The ink is considered as a medium for the humans to express their inner most thoughts and desires. The most comprehensible definition of the ink is that ink is a semi-liquid material used for writing, printing or drawing. Chemists consider it as a coagulated structure of magnificent pigment particles disseminated in a solvent, and the solvent may be aqueous or organic.
If we look at the history of evolution of ink then we can observe that inks developed before 2500BC, were deferment of carbon normally lampblack, in water stabilized with a natural gum or materials like egg albumen. However the present day ink formulations are an intricate affair.
In appendage to pigments, they include various components in differing levels. Broadly known as “Vehicle” these supplementary components entail pH modifiers, humectants to decelerate untimely drying, polymeric resins to transmit binding and allied properties, defoamer or antifoaming agents to control foam effectiveness, wetting agents such as surfactants to control surface properties, biocides to hinder the fungal and bacterial extension that lead to fouling, and thickeners or rheology modifiers to regulate ink application.
The majority of the ink supply caters to printing ink in which color is promulgated by pigments rather than the dyes that are utilized in writing inks. Pigments are insoluble whereas dyes are soluble. Sometimes these terms are used reciprocally in private enterprise. Ink pigments can be divided into inorganic and organic. The red writing ink has the red dye eosin. Blue color can be acquired with triphenylmethane dyes. In case of immutable writing inks comprise of iron sulfate and gallic and tannic acids as well as dyes. Ball point ink is made of a paste which has 40 to 50 per cent dye.
White inks consists of titanium dioxide as the pigment as rutile and anatase in tetragonal crystalline form. But the increasing relevance to the known toxicity of heavy metals have caused the substitution of various inorganic pigments such as chrome yellow, molybdenum orange and cadmium red with organic pigments. This provides better light, speed and diminishing toxicity. In addition, carbon black now exchanges spinel black, rutile black and iron black in nearly all black inks. The ink industry is the second largest purchaser of carbon black.