Ink is a

gel A gel is a semi-solid that can have properties ranging from soft and weak to hard and tough. Gels are defined as a substantially dilute cross-linked system, which exhibits no flow when in the steady-state, although the liquid phase may still dif ...

, sol, or solution that contains at least one

colorant A colourant/colour additive (British spelling) or colorant/color additive (American spelling) is a substance that is added or applied in order to change the colour of a material or surface. Colourants can be used for many purposes including printing ...

, such as a dye or

pigment A pigment is a colored material that is completely or nearly insoluble in water. In contrast, dyes are typically soluble, at least at some stage in their use. Generally dyes are often organic compounds whereas pigments are often inorganic compou ...

, and is used to color a surface to produce an image,

text Text may refer to: Written word * Text (literary theory), any object that can be read, including: **Religious text, a writing that a religious tradition considers to be sacred **Text, a verse or passage from scripture used in expository preachin ...

, or

design A design is a plan or specification for the construction of an object or system or for the implementation of an activity or process or the result of that plan or specification in the form of a prototype, product, or process. The verb ''to design' ...

. Ink is used for drawing or

writing Writing is a medium of human communication which involves the representation of a language through a system of physically inscribed, mechanically transferred, or digitally represented symbols. Writing systems do not themselves constitute h ...

with a

pen A pen is a common writing instrument that applies ink to a surface, usually paper, for writing or drawing. Early pens such as reed pens, quill pens, dip pens and ruling pens held a small amount of ink on a nib or in a small void or cavity wh ...

, brush,

reed pen A reed pen ( grc-gre, κάλαμοι '; singular ') is a writing implement made by cutting and shaping a single reed straw or length of bamboo. History and manufacture Reed pens with regular features such as a split nib have been found in Anci ...

, or

quill A quill is a writing tool made from a moulted flight feather (preferably a primary wing-feather) of a large bird. Quills were used for writing with ink before the invention of the dip pen, the metal- nibbed pen, the fountain pen, and, eventual ...

. Thicker inks, in paste form, are used extensively in

letterpress Letterpress printing is a technique of relief printing. Using a printing press, the process allows many copies to be produced by repeated direct impression of an inked, raised surface against sheets or a continuous roll of paper. A worker com ...

and

lithographic Lithography () is a planographic method of printing originally based on the immiscibility of oil and water. The printing is from a stone (lithographic limestone) or a metal plate with a smooth surface. It was invented in 1796 by the German a ...

printing Printing is a process for mass reproducing text and images using a master form or template. The earliest non-paper products involving printing include cylinder seals and objects such as the Cyrus Cylinder and the Cylinders of Nabonidus. The ...

. Ink can be a complex medium, composed of

solvent A solvent (s) (from the Latin '' solvō'', "loosen, untie, solve") is a substance that dissolves a solute, resulting in a solution. A solvent is usually a liquid but can also be a solid, a gas, or a supercritical fluid. Water is a solvent for ...

s, pigments, dyes,

resin In polymer chemistry and materials science, resin is a solid or highly viscous substance of plant or synthetic origin that is typically convertible into polymers. Resins are usually mixtures of organic compounds. This article focuses on n ...

s, lubricants, solubilizers, surfactants, particulate matter, fluorescents, and other materials. The components of inks serve many purposes; the ink's carrier, colorants, and other additives affect the flow and thickness of the ink and its dry appearance. In 2011, worldwide consumption of printing inks generated revenues of more than 20 billion US dollars. While demand by traditional print media (including newspapers) is shrinking; more and more printing inks are consumed for packaging.

History

Many ancient cultures around the world have independently discovered and formulated inks for the purposes of writing and drawing. The knowledge of the inks, their recipes and the techniques for their production comes from archaeological analysis or from written text itself. The earliest inks from all civilizations are believed to have been made with ''

lampblack Carbon black (subtypes are acetylene black, channel black, furnace black, lamp black and thermal black) is a material produced by the incomplete combustion of coal and coal tar, vegetable matter, or petroleum products, including fuel oil, fluid ...

