Paper testing – Stability of paper (ISO 20494)

Purpose

Paper that meets the requirements of ISO 20494 shows stability for general graphic applications. Examples of possible end products with this paper include newspapers, brochures, catalogs, books, office prints, etc.

The ISO 20494 standard is based on providing a paper where mechanical fibers and/or recycled fibers can be used in paper products, thereby reducing production costs while promoting sustainability and contributing to a significantly reduced environmental footprint.

Method

pH - Cold Water Extract 

Acidic paper deteriorates quickly, so pH is an important parameter to measure in paper. Electrolytes are extracted from the paper in a water solution, and the pH value is then measured on this cold water extract.

Alkali Reserve 

The formation of acids from air pollution in the surrounding air or natural ageing is harmful to the paper. Therefore, such paper usually contains some alkaline filler (e.g., calcium carbonate) to prevent acid attacks and neutralize the harmful acids, i.e., the paper has an alkali reserve. The alkali reserve can be measured through a titration process.

Tear Strength 

Tear strength is a measure of the paper’s mechanical strength and indicates the force (mN) required to tear a piece of paper. Preserving tear strength after ageing is a measure of the paper’s ability to remain durable in the future.

Requirements according to ISO 20494

• Tear Strength: The tear strength has a minimum value based on the paper’s surface weight.
• Preservation of Tear Strength: The tear strength must not decrease by more than 80% after 12 days of aging at 80°C and 65% RH.
• pH Cold Extract: Between 7.5 - 10.0.
• Alkali Reserve: At least 0.8 mol of acid per kg.

Accreditation 

The testing for paper stability maintain high quality through accreditation according to SS-EN ISO/IEC 17025:2018.

Delivery

Testing report from an accredited laboratory.