Printing on Exotic Substrates

No one said print has to reside on paper. The packaging world thrives on flexible films and foils, rigid plastics, metals, and a host of other media. The commercial offset print world also has exotic options that are outside the classic, tree-based cellulose products. Let’s take a look at these alternative substrates, ranging from stone to plastics -- while avoiding the uncharted territory that is the nightmare of productivity.

The substrate is any surface onto which you can apply a printed image. Some people call it material and others media. To the average general printer, substrate is paper or board. The main differentiator is often whether the finish is gloss or matte.

Offset inks are not compatible with a broad range of substrates although choices exist. These options appeal especially to environmental groups in search of what appears to be a greener alternative. 

True velum is made from the skin of a cat while true parchment derives from the skin of a sheep or goat, both highly specialized, costly, and not really used in the industrial world. Today’s exotic choices fall into just a few categories.

Options Free of Tree

Tree-free paper based on plants, one alternative to destroying old-growth forests, intrigues the marketplace if not the traditional papermakers in the U.S. The substrates look and feel like normal papers but the base sheet utilizes cellulose from plants other than trees. Botanically, these plants are grasses or bushes.

There are many choices, the first being Papyrus, a reed that grows along the banks of the Nile River and utilized by the ancient Egyptians for multiple purposes. The center of the reed was sliced into strips, laid in a crosshatch pattern, and pounded into a flat sheet. Although it is sparsely available today, it is still unique in that it can be folded in both directions without cracking.

Other naturally occurring wild plants include bamboo, straw, and switchgrass. Bamboo fiber is a high-yielding perennial already used extensively in India to make paper. Typically blended with tree fibers, bamboo paper is readily printable.

Switchgrass is a dominant component of Western prairie grass. It has been studied since the 1990s with positive results. In appropriate climates, switchgrass is an economical substitute for wood pulp and shows promise for the future. The substrates manufactured by blending these quick-growing crops with slower-growing wood pulps are a safer choice in American printing systems.

Kenaf Comeback?

More broadly available cellulose-based, tree-free paper falls into two additional categories: agricultural wastes and agricultural crops.

Agricultural wastes left over from food production are at the top of the second list. Making use of waste products instead of finding ways to dispose of them has appeal for obvious reasons. Perhaps the best-known agricultural waste is bagasse, the fibrous biomass left after juices have been extracted from sugar cane. Bagasse is harvested within a year or two of its planting, requires minimal bleaching, and is plentiful. Sugar cane is widely produced, and the use of its leftovers for paper is desirable. New capacity for pulping bagasse is coming on line in India -- an indication its place as a substrate is secure.

Printers of bagasse papers must use caution when printing. The bagasse fibers are short, and the strength of papers can be variable. Choose your supplier with care and ask for referrals.

Leftovers from the cotton crop finds their way into our money as well as top-of-the-line printing papers. Runnability, printability, and durability of the finished papers are superb. Most of the pulp comes from cotton linters, those short fine silky fibers that adhere to cotton plant seeds after ginning. The longer fibers are removed for use in fabric but the shorter fibers are still up to ten times stronger than wood pulp fibers. Rags or cotton clippings left over from clothing manufacture are an additional source of fiber for these papers.

Crops grown specifically for paper manufacture such as hemp, kenaf, and jute round out the list. Kenaf, a long-fiber plant that originated in the East Indies, is now grown in the U.S. A relative of okra and cotton, kenaf was determined by the USDA to be “the best option for tree-free papermaking.” Pioneering Vision Paper perseveres as the lone U.S. company with a stated objective of growing and pulping kenaf for use in paper products. Unfortuantely, many of the smaller mills that experimented with kenaf have closed, so kenaf paper is not currently available. Look to the future for this paper type to reappear.

Fiber-free, Too

Non-fiber based papers suitable for offset printing also are available. Inorganic paper, called Rockstock, is neither pulp nor synthetic made paper. This Rich Mineral Paper is a combination largely of mineral powder (Calcium Carbonate) with a small amount of a non-toxic resin creating an exotic and environmentally friendly paper. Note that Calcium Carbonate is a sequesterer of carbon dioxide and, therefore, its use in these types of papers is neutral on the global-warming scorecard. Different proportions of mineral powder and resin are used to impart various product attributes such as stiffness. The “paperless paper” is tear resistant, waterproof, and unique.

Williams Visual Solutions actively prints this product and claims it is unlike any substrate you have seen or felt. “Produced without any tree pulp, and without the use of water, Rockstock is a perfect alternative for organizations who are committed to sustainability,” according to Williams. Rockstock is available for digital and offset print projects, and comes in both cover and text weights.

Yupo has produced its polypropylene paper alternatives in the U.S. for 15 years. No longer rare nor on the bleeding edge of offset capability, this waterproof plastic provides unique communication alternatives. Yupo provides clear tips and techniques for printing, learned over years of actual offset printing experiences. Like most paper companies, Yupo customizes products for digital marking technologies and has just announced wider format products to better service the digital print world.

Crossing over to digital devices expands the list of printable substrates by several orders of magnitude. There is an almost endless number of materials that can be imaged using UV, inkjet, and other technologies. Vinyls, building wraps, cans, and a host of specialty substrates accept digital inks and toners.

As general guidance, it is probably fair to say that printing on any plastic or other product of petrochemical origin should be considered less environmentally friendly than alternatives. Sometimes the use of these materials is unavoidable — for instance, when printing on weatherproof materials for outdoor use. However, in many cases, and especially for general use and for indoor exhibition, more environmentally friendly options are viable alternatives.

Offset lithography is more limited in substrate choice. Conventional paper manufactured from trees in processes optimized over decades dominate the marketplace. But exotic choices are available, workable, and more readily obtainable.

Trish Wales is a 30-year veteran of the paper industry with experience ranging from commercial papers to packaging boards to inkjet specialty products. She has held positions in manufacturing, R&D, marketing and sales, working at the interface between paper manufacture and print. As a color management specialist, Wales is recognized for helping to educate the graphic arts community on the role of paper in color reproduction.

In This Case, It's the Ink -- Not the Paper

Color Logic products are unusual in the effects they achieve. The company facilitates printing on metallic-look substrates through a color communication and software tool developed for special-effect printing. A conventional substrate is transformed into a metallic look alike then the software blends process inks to achieve a broad range of metallic effects on press. According to sales/marketing director Mark Geeves, “With only five inks, the Process Metallic Color System in a single print run can consistently and predictably produce as many as 250 different metallic colors at a fraction of the cost of other options.” The system also supports digital press, inkjet, and flexo printing processes.