'', a kind of

soot Soot ( ) is a mass of impure carbon particles resulting from the incomplete combustion of hydrocarbons. It is more properly restricted to the product of the gas-phase combustion process but is commonly extended to include the residual pyrolysed ...

, as this would have been easily collected as a by-product of fire. Ink was used in Ancient Egypt for writing and drawing on

papyrus Papyrus ( ) is a material similar to thick paper that was used in ancient times as a writing surface. It was made from the pith of the papyrus plant, '' Cyperus papyrus'', a wetland sedge. ''Papyrus'' (plural: ''papyri'') can also refer to a ...

from at least the 26th century BC. Egyptian red and black inks included

iron Iron () is a chemical element with Symbol (chemistry), symbol Fe (from la, Wikt:ferrum, ferrum) and atomic number 26. It is a metal that belongs to the first transition series and group 8 element, group 8 of the periodic table. It is, Abundanc ...

and

ocher Ochre ( ; , ), or ocher in American English, is a natural clay earth pigment, a mixture of ferric oxide and varying amounts of clay and sand. It ranges in colour from yellow to deep orange or brown. It is also the name of the colours produced ...

as a pigment, in addition to

phosphate In chemistry, a phosphate is an anion, salt, functional group or ester derived from a phosphoric acid. It most commonly means orthophosphate, a derivative of orthophosphoric acid . The phosphate or orthophosphate ion is derived from phosph ...

sulfate The sulfate or sulphate ion is a polyatomic anion with the empirical formula . Salts, acid derivatives, and peroxides of sulfate are widely used in industry. Sulfates occur widely in everyday life. Sulfates are salts of sulfuric acid and many ...

chloride The chloride ion is the anion (negatively charged ion) Cl−. It is formed when the element chlorine (a halogen) gains an electron or when a compound such as hydrogen chloride is dissolved in water or other polar solvents. Chloride sa ...

, and

carboxylate In organic chemistry, a carboxylate is the conjugate base of a carboxylic acid, (or ). It is an ion with negative charge. Carboxylate salts are salts that have the general formula , where M is a metal and ''n'' is 1, 2,...; ''carboxylat ...

ions; meanwhile,

lead Lead is a chemical element with the symbol Pb (from the Latin ) and atomic number 82. It is a heavy metal that is denser than most common materials. Lead is soft and malleable, and also has a relatively low melting point. When freshly cu ...

was used as a drier. Chinese inks may go back as far as four millennia, to the Chinese Neolithic Period. These used plants, animal, and mineral inks based on such materials as

graphite Graphite () is a crystalline form of the element carbon. It consists of stacked layers of graphene. Graphite occurs naturally and is the most stable form of carbon under standard conditions. Synthetic and natural graphite are consumed on lar ...

that were ground with water and applied with

ink brush Ink is a gel, sol, or solution that contains at least one colorant, such as a dye or pigment, and is used to color a surface to produce an image, text, or design. Ink is used for drawing or writing with a pen, brush, reed pen, or quill. ...

es. Direct evidence for the earliest Chinese inks, similar to modern

inkstick Inksticks () or ink cakes are a type of solid Chinese ink used traditionally in several Chinese and East Asian art forms such as calligraphy and brush painting. Inksticks are made mainly of soot and animal glue, sometimes with incense or medici ...

s, is around 256 BC in the end of the

Warring States period The Warring States period () was an era in ancient Chinese history characterized by warfare, as well as bureaucratic and military reforms and consolidation. It followed the Spring and Autumn period and concluded with the Qin wars of conquest ...

and produced from soot and

animal glue Animal glue is an adhesive that is created by prolonged boiling of animal connective tissue in a process called rendering. In addition to being used as an adhesive it is used for coating and sizing, in decorative composition ornaments, and as a ...

