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An ink is a liquid containing various pigments and/or dyes used for coloring a surface to produce an image, text, or design. Ink is used for drawing and/or writing with a pen, brush or quill. Thicker inks, in paste form, are used extensively in letterpress and lithographic printing.

Ink is a complex medium composed of solvents, pigments, dyes, resins, lubricants, solubilizers, surfactants, particulate matter, fluorescers, and other materials. The components of inks serve many purposes; the ink’s carrier, colorants, and other additives are used to control flow and thickness of the ink and its appearance when dry.

Types of ink

Components and classifications of ink vary, but can commonly be broken into four components—colorants, vehicles (binders), additives, and carrier substances—and four classes—aqueous, liquid, pasty, and powdery.^[1]

Colorants

Pigmented inks are more frequently used than dyes because they are more color-fast, but they are also more expensive, are less consistent in color, and have less of a color range than dyes.^[1]

Pigmented inks

Pigments are solid, opaque particles suspended in ink that provide color.^[1] Pigment molecules are typically linked together in crystalline structures that are 0.1–2 µm in size and comprise 5–30 percent of the ink volume.^[1]

Qualities such as hue, saturation, and lightness vary depending on the source and type of pigment.

Dyes in inks

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, thus making the ink less efficient and also potentially allowing the ink to bleed at the edges of an image, producing poor quality printing. ^[2]

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 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, the material that paper is made of, is naturally charged, and so a compound that complexes with both the dye and the paper's surface will aid retention at the surface. Such a compound in common use in ink-jet printing inks is polyvinyl pyrrolidone.

An additional advantage of dye-based ink systems is that the dye molecules interact chemically with other ink ingredients. This means that they can benefit more than pigmented ink from optical brighteners and color-enhancing agents designed to increase the intensity and appearance of dyes. Because dyes get their color from the interaction of electrons in their molecules, the way in which the electrons can move is determined by the charge and extent of electron delocalization in the other ink ingredients. The color emerges as a function of the light energy that falls on the dye. Thus, if an optical brightener or color enhancer absorbs light energy and emits it through or with the dye, the appearance changes, as the spectrum of light re-emitted to the observer changes.

A more recent development in dye-based inks are dyes that react with cellulose to permanently color the paper. Such inks are not affected by water, alcohol, and other solvents. As such, their use is recommended to prevent frauds that involve removing signatures, such as check washing. Currently this kind of ink is most often offered for use in fountain pens.

History of ink

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 history of Chinese inks can be traced back to the 12th century BC, with the utilization of natural plant (plant dyes), animal (squid ink), and mineral inks based on such materials as graphite that were ground with water and applied with ink brushes. Evidence for the earliest Chinese inks, similar to modern inksticks, is around 256 BC in the end of the Warring States Period and produced using manual labour from soot and animal glue.^[6]

The India ink used in ancient India since at least the 4th century BC was called masi which was made of burnt bones, tar, pitch, and other substances.^[3]^[7] Indian documents written in Kharosthi with ink have been unearthed in Chinese Turkestan.^[8] The practice of writing with ink and a sharp pointed needle was common in early South India.^[9] Several Jain sutras in India were compiled in ink.^[10]

In ancient Rome, atramentum was used. In an article for the Christian Science Monitor, Sharon J. Huntington describes these other historical inks:

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 Europe (about AD 800 to 1500) wrote principally on parchment or vellum. One 12^th 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 fountain pen dates back to 953, when Ma'ād al-Mu'izz, the caliph of Egypt, demanded a pen which would not stain his hands or clothes, and was provided with a pen which held ink in a reservoir and delivered it to the nib via gravity and capillary action.^[11]^[12]

In the 15^th century, a new type of ink had to be developed in Europe for the printing press by Johannes Gutenberg. Two types of ink were prevalent at the time: the Greek and Roman writing ink (soot, glue, and water) and the 12^th century variety composed of ferrous sulfate, gall, gum, and water.^[13] Neither of these handwriting inks could adhere to printing surfaces without creating blurs. Eventually an oily, varnish-like ink made of soot, turpentine, and walnut oil was created specifically for the printing press.

Modern ink applications

Up until a few years ago, consumers had very little interest in ink other than refills for their pens. Fountain pens became a novelty as the disposable ball point pen took over the market. The introduction of home computing led to home printing. Today, in developed nations, most residences and businesses have a printing capability. As a result, buying ink in the form of a printer cartridge has once again become a part of the day-to-day shopping experience, similar to buying a bottle of ink fifty years ago.

Ink refilling services for printer cartridges are offered by large, official printing companies as well as smaller, "unofficial" refill companies. Customers can often cut printing costs by using refill services from a refill company, or buying the new non-OEM (original equipment manufacturer) brands instead of refilling. The refilling of ink cartridges and the use of continuous ink supply systems for inkjet printers is very common in most countries, with the exception of the United States. As printer manufacturers control the type of competition that they allow on retail shelves to a great extent, devices to ease the use of refill inks are usually only available online.

