Overview
ISO/TS 23885:2022 specifies a laboratory test method to evaluate the coating strength in the inner fold of coated paper and board. The method is intended for single- or multi-coated papers up to 150 µm thickness that can be folded without creasing. The test quantifies how resistant a paper coating is to cracking and particle separation when folded - a property that affects aesthetic quality, printing/finishing performance and customer acceptance.
Key topics and technical requirements
- Scope and principle
- Test combines controlled folding, impact separation of loose particles, image capture and digital image analysis to quantify particle separation from the inner fold.
- The test result is reported as the mean particle area (as specified in the document).
- Folding device
- Two rotatable non-compressible rollers, one driveable and one height-adjustable to apply a defined line pressure.
- Line pressure scale must include 80 N/cm; roller spacing adjustment procedure specified.
- Impact device
- Separates loose coating particles by a guided free-fall impact; impulse momentum specified as (6.8 ± 0.2) Ns.
- Detailed inserts and dimensions for mounting test piece and receptor are provided.
- Image capturing and analysis
- Digital camera with homogeneous, reflection-free illumination; 8‑bit greyscale images or RGB converted to greyscale.
- Minimum detectable particle size 12 µm and sufficient contrast required for reliable segmentation.
- Sampling, conditioning and preparation
- Conditioning in standard atmosphere per ISO 187; sampling and test-piece preparation protocols defined.
- Calibration, calculation and reporting
- Procedures for calibration/adjustment of folding, impact and imaging systems; calculation of mean particle area; sections on precision, bias and required report contents.
Applications and practical value
- Quality control: Acceptance testing of coated papers before printing or finishing to reduce customer complaints caused by visible particles in folded products.
- Print finishing prognosis: Predicts risk of coating cracking or particle transfer during post-press operations (e.g. saddle‑stitching, folding of signatures).
- Product development and R&D: Compare coating formulations, coating weights and substrate/coating interactions to improve fold durability.
- Troubleshooting: Identify coating weaknesses that could affect spine gluing, aesthetics or handling in downstream converting.
Who would use this standard
- Paper and board manufacturers and coaters
- Printing houses and finishing/convertors
- Conformity assessment and test laboratories
- R&D teams developing coatings or paper substrates
- Quality assurance personnel managing incoming material specifications
Related standards
- ISO 187 - conditioning and testing atmosphere for paper, board and pulps (normative reference)
- ISO 13655 - spectral measurement and colorimetric computation for graphic arts (referenced for imaging)
Keywords: ISO/TS 23885:2022, coating strength in the inner fold, coated paper testing, folding device, impact tester, image analysis, paper quality, graphic technology.