. The best inks for drawing or painting on paper or silk are produced from the resin of the pine tree. They must be between 50 and 100 years old. The Chinese inkstick is produced with a fish glue, whereas Japanese glue (膠 ''nikawa'') is from cow or stag. India ink was invented in China,Smith, Joseph A. (1992). ''The Pen and Ink Book: Materials and Techniques for Today's Artist''.p. 23. New York: Watson-Guptill Publications. . though materials were often traded from India, hence the name.Gottsegen, Mark D. (2006). ''The Painter's Handbook: A Complete Reference''.Page 30, New York: Watson-Guptill Publications. . The traditional Chinese method of making the ink was to grind a mixture of hide glue,

carbon black Carbon black (subtypes are acetylene black, channel black, furnace black, lamp black and thermal black) is a material produced by the incomplete combustion of coal and coal tar, vegetable matter, or petroleum products, including fuel oil, fluid ...

, lampblack, and bone black pigment with a

pestle and mortar Mortar and pestle is a set of two simple tools used from the Stone Age to the present day to prepare ingredients or substances by crushing and grinding them into a fine paste or powder in the kitchen, laboratory, and pharmacy. The ''mortar'' ( ...

, then pour it into a ceramic dish to dry. To use the dry mixture, a wet brush would be applied until it reliquified. The manufacture of India ink was well-established by the

Cao Wei Wei ( Hanzi: 魏; pinyin: ''Wèi'' < Middle Chinese: *''ŋjwei^C'' <

Kharosthi with ink have been unearthed in

Chinese Turkestan Xinjiang, SASM/GNC: ''Xinjang''; zh, c=, p=Xīnjiāng; formerly romanized as Sinkiang (, ), officially the Xinjiang Uygur Autonomous Region (XUAR), is an autonomous region of the People's Republic of China (PRC), located in the northwest ...

. The practice of writing with ink and a sharp pointed needle was common in early South India. Several

Buddhist Buddhism ( , ), also known as Buddha Dharma and Dharmavinaya (), is an Indian religion or philosophical tradition based on teachings attributed to the Buddha. It originated in northern India as a -movement in the 5th century BCE, and ...

and Jain sutras in India were compiled in ink. In

ancient Rome In modern historiography, ancient Rome refers to Roman civilisation from the founding of the city of Rome in the 8th century BC to the collapse of the Western Roman Empire in the 5th century AD. It encompasses the Roman Kingdom (753–509 BC ...

, atramentum was used; in an article for the ''

Christian Science Monitor Christians () are people who follow or adhere to Christianity, a monotheistic Abrahamic religion based on the life and teachings of Jesus Christ. The words ''Christ'' and ''Christian'' derive from the Koine Greek title ''Christós'' (Χρισ ...

'', Sharon J. Huntington describes these other historical inks: Oak galls and iron(II) sulfate - California State Archives

About 1,600 years ago, a popular ink recipe was created. The recipe was used for centuries. Iron salts, such as ferrous sulfate (made by treating iron with sulfuric acid), were mixed with tannin from gallnuts (they grow on trees) and a thickener. When first put to paper, this ink is bluish-black. Over time it fades to a dull brown.

Scribes in
medieval In the history of Europe, the Middle Ages or medieval period lasted approximately from the late 5th to the late 15th centuries, similar to the post-classical period of global history. It began with the fall of the Western Roman Empire ...
Europe (about AD 800 to 1500) wrote principally on
parchment Parchment is a writing material made from specially prepared untanned skins of animals—primarily sheep, calves, and goats. It has been used as a writing medium for over two millennia. Vellum is a finer quality parchment made from the skins o ...
or
vellum Vellum is prepared animal skin or membrane, typically used as writing material. Parchment is another term for this material, from which vellum is sometimes distinguished, when it is made from calfskin, as opposed to that made from other anima ...
. One 12th century ink recipe called for hawthorn branches to be cut in the spring and left to dry. Then the bark was pounded from the branches and soaked in water for eight days. The water was boiled until it thickened and turned black. Wine was added during boiling. The ink was poured into special bags and hung in the sun. Once dried, the mixture was mixed with wine and iron salt over a fire to make the final ink.

The reservoir pen, which may have been the first

fountain pen A fountain pen is a writing instrument which uses a metal nib to apply a water-based ink to paper. It is distinguished from earlier dip pens by using an internal reservoir to hold ink, eliminating the need to repeatedly dip the pen in an in ...

