THE BRITISH LIBRARY

Collection Care blog

9 posts categorized "Ink"

04 October 2017

Talk: Iron Gall Ink - Conservation challenges and research

Add comment

Join Zoë Miller and Paul Garside in a lunchtime Feed the Mind talk at the British Library to find out how conservators are treating manuscripts at risk of being destroyed by their own writing.

Iron Gall Ink: Conservation challenges and research
Mon 9 Oct 2017, 12:30 - 13:30

Full details and booking information can be found here.

So what is the problem with Iron Gall Ink?

IGI4

Conservators caring for the 150 million items in the British Library face many challenges, from crumbling paper to detached book boards. But arguably one of the biggest issues is the conundrum of how to care for one of the most widely used and inherently damaging historic inks - iron gall ink.

You have probably come across this ink with its distinctive brown colour and halo of discolouration. Made from a combination of tannins (from oak gall nuts), iron sulphate (extracted from cave walls or pyritic nodules) and gum Arabic, this ink can become corrosive and thereby damage the writing surface it lies upon. Why was such a damaging substance used so prolifically? Because iron gall ink can be made from readily available materials, and cannot be rubbed or scraped away without leaving a textual stain behind. Thus it was used to write important manuscripts and legal documents for thousands of years. These include such iconic ‘Treasures’ of the Library as Magna Carta and the Lindisfarne Gospels, and range from illuminated manuscripts to personal correspondence and formal maps to impromptu sketches including those of Leonardo Da Vinci.

IGI1

The beauty - and evil - of the recipe lies in its properties of corrosion. When applied to paper or vellum the ink ‘burns’ into it leaving a mark which is insoluble in water or alcohol, and which cannot be erased. Over time it may attack the underlying paper or parchment, weakening the material and causing areas of text to be damaged or lost. In the very worst cases, we can lose the text completely as it drops out of the sheet of paper! The work of conservators is vital in identifying vulnerable items and intervening when necessary.

IGI3

What can be done? Come and find out at our Feed the Mind talk on Monday 9th October where, using visual examples, we will examine the historic use of this ink, including the influence which different recipes and writing implements can have on its properties. We will illustrate the range of treatments that are currently used in the Conservation department to address this problem, some traditional and some very modern, as well as the ongoing research to develop new approaches. This will demonstrate one of the many ways in which conservation helps to safeguard the collection and ensure its survival for future generations. Book your place now.

IGI2

06 July 2015

Under the Microscope with Magna Carta

Add comment Comments (0)

We recently held a very successful public event sharing our conservation work in preparation for the British Library Magna Carta: Law, Liberty, Legacy exhibition. The exhibition marks 800 glorious years of Magna Carta since it was granted by King John of England in 1215. The conservation project involved removing six manuscripts from their frames and rehousing them for display. While they were out of their frames, the manuscripts were examined using various scientific techniques. High-resolution digital microscopy enabled incredible magnification of the iron gall ink and parchment which make up the charters. Here is a selection of the images captured of Cotton MS Augustus ii.106, one of the British Library’s two original Magna Cartas dating to 15 June 1215. Enjoy!

Imaging Scientist Christina Duffy

Magna Carta 1215

Magna Carta 1215 (Cotton MS Augustus ii.106) – one of four surviving original 1215 copies.

Iron gall ink

Iron gall ink has been used since the middle-ages and is found on many of our most treasured collections including the Lindisfarne Gospels, Beowulf and Magna Carta. The main ingredients of iron gall ink include iron sulphate, tannins from oak galls and water. Overall the ink is in very good condition on this charter allowing us to appreciate the beauty in the detail of some of the intials.

Magna Carta 1215 detail  Iron gall ink at 20x

Iron gall ink at 30x

Iron gall ink at 150x

At high magnification we can see that some areas have experienced ink loss, but the Great Charter is still legible due to the remaining ink shadow left behind. Find out more about iron gall ink in a previous post here.

