ISO 16938-1:2019

Overview

ISO 16938-1:2019 - "Buildings and civil engineering works - Determination of the staining of porous substrates by sealants used in joints - Part 1: Test with compression" specifies a laboratory method to evaluate the likelihood that a joint sealant will cause early staining or discoloration of porous building substrates (for example marble, limestone, sandstone, or granite). The standard defines specimen preparation, conditioning, compression, accelerated aging (heat, cold, actinic radiation) and visual/measured assessment of stains on the substrate surface and into the substrate depth. Results are specific to the tested sealant and the tested substrate and cannot be extrapolated to other formulations or materials. The standard also cautions that a negative result in this accelerated test does not guarantee absence of staining over longer real-world exposure.

Key topics and technical requirements

• Specimen assembly: two matching substrate pieces with spacers and sealant applied between them; masking tape to prevent contamination.
• Preparation and curing: follow sealant manufacturer’s instructions (primers, mixing); cure and condition specimens for 28 days at (23 ± 2) °C and (50 ± 10) % RH.
• Compression: specimens are compressed to a percentage equal to the sealant’s movement capability (typical compressions: 7.5 %, 12.5 %, 20 % or 25 %) and held under clamps.
• Aging procedures: selectable accelerated aging by
  • Heat aging (ventilated oven at (70 ± 2) °C),
  • Cold aging (refrigerated enclosure at (−20 ± 2) °C),
  • Actinic radiation using fluorescent UVA-340 lamps (ISO 4892-3) or xenon-arc (ISO 4892-2).
• Apparatus: spacers, non-adherent substrate (PE or PTFE), masking tape, ventilated oven, refrigerated enclosure, UV/xenon chambers, black standard thermometer, measuring device (0.5 mm scale).
• Evaluation: visual inspection and quantitative recording of maximum/minimum stain width and penetration depth; four specimens per sealant and per aging method.
• Limitations: accelerated exposures simulate early exudation-driven staining only; long-term behavior may differ.

Applications and who uses it

• Sealant manufacturers - to screen formulations for potential staining on specific porous substrates.
• Facade and stone contractors / specifiers - to assess compatibility of sealants with natural stone and porous cladding materials.
• Architects and building envelope consultants - to specify appropriate joint sealants for aesthetic-sensitive porous substrates.
• Materials testing labs - to provide standardized test reports for product qualification and comparative assessment.

Related standards

• ISO 4892-1, ISO 4892-2, ISO 4892-3 - methods for laboratory light-source exposures (xenon, fluorescent UV).
• ISO 6927 - sealants vocabulary.
• ISO 11431 - determination of adhesion/cohesion of sealants after exposure.

Keywords: ISO 16938-1:2019, staining of porous substrates, sealant testing, test with compression, accelerated aging, joint sealants, natural stone staining.