Overview
ISO 12632:2015 specifies standardized test methods for the behaviour of printed labels and label substrates when exposed to hot alkaline cleaning solutions. The standard addresses three interrelated test objectives: the penetrability of hot alkaline solution through labels, the removal time of wet-glued labels from refillable bottles, and the resistance of printed labels against hot alkaline solutions. Test results apply to the complete system of substrate, ink film and varnish (if present), and label substrates include metalized papers.
The standard is aimed primarily at the beverage industry and operations that refill and reuse bottles or containers where hot alkaline cleaning is used. It also supports ink and paper evaluation during label development and quality control.
Key Topics
- Test principles: penetration time (indicator colour change), removal time (separation from glass substrate) and resistance (visual inspection and solution colouration).
- Indicator and reagents: a thymolphthalein-containing glue is used to reveal penetration (blue colour) and sodium hydroxide solutions are specified (1 % NaOH for penetrability/removal tests; 2.5 % NaOH for resistance tests).
- Representative test conditions: when testing labels for glass bottles the NaOH solution temperature is (75 ± 2) °C for penetrability; resistance testing uses 2.5 % NaOH at 85 °C for 20 minutes with magnetic stirring at (250 ± 50) rpm (as specified in the standard).
- Specimens and preparation: ink films must be fully dried/cured prior to testing; multiple specimens are used and labels are glued onto petri dishes with the thymolphthalein glue.
- Evaluation criteria:
- Penetration endpoint: three-quarters of specimen area turns blue.
- Removal endpoint: label separates from petri dish.
- Resistance: integrity of substrate, integrity of printed image and no colouration of the alkaline solution after filtration.
- Safety: hot alkaline solutions can cause severe chemical burns and eye damage; use protective gloves and safety glasses.
Applications
- Quality control for printed labels and label substrates intended for refillable bottles.
- Screening and selection of inks and varnishes for alkali resistance and minimal contamination of cleaning solutions.
- Process stability in industrial bottle-cleaning systems and reduction of waste-treatment costs by avoiding dyeing of cleaning solutions.
- Supplier and contract testing to document compliance and support product development.
Related Standards
ISO 12632:2015 was prepared by ISO/TC 130 (Graphic technology) and the test methods are established in the European beverage industry and harmonized with corresponding DIN practices. For broader conformity assessment consult complementary ISO guidance from graphic-technology and packaging committees and local regulatory requirements.
Practical value: applying ISO 12632:2015 helps manufacturers, printers and beverage packagers ensure labels detach reliably during hot-alkali cleaning, preserve substrate integrity, and avoid contamination of recycling streams and cleaning effluents.
Open preview (PDF)Graphic technology — Ink, paper and labels — Requirements on hot alkali penetration and resistance