Magnca Carta 1215 detail right  Ink loss at 30x

Ink loss at 100x

Ink loss at 200x

Parchment

The parchment on which Magna Carta has been written is thought to be sheepskin. Parchment is an animal pelt which has had the hairs removed by liming or enzymatic action. It is then stretched and dried under tension creating a perfect writing surface with a thin opaque membrane. Below are some images showing damage to the  upper dermal layers of the parchment. Find out more about parchment here.

Magna Carta 1215 detail centre  Damage at 30x

Damage at 50x

Damage at 150x

CC by You can find out more about this charter on the British Library Magna Carta resource page.

Christina Duffy (@DuffyChristina)

07 October 2014

800 year old Magna Carta manuscript reveals its secrets

Add comment Comments (0)

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

09 June 2014

Know Your Yellow!

Add comment Comments (0)

This rather ancient looking Qur’an is deceptively young. In fact, it is thought to date back to the early 18th to late 19th century. The style is typical of African manuscripts originating south of the Sahara, and was presented to Lt. Heygate of the British Army, in Nigeria in 1916.

Front

Front Open

CC by Above: Manuscript in its wrapper. Below: Manuscript sandwiched between its boards with the wrapper open

It has a number of components; starting from the inside, there is an unbound textblock with thick tanned, haired goatskin boards on top and bottom. This in encased in a goatskin wrapper, which then fits into a goatskin satchel. This multi-faceted construction is similar to other 19th-century Qur’ans from West Africa, south of the Sahara.

Satchel

CC by Satchel lying on inert grey foam, with acid-free tissue padding to retain shape

First page

CC by Left: Manuscript open at first page with the letter detailing its origin inserted

As exciting as it is to have this fascinating object in the studio, it is responsible for some real headaches as a result of one particular element of its composition. Before an object comes to the studio to be worked on, a conservator will often carry out an assessment of its condition and write a treatment proposal, estimating the time and materials likely to be used. In this case, when my colleagues carried out the assessment, a large proportion of the textblock was ‘blocking’. This simply means pages were sticking together, which meant that most of the book was unreadable.

Strangely, in the period of time between the book arriving in the studio and the point where I took it out of the safe to work on, around a third of the textblock had released itself. This is not something conservators are trained to expect; most things get worse over time, so to see something improve without our intervention was exciting!

The only conclusion we can come to is that the studio’s environment is slightly different to the one the manuscript came from. The difference in the moisture levels in the air is the most likely culprit.

Pigment detail

CC by Detail of yellow pigment, orpiment

On closer inspection the ‘sticky element’ was discovered to be yellow dots painted intermittently within the text areas. These were tested by our Conservation Science team, and found to be orpiment (a poisonous, arsenic-based yellow pigment) mixed in a medium of gelatine. It is the gelatine that is fairly hydrophilic, which would have softened in a humid environment and stuck to anything in direct contact with it.

So the obvious solution to this is to change the humidity levels around the volume further, to release all of the sticky dots. If only it were simple! The brown ink you can see in the image is most likely iron gall ink, which has been used as a writing medium since ancient times. Its main characteristic is that once it’s a few years old it turns from purplish-black to brown. Another, less innocuous ageing property, is its potential to ‘burn’ through the paper it sits on. The extent of the damage can depend on the recipe the scribe followed to make the ink; some are more acidic than others. But it can also depend on the level of humidity the ink has encountered in its lifespan. The introduction of medium to high levels of moisture, even in vapour form, can solubilise ions contained in the ink, which can catalyse the oxidative degradation of the cellulose fibres of the paper. This leads to weakened paper and potentially a severely damaged collection item.

Text

CC by Detail of one of the illustrations amongst the text

So keeping it dry is the best option for the ink, but pulling apart the pages without moisture could lead to skinning off the top layer of fibres, or even tearing paper.

We’re still deciding what to do about this sticky dilemma, but as ever with conservation decisions, we will have to balance our need to enable access by our readers to collection items with the wellbeing of individual items. Never a dull moment!

