Overview
ISO 9961:1992 - Draughting media for technical drawings: Natural tracing paper defines minimum requirements and test methods for natural tracing paper used for technical drawings. The standard covers the qualities needed for draughting and reproduction across commonly used grammages (40–160 g/m² with typical nominal weights of 62.5, 72.5, 92.5 and 112.5 g/m²). It also includes two normative annexes: Annex A (measurement of transparency by the reflectance method) and Annex B (determination of tear growth resistance).
Key topics and technical requirements
- Definition: Natural tracing paper is a drawing paper for ink and pencil whose translucency is achieved by mechanical treatment during manufacture.
- Grammage: Specified nominal weights within the 40–160 g/m² range (listed values above).
- Appearance & cleanliness: Uniform appearance under transmitted light; free from dirt, wrinkles, pinholes.
- Surface classification: Papers are classified as smooth or matt; smooth/matt performance is assessed by standard surface-smoothness tests.
- Draughting quality:
- Tests with tubular technical pens (see ISO 9175 series) using India ink (ISO 9957) - line width tolerance after drying: +10% (±0.04 mm) for a nominal 0.35 mm line.
- Redraughting (drawing over erasures) criteria: ink-line thickness may differ up to 10% in corrected areas; minimum redraughting performance values are given in the standard’s table.
- Transparency: Measured by transmission densitometry or the reflectance method (Annex A) including total light and UV components (use of UV filter such as Wratten 18A).
- Tearing resistance: Measured by Elmendorf method (ISO 1974) or Brecht‑Imset (Annex B); values required are specified in the standard.
- Ageing & storage: Accelerated ageing tested per ISO 5630‑1; paper should retain at least 70% tearing resistance after ageing. Normal storage life expectation: usable for a minimum of 10 years under proper conditions.
- Packing, labelling & sizes: Sheet and roll sizes per ISO 216 / ISO 5457; packages must include identification, grammage and handling instructions.
Practical applications and users
ISO 9961 is used by:
- Paper manufacturers to specify and certify natural tracing paper for draughting.
- Engineering, architecture and drafting departments to select drawing media compatible with technical pens and reproduction workflows.
- Reprographic and archival services to verify transparency, permanence and tear resistance for long-term storage.
- Procurement/specification writers creating material requirements for technical documentation.
Benefits include consistent draughting performance, reliable reproduction quality, and standardized testing for transparency and mechanical resistance.
Related standards
Commonly referenced standards include:
Keywords: ISO 9961:1992, natural tracing paper, draughting media, technical drawings, transparency, tear resistance, grammage, draughting quality, reflectance method.
