ISO 4794:1982

Overview

ISO 4794:1982 - Laboratory glassware: Methods for assessing the chemical resistance of enamels used for colour coding and colour marking - specifies standardized test procedures to determine whether enamel markings on laboratory glassware resist typical cleaning and service treatments. The standard defines sample preparation, reagents, apparatus, test conditions and pass/fail interpretation for enamel durability under alkaline detergent and dilute acid exposure.

Key topics and technical requirements

• Scope: Tests focus on enamel used for colour coding/identification (e.g., pipette colour codes). The standard does not rank enamels by resistance level; it provides a reproducible method to determine if an enamel “resists the specified treatment.”
• Reagents:
  • Distilled or deionized water.
  • Alkaline detergent: 50 g sodium pyrophosphate (Na4P2O7) + 5 g dodecylbenzene sulfonate per litre.
  • Hydrochloric acid: c(HCl) = 2 mol·L−1 (analytical grade).
  • Cold acetone (for rinsing).
• Apparatus:
  • 1 L beaker complying with ISO 3819.
  • Watch glass, heating bath capable of maintaining 80 ± 1 °C.
  • Inert sample holder, thermometer, closed containers and pure cellulose cleaning cloth.
• Test procedures:
  • Sample preparation: cut specimens including full enamel mark, leave ≥5 mm glass margin; wash three times in water and acetone; dry.
  • Alkaline detergent test: immerse up to 10 samples in 700 ml detergent solution at 80 ± 1 °C for 120 ± 5 min, then rinse and dry.
  • Acid test: immerse up to 10 samples in ~700 ml HCl solution at 23 ± 3 °C for 60 ± 5 min, then rinse and dry.
• Acceptance criterion: enamel is satisfactory if no colour change occurs that would prevent correct identification or could cause confusion with another code colour (loss of gloss alone is not a failure).
• Reporting: test report must record lot/delivery description, enamel colour, number of samples, results for each test, any re-tests and date.

Applications and who uses it

• Quality control labs and manufacturers of laboratory glassware use ISO 4794 to verify the durability of enamel colour coding and identification marks.
• Procurement and testing departments in research institutes, clinical labs, and educational labs apply these methods when specifying or validating glassware markings.
• Standards bodies and conformity assessors use the method to produce consistent, comparable test data for enamel resistance.

Related standards

• ISO 1769 - Laboratory glassware - Pipettes - Colour code (reference to colour-coded pipettes).
• ISO 3819 - Laboratory glassware - Beakers (used for test beaker specifications).

Keywords: ISO 4794:1982, laboratory glassware, enamel chemical resistance, colour coding, colour marking, alkaline detergent test, hydrochloric acid test, enamel durability.