Jo Blackburn

06 May 2014

Recreating the Medieval Palette

Add comment Comments (0)

In February this year the British Library hosted a course called ‘Recreating the Medieval Palette’ run by pigment expert Cheryl Porter who is also Director of the Montefiascone Project and a freelance conservator. Those of us attending were a small group of conservators and material specialists from the British Library and other institutions hoping to deepen our knowledge of the materials we work with. The course was an interesting mixture of theory and practice, with the morning lectures covering the basic colour groups and the afternoons providing a more hands-on approach giving us the opportunity to prepare and paint out the pigments and inks on a variety of papers and parchment.

Recreating the Medieval Palette

CC by The group painting out some examples of earth colours made from rocks and minerals – the oldest pigments used by our ancestors

Alongside the history and manufacturing processes of the pigments we learnt about their chemical composition, visual characteristics, behaviour in response to their environment and modes of deterioration. This is essential background knowledge when undertaking a conservation treatment.

The medieval alchemists didn’t worry too much about health and safety in their search for vivid and enduring colours; hence the highly poisonous production methods for concocting pigments such as lead white, red lead, lead tin yellow, verdigris and cinnabar/vermilion. When preparing the pigments for painting, the powder has to be mixed with a binding medium to give viscosity and adhere it to the page. We experimented with different binding agents – egg white and gum arabic – which changed the working characteristics of the pigments when painted out.

Malachite

CC by Malachite or ‘mountain green’; a naturally mined carbonate of copper

Lead grinding

CC by Grinding lead white pigment on glass in a figure-of-eight motion

Making some of the lake colours provided an opportunity to see some real alchemy. A lake is a dyestuff made from organic matter which is precipitated onto a colourless mineral base. Plants such as buckthorn, weld and saffron were used to make a variety of colours, and insects such as kermes and cochineal produced shades of red.

Mixing saffron  Painted-out medieval blues
CC by Left: Experimenting with mixing saffron (yellow) with verdigris (green). Right: Painted-out medieval blues; the brighter colours are mineral-based azurite and ultramarine and the subtler shades, indigo and woad

We also had an opportunity to learn about inks used in manuscripts. This was extremely interesting from a conservator’s point of view as we discovered that inks can often be identified by the way in which they deteriorate over time. The earliest writing implements were reed pen and quill, and the group’s attempts at writing with these proved that both skill and practice were required!

 

Reed pen Quill pen

CC by Left: Practising writing with reed and quill pens. Right: A quill and block of Chinese carbon ink

Colour sample sheet

  CC by Left: One participant's colour sample sheets

 At the end of this highly informative and entertaining week we went away having learnt a lot from Cheryl’s wealth of knowledge and experience, as well as having enjoyed stories of her adventures collecting and researching pigments. Our array of sample sheets will also provide a valuable visual and chemical reference for identifying pigments in the future.

 

Vicky West

23 February 2014

‘No pigments were harmed in the making of this post’

Add comment Comments (0)

Conservator Joanna Blackburn reports on the conservation of a large collection of botanical watercolours.

When I was at school, chemistry was not my favourite subject. My young mind hadn’t quite made the connection yet between the inexplicable results I would get from my experiments, and the world I saw around me. So when I decided to become a conservator, imagine my horror when I realised I would have to take a course called ‘Chemistry for Conservators’!

I needn’t have worried though, because I found science so much more interesting when applied in context. And there is nothing more satisfying than looking at the deterioration of a collection item and being able to explain the ‘whys’, the ‘hows’ and the ‘what nexts’.

Below is an example of one of a large collection of botanical watercolours that my colleague, Patricia, and I have been working on over the past six months.

NHD 54 Item47

CC by NHD 54 item 47

The collection comprises of 309 watercolours by Chinese artists, dated to around 1800. Their exact provenance is unknown, but they would have been commissioned by a Western traveller to bring back to Europe. They would have fuelled the popular interest in botany of the time. The collection was received by the Library from the Foreign and Commonwealth Office in 1975. The watercolours are not unusual in British collections, many institutes have similar examples, but the reason ours is special is because the format they arrived in has remained almost untouched. They were inserted loose into volumes of simple quarter leather case style binding with plain cloth sides. Interestingly though they are sewn on three vellum supports which are still good even if the leather and sewing is not.

