ISO 9727-6:2007

Overview

ISO 9727-6:2007 specifies a standardized laboratory test method for determining the liquid tightness of cylindrical (straight) cork stoppers. The method applies to corks intended to be completely inserted into a bottle neck and defines the materials, apparatus, environmental conditions, stepwise pressure test and reporting requirements used to detect liquid leakage through or past a stopper.

Keywords: ISO 9727-6:2007, cylindrical cork stoppers, liquid tightness, cork stopper testing, straight cork stoppers

Key topics and requirements

• Scope: Applicable to all types of cylindrical cork stoppers ready for use (straight cork stoppers).
• Materials: Use acetone for cleaning glass tubes and a 10% hydro-alcoholic solution coloured with methylene blue as the challenge liquid.
• Apparatus:
  • Bottling machine with 4 jaws (jaw-compression diameter adjustable between 15.5 mm and 16 mm).
  • Glass tubes sized to bottle bore (internal diameter 18.5 mm ± 0.2 mm or d ± 0.2 mm).
  • Pressurization device with a manometer resolution of 0.1 bar (or equivalent pressure-measuring device).
• Test conditions:
  • Ambient temperature: 21 °C ± 4 °C.
  • Relative humidity: 60 % ± 20 %.
  • Cork temperature: 21 °C ± 4 °C; cork humidity targeted at 6 % ± 2 % (report if outside 4 %–8 %).
• Procedure:
  • Clean glass tubes with acetone, seat corks using the bottling machine, wait 1 hour, invert tubes and add 3–5 ml coloured hydro-alcoholic solution.
  • Place tubes on the pressurization device with filter paper contacting the stopper outside.
  • After one hour, increase pressure in 0.3 bar steps, holding 10 minutes at each step: 0.3, 0.6, 0.9, 1.2 and 1.5 bar. Observe for coloured stains on the filter paper to indicate leakage.
• Results and reporting:
  • Record which stoppers leaked and the minimum internal pressure at which leakage occurred.
  • Test report must reference ISO 9727-6, describe glass tube dimensions, sample identification, sampling plan, test results and any deviations.

Applications and who uses it

• Cork manufacturers: quality control for stopper design and production consistency.
• Bottlers and wineries: verifying stopper integrity before filling to prevent product loss and contamination.
• Independent test laboratories and certification bodies: providing objective leakage performance data.
• R&D teams: evaluating new cork treatments, agglomerated corks or alternative materials for sealing performance.

Practical benefits include improved packaging reliability, reduced bottle returns, and documented evidence of stopper performance for regulatory or commercial specifications.

Related standards

• ISO 9727 (full series) - Cylindrical cork stoppers - Physical tests:
  • Part 1: Determination of dimensions
  • Part 2: Mass and apparent density for agglomerated stoppers
  • Part 3: Humidity content
  • Part 4: Dimensional recovery after compression
  • Part 5: Extraction force
  • Part 6: Determination of liquid tightness (this document)
  • Part 7: Determination of dust content

Use ISO 9727-6:2007 alongside other parts of ISO 9727 to build a comprehensive cork quality and performance testing program.