THE BRITISH LIBRARY

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24 posts categorized "Imaging Science"

12 February 2015

Photographed by the Hand of a Sinner

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Senior Imaging Technician Kristin A. Phelps takes us behind the scenes of the British Library’s Imaging Services where there are several ongoing digital projects at any given time. 

Click here for an Arabic translation of this article, as translated by the Thesaurus Islamicus Foundation and Dar Al Kutub Manuscript Project.

Photographed by the Hand of a Sinner

Prior to the 14th Century, Byzantine artists who painted icons preferred to shun hubris and leave their works unsigned. Their work would be placed in churches to be seen and revered by thousands of the faithful over the centuries. Occasionally, an artist would sign their work with the phrase “Painted by the hand of a sinner.” This allowed the sacred value of the icon to remain unfettered by human presence.

Fast-forward to the modern world and a secular context: millions of digital images are accessed every day on websites of museums, libraries, archives and other collections. These images are taken by unseen photographers and are unsigned. The anonymity of the process allows for ‘pure’ and non-distracted understanding of the object by a viewer. But, who are these modern day artists who make invaluable works of art, faith and history accessible to all of us? How does their particular art form impact what we are able to view on our computer screens, tablets and smart phones?

To answer these questions we are going behind the scenes of the British Library’s Imaging Services where there are several ongoing digital projects at any given time. One project in particular, the Greek Manuscript Digitisation Project (GMDP), is working to digitise centuries old Greek manuscripts, some of which include illuminated portraits of the Evangelists executed by anonymous hands. The British Library’s third phase of the GMDP began in April 2014 and is scheduled to be completed March 2015 with a target of digitizing over 300 manuscripts, which is roughly equivalent to 120,000 images. The project has been funded by the Stavros Niarchos Foundation, the A.G. Leventis Foundation, Sam Goff, the Sylvia Iannou Foundation, the Thriplow Charitable Trust and the Friends of the British Library, among others.

British Library's Imaging Services

British Library's Imaging Services

The British Library’s Imaging Services currently employs eight full time photographers, or Senior Imaging Technicians, who represent approximately 110 years combined of photographic experience at the Library. While two of these photographers have been tasked with working on the GMDP, all of the photographers will work on the project at one point or another. 

The eight photographers come from a variety of backgrounds including more traditional photographic backgrounds as well as artists, a former school teacher, a former 3D graphic designer with a specialty in computer gaming and a former archaeologist.

Once a book is delivered to the Imaging Studio, the physical digitisation process can begin. Every manuscript is unique and its physical condition can vary widely. For this reason, a conservation assessment is being performed for each manuscript to be imaged for any of the digitisation projects. This written report guides the photographer responsible for the book to ensure that manuscript is returned in the same condition it was received.

 Once the assessment has been read and understood, the manuscript is set up for capture on a cradle. Many manuscripts can be photographed using an L-shaped cradle, designed by the Conservation Department, to allow photography without damage to the material. When the manuscript has been appropriately set up, it can be photographed in RAW format page by page utilising Phase One cameras with digital backs.

British Library's Imaging ServicesSenior Imaging Technician Neil McCowlenOnce the images are captured, they are reviewed and edited in Capture One (minor adjustments only including cropping, straightening and exposure adjustments).  

Finally, the RAW files are processed into both Tiff and Jpeg files before being passed back to the various digital project teams for online publication.

Does this process sound simple and straightforward? It rarely is. Often times, a manuscript needs to be carefully propped up to become level, or has a page which is not flat. The photographer is then responsible for manipulating the manuscript with a very gentle and cautious manner to make the resulting image provide the best view of a page. In addition, items may be housed in glass which cannot be removed for imaging. Senior Imaging Technician Tony GrantOr, objects may be large and unwieldy or extremely small. Lighting conditions may need to be changed if the manuscript contains significant amounts of gold leaf decoration. And, of course, there are always physical adjustments of the camera position and settings as well as employing a variety of lenses. Throughout the process the photographers have to use their judgment and experience in order to “do no harm” and yield images that represent faithfully the original material. After observing everything which must be considered to photograph a manuscript, the question arises: are these professionals artists or technicians? The Library photographers themselves are split when it comes to answering this question. Half of them consider their particular type of photography an art form whilst the rest view it as form of scientific imaging.

No matter what the answer to this question is, one thing is certain. These photographers deliver an impactful and important volume of work to the digital masses. Scholars from across the world have advanced their research without the need to physically visit the British Library. Thousands of people are able to connect with global cultural and religious heritage with a click of a button.

Of course, the GMDP project is just one example of a common wider trend of museums, libraries and archives digitising their holdings for online publication. In Europe alone as of 2014, 87% of cultural heritage institutions had digital collections. ENUMERATE’s 2014 survey found that the most important perceived reason for digital collections was academic research, which points to the growing field of Digital Humanities. With all the new material available online, a visual revolution of the democratisation of knowledge is happening. Now a scholar is no longer hindered by the inability to travel afar to libraries and museums to see objects; instant access to manuscripts and 3D objects is only a click away. Scholarship is becoming more diverse because open access to online collections allows those who wish to see something to be able to do just that. In fact, in its still young life, the third phase of the GMDP has already been the focus of scholarly research as well as being used and shared by a number of New Testament and Patristic blogs.

Of course, none of this would be possible without the diligent and specialised work of the photographers at institutions like the British Library. But if you asked one of the British Library Imaging Services’ photographers about their role in the process you receive humble responses, not dissimilar to what you would have expected from the original “sinners.”