NHD 52

CC by NHD 52 - Simple quarter leather case style binding with plain cloth sides

This housing has done a marvellous job of protecting these vivid and exotic watercolours. The vibrancy of the colours has been preserved by lack of light exposure, and the paper is in fine condition. Many of the drawings had little Chinese character labels attached with pins, none of which have been lost, or caused damage to the paper!

NHD53

CC by Detail of NHD 53 item 8, example of pins used to attach small labels to many of the watercolours.

In the following image, you can see a close up of the green pigment used to paint many of the leaves of the botanical specimens.

NHD 54 detail

CC by NHD 54 - Detail of typical damage seen in green pigment areas

As you can see, the pigment layer has cracked and is erupting into a tent shape along those cracks. So why is this happening to the green when all the other colours are happily bonded to the paper? As you can see from the shiny appearance of the leaf, it appears to have been varnished. This was done with a number of the watercolours to deepen the green of the leaves and to recreate their smooth, waxy texture. Such a beautiful effect has had unfortunate consequences, creating a rigid glassy surface, which is unforgiving if the paper substrate is flexed or expands in humid environments, leading to detachment and cracking of the pigment layer.

So what next? Consolidation of pigments is one of the most challenging treatments carried out by conservators. It is usually done through a microscope because the flakes tend to be extremely small, and it is crucial to choose the right consolidant for the materials involved. Several factors must be considered. Is there a risk that the consolidant will alter the surface appearance? What viscosity does it need to be to be effective? What long term impact will it have on the collection item? After considering all these factors we chose a traditional Japanese adhesive obtained from algae, called JunFunori.

Another reaction that has occurred during the lifetime of these items is the transformation of the white pigment, lead white (basic lead carbonate), to lead sulphide. This chemical reaction occurs in the presence of pollutants such as hydrogen sulphide and sulphur dioxide, and results in greying of the white areas. The petals that you see in the image below are tipped with that grey hue, which is the colour of lead sulphide.

NHD 54 Item28

CC by NHD 54 item 28 - An example of ‘blackened’ lead white, a pigment which turns into lead sulphide in the presence of pollutants

There are ways that the conservator can counteract this often unsightly reaction, but it is not a decision taken lightly. The treatment, which involves the use of ethereal hydrogen peroxide, does not turn the compound back into its original state. It changes it, once again, into lead sulphate, a more stable compound.

So the dilemma for the conservator is to balance their duty to preserve the aesthetic value of an object as well as the integrity of the materials that it is formed of. Each case must be considered on an individual basis, and at the Library we have yet to be presented with an item whose criteria justifies this particular treatment. So, these drawings will keep their funny little grey patches as evidence of the materials their creators chose.

NHD 53

CC by The finished article! NHD 53 item 1 in its volume after conservation

This beautiful collection is a prime example of how important it is for conservators to treat these heritage items with a light hand; retaining material in the format it comes to us wherever possible. This involves difficult decisions, and almost every project presents its own dilemmas. And that’s exactly why we do it!

Joanna Blackburn, Patricia Tena and Royston Haward

16 February 2014

Sea Snails and Purple Parchment

Add comment Comments (0)

Purple coloured pages of vellum are sometimes found in sacred texts adorned in gold or silver lettering. They can be seen in folios 2-5 of the recently digitised Cotton Titus C XV on the British Library's Digitised Manuscripts website. Fragments of the Codex Purpureus Petrolpolitanus (a 6th century copy of the Four Gospels in Greek) demonstrate the use of purple as an indicator of wealth, power and kingship. Purple parchment was once only used for Roman or Byzantine Emperors, but later found use in Anglo-Saxon illuminated manuscripts for the Emperors in Carolingian art and Ottonian art. The discovery of shell fragments in archaeological sites in Scotland and Ireland has pointed to the harvesting of sea snails for a gland which produces the purple colour. 

