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An ink is a liquid containing various pigments and/or
dyes used for coloring a surface to produce an image or
text. Ink is used for drawing or writing with a pen or
brush or quill. Thicker inks, in paste form, are used extensively
in letterpress and lithographic
printing.
Ink is a complex medium, comprising solvents, pigments, dyes, resins, lubricants, solubilizers, particulate matter,
fluorescers, and other materials. The components of inks serve many purposes; the ink’s vehicle, colorants, and other additives
are used to control flow, thickness, and appearance of the ink when dry.
Types of ink
Line of a Fountain pen, 50-times magnified
Early varieties include Egyptian ink, various natural dyes made from metals, the husk or outer
covering of beans or seeds, and sea creatures like the squid (known as sepia). India ink is black and originated in Asia. Iron gall ink was used by many of the old
masters for drawing. Walnut ink is erroneously thought to have also been used by
old masters, however, there is no proof of this. Walnut Inks, if they were used, would have
faded fairly quickly and would be therefore be unsuitable.
Pigmented inks
Pigmented inks contain other agents that ensure adhesion of the pigment to the surface and
prevent it from being removed by mechanical abrasion. These materials are typically referred to
as resins (in solvent-based inks) or binding agents (in
water-based inks).
Pigmented inks are advantageous when printing on paper because the pigment stays on the surface of the paper. This is
desirable because more ink on the surface means that less ink needs to be used to create the same intensity of color.
Pigments are the main components of ink, containing the different colors. The size of the pigment is very important for the
ability to diffuse in the solution inks. Qualities such as hue, saturation, and brightness or lightness are inherent in the ink,
and vary dependent 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.
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 disadvantage of dye-based inks is that they can be more susceptible to fading, especially when exposed to ultraviolet radiation as in sunlight.
History of ink
Approximately 5000 years ago, an ink for blacking the raised surfaces of pictures and texts carved in stone was developed in
China. This early ink was a mixture of soot from pine smoke, lamp oil, and gelatin from animal skins and musk. Other early cultures also developed many colors of ink from available
berries, plants and minerals.
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), was 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
on sheepskin parchment. 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.
In the 15th 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 12th century variety composed
of ferrous sulfate, gall, gum, and water.[1] 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, it is rare to find a
residence or a business that does not have a printing capability. As a result, buying ink in the form of a cartridge or having that cartridge refilled at an inkjet island in a local mall 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 brands instead of refilling.
Poisonous ink
There is a misconception that ink isn't harmful even if swallowed, but this is false. Once ingested, ink can be very 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 cause death, it can cause side effects such as a damaged nervous system and severe headaches. These effects are caused
by a chemical known as p-Anisidine, used in the process of creating the ink's color and shine.
The poison control center has stated that any consumption of ink should be reported to a local hospital or poison control
center.
Writing Inks and Preservation
The two most used black writing inks in history are carbon inks and iron and gall inks. Both types create problems for
preservationists.
Carbon Inks
Carbon inks were commonly made from lampblack or soot and gum arabic. Gum arabic keeps the carbon particles in suspension and
adhered to paper. The carbon particles do not fade over time even when in sunlight or 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 the ideal ink for permanence and ease of preservation. The ink has a tendency to
smudge in humid environments and can be washed off an item. The best method of preserving documents 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.[2]
Iron Gall Inks
Iron gall inks became prominent in the early 1100's and were used for centuries and
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 bircarbonate, 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).
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 Press of Virgina, ISBN 081390408
-
Reibland, 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, p. 121-129
-
Rouchon-Quillet, V. & et al. (2004), "The Impact of
Gallic Acid on Iron Gall Ink Corrosion", Applied Physics A 79: 389-392
-
Waters, C.E. (1940), Inks, U.S. Department of Commerce, National
Bureau of Standards, U.S. Government Printing Office
Footnotes
References
- "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.
Further reading
- Cuppers, Christoph (1989). "On the Manufacture of Ink." Ancient Nepal - Journal of the Department of Archaeology,
Number 113, August-September 1989, pp. 1-7. [The Tibetan text and translation of a work called, Bzo gnas nyer mkho'i za ma
tog by 'Jam-mgon 'Ju Mi-pham-rgya-mtsho (1846-1912) describing various traditional Tibetan techniques of making inks from
different sources of soot, and from earth, puffballs, dung, ser-sha - a yellow fungus,
and the fruit of tsi dra ka (Ricinus communis).]
See also
External links
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