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Principles of Ink

Inks were first made in ancient China as long as 50 centuries ago. They were made from soot suspended in vegetable oil. Eventually, petroleum was used in inks, which made them cheaper and more popular for offset printing. By the 1960s, petroleum-based inks had completely replaced vegetable-based inks in the printing industry. However, petroleum-based inks are not without their costs to the environment. They contain a variety of heavy metals (barium, copper, zinc) that leach into soil and groundwater. Volatile organic compounds (VOCs) are also released by petroleum-based inks. These contribute to smog in addition to being irritating to the human respiratory system. When considering the sustainability of printing, VOCs emitted during the printing process and the use of non-renewable resources and heavy metals in pigments must be considered. Designers should speak with their printer to keep these factors in mind.

Pollutants and Ink

VOC Content

Ink oil can be either petroleum-based or vegetable and agri-based. However, inks labeled petroleum-based may have some vegetable oil, and inks labeled agri-based may have some petroleum content. Unfortunately, all oils release some amount of VOCs. Higher petroleum oil content contains a higher concentration of VOCs. The vital role of oil in ink is to keep pigments, resins, drying oils and other additives in solution. There has been a shift towards using more vegetable oil such as soy, linseed, cottonseed, tung or china wood to reduce usage of petroleum oil. This is better for the environment because of fewer VOCs released into the atmosphere as well as a reduced consumption of a nonrenewable resource.

VOC Emissions

Inks do not necessarily emit all the VOCs they contain. In lithographic inks, very little of the ink oil used actually evaporates. The EPA states that for sheet fed and non-heatset web inks, only 5% of the VOCs contained in the ink is released into the atmosphere. For heatset web inks, 80% of VOCs are evaporated. This process occurs in a dryer, allowing the compounds to be captured and most of them destroyed by an oxidizer. Because heatset inks dry by evaporation and vegetable oils do not evaporate, the vegetable oil content that can be used in heatset inks is very low (5-7%).

Pigments and Heavy Metals

Heavy metals such as barium, copper and zinc can be found in some pigments. They are most often found in metallic inks that are green, orange or opaque yellow. Heavy metals are toxic and sometimes carcinogenic. Designers should speak with printers about finding alternative pigments to match their desired colors. Modern fluorescent inks do not require metal-based pigments.

Other Types of Inks

Recycled Inks

These can lessen the environmental impact of printing. Inks are not recycled in the same way as paper, plastics or glass. Some printers can reuse old or spent inks by blending them together to form other colors or black ink. Otherwise, such inks may be returned to ink vendors or disposed of through a registered disposal company. It should be noted that color quality could vary greatly when using recycled inks.

Vegetable and Soy Based Inks

Both soy and vegetable inks are made from renewable plant material. Soy inks are primarily made using soy oil, whereas vegetable inks can be made with any variety of plants. Inks based from vegetable oil contain fewer VOCs and IPA solvents than petroleum based inks. Using waterless or alcohol-free printing methods further reduces the environmental impact of using these inks. It should be noted that these inks might still contain some percentage of petroleum oil. Also, vegetable based inks are not 100% biodegradable because of the pigments and other additives.

UV Inks

UV inks are inks made to dry or cure instantly under ultraviolet light. Where conventional inks may lose intensity as they dry, UV inks produce sharp images as they leave little time for dot gain. UV inks typically use fewer solvents and contain small amounts of VOCs. However, UV inks are not normally made from renewable resources. In addition, finishes like foil stamping, varnishes and laminates are difficult to de-ink, making it hard to recycle paper.

Metallic Inks

Metallic inks use a varnish base to transport metallic powders such as aluminum and bronze. These inks can give images a metallic sheen and are best used on smooth, uncoated paper. Non-leafing inks with a varnish will work best while retaining rub protection.

Special Inks

Scented Ink – Scented inks are water based and can only be printed on unsealed paper or board. Scented inks come in a wide variety of smells and can also be synthesized to use a specific fragrance. The smells are suspended in a semi-clear base and then screen-printed onto the required substrate.
Heat-Sensitive – Heat-sensitive inks have a limited range of colors. Black tends to produce the most dramatic results. The heat-sensitive component is suspended in a semi-clear base and then screen printed. The reactive temperature can be changed in accordance with climatic conditions. Like scented inks, heat-sensitive inks are water based and work best on uncoated paper substrates. They can be made to work on plastic after a number of layers are applied. This is a time consuming process making it not cost effective. Heat-sensitive ink has the tendency to scuff when not properly.
Rub-Removable – Rub-removable inks are usually found on lottery tickets and other cards with scratch off sections. These inks are latex-based, opaque and metallic. The ink is fragile, allowing it to be rubbed off, and is rubbery in feel.
Pearlescent & Iridescent – These inks can be used with a variety of substrates and, depending on proximity, create a different shade of metallic color when viewing. They are most commonly found on gift cards. They can also work well as solid areas with text on top.

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