Purple parchment

CC zero Fragment of the Codex Purpureus Petropolitanus, 6th century, Cotton MS Titus C XV, f. 4v. Read more about this codex on the BL Medieval blog: A Papyrus Puzzle and Some Purple Parchment

In 1992 marine shell remains were recovered from caves in Sutherland County in Scotland. Archaeologists used sieves to isolate shells of the whelk known scientifically as Buccinum undatum. These whelks survive in shallow water (down to about 100m) and are found in sand and mud. Their usual capture occurs using baskets or baited pots. The fragmented state of the shells dispersed around the site suggested that they had been purposely collected and broken.

Buccinum undatum

CC by The sea snail Buccinum undatum

Another type of whelk mollusc, known as Nucella lapillus (dogwhelk or Purpura lapillus) was found at the Scottish site in Wetweather Cave. Nucella lapillus are found in crevices around rocky shores and estuarine conditions. They are a species of predatory sea snail found around the coasts of Europe and in the north west Atlantic coast of North America where they feed on barnacles and mussels. The deliberately broken shells indicated to researchers that the whelks, which are not edible and were not being used as fishing bait, were being gathered for the production of purple dye.

Nucella lapillus

CC by Nucella lapillus feeding on barnacles

Nucella lapillus was also found in Connemara in the West of Ireland in 1919 by J. Wilfred Jackson. Heaps of shells (referred to as Purpura-mounds) had previously been found in 1895, but Jackson noted that the shells had deliberately broken apical whorls (a whorl being a turn of the whelk's spiral shell), but the lower whorl with the mouth had been left intact. The shells were smashed in such a way as to retain the cumella allowing the beast to be removed easily. It was clearly a serious business with one of the Irish Purpura-mounds measuring about 50 by 14 m  - over 200 whelks were found in a single square foot!

The dye is comprised of a mucous secretion from the sea snail's hypobranchial gland and is an organic compound of bromine. The secreted fluid is released by the sea snail as a defence mechanism when agitated. The secretion can be collected by "milking" the sea snails, however this is a very labour intensive process and more often than not the snails are crushed instead. It can take thousands of snails to produce a single gram of pure dye. After salting, boiling and sitting for a few days the gland fluid begins to turn from a pale cream to a purple colour. This process is accelerated by sun exposure. After about 10 days the dye is ready for use.

Wulfila bibel

CC zero A purple parchment page of the 6th century Codex Argenteus with gold and silver lettering

Christina Duffy  (@DuffyChristina)

Further reading

Pollard, Tony (2005) 'The excavation of four caves in the Geodha Smoo near Durness, Sutherland'. Scottish Archaeology Internet Report 18

Jackson, J.W. (1917) 'Shells as Evidence of the Migrations of Early Culture'

Henderson, George, Vision and Image in Early Christian England, Cambridge University Press, 1999, paperback edition 2010, Chapter 3, pp.122-135, 'The Colour Purple: A Late Antique Phenomenon and its Anglo-Saxon Reflexes'.

10 February 2014

The Colour Red

Add comment Comments (0)

The colour red has long been associated with seduction, sexuality and love. It is the colour we use to symbolise the heart, and the colour most in our minds on Valentine's week. Take a moment out from the important work of colouring in your Valentine's cards with red crayons to appreciate the colour itself. Forget about wooing with poems - what could be more romantic than sharing some facts about the colour red?

MS 35166

CC zero February 14th: The apocalypse is coming. Surprise your loved ones with a beautiful bunch of hand-picked flames. Additional MS 35166 f. 8v

Pigments and dyes are colourants which have been used throughout history on wall murals, ceilings, paintings, illuminated manuscripts and textile materials. The difference between pigments and dyes is that pigments are insoluble (resulting in a suspension), while a dye is either itself a liquid, or is soluble (resulting in a solution). 

Red ochre

The colour of red ochre comes from the mineral hematite, or iron ore. Red ochre has been found in prehistoric cave paintings and is believed to be the first pigment used by man.