, dates back to 953, when Ma'ād al-Mu'izz, the

caliph A caliphate or khilāfah ( ar, خِلَافَة, ) is an institution or public office under the leadership of an Islamic steward with the title of caliph (; ar, خَلِيفَة , ), a person considered a political-religious successor to th ...

of Egypt, demanded a pen that would not stain his hands or clothes, and was provided with a pen that held ink in a reservoir. In the 15th century, a new type of ink had to be developed in Europe for the

printing press A printing press is a mechanical device for applying pressure to an inked surface resting upon a print medium (such as paper or cloth), thereby transferring the ink. It marked a dramatic improvement on earlier printing methods in which the ...

by Johannes Gutenberg. According to Martyn Lyons in his book ''Books: A Living History'', Gutenberg's dye was indelible, oil-based, and made from the soot of lamps (lamp-black) mixed with varnish and egg white. Two types of ink were prevalent at the time: the Greek and Roman writing ink (soot, glue, and water) and the 12th century variety composed of ferrous sulfate, gall, gum, and water. Neither of these handwriting inks could adhere to printing surfaces without creating blurs. Eventually an oily, varnish-like ink made of soot,

turpentine Turpentine (which is also called spirit of turpentine, oil of turpentine, terebenthene, terebinthine and (colloquially) turps) is a fluid obtained by the distillation of resin harvested from living trees, mainly pines. Mainly used as a spec ...

, and walnut oil was created specifically for the printing press.

Types

Ink formulas vary, but commonly involve two components: * Colorants * Vehicles (binders) Inks generally fall into four classes: * Aqueous * Liquid * Paste * Powder

Colorants

Pigments

Pigment inks are used more frequently than dyes because they are more color-fast, but they are also more expensive, less consistent in color, and have less of a color range than dyes. Pigments are solid, opaque particles suspended in ink to provide color. Pigment molecules typically link together in

crystal A crystal or crystalline solid is a solid material whose constituents (such as atoms, molecules, or ions) are arranged in a highly ordered microscopic structure, forming a crystal lattice that extends in all directions. In addition, macro ...

line structures that are 0.1–2 µm in size and comprise 5–30 percent of the ink volume. Qualities such as

hue In color theory, hue is one of the main properties (called color appearance parameters) of a color, defined technically in the CIECAM02 model as "the degree to which a stimulus can be described as similar to or different from stimuli that ...

saturation Saturation, saturated, unsaturation or unsaturated may refer to: Chemistry * Saturation, a property of organic compounds referring to carbon-carbon bonds **Saturated and unsaturated compounds ** Degree of unsaturation **Saturated fat or fatty aci ...

, and lightness vary depending on the source and type of pigment.

Dyes

Dye-based inks are generally much stronger than pigment-based inks and can produce much more color of a given density per unit of mass. However, because dyes are dissolved in the liquid phase, they have a tendency to soak into paper, potentially allowing the ink to bleed at the edges of an image. To circumvent this problem, dye-based inks are made with solvents that dry rapidly or are used with quick-drying methods of printing, such as blowing hot air on the fresh print. Other methods include harder paper sizing and more specialized paper coatings. The latter is particularly suited to inks used in non-industrial settings (which must conform to tighter toxicity and emission controls), such as

inkjet printer Inkjet printing is a type of computer printing that recreates a digital image by propelling droplets of ink onto paper and plastic substrates. Inkjet printers were the most commonly used type of printer in 2008, and range from small inexpensi ...

inks. Another technique involves coating the paper with a charged coating. If the dye has the opposite charge, it is attracted to and retained by this coating, while the solvent soaks into the paper.

Cellulose Cellulose is an organic compound with the formula , a polysaccharide consisting of a linear chain of several hundred to many thousands of β(1→4) linked D-glucose units. Cellulose is an important structural component of the primary cell w ...