Kristin A. Phelps, Senior Imaging Technician

Senior Imaging Technician Laurence Pordes

21 October 2014

Paper cuts: small but mighty!

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Hardly noticeable and barely bleeding, paper cuts are the mother of all library injuries. Anyone who deals with paper on a daily basis will have at some point suffered such an affliction. Paper cuts cause a seemingly out of proportion amount of pain due to the anatomy of our skin and the structure of paper. When very thin and held in place, a sheet of paper becomes inflexible and can exert very high levels of pressure – enough to slice through flesh! Yikes! Let’s go under the microscope to see what's happening...

Paper of the night  Paper cut
CC by Left: A single sheet of paper at x30. Right: Paper cut (image source).

Most paper cuts result from new sheets of paper held strongly in place. A rogue sheet may come loose from the pack but remain held in position by the rest of the tightly-knit sheets. In paper, more resistance is felt when a force is applied parallel to a sheet of paper. This has to do with the paper’s tensile strength. Tensile strength measures the ability of a material to resist rupture when force is applied to one of its sides under certain conditions. Held in place, the sheet of paper becomes extremely resistant to buckling, stiffens, and acts as a razor.

Dislocated sheet

CC by A sheet of paper that strays from the pack can cause serious paper cuts!

A paper’s edge may appear to be smooth and flat, but on a microscopic scale paper edges are jagged. Paper cuts leave a wound more like one from a saw than a knife (a miniature papery saw).

Copy book paper

CC by Pages from a copy book at x30 magnification. Fibres at the surface give paper a serrated edge. The black lines are page lines.

Paper cuts are remarkably painful. They usually occur in the fingertips, which have a greater concentration of nerve cells (neurons) than the rest of the body – an evolutionary trait to protect us during the exploration of our environment. Neurons send chemical and electrical signals to our brain, and some of them, called nociceptors, detect potential harm. Paper cuts stimulate a large number of nociceptors in a very small area of the skin. Shallow paper cuts don’t bleed very much so pain receptors are left open to the air resulting in continuous pain as the wound cannot clot and seal. As we continue to use our hands, the wound flexes open, continually distressing these neurons.

Not only do paper cuts part the flesh with a micro-serrated paper edge, but they also damage skin either side of the wound due to the composition of the paper. Pain receptors are continuously irritated by the combination of cellulosic wood pulp, rags, grasses, chemically-coated fibres, and bacteria that make up paper. Paper may also include other additives such as chalk or china clay to make the paper easier to write on. Sizing gives us a great variety of papers to suit the specific type of ink we wish to apply, but involves mixing many additives into the pulp to determine the correct surface absorbency.

Paper cuts from envelopes can be particularly stingy due to the layer of glue along the sealing tab. The glue is made from gum arabic, which although edible to humans, can pack a punch if embedded inside a wound. Gum arabic is the product of hardened sap taken from two species of acacia trees, and is also used as a binder for watercolour painting, and in traditional lithography.

Envelope adhesive x30

Envelope adhesive x200

CC by Gum arabic glue at x30 and x200 magnification coats the paper tab on an envelope. When the gum is moistened it forms a seal with the adjacent paper.

When skin closes around the paper cut these foreign particles become trapped inside causing a great deal of pain. This is why a cut from a razor blade is usually less painful than that from a paper cut: razor blades make clean incisions without leaving behind any foreign particles. It hurts initially, but the pain soon ebbs away. Bleeding caused by a razor cut helps to wash away any infection-causing particles, while paper cuts bleed very little (this also reduces your chances of getting any sympathy!)

Razor at x50

Razor at x200

CC by Razor blade at x50 (upper image) and x200 (lower image). The razor’s edge is smooth allowing a clean incision without introducing foreign bodies.

It might seem strange that sometimes needles for a flu jab require quite a bit of force to pierce the skin, yet paper (PAPER!) can slice through. This is due to the random orientation of collagen fibres in our skin allowing us to withstand pinpoint forces.

Point forces at x20

CC by Human skin feeling the pressure under a sharp pin.

Our skin does not have a comparable strength against shearing forces such as those exerted by paper, and so, we are susceptible to the small but mighty paper cut. Libraries can be dangerous places. Be careful out there!

Christina Duffy (@DuffyChristina)

 

Further learning:

Paper May Be the Unkindest Cut, Scientific American, Volume 306, Issue 3 , Mar 1, 2012 |By Steve Mirsky 

Why Do Paper Cuts Hurt So Much? Scientific American - Instant Egghead #25

 

07 October 2014

800 year old Magna Carta manuscript reveals its secrets

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Ground-breaking multispectral imaging work of the British Library’s burnt copy of the 1215 Magna Carta has recovered text which has not been read in 250 years.

This work has been completed by British Library conservators and scientists in preparation for next year’s 800th anniversary of the sealing of the Magna Carta. The so-called ‘burnt’ copy of the Magna Carta is one of four original manuscripts from 1215 which survive. In February 2015, the four manuscripts will be brought together for the first time in history for a special 3-day event, which will allow further academic study of them side by side, as well as the once-in-a-lifetime opportunity for 1,215 people to view them together – you can enter our ballot to win your chance to be part of that event here.

Multispectral camera Colour image

Processed image

CC by Top left: The “Burnt Magna Carta” ready for multispectral imaging. Top right: A real colour image of a section of the charter. Bottom: A processed image of the charter enhanced to reveal text thought to be lost.