Altamira Bison

CC zero Red ochre used on a painting of a bison in the cave of Altamira, Spain, dating between 15,000 and 16,500 BC

Vermilion

The colour of vermilion comes from the mineral cinnabar which is the ore of mercury. It was used in Roman times and sourced from mines in Almadén in Spain. Due to the highly toxic nature of mercury, many of the miners (who were usually prisoners or slaves) died from poisoning. Vermilion pigment has been found on wall murals in Pompeii and on Chinese lacquerware dating to the beginning of the Song Dynasty.

Vermilion

CC by Vermilion pigment made from cinnabar

Madder red

Madder red comes from the roots of Rubia tinctorum, a yellow greenish flower. This dye was the most common red dye used until the nineteenth century. The first synthetic red dye, called alizarin, was created by German chemists in 1868 to duplicate the red colour of the madder plant.

Alizarin

CC zero The relative cheap production and long-lasting nature of Alizarin meant dyes from the madder plant significantly declined in production

Red lead

Red lead, or minium, (chemically known as lead tetroxide) has been used since the ancient Greeks. It was prepared by the Romans by roasting lead white pigment. Its use was common and is observed on some illuminated manuscripts at the British Library.

Red lead

CC by Red lead is found on initials in some gospel manuscripts to heighten the significance of the text. Image attribution: BXXXD at the German language Wikipedia

Lake pigments

Lake pigments are pigments manufactured from a dye by precipitating the soluble dye with an inert binder, usually a metallic salt. Red lac (red lake, crimson lake, carmine lake) is a lake pigment used widely in Renaissance and Baroque art. A red sinuous substance secreted by scale insects, called gum lac, was used to make red lac. Carmine lake is made from crushed cochineal insects. This anthropod feeds on the sap of live oak trees and is native to Mexico and South America. Red lake pigments were translucent, and so thin layers had to be built up on paintings. Due to their organic dye composition, lake pigments become unstable and faded when exposed to sunlight.

The Vendramin Family

CC zero Red lac used by artist Titian, oil on canvas 1540-1545: The Vendramin Family Venerating a Relic of the True Cross

Rubrication

We see many examples of the colour red in manuscripts at the British Library. During the times of medieval manuscript production scribes known as rubricators (from the Latin rubric “to colour red”) were responsible for enhancing manuscripts already laid out and written by another scribe. Rubricators would add titles, chapter headings or instructions not strictly part of the text, but as an aid to separate out components. These additions were known as rubics which can also refer to the red ink or pigment used. Notes in the margins are often seen on manuscripts instructing rubricators where to add the red text.

Harley MS 2367

CC zero Rubrication in BL Harley MS 2367, f. 70v

Harley MS2893

CC zero Rubrication in BL Harley MS 2893, f. 93v

There will undoubtedly be many amateur rubricators in action this week. Take some inspiration from the professionals by perusing the Digitised Manuscripts website.

Christina Duffy (@DuffyChristina)

03 February 2014

I’ve got tone, halftone: under the microscope with a printing block

Add comment Comments (0)

As an Imaging Scientist it is very difficult to look at ordinary objects without wondering what they would look like under a microscope. This was just the case when shown a beautiful printing block with a portrait of Steve Fairbairn, founder of the Head of the River Race, etched on the front. Printing blocks like these were used alongside similar-sized blocks containing type in a printing press to commercially produce images and text for publications. But how does it work?

Printing block of Steve Fairbairn Printing block of Steve Fairbairn
CC by The Fairbairn printing block, belonging to Pauline Churcher of Thames Rowing Club, consists of type metal (lead, tin and some antimony) with a copper electrolytic layer attached with steel screws to a 21 mm thick wooden block

The traditional printing method of letterpress is capable of printing solid colour from printing plates. In order to convey an image with varying shades and tones using a single colour, a reprographic technique called halftone is used. Halftone simulates continuous tone through the use of dots of various sizes, shape and spacing. The image is broken up into many small solid areas for printing. This gives the illusion of a continuous tone – but if we look up-close, we can see that the image is just an intricate pattern of dots.

Halftoning
CC zero A series of dots of various sizes creates an optical illusion of continuous tone when viewed from a distance

This pattern is created using a printing block with tiny holes etched into a metal plate where ink can sit and be transferred onto paper. Below we see what the Fairbairn printing block looks like at 20x, 50x and 200x magnification.

