| |
|
"Words are things; and a small drop of ink,
Falling like dew upon a thought, produces
That which makes thousands, perhaps millions think."
- Lord Byron (1788-1824)
The Bible says "Go to the ant thy (you) sluggard, consider its ways and be wise…" Sometimes, in our lives we tend to ignore some small things, but when you really think, those small things turn out to be really big. When we appreciate the invention of paper, printing press, digital technology etc. we tend to forget the importance of ink which helps us to have those multi colored literatures.
The history of ink also bears the same destiny of oblivion. Very less is written about the history of ink. The reasons identified are two: 1. the progress in ink development was very slow, with several centuries passing between improvements. 2. Most printers keep their formulations secret. A book by Sir Thomas Astle, "The Origin and Progress of Handwriting," which considers every aspect of written records puts the history of ink in just seventy lines. Interestingly ink holds back a history of more than four thousand years.
History of Ink
The origin of Ink is traced back to 2500 BC by Egyptian and Chinese cultures. The only pigment they used was the lamp black, the carbon you get while an oil lamp is lit. Between the 3rd and 5th century with the help of tree sap, lamp black, water and various gums the Chinese made minor advancements in Ink. And later reached India and through India to Europe. The ink, thus came to Europe was called "India Ink". During 14th century, European printers found the India Ink does not work well with metal plates and started using an oil, extracted from 'linseed', seed of 'flax plants'. In 15th century, Gutenberg formulated a new ink based on the older linseed oil which formula remained un-altered for the next 3 centuries. Only in 18th century world saw colored inks. (The fact that the Chinese made red pigmented ink way back around 4th century is worth mentioning). The real transformation of ink started happening from 19th century. And during this century, the proliferation of various printing technologies made compelling changes to the Ink chemistry.
What is Ink made up of?
All Inks have the following basic components
- colorants (pigments, dyes) - gives the color
- vehicles (binders) - helps to hold the ink onto the substrate
- additives - controls the drying, flowing properties and abrasion resistance
- carrier substances (solvents) - substance that carry the pigments such as mineral oil.
How it works - the science of Ink
The science of ink involves lot of physics and chemistry. The colorants, for example pigments, decide what color the ink should be. Pigments consist of molecules that are cross linked. Though a pigment particle contain millions of molecules, only around 10% of them lie on surface. These 10% molecules absorb light and give us the feeling of color.
- Types of Inks
Depending on the printing process involved, the ink varies in its properties. For example offset ink is highly viscous, where as the gravure ink is liquid.
Below are some major types of inks
- Offset Ink
- Gravure Ink
- Flexography Inks
- Letterpress Inks
- Screen Printing Inks
- Pad Printing Inks
- Ultra Violet (UV) / Electron Beam (EB) Inks
- Inks for Non-Impact Printers (Laser printers, Inkjet printers etc)
We will discuss about two types of inks now. Offset and Inks for Non-Impact Printers, as we are more familiar with these inks than the rest.
Offset Printing Ink
Offset ink is highly viscous. This is essential to make sure that the ink will not get hard while being transferred to the rollers, plate, blanket and finally onto the substrate.
The basic components of offset printing ink are
- The varnish (binding agent): This consists of hard resins, vegetable and mineral oils and various drying agents.
- Coloring Agents (Pigments): This defines the color of the ink.
- Additives: Additives hold up to 10% of ink composition. This helps drying catalysts like, cobalt, manganese etc.
Over and above, depending on the requirements of printing machine, substrate etc, the percentage of composition may vary and additional components may be added also.
Inks for Non-Impact Printers
Non-impact printing is the method of printing where in the substrate is not in direct contact with the imaging unit. Laser printers and inkjet printers works in this principle. The ink for Laser printers is called 'toner' or 'dry ink'. The toner is transferred to the substrate through an electrostatic force. The imaging drum is not directly touching the substrate. In Inkjet printing the ink is sprayed. Ink for inkjet printers are mostly water based and in liquid form.
Current trends
Towards later half of this century, the Ink industry witnessed interesting changes and evolved to become a more than $12 billion business. Now we have many types of inks. Some of those are Metallic Inks, Fluorescent Inks, High Density Inks, Security Inks, Perfumed Inks, and Vegetable Inks etc. There are tremendous developments on the non-impact printing inks also.
Major Ink Companies
Sun Chemical
Flint Ink
INX International
CR/T
DuPont
|
|
|
