Newsprint paper — In the intricate world of newsprint, where every print and press run demands precision, understanding the metrics that define paper quality is paramount.

From grammage to moisture content, each factor plays a crucial role in determining the success of a newspaper's print job. Let's delve into the key newsprint metrics that matter and explore the recommendations for achieving optimal results.

Newsprint Grammage

Definition:
Newsprint grammage, also known as basis weight or substance, measures the mass of the paper per unit surface area in its as-taken condition. Preferred units include g/m2 or pounds/ream for the American standard.
Recommendations:
Standard newsprint grammages range from 48.8 g/m2 (30 lbs/ream), 45 g/m2, to 40 g/m2. For those opting for higher or intermediate grammages, specific recommendations such as 52 g/m2 and 42.5 g/m2 are suggested.
General Trend:
Historically, there has been a trend toward grammage reduction, with a shift from the global standard of 52 g/m2 in the 70s to 48.8 g/m2 in 1974, driven by energy cost considerations.
Advantages of Lower Grammage:
Lower grammage brings benefits like increased web length per reel, reduced weight per copy, and the possibility of higher pagination.
Parameters for Decision:
Deciding on the grammage involves considering factors such as product type, print quality, and distribution characteristics, necessitating individual estimations for each newspaper.

Moisture Content

Definition:
Moisture content reflects the reduction in mass of a paper sample when dried, expressed as a percentage of the mass of the moist sample.
Recommendations:
Maintaining moisture content above 8%, particularly for high-filler content grades, is crucial. However, it should not exceed excessively high values.
Impact of Moisture:
Moisture significantly affects mechanical and printing properties, with low moisture leading to issues like web breaks and static electricity.
Moisture Control:
Achieving equilibrium with ambient air is essential, as moisture problems, especially in offset printing, can arise due to the damping application on the press.

Ash Content

Definition:
Ash content denotes the mineral matter in the finished sheet, expressed as a fraction of the moisture-free mass.
Recommendation:
While generally ranging from 0-12%, specific limits may be specified by some users, especially when extended plate runs are necessary.
Sources of Ash:
Ash in newsprint can originate from additives, mineral matter in pulp, and filler materials. Loading paper with fillers improves brightness but reduces mechanical properties.
Variations:
Recommendations for ash content depend on manufacturing conditions, with variations advised to be kept to a minimum.

Sheet Thickness and Density

Thickness:
Sheet thickness, or caliper, is the measurement of a single sheet's thickness, expressed in micrometers. A study published in the International Journal of Mechanical Engineering and Mechatronics (IJMEM) examined the relationship between paper properties and linting behavior in offset printing. They found that increasing sheet thickness and grammage reduced linting, while higher surface roughness increased it.
Density:
Sheet density, the ratio of mass to volume, is expressed in kg/m3 or g/cm3.
Recommendation:
While there's no general recommendation for sheet density, variations should be minimized during manufacture.

Surface Roughness - Smoothness

Definition:
Surface roughness measures the physical irregularity of the paper sheet.
Units:
Measured in Bendtsen roughness number, Bekk seconds, or Parker Print Surf.
Recommendation:
For newsprint, specific ranges are suggested for Bendtsen, Bekk, and PPS measurements.
Influence of Smoothness:
Smoothness affects printability, ink consumption, and print-through, necessitating a careful balance.

Compressibility

Definition:
Compressibility gauges the extent to which sheet thickness is compressed when pressure is applied.
Units:
Expressed as a percentage.
Recommendation:
While no specific recommendation is provided, it is noted that high smoothness correlates with low compressibility.

Porosity - Air Permeability

Definition:
Porosity measures the combined volume of pores and voids between fibers.
Units:
Measured in m/Pa.s or μm/Pa.s.
Recommendation:
No specific recommendation is given, but variations should be kept to a minimum during manufacture.

Oil Absorption/Water Absorption

Definition:
Oil absorption measures the amount of liquid absorbed by a piece of paper, simulating ink behaviour.
Units:
Expressed in kg/m2 or g/m3.
Recommendation:
While no general recommendation is given, the difficulty of measurement and correlation with printing are acknowledged.

Sheet Formation

Characteristics:
Sheet formation, checked visually by transmitted light, involves the tendency of fibers to form flocculations, addressed by the headbox.

ISO-Brightness and Newsprint Shade:

ISO-Brightness:
Reflectance factor in the blue region, providing an indication of the brightness of the furnish used in newsprint. A study published in the Journal of Imaging Science and Technology analyzed the relationship between newsprint brightness and ink consumption. They found a non-linear relationship, where increasing brightness initially led to decreased ink consumption, but the effect plateaued at higher brightness levels.
Newsprint Shade:
Characterized by Y-value, dominant wavelength, and excitation purity, reflecting the visual perception of color.
Recommendation:
While ISO-brightness offers insights into furnish brightness, no general recommendation is provided for newsprint shade.

Opacity:

Definition:
Opacity measures the ability of the sheet not to transmit light, expressed as a ratio.
Units:
Expressed in percentage.
Recommendation:
Higher opacity is desired for better print quality, with specific values suggested for various grammages.

Mechanical Characteristics:

Mechanical Strength:
The mechanical strength of a sheet depends on fiber strength, orientation, and bonds between fibers, influenced by furnish and processing conditions.
Tensile Strength & Elongation:
Tensile strength measures maximum force before breaking, while elongation gauges the increase in length under stress.
Tearing Resistance:
Measures force required to continue tearing, with values provided for machine direction and cross direction.

Newsprint Quality Control: Navigating the Maze

Why Quality Control:
Heterogeneous nature of paper, varied measurement methods, and diverse quality requirements necessitate a robust quality control program
.

ISO 9000:

Standards defining requirements for in-plant quality assurance, focusing on a business's capacity to produce quality.
Establishing a Quality Control Program:
Involves educational, qualitative, and quantitative stages, aligning properties with printability, linting, runnability, and economic aspects.
Control of Deliveries:
Checking usable paper amounts, average grammage, and cross-direction variations, ensuring consistency and notifying variations.
Day-to-Day Service Support:
Running random reels on the press from new consignments, categorising deliveries, and addressing potential issues.
Troubleshooting & Complaints:
Utilising a reference point for efficient problem-solving, involving continuous measurement and dialogue between printer and papermaker.
Which Properties to Test:
Evaluating properties based on their influence on printability, linting, runnability, and economic aspects, providing rates of influence.

In conclusion, mastering the metrics that matter in newsprint quality is a journey of precision and understanding. Each property, from grammage to surface roughness, contributes to the intricate dance of ink on paper.

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Footnote:

“Newsprint Properties and Specification List for Newsprint Purchase and How to Establish a Quality Control Programme for Newsprint.” Nanyang Technological University , NTU Digital Repository , 1995, https://hdl.handle.net/10356/87292. Accessed 29 Dec. 2023

Newsprint Mastery: Quality Metrics for Print Perfection