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 printers, and even those found in a common pen can be harmful. Though ink will not easily cause death, inappropriate contact can cause effects such as severe headaches, skin irritation, or nervous system damage. These effects can be caused by solvents or by pigment constituents such as p-Anisidine, which is used in the process of creating the ink's color and shine.

Three main issues with the environmental impact of inks is the use of volatile organic compounds, heavy metals and non-renewable oils. Standards for the amount of heavy metals in ink have been set by some regulatory bodies.^[14] There is a trend toward using vegetable oils rather than petroleum oils in recent years in response to a demand for better environmental sustainability.

Writing inks and preservation

The two most used black writing inks in history are carbon inks and iron gall inks. Both types create problems for preservationists.

Carbon inks

Chinese inkstick; carbon-based and made from soot and animal glue

Carbon inks were commonly made from lampblack or soot and a binding agent such as gum arabic or animal glue. The binding agent keeps the carbon particles in suspension and adhered to paper. The carbon particles do not fade over time even when in sunlight or when bleached. One benefit of carbon ink is that it is not harmful to the paper. Over time, the ink is chemically stable and therefore does not threaten the strength of the paper. Despite these benefits, carbon ink is not ideal for permanence and ease of preservation. Carbon ink has a tendency to smudge in humid environments and can be washed off a surface. The best method of preserving a document written in carbon ink is to ensure it is stored in a dry environment (Barrow 1972). Recently, carbon inks made from carbon nanotubes have been successfully created. They are similar in composition to the 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.^[15]

Iron gall inks

Iron gall inks became prominent in the early 1100s; they were used for centuries and were widely thought to be the best type of ink. However, iron gall ink is corrosive and damages the paper it is on (Waters 1940). Items containing this ink can become brittle and the writing fades to brown. The original scores of Johann Sebastian Bach 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 "the proportions of the ink ingredients, the amount deposited on the paper, and the composition of the paper" (Barrow 1972:16). The corrosion is caused by "two major degradation processes: acid catalysed hydrolysis and iron(II)-catalysed oxidation of cellulose" (Rouchon-Quillet 2004:389).

Treatment is a controversial subject. There is no treatment that will undo the damage already caused by the acidic ink. Deterioration can only be stopped or slowed for a period of time. There are some people who 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. And then, there are some that believe an aqueous procedure may provide the answer for preserving 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 would further weaken the paper. The color of the paper or ink may change and ink may bleed. Other consequences that might arise from aqueous treatment are a change of ink texture or the formation of on the surface of the ink (Reibland & de Groot 1999).

Iron gall inks are generally stored in a stable environment, because fluctuating relative humidity increases the rate at which formic acid, acetic acid and furan derivatives form in the material on which the ink was used. 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.^[16]

Indelible ink

The word "indelible" means "cannot be removed". Some types of indelible ink have a very short shelf life because of the solvents used, which evaporate rapidly.

India, Philippines, Indonesia and other developing countries have used indelible in the form of electoral stain to prevent electoral fraud. The Election Commission in India has used indelible ink for many elections. Indonesia used it in their last election in Aceh. In Mali, the ink is applied to the fingernail.

References

^ ^a ^b ^c ^d Kipphan, Helmut (2001). Handbook of print media: technologies and production methods (Illustrated ed.). Springer. pp. 130–144. ISBN 3540673261.
^ Castle Ink: How Dye-based Inks and Pigment-Based Inks Affect Printers, 2009.
^ ^a ^b Banerji, page 673
^ Sircar, page 62
^ Sircar, page 67
^ 蔡, 玫芬, 二、墨的發展史, National Chang-Hua Hall of Social Education {{citation}}: Cite has empty unknown parameter: |unused_data= (help); Unknown parameter |　url= ignored (help)
^ "India ink." in Encyclopædia Britannica. 2008 Encyclopædia Britannica Inc.
^ Sircar, page 206
^ Sircar, page 62
^ Sircar, page 67
^ Paul Vallely, How Islamic Inventors Changed the World, The Independent, 11 March 2006.
^ Origins of the Fountain Pen, Foundation for Science Technology and Civilisation.
^ Many recipes for iron gall inks are featured in A booke of secrets: shewing diuers waies to make and prepare all sorts of inke... tr. out of Dutch into Englishe by W.P. [i.e. William Philip], London, 1596.
^ Canadian Printing Ink Manufacturers' Association
^ Simmons, Trevor (2007). "Large Area-Aligned Arrays from Direct Deposition of Single-Wall Carbon Nanotubes". J. Am. Chem. Soc. 129 (33): 10088–10089. doi:10.1021/ja073745e.
^ Henk J. Porck and René Teygeler, Preservation Science Survey (Washington, D.C.: Council on Library and Information Resources, 2000).