The British Library owns two of the original 1215 Magna Carta manuscripts (the other two are held at Lincoln and Salisbury Cathedrals). The story of the ‘Burnt Magna Carta’ (Cotton charter xiii 31a) held in our collections is a truly remarkable one of survival against all the odds. In 1731 it was damaged in the Cotton Library fire, and subsequently staff at the British Museum Library used 19th century techniques to try to flatten and mount it, which has contributed to its current condition today rendering the text very difficult to see.

The multispectral imaging of the burnt Magna Carta was conducted as part of a major project involving the reframing and scientific analysis of all the Magna Carta charters held in our collections ahead of the 2015 anniversary. The Collection Care team provided an initial examination of the original frames to determine their structure and composition. All original mounting materials in contact with the charters were tested using infrared spectroscopy, pH tests, and lignin tests to determine their stability and compatibility with new materials. Once the charters were removed from the frames, near-infrared spectroscopy and high resolution digital microscopy was used to investigate the condition of the ink and parchment as part of the overall condition assessment.

With the frames and glass removed there was a rare opportunity to employ the cutting-edge technique of multispectral imaging enabling us to virtually peel away the layers of damage currently affecting the manuscript.

Conservator Kumiko Matsuoka Conservation Scientist Dr Paul Garside

Conservator Gavin Moorhead Imaging Scientist Dr Christina Duffy
CC by Clockwise from top: Temporary housing is prepared to store the charter when removed from the frame; the original wooden frames are removed to enable access to the charter; the charter is released from the mounting; once the charter is free from the frame it can undergo condition assessment.

Burnt Magna Carta  Ink loss

CC by Left: The “burnt” copy of the Magna Carta, Cotton charter xiii 31a, is one of the four original manuscripts from 1215 which survive. Right: Much of the ink has been lost with only a few remaining initials (shown here at 50x magnification).

Multispectral imaging is a non-destructive, non-invasive imaging technique using different colour lights, including ultra-violet and infrared, to recover faded and lost text. A high-resolution camera is securely mounted directly over the charter, which is then illuminated with LED lights ranging from the ultraviolet at a wavelength of 365 nm, through the visible region, and right up to a wavelength of 1050 nm in the infrared region. The chemical composition of the material in the charter is varied (ink, parchment, etc.), and so reacts differently to the lights. We are able to see, and capture, additional information undetectable by the human eye.

CC by  An animated gif comparing the original colour and processed images. 

Ultra-violet colour image

CC by A colour UV image reveals regions of text which are completely faded to the naked eye.

Using this technology and expertise available to us in the 21st century, we are able to preserve the Magna Carta for the next 800 years and present these iconic documents in the best possible condition for visitors who come to see them during the anniversary year.

Multispectral data is still being processed and will be published along with other scientific data collected after the British Library’s exhibition ‘Magna Carta: Law, Liberty, Legacy’ which runs from 13 March – 1 September 2015.

You can see this Magna Carta manuscript alongside the 3 other surviving copies at the British Library on 3 February 2015 – find out more details and enter for your chance to win a place on www.bl.uk/magna-carta

Christina Duffy (@DuffyChristina), Imaging Scientist

27 July 2014

Fleas, mould and plant cells: under a 17th century microscope with Robert Hooke

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This week we celebrate the 379th birthday of Robert Hooke, a Fellow of the Royal Society and key figure of early modern natural history and natural philosophy, born on 28 July 1635. Many of Hooke's innovations paved the way for a more rigorous scientific analysis of materials, for which we in Collection Care are very grateful. To mark the occasion we are thrilled to host a guest post from Puck Fletcher who has just completed a doctorate on space, spatiality, and epistemology in Hooke, Boyle, Newton, and Milton at the University of Sussex:

Hooke’s most famous work is the Micrographia: or Some Physiological Descriptions of Minute Bodies Made by Magnifying Glasses with Observations and Inquiries thereupon, published in 1665 by the Royal Society. It is a descriptive work detailing sixty observations of specimens at magnification, starting with the point of a needle, ranging through silk, glass drops, hair, and various plants, seeds, and tiny insects, all viewed through a microscope. It closes with observations of the fixed stars and the moon as seen through a telescope. 

Two cross sections of cork

CC zero Two cross sections of cork and a ‘sensible’ plant. In his description of cork, Hooke coined the term ‘cell’ for biological contexts. Image source.

The project was a collaborative one started by Christopher Wren who, in 1661, so impressed Charles II with his drawings of magnified fleas and lice (possibly the ones on which the corresponding Micrographia engravings were based), that the King requested more. Wren persuaded Hooke to undertake the bulk of this work and over the next few years, Hooke amassed his collection of observations, regularly bringing new drawings to the meetings of the Royal Society for approval by the other members.  

Illustration of a flea

CC by Among the drawings and observations in Micrographia is this famous and extraordinarily detailed large-scale illustration of a flea. BL Shelfmark: 435.e.19, XXXIV. Image copyright The British Library Board. Read more.

The impressive folio volume contains thirty-eight highly detailed engravings, which turned the book into an instant bestseller and secured its reputation as the most beautiful and lavish work of early European microscopy. The sense of magnified scale is staggering. A head or body louse, for example, is just a few millimetres long, but the engraved image is 52 cm long, roughly two hundred times actual size, a level of exaggeration that is emphasized by the fact that, large as the volume is, the reader must still unfold the oversized plate to view it.

Head or body louse

CC zero Engraved image of a head or body louse, roughly two hundred times actual size. Image source.

