Offset sheetfed printing presses would be nothing without ink. It's the reason the press exists. Good print starts with good ink that performs well in the press and in the press room and printing ink can be one of the largest indicators of overall print quality.

Inks can come in many varieties beyond just the color. Inks can come in different tack and finish. Inks can also come with different additives that can help them to dry more quickly. Ink technology in the 21st century is quite advanced and as time goes on we are sure to see very interesting inks in the future

Printing press ink is a paste style ink that is much more viscous than inks used for other applications. Printing press ink is usually of a dynamic viscosity of 40–100 Pa·s. This broad range of viscosity is a key component of the inks behavior in the printing process. Ink is loaded into a fountain which is essentially a hopper to hold the ink. From there ink is metered out into an inking system where it is very accurately controlled depending on sheet coverage. In most all printing presses coverage is controlled in vertical ink zones called stripes. Depending on the sheet size of the press there can be a large number of ink zones for an operator to control. In modern printing presses ink zones are computer controlled and can be set automatically by software that analyzes the print job. This automatic ink system, called CIP3, greatly increases productivity in the printing environment by allowing the operator to multitask while the press is setting itself up.

Ink Drying

There are multiple approaches to ink drying. Drying style is typically dependent on the application for the printed piece or the production needs of the facility producing the work. Most commonly inks are cold setting inks; which dry by means absorption into uncoated paper exposure to air without any added heat. Cold setting inks are the least expensive but can slow production as a job must have time to dry before it is handled downline.

The other family of drying style of ink is energy curable. Energy curable ink is the addition of some form of energy, light, or heat to induce accelerated or instant drying. Some forms of energy curable ink are ultraviolet inks and heat curable inks. With energy curable inks there is typically a drying section installed into the printing press. The drying section can include infra-red arrays that radiate heat into the sheets as they pass by. Ultra violet inks are instantly cured with light which allows for extremely productive operations that can take product from the press and immediately run it through other equipment.

PMS and Pantone

Inks are most commonly ordered in a set of process colors. Process colors are the four base colors used in 4 color printing presses. From these 4 colors a full color image can be printed. There are also custom colors such as Pantone and PMS colors.

PMS colors are a set of standardized colors that are organized and named by number. These inks range from light pastels to bright vivid oranges and even silver or gold. Pantone colors are another class of colors that are often used as a medium sized set of colors that can be mixed together in precise formulas to generate PMS numbered colors. PMS and Pantone colors are usually offered in two tables, coated and uncoated. These terms refer to finish of the paper which can have a drastic impact on how a color is perceived by the eye.

Ink Tack

Ink tack can be a very important factor when ordering, handling and especially when printing with the ink. Differences in ink tack bring several physical differences to the ink, but as a general rule of thumb, Ink tack can be thought of as a measure of how sticky ink is. A common measure of ink tack would be to think of having a blob of ink between your fingers and feeling them stick as you pull you fingers apart. A lower tack ink will be less sticky and a higher tack ink will feel like glue.

Ink tack can make a large difference in the printing process. The sequence in which different inks are laid onto a sheet of printer is a decision in which tack must be considered. The printing press ink must be laid in order from highest tack to lowest tack to prevent from ink transfer from unit to unit. There are also some printing presses that require low tack inks to operate normally.

Soy Inks

Due to environmental concerns and nature friendly approaches to the process of manufacturing printing press ink soy has become a common substitute for other oils. Soy inks are derived from soybean oil that is mixed with pigments, resins, and waxes. Soy inks tend to cost slightly more than traditional inks due to higher cost of raw ingredients.

Soy ink also offers some disadvantages in the press room such as longer dry times. Often this trade off is worth the benefit to our environment Any printing process that is able to operating with green mentalities and nature friendly operations should do all they can do protect our environment.