, the wood-derived material most paper is made of, is naturally charged, and so a compound that complexes with both the dye and the paper's surface aids retention at the surface. Such a compound is commonly used in ink-jet printing inks. An additional advantage of dye-based ink systems is that the dye

molecule A molecule is a group of two or more atoms held together by attractive forces known as chemical bonds; depending on context, the term may or may not include ions which satisfy this criterion. In quantum physics, organic chemistry, and bioche ...

s can interact with other ink ingredients, potentially allowing greater benefit as compared to pigmented inks from

optical brightener Optical brighteners, optical brightening agents (OBAs), fluorescent brightening agents (FBAs), or fluorescent whitening agents (FWAs), are chemical compounds that absorb light in the ultraviolet and violet region (usually 340-370 nm) of the ...

s and color-enhancing agents designed to increase the intensity and appearance of dyes. Dye-based inks can be used for anti-counterfeit purposes and can be found in some gel inks, fountain pen inks, and inks used for paper currency. These inks react with cellulose to bring about a permanent color change.

Health and environmental aspects

There is a misconception that ink is non-toxic even if swallowed. Once ingested, ink can be hazardous to one's health. Certain inks, such as those used in digital printers, and even those found in a common pen can be harmful. Though ink does not easily cause death, repeated skin contact or ingestion can cause effects such as severe headaches, skin irritation, or nervous system damage. These effects can be caused by solvents, or by pigment ingredients such as ''p''-Anisidine, which helps create some inks' color and shine. Three main environmental issues with ink are: * Heavy metals Eisengallustinte selbstgemacht schriftbild

Eisengallustinte selbstgemacht schriftbild

* Non-renewable oils *

Volatile organic compound Volatile organic compounds (VOCs) are organic compounds that have a high vapour pressure at room temperature. High vapor pressure correlates with a low boiling point, which relates to the number of the sample's molecules in the surrounding air, a ...

s Some regulatory bodies have set standards for the amount of heavy metals in ink. There is a trend toward

vegetable oil Vegetable oils, or vegetable fats, are oils extracted from seeds or from other parts of fruits. Like animal fats, vegetable fats are ''mixtures'' of triglycerides. Soybean oil, grape seed oil, and cocoa butter are examples of seed oils, or f ...

s rather than

petroleum oil Mineral oil is any of various colorless, odorless, light mixtures of higher alkanes from a mineral source, particularly a distillate of petroleum, as distinct from usually edible vegetable oils. The name 'mineral oil' by itself is imprecise, ...

s in recent years in response to a demand for better

environmental sustainability Specific definitions of sustainability are difficult to agree on and have varied in the literature and over time. The concept of sustainability can be used to guide decisions at the global, national, and individual levels (e.g. sustainable livin ...

performance. Ink uses up non-renewable oils and metals, which has a negative impact on the environment.

Carbon

Carbon inks were commonly made from lampblack or soot and a binding agent such as

gum arabic Gum arabic, also known as gum sudani, acacia gum, Arabic gum, gum acacia, acacia, Senegal gum, Indian gum, and by other names, is a natural gum originally consisting of the hardened sap of two species of the ''Acacia'' tree, '' Senegalia se ...

. The binding agent keeps carbon particles in suspension and adhered to paper. Carbon particles do not fade over time even when bleached or when in sunlight. One benefit is that carbon ink does not harm paper. Over time, the ink is chemically stable and therefore does not threaten the paper's strength. Despite these benefits, carbon ink is not ideal for permanence and ease of preservation. Carbon ink tends to smudge in humid environments and can be washed off surfaces. The best method of preserving a document written in carbon ink is to store it in a dry environment (Barrow 1972). Recently, carbon inks made from carbon nanotubes have been successfully created. They are similar in composition to traditional inks in that they use a polymer to suspend the carbon nanotubes. These inks can be used in inkjet printers and produce electrically conductive patterns.

