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.
Open preview (PDF)Laboratory glassware — Methods for assessing the chemical resistance of enamels used for colour coding and colour marking