For his readers, Hooke’s illustrations brought a whole new world into view. Hooke captures this excitement in his preface, describing how, by means of instruments like the microscope, ‘the Earth it self, which lyes so neer us, under our feet, shews quite a new thing to us, and in every little particle of its matter; we now behold almost as great a variety of Creatures, as we were able before to reckon up in the whole Universe it self.’ Pepys was famously so enamoured of the book that the day after he brought home his copy, he stayed up until two in the morning reading it, describing Micrographia in his diary as, ‘the most ingenious book that I ever read in my life’. 

When looking at the large-scale, clear engravings in Micrographia, it is easy to imagine that this was the view Hooke had in his lens and that his task was simply that of looking and then recording what he saw. However, the practice was much more difficult and required considerable skill and experience – when Pepys looked through his microscope, he was disappointed to find that at first he couldn’t see anything at all! The lens making technology of the time meant that impediments to clear vision such as chromatic aberration or artefacts in the glass were not uncommon, and the view through a microscope was often blurred, distorted, and dark. It was difficult to make out true colours or to tell whether a shadow was a depression or protuberance, and the field of vision was quite small.1

Part of Hooke’s contribution in Micrographia was his skill as an instrument maker and technician. Although, as he reports, he had difficulties in seeing through his microscope, Hooke made his own adaptations to the commercially manufactured instrument, in particular devising an improved light source, which he called his ‘scotoscope’.  

The 'Scotoscope'

CC zero The microscope, featuring an improved light source. Image source.

Hooke also worked diligently and looked very carefully, making multiple observations from multiple angles, of multiple specimens, created with various preparation techniques, to gather enough visual information to be able to produce a single image of what the whole object looked like, as near as he could make out. For Hooke, the act of looking through the microscope and recording what he saw was an interpretive one.

Hooke’s observations have been praised by modern scientists for their accuracy, and Howard Gest even credits him with the first accurate description and depiction of a microorganism, the microfungus Mucor, described by Hooke as ‘blue mould’.2 

‘Blue mould’

CC zero The microfungus Mucor (‘blue mould’). Image source.

In his preface to Micrographia, Hooke heralds ‘artificial Instruments’ such as the microscope and telescope, and the methods of the new science based on observation and the careful and rational scrutiny of results, as at least partial correctives for the failings of fallen man and his limited sensory faculties. He also looks forward to the technology of the future, which he believes will enable man to see even more clearly.

‘’Tis not unlikely, but that there may be yet invented several other helps for the eye, at much exceeding those already found, as those do the bare eye, such as by which we may perhaps be able to discover living Creatures in the Moon, or other Planets, the figures of the compounding Particles of matter, and the particular Schematisms and Textures of Bodies.

Puck Fletcher

1Brian Ford’s wonderful book, Images of Science: A History of Scientific Illustration (The British Library, 1992), pp. 182–83, contains a photograph of the partial and distorted view through the sort of lens used by Hooke.  

2Gest, Howard, ‘The Remarkable Vision of Robert Hooke (1635–1703): First Observer of the Microbial World, Perspectives in Biology and Medicine, 48.2 (2005), 266–72 (p. 267).

19 July 2014

Secret underdrawings & cover-ups in the Mewar Ramayana

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The Ramayana – “Rama’s journey” – is one of India’s oldest stories having first being written some two and a half thousand years ago. It follows the hero Rama from his birth and childhood in Ayodhya to his exile in the forest where his wife Sita is kidnapped by the wicked (and ten-headed!) demon king Ravana. With his valorous brother Lakshmana and helped by an army of monkeys and bears he leads the search for Sita, finally rescuing her from Ravana’s stronghold in Lanka. It is an epic story embodying the Hindu idea of dharma (duty). There are several thousand known surviving manuscripts and many different versions of the story across Asia. The Mewar Ramayana is one of the finest copies of the work, lavishly illustrated with over 450 paintings in large format. Recent digitisation by the British Library in partnership with leading Indian institutions has reunited the long-separated text and it can be viewed online featuring an introduction including links to contextual documents and high resolution images in ‘Turning the Pages’ with descriptive text and audio.

Multispectral imaging

We recently examined two paintings from the Mewar Ramayana using multispectral imaging to investigate the methods and workflow of the artist. Images are captured over fourteen spectral bands from the ultraviolet (UV: 365 nm) to the infrared (IR: 1050 nm) revealing information about underdrawings and techniques that can’t be seen under normal light. The two full page paintings are illustrations from Book 6 (Yuddhakanda, Book of war) of the Mewar Ramayana manuscript.

Book 6 fol. 27r (Add. MS 15297(1), f.27r)


Book 6 fol. 27r depicting the siege of Lanka in colour, ultraviolet, infrared, and blue light with an orange filter. Rama’s army of monkeys takes control of the four gates of the city as the ten-headed Ravana leads the defence after consulting his ministers.

Book 6 fol. 27r: Rama’s army of monkeys and bears hurl stones at their enemies. White pigment, possibly added as a later touch up, is observed under ultraviolet light on the elbows, arms and tails of the attacking monkeys.

Book 6 fol. 27r: Colour, ultraviolet, infrared sequence. In front of the gates to Lanka, a man struggles with a monkey. Under ultraviolet light the rough application of paint is evident on the man's hand where no attempt is made to stay within the lines. In the infrared image, the guidelines used to initially draw the figure (chest, back, elbow) are observed.

Book 6 fol. 27r: An archer fends off the monkey army. Incorporating high levels of detail in these paintings often led to a change in design layout. In the painting the archer is shown to be sitting cross-legged on the cart, but in the infrared image he is standing. The late addition of the cart is evident by the over painting of the wheel in order to indicate its attachment to the main frame of the cart. Other alterations were made such as the size of the soldier's orange foot in the top left, and the painting over of an isolated monkey tail on the horse's body in the bottom left.

