ISN’T A COMMODITY.CONSISTENCYWestRock DiamondTop™. A complete line of white containerboard products

delivering unbeatable consistency for all of your printing needs.

Together, we win.Get the facts at westrock.com/diamondtop

© 2017 WestRock Company. DiamondTop is a trademark for WestRock Company. All rights reserved.

NATURAL BRIGHTNESS BROAD PORTFOLIOSTEADY SUPPLYMade with no Optical

Brightener Additives (OBAs).Flexo to digital, retail-ready

corrugated to club store packaging.3 mills and 4 machines,

so capacity is never an issue.

WestRock DiamondTop™ White Containerboard Products

89920_WR_DiamondTop_Print_8x10_75.indd 1 6/29/17 11:58 AM

PaperWiseTM

June 2017

Delivering Consistency. A Recipe for Success.

WestRock DiamondTopTM White Containerboard Products

INSIDE:

PUBLISHED FOR EMPLOYEES AND CUSTOMERS OF WESTROCK AND ITS SUBSIDIARIES

Why should you care about optical brightening agents?

Measuring visual consistency for printers

Together, we win.

DiamondTopTM White Containerboard Products

2

PaperWiseTM

PaperWiseTM

is a contribution-based publication. To submit a story idea, call 877.785.7835 or email paperwise@westrock.com

PUBLISHED FOR EMPLOYEES AND CUSTOMERS OF WESTROCK AND ITS SUBSIDIARIES

© 2017 WestRock Company. PaperWise, DiamondTop, WESTROCK, WestRock and Design, and the WestRock Logo are trademarks owned by WestRock Company. All rights reserved.

About the AuthorAndrew Woodroffe, Vice President of Containerboard Mill Quality & Technical Services, leads a team responsible for managing the quality programs, customer-oriented technical services program, and product management systems for WestRock’s containerboard mills. Andrew is a leading authority on the production and use of white containerboard products. He has been involved in WestRock’s white top product line for the last 20 years, including at predecessor companies RockTenn, Smurfit Stone, and St. Laurent Paperboard.

A chemical engineer (McGill University) by training, Andrew started his career in an R&D role and moved on to various technical support, product development, and marketing roles at several different pulp and paper companies. While an expert in containerboard, Andrew also has experience in many other segments of the paper industry, including newsprint and single service food packaging.

Once an active member of TAPPI, Andrew has successfully dodged or delegated away his duties as an expert serving on various industry committees. Together, he and his team are essentially the encyclopedia of containerboard technology and its applications in sheet feeding, corrugating, and printing for WestRock and its customers. Based at WestRock’s West Point mill in Richmond, VA, Andrew has also lived and worked in Canada and the UK, which explains his fondness for the Queen’s English (e.g., colour, fibre, etc.).

PaperWiseTM DiamondTopTM White Containerboard Products

3

If you consider yourself a knowledgeable printer, you are undoubtedly familiar with basic colour theory and the importance that colour consistency plays in meeting the needs of your customers.

In today’s brand image conscious world, being able to hit your image targets consistently has never been more important. Specifying limits on colour variability, or delta E, is a common way to quantify tolerances in this area. Delta E in general terms, is calculated through a relatively simple equation that calculates differences in colour from a standard or target.

There are many factors that affect making an image repeatable from run to run, including inks, paper, and a variety of variables on the press. One area of colour theory that is sometimes forgotten in corrugated postprint is how large a role the visual consistency of the substrate plays into the result. It’s often taken for granted that grades of liner designed specifically for higher end printing applications such as white top liner, are inherently visually stable.

Unfortunately, like all manufactured products, the degree of variability depends on a variety of raw material inputs as well as the efforts of the paper mill to control those variables discretely. Additionally, some mills have more variables to control than others because of the nature of their raw materials. This further complicates their processes and introduces additional opportunity for their white top liner to look different and print inconsistently.

Even if your customers do not specify a maximum delta E for a given print job, using a single brand of white top that is capable of inherently meeting brand owner delta E requirements is a best practice in the marketplace. Utilizing a brand of white top liner with inherent consistency can help you minimize SKU proliferation, avoid supply chain and inventory complexity, and rest assured that the brand owner you supply will be satisfied with the colour and appearance of their brand. Optical BrightenersLooking closer at white top liners, there is one variable that is often not factored in when a printer selects a substrate – that is, to what degree the paper will appear different under various light sources such as daylight, halogen, fluorescent, LED, etc. As mentioned above, there are variables that some white top mills must contend with that others don’t.

