Ink (Latin: tincta [aqua] = colored water) is an intensively colored liquid for use in quills, brushes or fountain pens. In addition to manual application in writing, calligraphy and drawing, automated inkjet processes are also of increasing importance in word processing or product labeling. Ink usually consists of a solution or dispersions of dyes in water or other solvents containing little or no binder. Inkjet ink is a special form of ink that is characterized by a very strong color and often contains a binder.
What is today's inkjet ink made of?
Ink is a mixture of water, glycols, alcohols of various additives to achieve the necessary physical values and dye or pigments for the desired color. The development is slowly moving from dye to pigment inks. These are a lot more UV and water resistant, but not quite as high quality in the frabbrillanz.
History of ink:
Ink was used in Egypt as early as 3000 BC, and in China around 2600 BC. Ordinary black ink was made from soot and gum water (gummi arabicum) for a long time and was not replaced by India ink (so-called Indian ink) until around 1000 BC in the Far East. This was made from the soot of burnt coniferous charcoal and lamp oil and, mixed with a glue made from gelatin, pressed into sticks and dried. When in use, the ink stick was rubbed with water until the desired opacity was achieved, a method that has survived in calligraphy to this day.
An important invention in the 3rd century BC was the production of iron gall ink by boiling gall apples with iron sulfate and then adding gum water. Iron gall ink is considered particularly durable and is still used today as a document-proof ink.
Cicero first reported a recipe in which the ink bladders of squid were dried and ground. The resulting brown-black dye is called sepia after their generic name and is used today to color food. However, the actual use of a sepia ink is not confirmed until 1780.
In the Middle Ages, several formulations were developed with pigments of different colors. For example, arsenic(III) sulfide reacted with mercury was used to obtain a gold-colored pigment. The spread of quills later also led to the development of briar ink, which did not dry up as quickly as iron gall ink and therefore clogged the quill less frequently. However, the latter remained the most commonly used formulation, especially for long-term documentation and in archives.
A typical ink of the 15th to 18th centuries is also bister.
With the development of modern chemistry in the 19th century, a wide variety of dyes were discovered and, where possible, used for writing and painting. However, since water-soluble dyes often have low lightfastness and are also easily washed out, guidelines soon emerged for the composition of inks used to create permanent documents. In 1856, for example, a recipe was published for the first time for an iron gall ink whose components became water-insoluble only after drying, and which contained an artificial, water-soluble dye so that the lines were visible even before they dried.
Today, a wide range of inks is available for various applications. The invention of automated systems such as the inkjet printer also created the need for inks that combine special properties such as free mixability (to produce different shades) and extremely fast drying times.
For most printers, remanufactured cartridges, refill inks or refilled original cartridges are available. Due to the large price difference between original and refill cartridges, printer manufacturers often take legal action (patent law) or marketing measures against the sometimes well-known secondary manufacturers and refillers to secure their sales.
A distinction is made between piezo and thermoactive inks.
Colorfulness of inks:
The color of an ink depends on the type of dye used. Virtually any soluble or insoluble dye can be used in modern inks. While pigments have a characteristic inherent coloration, the color of a dissolved dye or complex may also depend on the solvent used. Some common dyes are summarized below:
* For writing, blue triarylmethane dyes (often derived from resorcinol) such as Helvetia Blue or Water Blue, which have good water solubility, are commonly used.
- For red inks, the dye eosin can be used.
- A green coloration is obtained via acid indigotine.
- White inks with good coverage often contain the same pigments as opaque white.
- The fluorescent dyes used in highlighters are often derived from fluorescein.
- Numerous pigment dyes are also used for black inks that are intended to have good opacity.
Modern iron gall inks, for example, have a two-stage structure. In the liquid, iron(II) sulfate is present in colorless solution alongside gallate, and the dark coloration is achieved by a dark dye that is also soluble. When dried in air, the iron is then oxidized to iron(III) and the deep black colored iron(III)-gallate complex is formed. Therefore, iron gall inks have a limited shelf life after opening.
Many secret inks are based on organic acids which, when heated, accelerate the decomposition of the paper at the point described, making it the first to darken and thus become visible. Another way to make the writing visible is to react it with iodine, which oxidizes the ingredients and makes them stand out. This method is also used in forensics to treat fingerprints.
Ink-jet inks usually contain selected, low-salt and mostly lightfast dyes. In the case of black ink, the major inkjet printer manufacturers usually use a pigment (Pigment Black 7) instead of a dye. This then has excellent lightfastness, water resistance and color depth. Direct Blue 199, Acid Yellow 9, Reactive Red 180, Acid Red 52, Direct Black 19, Pigment Black 7 can also be used as colorants. The color specifications are the nomenclature from the Colour Index, an international directory of colorants.