Book 6 fol. 142r (Add. MS 15297(1), f.142r)

As the battle escalates Rama’s brother Lakshmana is seriously wounded by a spear. Hanuman the monkeys’ army general is sent to the Himalayas to pick up medicinal herbs.

Book 6 fol. 142r: Colour, ultraviolet, infrared, and blue light with an orange filter sequence of the painting.

Book 6 fol. 142r: Colour, ultraviolet, infrared sequence. Rama’s loyal brother Lakshmana is seriously wounded by a spear. In the ultraviolet image we can see touch-ups on the hands, arms and legs of the two monkeys trying to take the spear off Lakshmana. Under infrared light we can see underdrawings of the far left monkey who was originally positioned higher up.

Book 6 fol. 142r: Colour, ultraviolet, infrared sequence. In the ultraviolet image alterations to Rama’s clothing and the direction of arrows is observed. Under infrared light, the boat at the top of the painting with the three figures is shown to have been altered. It may have started out as a representation of deities in the sky similar to those seen in Mughal Mahabharata (Razmnamah) Or. 12076 f.76r. Other arrow positions have also changed.

Book 6 fol. 142r: In the infrared image, a different position for the ten-headed Ravana is shown to the right, where a single face in profile is revealed adjacent to a vertical line. This is completely obscured by the green pigment which we now see.

Multispectral imaging has proven a wonderful technology in allowing us to study collection items in new and exciting ways. These are just some of the observations made and we hope to share more in the future.

Christina Duffy (Imaging Scientist) and Pasquale Manzo (Curator Sanskrit)

20 May 2014

Discovery of a watermark on the St Cuthbert Gospel

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A watermark of a post horn surrounded by a shield was recently discovered on the rear pastedown of the St Cuthbert Gospel (Add. MS 89000). The finding has just been published in the Electronic British Library Journal. The St Cuthbert Gospel is a late seventh century parchment volume and is the oldest intact European book. This Anglo-Saxon pocket gospel belonged to St Cuthbert of Lindisfarne (c. 635–687) and was discovered in 1104 in his tomb.

The pastedown, which is the endpaper attached to the inside cover board of a book, records the donation of the St Cuthbert Gospel (then known as the Stonyhurst Gospel) to the British Province of the Society of Jesus from the Reverend Thomas Philips, S. J. in 1769.

  St Cuthbert GospelRear pastedownWatermark location
CC by Left: Front cover of the St Cuthbert Gospel. Centre: The rear pastedown showing a record of the donation: ‘Hunc Evangelii Codicem dono accepit ab Henrico Comite de Litchfield, et dono dedit Patribus Societatis Iesu, Collegii Anglicani, Leodii, Anno 1769; rectore eiusdem Collegii Ioanne Howard: Thomas Phillips Sac. Can. Ton.’ which translates to: ‘This Gospel Book was received as a gift from Henry, Earl of Litchfield, and given to the Fathers of the Society of Jesus, of the English College, Liège, in the year 1769, the rector of the college, John Howard, Thomas Phillips Canon of Tongres.’ Right: The watermark is located in the lower right hand corner

What are watermarks?

Watermarks are created by manipulating a piece of wire into a recognisable shape and fixing it to a paper mould such as the Japanese papermaking bamboo screen below.  Here the bamboo has been cut into strips and arranged into parallel lines called laid lines. The bamboo strips are held together by sewing thread at one inch intervals, which form the chain lines on a sheet of paper. Chain lines, laid lines and watermarks are visible when held up to a light source. Light can pass through watermarks easily because the paper thickness is reduced where wire is present in the mould.

Paper mould

CC zero A Japanese papermaking bamboo screen

We typically notice watermarks on paper when they are held up to the light revealing a motif, initials or a date relating to the original paper mill. Watermarks are therefore useful in determining the provenance of paper and can help to identify its intended function. Watermarks can be difficult to image because they are often obscured by print on the page, or are located in the gutter (the space between the printed area and the binding).

An example of a partial watermark from a woodblock reprint dating to about 1476 is shown below. The reprint is of the Astronomical Calendar first published by Johann Müller (Regiomontanus) in Nuremberg in 1474 (British Library shelfmark IA.7). The watermark is found in the gutter with the other half located several folios later due to the ordering and cutting of the folios.

Partial watermark in book gutter

CC by Watermark in the gutter of BL IA.7 when viewed through a light sheet 

When the page is adhered to a board on one side, such as the rear pastedown of the St Cuthbert Gospel, it is impossible for light to transmit and watermarks can remain undetected. A pastedown conceals the raw edges of the covering material and forms a hinge between the board and the text block.

Pastedown example

CC zero An example of a front pastedown where one side of the endpaper is adhered to the front cover. Since the endpaper is fixed to the board it is difficult for light to penetrate and illuminate potential watermarks

The St Cuthbert Gospel watermark

A high resolution digital image of the pastedown was processed using ImageJ, an open source image processing software package. An image is comprised of a variety of layers or textures which can be separated. This allows pixels of interest to be isolated which may include faded writing, obscured text or watermarks. The watermark was revealed by converting the image from the standard RGB (red green blue) colour space into another space where tiny contrast differences were enhanced. The process of colour space analysis is fully explained in the publication: The Discovery of a Watermark on the St Cuthbert Gospel using Colour Space Analysis

No watermark observed   Watermark visible
CC by Left: An image of the rear pastedown of the St Cuthbert Gospel where no watermark is observed. Right: The same image reveals a watermark in the lower right hand corner of the pastedown when processed into another colour space

Non-destructive science

Colour space analysis is being used at the British Library to enhance faded designs on binding covers, disclose watermarks and hidden inscriptions and to reveal text which has been chemically treated or erased. In many cases applying colour space analysis to certain multispectral images has proven successful.