Iron gall (common ink)

Iron gall inks became prominent in the early 12th century; they were used for centuries and were widely thought to be the best type of ink. However, iron gall ink is corrosive and damages paper over time (Waters 1940). Items containing this ink can become brittle and the writing fades to brown. The original scores of

Johann Sebastian Bach Johann Sebastian Bach (28 July 1750) was a German composer and musician of the late Baroque period. He is known for his orchestral music such as the '' Brandenburg Concertos''; instrumental compositions such as the Cello Suites; keyboard wo ...

are threatened by the destructive properties of iron gall ink. The majority of his works are held by the German State Library, and about 25% of those are in advanced stages of decay (American Libraries 2000). The rate at which the writing fades is based on several factors, such as proportions of ink ingredients, amount deposited on the paper, and paper composition (Barrow 1972:16). Corrosion is caused by acid catalysed hydrolysis and iron(II)-catalysed oxidation of cellulose (Rouchon-Quillet 2004:389). Treatment is a controversial subject. No treatment undoes damage already caused by acidic ink. Deterioration can only be stopped or slowed. Some think it best not to treat the item at all for fear of the consequences. Others believe that non-aqueous procedures are the best solution. Yet others think an aqueous procedure may preserve items written with iron gall ink. Aqueous treatments include distilled water at different temperatures, calcium hydroxide, calcium bicarbonate, magnesium carbonate, magnesium bicarbonate, and calcium phytate. There are many possible side effects from these treatments. There can be mechanical damage, which further weakens the paper. Paper color or ink color may change, and ink may bleed. Other consequences of aqueous treatment are a change of ink texture or formation of plaque on the surface of the ink (Reibland & de Groot 1999). Iron gall inks require storage in a stable environment, because fluctuating

relative humidity Humidity is the concentration of water vapor present in the air. Water vapor, the gaseous state of water, is generally invisible to the human eye. Humidity indicates the likelihood for precipitation, dew, or fog to be present. Humidity dep ...

increases the rate that formic acid, acetic acid, and furan derivatives form in the material the ink was used on. Sulfuric acid acts as a catalyst to cellulose hydrolysis, and iron (II) sulfate acts as a catalyst to cellulose oxidation. These chemical reactions physically weaken the paper, causing brittleness.

Indelible ink

''Indelible'' means "unremovable". Some types of indelible ink have a very short shelf life because of the quickly evaporating solvents used. India, Mexico, Indonesia, Malaysia and other developing countries have used indelible ink in the form of electoral stain to prevent electoral fraud. Election ink based on

silver nitrate Silver nitrate is an inorganic compound with chemical formula . It is a versatile precursor to many other silver compounds, such as those used in photography. It is far less sensitive to light than the halides. It was once called ''lunar causti ...

was first applied in the 1962 Indian general election, after being developed at the

National Physical Laboratory of India The CSIR- National Physical Laboratory of India, situated in New Delhi, is the measurement standards laboratory of India. It maintains standards of SI units in India and calibrates the national standards of weights and measures. History of me ...

. The election commission in India has used indelible ink for many elections. Indonesia used it in its last election in Aceh. In Mali, the ink is applied to the fingernail. Indelible ink itself is not infallible as it can be used to commit electoral fraud by marking opponent party members before they have chances to cast their votes. There are also reports of "indelible" ink washing off voters' fingers in Afghanistan.Afghanistan election: 'indelible' ink washes off voters' fingers
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References

Sources

* Ainsworth, Mitchell, C., "Inks and Their Composition and Manufacture," Charles Griffin and Company Ltd, 1904. * * Banerji, Sures Chandra (1989). ''A Companion to Sanskrit Literature''. Motilal Banarsidass. . * * Martín-Gil J., Ramos-Sánchez MC, Martín-Gil FJ and José-Yacamán M. "Chemical composition of a fountain pen ink". ''Journal of Chemical Education'', 2006, 83, 1476–78. * * * Sircar, D. C. (1996).''Indian epigraphy''. Motilal Banarsidass. . *

External links

Forty Centuries of Ink (David N. Carvalho); A detailed online textbook

* ttp://www.djmcadam.com/ink-recipe.html Ancient and Modern Ink Recipes (David N. Carvalho)
Gorgeous Portrayal Of How Ink Is Made
– video at ''

The Huffington Post ''HuffPost'' (formerly ''The Huffington Post'' until 2017 and sometimes abbreviated ''HuffPo'') is an American progressive news website, with localized and international editions. The site offers news, satire, blogs, and original content, and ...

''
"A Light Note on the Science of Writing and Inks"
is a manuscript, in Arabic, from 1852. It discusses the process of making inks. {{Authority control Printing materials