ISO 2426-4:2018

Overview - ISO 2426-4:2018 (Palm‑plywood, surface appearance)

ISO 2426-4:2018 specifies how to assess and classify the surface appearance of palm‑plywood - plywood whose surface veneers are made from oil palm trunk. The standard defines the nature and limits of inherent palm‑veneer characteristics and manufacturing defects to enable a consistent visual assessment and allocation of panels into appearance classes. It is part of the ISO 2426 series on plywood surface classification and refers to ISO 2074 (vocabulary) and ISO 2426-1 (general assessment rules).

Key topics and technical requirements

• Scope and materials: Applies specifically to plywood with surface veneers produced from the oil palm trunk (defined terms: oil palm trunk, oil palm veneer, outer and inner veneer).
• Appearance classes: Surfaces are assigned to one of five classes: E, I, II, III, IV, based on permissible characteristics and defects.
• Inherent palm‑veneer characteristics: The standard lists allowed natural features and their limits, including:
  • Pin holes (e.g., ≤ 1.5 mm diameter; limited number per sheet)
  • Splits, irregular grain (tiger grain), discoloration, bark pockets, and insect/borer marks - with class‑dependent size and quantity limits
  • Distinction between outer veneer (denser, higher fibre content, lower parenchyma) and inner veneer, which affects appearance
• Manufacturing defects: Defines acceptable limits for defects such as open joints, overlaps, blisters, hollows, roughness, sanding‑through, glue penetration, foreign particles and repairs. Numeric limits include maximum widths, counts per metre or sheet, and percentage of panel area in certain cases.
• Assessment method: Visual assessment and classification follow the procedures in ISO 2426-1; defects are judged per the tables of permissible types, sizes and frequencies.

Practical applications and users

Who uses ISO 2426-4:

• Plywood manufacturers (quality control, production specification)
• Panel product engineers and veneer processors working with oil palm trunk material
• Procurement/specifiers in furniture, interior fit-out, and building products who need appearance grades
• Quality inspectors, testing bodies, and traders for acceptance criteria and dispute resolution
• Architects and designers specifying aesthetic grades for visible plywood surfaces

Practical value:

• Ensures consistent appearance grading, improving transparency in trade and procurement
• Helps producers set manufacturing tolerances and surface‑finishing processes for palm‑veneer panels
• Facilitates clear communication of visual quality requirements in contracts and technical specifications

Related standards

• ISO 2426-1 - Plywood - Classification by surface appearance - Part 1: General (assessment procedure)
• ISO 2074 - Plywood - Vocabulary

Keywords: ISO 2426-4, palm‑plywood, oil palm veneer, surface appearance classification, plywood standards, appearance classes, manufacturing defects, visual assessment.