Digitisation projects generate large amounts of high-resolution images which can be manipulated to discover hidden information without the need to access the item. This has significant implications for the long-term study and preservation of cultural heritage collection items. The rear pastedown in the St Cuthbert Gospel was formerly numbered f. 91 and is available to view on the internet as part of the Digitised Manuscripts website.

Christina Duffy (@DuffyChristina)

08 May 2014

Microscopy of the Lindisfarne Gospels, folio 3r

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The Lindisfarne Gospels is one of the most magnificent manuscripts of the early Middle Ages. It was written and decorated at the end of the 7th century by a monk named Eadfrith who would go on to become Bishop of Lindisfarne and serve from 698 until his death in 721. An Old English gloss between the lines translates the Latin text of the Gospel and is the earliest surviving example of the Gospel text in any form of the English language. This translation was a late (mid-10th century) addition by Aldred, Provost of Chester-le-Street.

As one of the Treasures of the British Library the Lindisfarne Gospels undergoes strict condition assessments to ensure it is kept at ideal environmental conditions. Part of this assessment involves using microscopy to take a detailed look at the pigment behaviour. We posted some images in a previous post: Under the microscope with the Lindisfarne Gospels, and here we share some of the exceptional exuberance found on folio 3r.

Folio 3r

CC zero Folio 3r of the Lindisfarne Gospels, Cotton MS Nero D IV. Examine in full detail here

The abstracted decoration found throughout the Lindisfarne Gospels is a spectacular example of Anglo-Saxon art. There are five major decorated openings in the manuscript, the first of which is found on ff. 2v – 3 and introduces the letter which St Jerome addressed to Pope Damasus. It was Pope Damasus who requested a revision of the Latin Bible text during the late 4th century. Folio 2v consists of an elaborate cross-carpet page and faces Jerome’s letter to Damasus in Latin with the opening Novum opus (New work). The intricate detail on this page has been interpreted as an act of personal spirituality and devotion. A few examples are shown below. Enjoy!

Top of folio 3r

Top of folio 3r

Folio 3r letter 50x

Folio 3r 150x

Folio 3r detail 50x

CC by Top: Upper section of folio 3r. Centre: Crackled pigment of lettering reading incipit prologus at 50x and 150x magnification. Bottom: Celtic-influenced spiral motif at 50x magnification

Centre of folio 3r

Tiny drops of red lead are also observed in early Irish manuscripts which heavily influenced the Lindisfarne Gospels. The Germanic zoomorphic style is evident with interlacing animal and bird patterns.

Centre of folio 3r

Folio 3r 20x

Folio 3r pigment 50x

Folio 3r red lead 20x CC by Top: Central section of folio 3r from the British Library Catalogue of Illuminated Manuscripts with creature detail at 20x and 50x magnification. Bottom: Drops of red lead in a geometric pattern at 20x magnification

Bottom of folio 3r

Decorated initials exhibit yellow pigment (orpiment) bordered with drops of red lead. Craquelure is a network of tiny cracks caused by pigment shrinking due to age. When the disruption consists of perpendicular lines it is referred to as crackling.

Bottom of folio 3r

Folio 3r 30x

Folio 3r 100x

Folio 3r pigment loss 20x

Folio 3r 50x

CC by Top: Lower section of folio 3r. Detail of decorated initals at 30x and 100x magnification. Bottom: evidence of loss of green pigment (verdigris or vergaut) from a decorated initial at 20x and 50x magnification. Text from the reverse (f. 3v) is shown through the parchment

For more details on the pigments used in the Lindisfarne Gospels see our previous post. The entire manuscript is digitised and available online here.

Christina Duffy (Twitter: @DuffyChristina)

28 April 2014

As white as a...colour calibration target

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The Macbeth ColorChecker(R) is often observed in digitised images adjacent to the subject being imaged. It is a colour calibration target used widely by photographers to achieve consistent colour within a studio environment. Good colour management allows the photographer to have continuity to achieve the same result with any camera. The rectangular cardboard target consists of a grid of 24 squares of colour samples, each with a measureable spectral reflectance. Reflectance refers to the fraction of incident light reflected at an interface. The spectral reflectance of these patches does not change under different lighting conditions in the visible spectrum (this is not the case in the ultra-violet and infra-red – see footnote* below), so are reliable to track colour changes in this range.

Cotton Nero Ax f86v

CC by Calibration target shown over f.86v of Cotton Nero A.x. during imaging of Sir Gawain & the Green Knight. The target is set to be on the same focal plane as the folio. Targets are often cropped out of final processed images

The idea of a colour chart came about in a 1976 paper in the Journal of Applied Photographic Engineering by C. S McCamy, H. Marcus and J.G. Davidson entitled A Color-Rendition Chart. The abstract states “A color chart has been developed to facilitate quantitative or visual evaluations of color reproduction processes employed in photography, television, and printing.” Their paper has been cited over 350 times to date. The original chart consisted of a 4 x 6 array of patches, each 5 cm square.

Original size target

CC zero The original colour chart consisted of square patches of side 5 cm. The same size chart is still available and used today

There are still 24 patches on modern colour calibration targets but smaller versions are now available with patches measuring 1 cm wide. The X-Rite ColorChecker(R) Classic target used in our lab is shown below with a scale, focusing target, and reference number that we attached.

