The two most used black writing inks in history are carbon inks and iron 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.
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 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.
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.
