Standard Ink Types
Web Offset Non-Heatset Ink
The non-heatset variety of web offset printing ink is a common type of ink used on web presses for newspaper and business forms printing. Non-Heatset ink is printed on absorbent, uncoated paper stock. Coated stocks should not be used with this type of ink because the paper will not completely absorb the ink, resulting in excess smudging and smearing.
Web Offset Heatset Ink
The heatset variety of web offset ink contains special varnishes that help the ink dry when heat is applied. Heatset presses are equipped with drier units for this purpose. Due to the varnishes, the ink printed on the paper is highly flammable, so the drying units must be specially built and properly maintained to avoid potential hazards. The main advantage of heatset ink is a printed product with a higher degree of quality.
Quickset ink contains a special varnish to speed the drying process. Unlike heatset ink, quickset ink does not require a heat source for proper drying and curing. The ink will not dry out on the press, but will dry quickly after it has been printed onto the substrate.
The are four basic processes that allows quickset ink to dry depending on the formulation: evaporation, absorption, oxidation, and polymerization. Newer types of quickset ink have a greater proportion of antioxidants and higher boiling-point distillates, which evaporate more slowly, so the absorption process plays a greater role with the newer inks. All four processes share equally in the ink curing process with older ink types.
Uncoated paper stocks are best suited for quickset ink. This is because the low viscosity distillates and antioxidants are quickly absorbed by the substrate, which leaves the remaining pigment and vehicle to dry quickly on the surface.
Sheet-fed ink is manufactured specifically for sheet-fed presses and usually has a higher tack than web offset inks. The reason for this is that most sheet-fed presses run at slower speeds than web presses and a higher tack is necessary to provide the necessary quality.
Ink formulated with a rubber base is a good choice when flexibility in the printing process is important. Rubber-base ink can be printed on coated and uncoated paper and it dries quickly. It is most often used on small sheet-fed presses.
Soybean-base ink is becoming a popular alternative to petroleum-base ink because of the ease in which it is used and because it is environmentally friendly. Soy-base ink prints and handles similar to petroleum-base ink, but it is much less toxic because of the soybean oil. The soybean ink is biodegradable, meaning that it is eventually broken down and is much less hazardous to the environment. Some soy inks may contain petroleum additives, so if a client requires 100% soy-based ink for a print application, it is important to be fully informed on the type of soy ink that is used.
Water-base ink has been around for awhile, but it is still not as popular as other ink types. The usage of water-base ink may increase as environmental laws get tougher on the acceptable VOC (Volatile Organic Compounds) emissions generated from petroleum-base ink. Water-base ink emits no VOC's. It is safe to work with and the print quality is comparable to other ink types. Water-base ink is used mainly in flexography and gravure printing. It is a good choice for printers and customers who want their projects manufactured with nontoxic materials.
Laser ink is specially formulated to withstand the extreme heat of the laser printer. If conventional ink is used for the preprinted portion of a document (such as an invoice or statement), the ink will melt in a laser printer because of the excessive heat produced by the laser printer. This results in damage to the preprinted document and possible damage to the laser printer because of ink adhering to the internal parts of the printer.
UV (Ultraviolet) Ink
Ultraviolet ink is formulated to cure and dry when exposed to a UV light source, unlike conventional ink, which dries through evaporation and absorption. Instead of being absorbed into the paper, the UV ink remains on the surface until it is exposed to the UV rays, which instantaneously transforms the ink into a hard film. UV ink can be applied to many types of substrates including paper, metal, vinyl, and glass.
Process Ink Colors
Process ink colors are used in Four Color Process Printing. Cyan, magenta, yellow, and black are the colors necessary for this process and are formulated differently for different types of printing processes.
High-Fidelity Ink Colors
High-fidelity ink colors are use in an advanced form of color printing, combining the standard four process colors of cyan, magenta, yellow, and black, with two more colors - usually orange and green. This allows for a greater color range, increased subtlety in the gradations of color, and additional vibrancy.
Specialty Ink Types
Non-porous ink is used for printing on substrates, such as metal or plastic, that do not allow ink to be absorbed into the material. Because the printing surface of these materials is nonabsorbent, the ink dries solely through oxidation rather than absorption.
Metallic ink provides a distinctive look to a variety of print applications. The ink is produced by blending different types of metallic powders into the ink mixture, such as aluminum powder to create a silver appearance and bronze powder to create a gold appearance. Some metallic inks can nearly duplicate the look of foil on some applications without the need to purchase the additional equipment required for foil stamping.