ColorChecker(R) Classic

CC by The ColorChecker(R) Classic target has 24 colours in a 6 x 4 grid. The colours are painted in matte on smooth paper and surrounded by a black cardboard border. 

The colours are roughly divided into four kinds. The top row is composed of colours which approximate natural objects such as human skin (dark and light), blue sky, the green colour of a leaf, and a blue chicory flower. The second row is made of miscellaneous colours encompassing a good range of test colours. The third row is comprised of the primary (blue, green, red) and secondary (yellow, magenta, cyan) colours, and the fourth row represents a uniform gray lightness scale ranging from brilliant white to black.

Colours labelled
CC by Colours in the calibration target. These colours are precisely measured and can be described in terms of the Munsell color system (a colour space describing colours in terms of their hue, lightness and chroma)

Larger colour calibration targets do exist such as the ColorChecker(R) Digital SG which boasts a gamut of 140 colours.

ColorChecker(R) Digital SG
ColourChecker(R) Digital SG boasts the widest colour gamut available. Its design is based on the original ColorChecker(R) target but is enhanced for digital photography. Image copyright X-Rite, from X-Rite website

For consistent colour, photographers can take a shot of the calibration target with the camera set to capture raw files. Shooting raw is the only way the camera chip can capture all of the information available in the scene. The image is opened in image processing software such as Photoshop, and a script is run on the image which opens it multiple times with different settings. Results are measured and a status is generated with values which can be used to fine-tune the camera’s colour calibration and get processed colour to match the original scene (or alternatively to distort the colour for special effects!).

While colour calibration targets are on the whole produced in the same way using the same materials, on average, every colour target is ever-so-slightly different. The colour difference may be very small and only measureable using other scientific methods. Colour difference is a metric of interest in colour science - the standard metric being Delta E (ΔE). This definition allows colour difference to be quantified in a way which is more reliable than just using adjectives, a practise which is detrimental to anyone whose work is colour critical!

Our multispectral imaging system captures images in Lab colour space, where L is lightness and a and b are colour-opponent dimensions. Lab colour space approximates human vision and is device independent. It includes all perceivable colours with RGB and CMYK spaces (see our previous post What the CMYK? Colour spaces and printing) sitting within its larger gamut, so file sizes are generally much larger. Values for L, a, and b can be tracked once the image has been white balanced using the white colour patch on our calibration target as a reference. However, Lab files don’t open in all software packages so quite often it is necessary to transform images into other spaces such as RGB, but the original Lab file is always stored.

Colour Science is a fascinating and growing area of research. For fun you can try out this Color IQ test from the X-Rite website to learn more about how you see colour, and to find out where you can get your own targets.

Christina Duffy (@DuffyChristina)

Footnote:

*While the Macbeth ColorChecker(R) provides 24 colours with consistent spectral reflectance under typical lighting conditions in the visible spectrum, it does not behave similarly in the ultra violet or infrared parts of the Electromagnetic Spectrum. Another material such as Spectralon is required for imaging outside of the visible range. The property which defines a diffusely reflecting surface (i.e. an ideal “matte”) is called Lambertian reflectance and Spectralon exhibits highly Lambertian behaviour with a spectral reflectance of >99% from 400-1500nm and >95% from 250-2500 nm. Spectralon is a fluoropolymer - others include PVF, PVDF and PTFE (Teflon). Spectralon has the highest diffuse reflectance of any known material over IR (infra-red), VIS (visible) and NIR (near-infrared) regions of the spectrum, and is therefore very expensive, but necessary to track colour difference during multispectral imaging.

Reference

McCamy, C.S.; Marcus, H.; Davidson, J.G A, 1976, A Color-Rendition Chart, Journal of Applied Photographic Engineering Volume 2, Number 3, pp 95-99

X-Rite website, or follow X-Rite on Twittter

25 April 2014

Time-lapse video of Kitaj Tapestry rehanging

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We recently rehung the R.B. Kitaj Tapestry If not, not in the St Pancras Entrance Hall after it was removed for conservation cleaning. You can read about the process and all the gritty details (hoho!) here.

Working with a 6.75 metres high by 6.75 metres wide tapestry is no mean feat and required the help of many people, so we thought we would honour all those involved by immortalising them in a time-lapse video! (Best viewed with Chrome)

The rehanging required the erection of scaffolding several days before and the hoisting of the tapestry up to the top platform. For safety purposes the rehanging was undertaken under darkness when the library was closed to the public. It was just like Night at the Museum, but in a library...and without anything coming alive...but exciting nonetheless.

Collection Care staff were guided by tapestry experts from Textile Conservation Ltd. and we are really pleased with the result. Come visit the British Library and take a look for yourself!

Christina Duffy (@DuffyChristina)

24 March 2014

Father Kögel and the ultra-violet examination of manuscripts

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2014 marks the hundredth anniversary of another important event: the first use of ultra-violet radiation for the examination of manuscripts, and particularly the deciphering of palimpsests. Scholars are frequently challenged by manuscripts which have faded to the point of illegibility, or which have been deliberately erased, or, most challenging of all, which have been erased and then written over. The Archimedes Palimpsest is one of the most famous recent examples, but palimpsests have long been exercising the minds and eyes of scholars, certainly since the middle of the 19th century.

Archimedes palimpsest

CC by The Archimedes Palimpsest is a medieval parchment manuscript, now consisting of 174 parchment folios 

Early attempts to make unreadable manuscripts readable, dating from the 18th century, used chemicals that would react with traces of iron in the fibres of the parchment which remained after the iron gall ink used to write the text had faded or had been removed. The trouble with these techniques was that, while they might initially be successful, they ended up staining the parchment blue or brown, leaving it even less legible than it was to begin with.

