its discovery, the process to study and understand the hoard continues. The coins were handed to two conservators–Ana Tam and Natalie Mitchell–for further work to reveal the fine details hidden beneath the corroded surfaces. The next few posts will show what goes on when tens of thousands of coins require conservation.

Here’s an idea of what the coins looked like at the start:

The Frome hoard has been valued at £320,250

Art Fund to match-fund public donations to appeal

Victor Ambrus' water colour of his view of the hoard being deposited Today, the value of the Frome Hoard has been announced at £320,250. Somerset County Council Heritage Service now has until 1 February 2011 to raise the funds in order to keep this important treasure on public display in the county in which it was discovered. The rare find, made up of 52,503 Roman coins dating from the 3rd century AD, was unearthed tightly packed in a pot and is the largest coin hoard to have been found in a single container.

The Art Fund, the national fundraising charity for works of art, today announces a grant of £40,250 to kick-start the appeal. For the first time, the Fund is offering members of the public the chance to double the value of their donation to the appeal. For every £1 donated by a member of the public, the Art Fund will match fund it – up to a total value of £10,000, thereby boosting the appeal with up to a further £20,000.

Stephen Deuchar, director of the Art Fund, said:

“We’re extremely excited to be part of Somerset’s campaign to acquire this extraordinary treasure. To think that this pot packed full of coins lay buried beneath the soil for almost 2,000 years – it really is incredible. We need to save the hoard so that experts can carry out vital research – and so that new generations can enjoy and be inspired by it. As a way to encourage philanthropic giving and support from the public, we are also pleased to be offering members of the public the chance to double the value of their donation to the appeal by donating via us.”

Roger Bland, Head of Portable Antiquities & Treasure, British Museum said:

“Dave Crisp, the finder, behaved in an exemplary way. When he found the hoard he didn’t try and dig it out himself, but reported it to the Portable Antiquities Scheme, so that an archaeological excavation could be organised to recover the find systematically. As a result there is enormous potential to properly understand why and how this coin hoard was buried, and perhaps change pre-existing views on the hoarding and burial of such assemblages”.

Dave Crisp discovered the hoard on 11 April 2010 while metal-detecting near Frome, Somerset. The ‘Frome Hoard’ was declared Treasure under the Treasure Act 1996 on 22 July. The coins range from c. AD 253 to c. 293 and except for five silver coins are all base-silver or bronze ‘radiate’ coins. Weighing 160 kilograms, it is said to be one of the largest and most important hoards of coins of this period in Britain. There are still mysteries surrounding why it was buried, and Dr Bland says that its discovery could make experts

“rethink the nature of such hoards.”

Over 760 of the coins belong to the emperor Carausius, a general in the Roman army who usurped against the Central Empire. Carausius set up his own empire in northern Gaul and Britain, and This is the largest group of his coins found anywhere. The entire hoard includes coins minted by 21 emperors and three emperors’ wives.

Because the coins were excavated by layer, experts were able to detect that most of the latest coins (those of Carausius) had lain over half-way down the pot. This led to the conclusion that the hoard was almost certainly buried in one event. The pot could not have held 160kg of metal without breaking. It therefore must have been buried in the ground before the coins were tipped in from smaller containers.

There has already been considerable local enthusiasm for the hoard. On 22 July, the County Council Heritage Service organised a special event showcasing a selection of coins from the find. Over 2,000 people and two school groups attended, many having to queue for up to an hour. A second event is planned for 23 October 2010. This will be a major opportunity for the public to find out more about the find and what they can do to help save it.

In addition to the target £320,250 needed to acquire the hoard for Somerset, an additional £35,000 will be needed for its long-term conservation.

The first book on the Frome Hoard, written by experts Sam Moorhead, Roger Bland and Anna Booth, and published by the British Museum Press, is now available from www.britishmuseumshoponline.org

50 pence of every sale will go towards the vital conservation costs..The Frome Hoard tells the remarkable story of the discovery of the hoard, describes the fascinating collection of coins it contains and offers an initial interpretation of the treasure, and its significance. Close-up photographs show intricate details of the amazing coins.

How to donate

To donate towards the appeal to save the hoard for Somerset, please register your interest via savefromehoard@artfund.org and the Art Fund will be in touch with details about how to donate. Every public donation will be match-funded by the Art Fund, up to a total of £10,000.

Ends

Notes to editors

The Art Fund is the national fundraising charity for works of art and plays a major part in enriching the range, quality and understanding of art in the UK. It campaigns, fundraises and gives money to museums and galleries to buy and show art, and promotes its enjoyment through its events and membership scheme. Current initiatives include sponsoring the UK tour of the ARTIST ROOMS collection, and running a major campaign in partnership with the National Trust to raise £2.7 million to save Brueghel’s The Procession to Calvary for Nostell Priory. The Art Fund is funded by its art-loving and museum-going members and supporters who believe that great art should be for everyone to enjoy. Find out more at www.artfund.org.

