Not All Pulp Is Created Equal

The venerable paper industry is steeped in history and tradition, shaped by advances in science, genetic engineering and the Environmental Protection Agency. Paper jargon is frequently obscure. No wonder there are libraries of books explaining the meaning of such terms as CWT, deckle and basis weight. You need to know how the stuff will run through the press and the finishing line, and how it will print—or why the paper you run every day suddenly causes a problem.

Answering such questions requires you to have some knowledge of the raw material from which the paper is made. But what aspect of paper do you investigate? You know that up to 50% of the cost of a print job is paper, and that paper impacts press and mailing yield. But what about paper really matters?

Press performance is critical to a profitable operation and paper contributes to press uptime as well as yield. And this fundamental property of paper starts with a seldom discussed raw material: the tree.

Most domestic paper is made from local trees. Globally traded pulp augments the base sheet when trees in the local wood basket are too expensive or come from the wrong species. The great boreal (softwood) forests of the Northern Hemisphere in both North America and Europe provide the best and costliest fiber, providing substrates that are strong, smooth and easy to process.

Hardwood pulp is a less expensive fiber filler used in coated and uncoated free sheet papers to provide their characteristic smoothness.

Lately, a relatively new hardwood pulp is gaining ground. Eucalyptus, indigenous to Australia, is the darling tree of the paper world. It grows fast, particularly when planted in tropical regions, withstands low water conditions, is economical, sustainable and increasingly being used in papers. Monoculture eucalyptus forests are springing up from Brazil to China, as papermakers learn to manufacture a better paper from this less valuable feedstock. Although the eucalyptus fiber is shorter than most hardwoods and lacks strength, it is today's fiber of choice and comprises an increasing portion of the fiber mix.

Non-cellulose papers are not yet commonplace or suitable for the demanding offset process. While current papers are a mix of hardwood and softwood tree fibers, those with greater softwood content have better strength, better dimensional stability and better runnability.

The amount of fiber in the paper is also important. It stands to reason that higher basis weight papers have more fiber than lower basis weight papers. However, not all papers of a given basis weight have the same type or quantity of fiber.

Coatings and additives are less expensive than fiber and frequently substituted for tree cellulose when possible. Double and triple coated papers, as well as highly filled uncoated papers, are signs of economizing by mills, but sometimes at the expense of press performance.

Check caliper (thickness), not basis weight, to compare the amount of fiber in similar finish papers. Higher caliper means more fiber and typically better runnability. When testing new papers, the wise printer monitors press yield and downtime to understand not just cost but “cost in use.” A fiber discussion is an appropriate conversation to have with your paper rep when you consider a new brand, a lighter basis weight, or have runnability issues.