"Think Ink!" by Sharon J. Huntington, Christian Science Monitor, September 21, 2004, retrieved January 17, 2006.
"A History of Technology and Invention" by Maurice Audin, page 630.
Ainsworth, Mitchell, C., "Inks and Their Composition and Manufacture," Charles Griffin and Company Ltd, 1904.
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
Banerji, Sures Chandra (1989). A Companion to Sanskrit Literature. Motilal Banarsidass. ISBN 812080063X.
Sircar, D.C. (1996).Indian epigraphy. Motilal Banarsidass. ISBN 8120811666.

Sources

N.a. (March 2000), "Bach Scores Turning to Dust in German Library", American Libraries: 24–25
Barrow, W.J. (1972), Manuscripts and Documents: Their Deterioration and Restoration, Charlottesville: University of Virginia Press, ISBN 081390408 {{citation}}: Check |isbn= value: length (help)
Reiβ̞land, Birgit; de Groot, Suzan (August 15–21, 1999), "Ink Corrosion: Comparison of the Currently Used Aqueous Treatments for Paper Objects", Preprint from the 9th International Congress of IADA, pp. 121–129{{citation}}: CS1 maint: date format (link)
Rouchon-Quillet, V.; et al. (2004), "The Impact of Gallic Acid on Iron Gall Ink Corrosion", Applied Physics A, 79: 389–392, doi:10.1007/s00339-004-2541-1 {{citation}}: Explicit use of et al. in: |last2= (help)
Waters, C.E. (1940), Inks, U.S. Department of Commerce, National Bureau of Standards, United States Government Printing Office {{citation}}: Cite has empty unknown parameter: |unused_data= (help); Text "Circular C426" ignored (help)

External links

[kipphan130-144-1] Kipphan, Helmut (2001). Handbook of print media: technologies and production methods (Illustrated ed.). Springer. pp. 130–144. ISBN 3540673261.

[2] Castle Ink: How Dye-based Inks and Pigment-Based Inks Affect Printers, 2009.

[Banerji,_page_673-3] Banerji, page 673

[4] Sircar, page 62

[5] Sircar, page 67

[6] 蔡, 玫芬, 二、墨的發展史, National Chang-Hua Hall of Social Education {{citation}}: Cite has empty unknown parameter: |unused_data= (help); Unknown parameter |　url= ignored (help)

[7] "India ink." in Encyclopædia Britannica. 2008 Encyclopædia Britannica Inc.

[8] Sircar, page 206

[9] Sircar, page 62

[10] Sircar, page 67

[Vallely-11] Paul Vallely, How Islamic Inventors Changed the World, The Independent, 11 March 2006.

[12] Origins of the Fountain Pen, Foundation for Science Technology and Civilisation.

[13] Many recipes for iron gall inks are featured in A booke of secrets: shewing diuers waies to make and prepare all sorts of inke... tr. out of Dutch into Englishe by W.P. [i.e. William Philip], London, 1596.

[14] Canadian Printing Ink Manufacturers' Association

[15] Simmons, Trevor (2007). "Large Area-Aligned Arrays from Direct Deposition of Single-Wall Carbon Nanotubes". J. Am. Chem. Soc. 129 (33): 10088–10089. doi:10.1021/ja073745e.

[16] Henk J. Porck and René Teygeler, Preservation Science Survey (Washington, D.C.: Council on Library and Information Resources, 2000).

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 An additional advantage of dye-based ink systems is that the dye [[molecule]]s interact chemically with other ink ingredients. This means that they can benefit more than pigmented ink from [[optical brightener]]s and color-enhancing agents designed to increase the intensity and appearance of dyes. Because dyes get their color from the interaction of [[electron]]s in their molecules, the way in which the electrons can move is determined by the charge and extent of electron [[delocalization]] in the other ink ingredients. The color emerges as a function of the light energy that falls on the dye. Thus, if an optical brightener or color enhancer absorbs light energy and emits it through or with the dye, the appearance changes, as the spectrum of light re-emitted to the observer changes.
-A more recent development in dye-based inks are dyes that react with cellulose to permanently color the paper.  Such inks are not affected by water, alcohol, and other solvents.  As such, their use is recommended to prevent frauds that involve removing signatures, such as [[check washing]].  Currently this kind of ink is most often offered for use in [[fountain pen]]s.  The most popular manufacturer of this ink is [[Fountain pen inks#Noodler's|Noodler]]{{Citation needed|date=September 2009}}.
+A more recent development in dye-based inks are dyes that react with cellulose to permanently color the paper.  Such inks are not affected by water, alcohol, and other solvents.  As such, their use is recommended to prevent frauds that involve removing signatures, such as [[check washing]].  Currently this kind of ink is most often offered for use in [[fountain pen]]s.
 ==History of ink==