The Chemistry of Ink

Introduction

Ink is a liquid or paste containing some kind of colorant used mostly for writing, printing and drawing. I have always loved to read and write stories, therefore I wanted to know how ink was made and how it works. Besides, I thought doing research on paper might not be that great for me.

Composition of ...

Using black ink recipe from http://chemistry.about.com/od/inksandinkchemistry/ as an example

Carbon black or lamp black pigment (mostly made up of pure carbon)
- C
egg yolk, mostly made up of carbohydrates (also called saccharides), fats (triglycerides, made of glycerol and three kinds of fatty acids), cholesterol and proteins (made up of amino acids)
- saccharide (consists of C, H, O),
- glycerol (C3H8O3)
- fatty acid (made of long chains of C, H and sometimes O)
- cholesterol (C27H46O)
- amino acid (mainly consists of C, H, O, N)
gum arabic, mostly made up of arabinogalactan, a polymer made up of two monosaccharides, arabinose and galactose
- arabinose (C5H10O5)
- C6H12O6 (galactose has same formula as fructose and glucose but different structure)
honey, made of mostly water, fructose and glucose
- H2O
- C6H12O6 (fructose and glucose have same formula but different structures)
water (added later to the recipe)

H2O

Main Chemicals, Compounds, Components

3 main chemicals used in ink

The Colorant
- This is one of the most important ingredients in ink because it is what gives the ink its color. There are two different types of colorant used in ink, which are pigments and dyes. The primary difference in these two are their solubility. For instance, pigments are insoluble in water and most solvents, whereas dyes are not. Colorants can be organic or synthetic, although in modern days ink manufacturers mostly use synthetic colorants.
The Vehicle/Varnish
- This is another important ingredient for three main reasons. First, it is used as a solvent for the dye to dissolve in or, in the case of pigments, a liquid that the pigment is suspended in evenly. Second, it helps the ink to transfer from the pen to paper. Finally, it helps bind the ink to the paper so it doesn’t easily rub off the paper. For these reasons, many vehicles/varnishes are used in making ink.
The Additive
- They are often added to give the ink characteristics that vehicles/varnishes and pigments wouldn’t give by themselves. For example, oils can give the ink certain flow and lubrication properties, waxes give the ink toughness and durability, and driers help promote rapid drying mechanisms.

Chemistry's Role

Carbon black pigment is the colorant used in this ink. The vehicles/varnishes used in this ink are water, egg yolk, and gum arabic. The water is used as a solvent to suspend the pigment while the gum arabic helps spread the pigment in the solution evenly. The water also helps the pigment to transfer to the paper and then once it has evaporated, the gum arabic binds the pigment to the paper. The egg yolk assists in all of these stages. The honey acts as an additive which, in this case, gives the ink a higher viscosity (thickness).

Background Research

Many ancient cultures have independently developed their own recipes for ink used in drawing and writing. For example, the Chinese and Japanese both created a solid ink made mostly from soot and animal glue, an adhesive made from boiling animal tendons and other parts. This solid ink was called an inkstick. In India, their ink, called ‘masi’, was made from burned bones, tar, pitch and other substances. In ancient Rome, one popular ink recipe called for two chief ingredients: iron salts, such as ferrous sulfate, and tannin from gallnuts. This recipe was appropriately called iron-gall ink. The first printing ink came out along with the invention of the printing press by Johannes Gutenberg. It was an oily, varnish-like ink made from turpentine, walnut oil, and soot created to adhere to the paper without creating blurs.

Resources

http://humantouchofchemistry.com/interesting-facts-about-ink.htm

Types of ink

Brief description of process of making ink

Hazards of ink

http://humantouchofchemistry.com/the-colourful-truth-about-dyes.htm

Definition of dyes

http://pffc-online.com/mag/782-paper-brief-chemistry-lesson

The difference between pigments and dyes

http://www.rsc.org/chemistryworld/issues/2003/march/inkchemistry.asp

More complete description on process of making ink

Description on structure of some of the ingredients of ink