ISO 9073-9:2008

Overview - ISO 9073-9:2008 (Drapability test for textiles)

ISO 9073-9:2008 is the international test method for determining drapability and the drape coefficient of fabrics, including nonwovens, wovens and knits. The standard describes how to hold a circular specimen on a drape meter, cast its shadow, and quantify the projected shadow area as a percentage of the flat specimen area (the drape coefficient). SI units are the official measurement system and the standard references ISO 139 (conditioning) and ISO 186 (sampling).

Key topics and technical requirements

• Scope & principle
  • Measures the ability of a circular specimen to deform when suspended and form folds (drapability).
  • Drape coefficient = (area of projected shadow / area of undraped specimen) × 100%.
• Two evaluation methods
  • Method A (manual / paper rings): shadow traced onto rings of translucent paper, cut out and weighed. Percentage mass of shaded paper gives the drape coefficient.
  • Method B (automatic / image processing): digital camera captures shadow on a white sheet; software converts to monochrome, performs Fourier analysis and derives drape coefficient plus shape parameters.
• Measured parameters (method B)
  • Node number (count of drape waves), wave amplitude (cm), wavelength (degrees), minimum/maximum/average amplitude, variance, and Fourier fitness metrics.
• Apparatus highlights
  • Drape meter with two concentric horizontal discs (18 mm stated in standard for discs), point light source and parabolic mirror; paper rings with internal 18 cm and external diameters 24, 30, 36 cm; templates for specimen cutting; optional camera frame and software for Method B.
• Sampling, specimen size & conditioning
  • Preliminary test on 30 cm diameter specimen. Use 30 cm if drape coefficient is 30–85%; use 24 cm for limp fabrics (<30%) or 36 cm for stiff fabrics (>85%); always also test at 30 cm. Condition specimens at least 24 h per ISO 139.

Applications - who uses it and why

• Textile testing and quality assurance laboratories performing textiles test methods and nonwoven testing.
• Manufacturers and product developers assessing garment drape, upholstery, home textiles, technical nonwovens and appearance-related performance.
• R&D teams comparing drapability across materials, optimizing fabric hand and aesthetic behavior, or validating simulations (3D drape reconstruction from images).
• Procurement and compliance teams that require standardized, reproducible drape data for specifications and supplier acceptance.

Related standards

• ISO 139 - Standard atmospheres for conditioning and testing
• ISO 186 - Sampling to determine average quality
• Other parts of ISO 9073 (e.g., thickness, tensile, bending) for complementary nonwoven test methods

Keywords: ISO 9073-9:2008, drapability, drape coefficient, nonwovens, drape meter, textiles test methods, image processing, fabric drape, test standard.