One of these variables has a significant impact on visual appearance under different light conditions – that is the presence or absence of a class of chemical additives known as Optical Brightening Agents (OBAs). Paper mills will often incorporate OBAs into their white top recipe to make a dull white sheet seem brighter. To the naked eye, the result may seem brighter, but under different lighting conditions,

the amount of brightness and the degree of “blueness” will vary considerably. This is an especially important when considering the amount of ultraviolet in the light source.

Consider for example a well-known brand of infant diapers in a greenish box sitting on a shelf in a large wholesale store vs on a shelf in a brand new state-of-the-art, upscale neighborhood supermarket. Each of these retail outlets utilizes different types of lighting. Printing the diaper brand image on a corrugated box made with white top containing OBAs could result in mismatches in visual appearance. What you see under different light sources may be different, and certainly what you measure vs the brand’s colour targets (delta E) will be different, especially when transparent or semi-transparent inks are used.

Mills that deliberately add OBAs in controlled quantities can sometimes mitigate the variability of visual appearance . Where OBAs can be a problem however, is when they are indirectly added due to the use of recycled fibre sources. This is especially a problem with white top liners that use recycled fibre as the white layer. Poor control of the incoming recycled fibre can have a dramatic impact on how much OBA is added to the recycled white top, which could result in wide swings in visual appearance.

DiamondTopTM White Containerboard ProductsPaperWiseTM

Variability of Various White Top Producers: High Fluorescence

Variability of Various White Top Producers: Low Fluorescence

WestRock DiamondTopTM paper machines

WestRock DiamondTopTM paper machines

Asian Producer 1

NA Producer 1

NA Producer 2

NA Producer 3

EU Producer 1

4

Below is an example of the b-value (blue -yellow measurement) variability for white top produced at nine different paper machines. The four WestRock paper machines represented do not utilize any

It’s easy to see how variability in the recycled white fibre yields tremendous difference in the visual appearance of the finished white top product – an undesirable outcome if, as a printer, you are serious about colour matching. Looking at this in a different way, it’s also quite eye opening when comparing the b-value of these

6.0

5.0

4.0

3.0

2.0

1.0

0.0

-1.0

-2.0

-3.0

-4.0

-5.0

-6.0

6.0

5.0

4.0

3.0

2.0

1.0

0.0

-1.0

-2.0

-3.0

-4.0

-5.0

-6.0

b*-v

alu

e (fl

uor

esce

nt)

More Yellow

More Yellow

More Blue

More Blue

b*-v

alu

e (u

ltra

viol

et)

OBAs when producing white top. The other non-WestRock paper machines use primarily recycled content in their white top and therefore large quantities of OBA containing bleached fibre.

same paper machines under different common light sources. The table below shows the b-values of the same nine paper machines utilizing an ultraviolet light source. Clearly, in both examples the white top produced by WestRock demonstrates more consistency or less variability.

0.5

0.5

0.5

0.5

0.5

0.5

-1.1

2.8

-4.4

2.4

-3.8

2.3

-1.0

2.4

1.4

1.4

0.6

0.6

Asian Producer 1

NA Producer 1

NA Producer 2

NA Producer 3

EU Producer 1

If you are serious about colour and want to avoid supply chain and inventory complexity by utilizing a single source of a consistent white top suitable for all of your colour matching needs, we recommend WestRock DiamondTopTM, a family of white containerboard products that is made without added OBAs. WestRock DiamondTop product line is the best choice for minimizing variability in demanding print applications. If you have very high end printing and graphic needs, DiamondTop products are also available for solid coverage requirements (DiamondTop Solid), with a single clay coating (DiamondTop 1C), and with a double clay coating (DiamondTop 2C).

The DiamondTop family of products is supported by a WestRock team of highly experienced Technical Service professionals with specialized expertise in graphics and printing. The WestRock Technical Services team is available to our customers for advice and troubleshooting on a consultative basis. Contact them at paperwise@westrock.com.

PaperWiseTM DiamondTopTM White Containerboard Products