Portable Antiquities Scheme

The Portable Antiquities Scheme was established to encourage the recording of archaeological finds found by the public, and also supports the mandatory reporting of Treasure (such as the Frome Hoard) under the Treasure Act 1996. The Scheme is managed by the British Museum on behalf of the Museums, Libraries & Archives Council. Across England and Wales its Finds Liaison Officers liaise with finders and record their finds, which are published on its online database (www.finds.org.uk) so that people can learn about the archaeology of their local area, and also for the advancement of archaeological knowledge.

Contact Roger Bland, Head of Portable Antiquities and Treasure, 020 7323 8611; e-mail: rbland@thebritishmuseum.ac.uk

Museum of Somerset

The Frome Hoard will be prominently displayed in the Museum of Somerset, Taunton, when it re-opens in the Summer of 2010. The museum is presently undergoing a £6.9 million refurbishment largely funded by the Heritage Lottery Fund.

Locally, support for the hoard’s acquisition has been shown by a contribution of £10,000 from the Somerset Archaeological and Natural History Society.

Contact Stephen Minnitt, Head of Museum 01823 347440 or 01823 278805. Email: scminnitt@somerset.gov.uk

Details on the Book

The first book on the Frome Hoard, written by Sam Moorhead, Roger Bland and Anna Booth, and published by the British Museum Press, available from www.britishmuseumshoponline.org, 48 pages, 50 colour illustrations, ISBN 978 0 7141 2334 9, PB £4.99. The Frome Hoard has been printed with the generous support of local Frome-based printers, Butler, Tanner & Dennis

The Authors

Cover image for The Frome Hoard

Sam Moorhead is National Finds Adviser for Iron Age and Roman coins in the department of Portable Antiquities and Treasure at the British Museum.

Anna Booth was Somerset County Council’s Finds Liaison Officer, and worked on the excavation of the hoard. She is now researching for a PhD at the University of Leicester.

Roger Bland is Head of Portable Antiquities and Treasure at the British Museum. He is the co-author of The Staffordshire Hoard (British Museum Press)

Contact: Roger Bland
rbland@britishmuseum.org 0207 323 8611

Frome hoard press release from the Art Fund

Minelab owners TV video interview with Dave Crisp

Gary Brun kindly sent me a link to a video interview made by his team. In this video, Gordon Heritage discusses finding the hoard with the finder – Dave Crisp.

Time-lapse video of the excavation

Photos of the event at Frome Library

Further photos of the event which took place at Frome Library on 22nd July can be found on the library’s Flicker account:

http://www.flickr.com/photos/somersetlibraries/page1/

Everyone involved in the event would also like to thank the library staff for their support and help on the day as they rearranged the library to accommodate us!!!

Hoard declared Treasure by coroner

On 22 July, the hoard was declared to be Treasure at a coroner’s inquest in Frome. It will now be valued by the Treasure Valuation Committee at their meeting in October and the Committee has commissioned valuations from two of the leading trade experts in Roman coins.

A selection of coins from the hoard was put on show in Frome library on the 22nd and over 2,000 people came to see the coins and hear Sam Moorhead, Roger Bland, Anna Booth and Katie Hinds talk about them.

Roger says:

We were all amazed and greatly encouraged at the huge interest shown by the people of Frome in this hoard and hope to work with Somerset County Council Heritage Service on arranging more events like this in the county. At the moment we are only at the start of the project to study the hoard. Although all the coins have been washed and identified by emperor, many thousands are unidentified and it will be a year’s work for a conservator to clean all the coins. At present we trying to raise the funding for this. Once the valuation of the hoard has been agreed, Somerset County Council Heritage Service will need to raise the funding to acquire the hoard for Somerset. British Museum Press are publishing a small book on the hoard in order to help the fundraising campaign.

Sam said:

‘It is wonderful that a new discovery can generate so much interest. It shows that the public have a thirst to see and hear about major new finds. Furthermore, having over 2,000 people (including two groups of school children) come in person to look at the coins will have an enormous impact on the local community and its engagement with history. There is no doubt that Britain’s forgotten emperor, Carausius, is now beginning to enter the psyche of people who have been following the media reports on the hoard. The Portable Antiquities Scheme might have a major responsibility to record new finds by the public, but it also plays a crucial role in the wider dissemination of knowledge about the past. Has any coin hoard ever generated this much interest in the past? I don’t think so.’

Frome coins on display and a gallery talk

A small selection of the 52,503 coins from the recently discovered Frome Hoard are now on display in the British Museum. These can be found in the central case of Gallery 68. They will be on display from today until August 31st. Sam Moorhead will be giving a talk on Roman coin finds from Britain at 1:15pm on the the 23rd July, starting in Gallery 49. This will end by the Frome Hoard, where Sam will talk about the contents and context. No booking required and entirely free!