Printing Inks

Commercial Printing

Printing inks may contain material that makes them hazardous, such as metals used for coloring and solvents used to accelerate drying. In addition, because most printing inks are petroleum-based, they may have significant volatile organic compound (VOC) content. The Clean Air Act Amendments regulate overall VOC emissions from printers, so the extent to which inks contribute to VOCs is important (see Fact Sheet #10: "Printer's Guide to Environmental Regulations"). In response to increased demand and more stringent regulations, ink manufacturers are making a concerted effort toward eliminating VOCs. This fact sheet describes some of the pollution prevention and waste management options for printers related to ink.

Best Management Practices

Printing inks are expensive and any opportunities to minimize waste ink can help save money. Waste ink is generated through color changes, press cleaning and poor ink management, which allows drying and skinning. But effective management techniques can help reduce waste ink. Don't treat excess ink as waste ­ instead, manage it like a product that should be reintroduced into the system when possible. Best management practices to help avoid waste include:

• Help press operators accurately estimate the amount of ink needed for each job through training in ink estimating techniques. Keep accurate records of the quantity of ink that is used for specific jobs, particularly for reorders or repeat customers.
• Keep ink containers sealed and contents level; place plastic or wax paper on top of the ink to prevent drying; use anti-skinning sprays.
• Scrape as much ink from empty containers as possible prior to disposal or recycling.
• Use a standard ink sequence and try to schedule print runs from light to dark, if possible.
• Carefully monitor inventory to ensure a "first in-first out" strategy.
• Donate off-spec ink to schools or give it to another printer rather than paying for disposal.

Reuse Excess Ink

Excess ink is the result of overestimating ink usage at the press or at the time of ink purchase. Whenever possible, return unopened cans of excess ink to the supplier. Reusing excess ink can reduce both disposal and purchase costs. Some options:

• Mix excess ink, including black or colored inks, on-site to produce black ink. Many printers like the quality of the black ink produced from mixing colored inks because of the high quality of colored inks.
• Mix non-contaminated excess ink with virgin ink of the same color.
• Use a computer-controlled mixing program in conjunction with a digital scale for mixing PMS colors. Mixing programs range in price from $300 ­ $2500. Many printers find the systems very user friendly and are satisfied with the inventory reduction they achieve.

Soy and Vegetable Inks

Soy- and vegetable-based inks were popular during the oil crisis in the early 1970s. But as presses became faster, petroleum-based inks displaced slow-drying vegetable-based inks. Now increased emphasis on improving worker safety and reducing environmental emissions has sparked renewed interest in vegetable oil-based inks, and many printers and suppliers are trying to address quality concerns found in early versions of these and other alternative inks. Vegetable oils can reduce total VOCs in an ink formulation. Among the vegetable candidates for oil base in ink, soybean oil is the most promising. Some advantages of soy-based inks:

• Some printers, especially newspaper printers, have managed to achieve high quality with all color soy inks except black. Newspaper inks can contain a high vegetable oil content due to the absorbency of newspaper. Because the ink dries solely by absorption, it is possible to substitute all of the petroleum and 100% soy formulations are available.
• Soy inks are less likely to build up on the plate, have less tendency to skin over, and have greater stability.
• They permit greater latitude in ink-water balance, allowing more flexibility in press settings, and provide greater coverage per pound of ink.
• Soy oils tend to be clearer than petroleum oils, so the colors can be brighter. Also, some printers claim that soy ink pickup and transfer is quicker, resulting in shorter start-ups and less waste.
• Many printers claim that soy inks are more forgiving and thus make it easier to run a high quality job on older equipment. It is sometimes easier and faster to change from a dark to a light color ink with soy than with petroleum-based inks.

• Soy inks tend to work well with recycled paper. Because of the flow of ink, soybean inks don't pick out the fibers of the paper and they adhere better.
• Soy-printed products are easily deinkable by wastepaper processors and they produce a less hazardous sludge, making them more recyclable than petroleum-printed products.

But there are drawbacks. Soy ink often costs more than conventional inks, but the cost is expected to decrease. The drying times for soy inks are considerably slower, particularly on coated paper. Thus, pure soy-based inks cannot be used in the heatset process. As a result, soy-based oils still contain a certain percentage of petroleum. The American Soybean Association (ASA) has developed a "Soy Seal" certification program. Table 1 summarizes the percentages of soy content necessary for qualification. Another disadvantage is that soy inks may still contain small quantities of hazardous substances, and may have to be managed as hazardous waste.

SUMMARY OF PRODUCT SUBSTITUTION ALTERNATIVES TO SOLVENT-BASED INKS

Radiation-curable Inks

Ultraviolet (UV) and electron-beam (EB) inks cure by polymerization upon exposure to UV or EB energy. They contain no solvents and therefore release no VOCs. They will not cure until exposed to the energy source so they can be left in the fountain for long periods of time, thereby reducing cleanup. They can be used on both web and sheetfed presses.

The major drawback is cost. Small printers will not be able to afford the $1 million starting price and the inks are more expensive than conventional or soy inks. Also, there is the risk of employee exposure to UV and x-ray energy, so safety devices are necessary. Finally, paper printed with these inks are often difficult to recycle because of the high molecular weight and difficult fiber/ink separation.

Vendors and Suppliers

Indication herein of specific vendors and suppliers does not imply endorsement, nor does omission imply a refutation by the Montana State University Extension Service Pollution Prevention Program.