20x magnification

50x magnification

200x magnification

CC by Increasing magnification of halftone detail on the printing block (top 20x, centre 50x, bottom 200x). Ink is brushed over the plate and fills the hollows

Before the inception of halftone printing, images were printed in books and periodicals using hand engraved metal plates or wood blocks. Wood engraving involves working an image or group of images into a block of wood for use as a printmaking and letterpress technique. Ink is applied to the face of the block and paper is pressed against it.

In ordinary engraving such as etching, a metal plate is used and is printed by the intaglio method where the ink fills the removed areas. When the excess ink is wiped away a sheet of paper is placed on top of the plate, and a blanket covers both to ensure even pressure when pressing. The paper is pushed onto the ink creating an image.

The idea of halftone printing is attributed to William Fox Talbot in the late 1850’s. There were many different methods to produce the halftoning effect, and the earliest trials involved directly etching the images formed on Daguerreotype metal plates. However, the time and skill required to perform such an etching, the inability to print images next to type, and the quick to wear out fragile plates, meant that the process was impractical for commercial publishing. The turning point came in 1881 when Frederic Ives patented a commercial halftone method in the United States.

Frederic Ives

CC zero Frederic Eugene Ives inserting a Kromogram into his Kromskop, circa 1899

Ives wanted to find a process to convert photographs into small black or white lines or dots, and to use a printing block which could be used alongside text blocks in an ordinary printing press. The lines and dots could vary in size, but had to be small enough that from a normal viewing distance they blended together giving the illusion of shades. 

The “Ives’ process” was gradually refined and photographs were rephotographed directly onto a metal plate coated with photoresist (a light sensitive material). The popularity of the process spread quickly and by the 1890’s it was used widely replacing earlier hand-engraved wood block and steel plate illustrations. This was the standard process for photographically illustrating books for the next eighty years.

A 3D rendering and colour scale display of the Fairbairn printing block shows that the depth of the stippling is about 86 microns.

3D view at 200x magnification

Colour scale display at 200x magnification

CC by 3D visualiation of the halftone printing block. The dots are typically 86 microns in depth

Electrolytic copper layer

Type metal (or hot metal) is the metal alloy used in typefounding and hot metal typesetting. It consists of mostly lead with some tin and antimony. The type metal in this block has a copper electrolytic layer and is screwed onto a wooden block. The electrolytic layer is very thin and can be scratched easily revealing the type metal underneath.

Electrolytic layer scratches at 100x

Loss of electrolytic layer at 200x

CC by The copper electrolytic layer is easily scratched. Areas of damage where the copper electrolytic layer has been lost reveal the type metal (lead with some tin and antimony) underneath

The printing block is backed with a paper sheet and ink stains pervade both the backing sheet and the wood block giving a wonderful insight into the history of the item. We often forget that collectibles which today gather dust were heavily used at some point in their lives.

Microscopy of wood block

Block profile at 50x magnification

CC by Profile of the printing block under the microscope showing printer’s ink residue and paper backing

Halftones are considered to be what is known as a photomechanical or process print. Other photomechanical prints include line blocks, photogravures, photolithographs and collotypes. Digital halftoning replaced photographic halftoning in the 1970’s and the theory forms the basis for how the CMYK colour space works using dots of cyan, magenta, yellow and black. You can read more about CMYK in a previous @BL_CollCare post: What the CMYK? Colour spaces and printing.

The printing block in this article depicts Steve Fairbairn (1862-1938) and was kindly loaned by Pauline Churcher of Thames Rowing Club. The Head of the River Race is a 6.8 km processional rowing race held on the Thames each year from Chiswick to Putney with the tide. It was founded in 1926 by Steve Fairbairn who dedicated his life to the sport by both competing and coaching to high levels. The race began with 23 entries and today boats well over 400 crews. The coveted prize is a bronze cast bust of Steve Fairbairn - which is the image observed in the printing block.

Christina Duffy (@DuffyChristina), Imaging Scientist