Trending Content

Substrate Update

By Serge Desgagnés

June 1, 2018

Gone are the days when the Fourdrinier Kraft Paper Group technical committee of the American Paper Institute used the Institute of Paper Chemistry at Lawrence University (formerly Lawrence College), and sometimes the U.S. Forest Product Labs, for research and publishing their findings for the entire industry. We still have TAPPI, ASTM, and IOPP for third-party technical assistance and standards and methods. Canada also has research facilities such as FPInnovations, but is anyone examining linerboard structural and printing characteristics?

What Are Substrates?

While Kruger is a white-top, colored, and 100 percent recycled brown linerboard producer, there are many other substrates that can find their way into corrugated, especially in the microflute grades. Let’s start with 50#/3MSF kraft/recycled bag and bleached bag papers, which are equivalent to 16.7#/MSF linerboard. Then, we move to 60–100# (8#–30#/MSF linerboard equivalent) coated one-side (C1S) label stock used in single-wall and single-face laminations. Now consider solid bleached sulfate (SBS) that can be manufactured as low as 7-point, or about the 21#/MSF linerboard equivalent, which is also used primarily for single-face and single-wall applications. Adding to this in the graphic substrate arena would be solid bleached linerboard in basis weight, generally from 33# to 47#. Do not confuse solid bleached linerboard with solid bleached sulfate. And then there are the imported KemiArt US grades, along with domestic producers, such as WestRock.

There are treatments to linerboard roll stock that can shorten your manufacturing time so that you will not have to treat the products before or during converting. These include wet-strength, high-porosity, grease resistance, waxable white-tops, and lightly coated treatments, as well as those that are made to a very narrow basis weight variation and a maximum 30-minute Cobb water pickup, so as to pass the requirements of UN HazMat. There may be at least one nontraditional substrate mill out there that buffers the product to achieve a higher alkaline pH so that the corrugated boxes can be used for archival records. Several recycled fiber-based substrate products that are neutral pH can also be used.

If a mill system has an associated corrugated medium operation that can accept the coarse rejects from corrugated recycling, then the best fibers should be diverted to the linerboard operation.


Let’s not forget to at least mention our sister side of paper packaging. First comes unbleached kraft (UBK), or what we might call real cardboard. Then comes solid unbleached sulfate (SUS) and its sister grade, coated natural kraft (CNK), and SBS, which we have already discussed. Somewhat new to the North American market is folding box board (FBB), which is a multilayer substrate that contains semichemical ground wood. It is generally imported from Europe, but we have seen a few domestic operations appear.


It was timely that AICC looked at disruption in supply at its Spring Meeting in Phoenix. Our security analysts and media sources have reported press releases of newsprint conversions using some existing pieces, an operation shutting down three old machines and installing one machine in its place, a limited conversion of a coated paper machine, and a complete gutting of one machine and replacing all components to manufacture linerboard. All reports are that we will not run out of the lighter-weight linerboard here in North America, given that corrugated shipments are growing between 1.5 and 2 percent annually.

Alternative Fiber Disruptions

As the quality of recycled fiber from DLK and OCC #11 and #12 diminishes because of reuse and the importing of corrugated packaging outside North America, it becomes imperative that linerboard operations install multilevel and multistage cleaning systems. If a mill system has an associated corrugated medium operation that can accept the coarse rejects from corrugated recycling, then the best fibers should be diverted to the linerboard operation. Most mills that have not invested in advance cleaning technology for their operations in the last 10 years do not have this level of screening.

Both linerboard strength and printability suffer when we have both coarse fibers and fine fibers in single-ply sheets, which are generally at 35#/MSF basis weight and below. At least one mill system here has been quoted in the media as blending up to 75 percent mixed office waste, along with OCC, into its containerboard products. DS Smith Recycling in Kent, U.K., has announced its ability to repulp one-use coffee cups into new paper products. This latter company has created enough in their entire approach to corrugated packaging that they may know or find the way to make this happen for linerboard.

State of the Art in Linerboard Today

The industry, and especially the younger members, have incomplete knowledge of kraft (virgin) linerboard, recycled liner, semichemical medium, and recycled medium, nor do they know the definitions as expressed by the American Forest and Paper Association. Suffice it to say that names and categories do not indicate value, corrugator performance, and load-sharing ability of the components, image reproducibility, trust, and personal relationships with the suppliers. One must look at the actual physical property values results and build a conduit so as to receive certificates of analysis on a regular basis. A quality program should be built on open and honest communications in which corrective action reports are produced and changes made. There are voluntary semiannual studies that show the ranges in various containerboard attributes, but not all that can give a buyer guidelines about the performance and value of the substrate they purchase.

A quality program should be built on open and honest communications in which corrective action reports are produced and changes made.

Both CD and MD moisture profiles need to have minimum variation. A good specification from a machine would be in the range of 1.5 and maybe 1 percent. Today we have seen even flatter profiles, with one new machine stating ±0.6 percent. The technology that has been available for monitoring and then adjusting moisture content on paper machines is now available for corrugators. Full-web constant scanning is now available from Valmet for corrugators so that every location in the combined sheet can be monitored.

Newer systems are able to dye the sheet to provide a uniform “a” hue. Formation and basis-weight uniformity within the sheets are better on modern machines.

We have seen that some linerboard manufacturers have become so successful in the marketplace that they become known as their brand and not necessarily associated by the manufacturer. While this is not necessarily new to containerboard, we have seen this in the case of the new XTR from Kruger’s Trois-Rivières mill.

width=150Serge Desgagnés is general sales director at Kruger Packaging LP in the Montréal office. He can be reached at 514-231-5781 or

Expressing Gratitude

First, thank you for allowing us to share our thoughts on substrates. This article was limited to just linerboard and substrates used by the folding carton and rigid box sectors of our industry, and not corrugated sheets, which can also be thought of as a substitute! Maybe it could be that, as the newest entrant into 100 percent recycled board with the latest technology in North America, we believed there was a story to tell.

Second, I would like to thank the Association for having the insight years ago to develop seminars, webinars, brochures, The Packaging School in conjunction with Clemson University with more than 40 free online learning modules, many brochures—such as Understanding the Key Characteristics of Linerboard and Medium and Their Impact on Combined Corrugated Board—DVDs, leadership for the International Corrugated Packaging Foundation, connections with many packaging and printing schools, and the list goes on. Allow me give a shout-out to those who captured Ralph Young and his 35 years of knowledge about our industry and its technical aspects. He remains a great resource and is the gatekeeper of and conduit to untold resources and networks. He has written more than 60 BoxScore articles, answered more than 3,500 Ask Ralph inquiries, and taken countless phone calls. There have been almost 100,000 hits and 46,000 visitors to the blog! Check out the search feature on the website.

That’s not to say that Ralph is the only one on the substrate side. We are grateful to those such as Allie O’Brien at KemiArt US and Steve Rote at Metsä Board, along with Randy Banks at SHARP International and industry consultant Sarilee Norton. Other linerboard manufacturers such as Jim Porter at WestRock and Tony Smurfit at Smurfit Kappa have also given back and made open contributions at national and international meetings for the good of all. We also need to be thankful to RISI and Fisher, who regularly sponsor conferences where open dialogue can occur.

*Editor’s note: Kruger is the latest AICC member to support the Association’s Education Investor program.