Photographic techniques had also been used to enhance faded writing almost since the invention of photography in 1839. In 1894 a process was developed for revealing palimpsests which used two plates: an over-exposed plate which would show both the upper and the lower writing, and an under-exposed plate that would show only the upper writing. A positive made from the under-exposed plate could then be used as a mask to permit an image of the lower writing only to be made. While this process was successful, it was time consuming because two plates had to be made, and their registration had to be very accurate in order for the upper writing to be cancelled out as nearly as possible.

In 1914, Father Raphael Kögel OSB published a paper in the Reports of the Royal Prussian Academy of Sciences in which he explained how ultra-violet radiation from an electric arc or a mercury vapour lamp could be used to excite fluorescence in parchment, but the fluorescence would be blocked (quenched) where the ink had originally been. A photograph of the visible fluorescence could then be taken, using filters to exclude the invisible ultra-violet which would obscure the image. This paper was in distinguished company: other authors in the same volume included Einstein and Planck. UV fluorescence photography should be distinguished from UV photography: in UV photography an image is made of the invisible ultra-violet radiation reflected from the manuscript; in UV fluorescence photography an image is made of the visible light emitted by the manuscript where it has been excited by ultra-violet radiation.

Father Kögel was born Gustav Alfred Kögel in Munich in 1882; he took the religious name of Brother Raphael when he joined the Benedictine abbey at Beuron, in the south of Baden-Württemburg, in 1898. He was sent to Brazil as a missionary, but fell ill and had to return to Germany. He then entered Wessobrunn Abbey, south-west of Munich, and was ordained priest in 1906. He later studied chemistry in Vienna, and in 1912 began working with the Palimpsest Institute at Beuron, which had been set up by Father Alban Dold specifically to study the Abbey’s rich collection of Carolingian and other medieval manuscripts. Here he developed his ultra-violet imaging techniques. He had previously experimented with coloured filters and photographic plates with different spectral sensitivities to improve the visibility of the under-writing, and also with chemical methods for enhancing faded writing, even though these had been condemned at the St Gallen conference on the conservation of manuscripts more than ten years before (“… this barbaric method …”).

Kögel became a professor at the University of Karlsruhe in 1921, and set up an Institute for Technical Photochemistry and Scientific Photography. Whether because of a crisis of faith, perhaps caused by the war, or simply because he found the academic life more congenial, Kögel left the church in 1922 and married in 1924. Kögel made important advances in using UV examination in forensics, and was also a pioneer in X-ray fluorescence analysis. His greatest commercial success was the development of the Ozalid diazo photocopying process, which was widely used until the 1970s. He died in 1945.

Because of the outbreak of war, Kögel’s publication does not seem to have been noticed in English-speaking countries until the early 1920s. For example, the first edition of C. A. Mitchell’s Documents and their scientific examination (1922) does not mention the use of UV, while the second edition (1935) does. Awareness of the technique grew in the 1920s and its use was well established by the 1930s. R.B. Haselden’s Scientific aids to the study of manuscripts, published by the Bibliographical Society in 1935, gives several examples of palimpsests that had been revealed by UV photography. He warns that users should wear protective goggles and protect their skin against excessive exposure to UV, and also that “prolonged exposure to UV light is injurious to a manuscript”. Unfortunately this message was not taken on board by everybody, and I have seen manuscripts where features that were seen and photographed under UV in the 1930s are no longer visible today. Haselden advises against the use of chemical reagents to restore faded ink, but goes on to recommend the use of a solution of anthracene in alcohol (“perfectly harmless”) to enhance faded writing – the solution penetrates the paper or parchment more rapidly where there is no ink, so the writing stands out against the vivid fluorescence of the anthracene under UV. Other writers recommend the use of a mixture of Vaseline and mineral oil for the same purpose, but it hardly need be said that these techniques are not recommended.

For best results, UV examination needs to be carried out in a darkened room, using a good-quality UV lamp and while wearing UV protection glasses. It has not always been thus. My wife remembers that when she was researching in a very well-known library in the 1970s, there was only one electric socket into which a UV lamp could be plugged, and this was underneath a table. She was therefore obliged to lie underneath the table with her manuscript and the UV lamp, sometimes with a member of the library staff to invigilate.

54v_02

U54v_02_RGB_unsharp

CC by The Electronic Beowulf project experimented with ultraviolet, first scanning fol. 54 verso under an ultraviolet lamp with a Kontron digital camera

UV examination is now being superseded in libraries such as the British Library which own multi-spectral imaging equipment. This gives better results as it can be much more selective than any process using filters to choose the wavelengths of fluorescence that are photographed. It uses much shorter exposures and therefore minimises the risks of exposing manuscripts to intense ultra-violet radiation. (See Christina Duffy’s blog post ‘Revealing hidden information using multispectral imaging’)

Dr Barry Knight, Head of Conservation Science & Research

 

References

Haselden, R.B., Scientific aids to the study of manuscripts, Supplement X to Transactions of the Bibliographical Society, 1935.

“Kögel, Gustav”, in Neue Deutsche Biographie 12 (1980) 295-6. www.deutsche-biographie.de/sfz43637.html

Kögel, P.R., Die Palimpsestphotographie, Sitzungsberichte der königlich Preussischen Akademie der Wissenschaften, 1914, 974-978

Mitchell, C.A., Documents and their scientific examination. London: C. Griffin & Co. (1922).