Metallic ink is more challenging for the press operator to control than conventional ink. One reason for this is that the metallic powder blended into the ink mixture cannot be ground as fine as other pigments because the metallic ink will lose its luster. The larger particles create problems on the press, especially with the offset lithography process. To overcome some of the special print problems, some printers do a double hit (running the piece through the press a second time to apply another coat of ink to strengthen the coverage).
Most printers require an upcharge for the use of metallic ink on an application because the ink is more expensive to produce and makes the print job more time consuming. Metallic ink tends to have a much shorter shelf life than standard ink.
Magnetic ink is comprised of a petroleum-base ink blended with magnetic iron oxide particles. The magnetic iron oxide particles allow documents printed with this type of ink to be read and sorted by electronic scanning equipment. Checks are an example of a document printed with magnetic ink. The MICR (Magnetic Ink Character Recognition) number at the bottom of the check is the only portion of the check printed with the magnetic ink. The remaining copy on the check is printed with standard ink to ensure that no other printed area on the check interferes with the ability of the scanner to read the magnetic MICR number.
Fluorescent is another type of ink that can provide a distinctive look for a variety of print applications. Fluorescent ink colors are most often printed on labels, posters, and signs that are used for alerting people to hazards or attracting their attention to advertising pieces.
There are several points to consider when using fluorescent colors. The ink tends to fade quickly, so they should be kept out of direct sunlight. Because of their tendency to fade, fluorescent inks have a short shelf life. Another point to consider is that fluorescent ink is very transparent, so it may require a double hit (a second run through the press) in order to achieve the desired results. In spite of this potential problem, fluorescent ink is a good choice for creating emphasis and increased visibility.
Applications printed with phosphorescent inks acquire a "glow in the dark" property after the phosphorescent area has been exposed to light. The length of time that an application will glow in the dark depends upon the ink ingredients and the length of time that the application is exposed to light. In some cases, a 10-30 minute exposure to light can yield an afterglow of up to 12 hours. The ingredients of phosphorescent ink are nontoxic and are free of radioactive additives. It is very useful for road signs, sporting goods, exit signs, safety products, toys, and novelty items.
Pearlescent ink is a specialty ink that is used to add highlights and depth to the printed area of an application. It is able to provide an almost 3-dimensional effect to some applications.
Edible ink is used on print applications that may come into contact with food or the ink may be part of the food product and therefore it must be made of totally nontoxic ingredients. An example where edible inks are used would be in the monogramming found on some confectionery items. Because the inks are used on food items, they are strictly regulated by the government.
Scratch and Sniff Ink
Also known as a microencapsulated ink, scratch and sniff ink releases a fragrance when the microcapsules are broken. The scratch and sniff ink is commonly used in magazines for perfume advertisements. When the consumer scratches the surface of the designated area of the ad, the capsules are broken, releasing the fragrance.
Medical Device Ink
Ink used for printing on medical devices is made of nontoxic ingredients so that direct printing on noninvasive surgical and medical disposable items is possible.
Moisture Resistant Ink
Moisture resistant ink is most often used for different types of packaging or for applications that may be used outdoors.
There are a variety of inks that provide added security features to print applications. Some security inks allow documents to be created that are tamper proof, while the use of other types of security inks prevent documents from being copied. Security inks include the following varieties:
- Coin Reactive
- Heat Reactive
- Visible Infrared
- Optically Variable
- Pen Reactive
- Solvent/Chemical Reactive
- Water Fugitive
- UV Invisible Fluorescent
Desensitizing ink is a transparent ink that is applied to the face of CF (Coated Front) and/or CFB (Coated Front and Back) carbonless paper in order to deactivate the CF coating. The use of desensitizing ink is important when an application requires that handwritten or imprinted data not be transferred through the various pages of a carbonless form in specific areas.
Electronic ink can be transformed from bright white to dark and then back to bright white again with a small electrical charge. The ink consists of plastic microcapsules that contain both dark dye and white ink chips. The microcapsules are sandwiched between thin layers of flexible material, which substitutes for traditional paper. When an electrical charge is applied, some of the white chips float to the top of some capsules to create a white surface and in other capsules, the white chips remain at the bottom allowing the dark fluid to remain visible. Different characters are created by applying the electrical charge under different combinations of capsules. After the initial electrical charge is applied, no further charge is required to hold the image in place, (unlike a computer monitor, which requires a constant stream of energy in order to display an image). The content of the flexible page can be changed instantly and then be held on the page for as long as necessary. Although, this technology is still being perfected, it could be a major advancement in variable imaging and in the reduction of paper usage for some print applications.