Overview
ISO 3248:2016 - Paints and varnishes: Determination of the effect of heat - defines a laboratory method to evaluate how single coatings or multi‑coat systems respond to elevated temperatures. The procedure measures changes in gloss and colour, and detects blistering, cracking or detachment after exposure to a specified temperature. It is specifically applicable to coatings intended for domestic radiators and other articles subject to similar thermal stress.
Key topics and requirements
- Scope: Assesses resistance of paint/varnish systems to heat-induced deterioration (colour/gloss change, mechanical failure).
- Principle: Coated test panels are oven‑heated for a specified time, cooled to ambient and compared with unheated control panels; optional follow‑up mechanical tests may be performed.
- Test conditions:
- Preferred temperature and duration: 125 ± 2 °C for 24 h, unless otherwise agreed.
- Panels are placed in a circulating‑air oven, not less than 100 mm from oven sides and 20 mm apart.
- Preferred support: suspend panels by fine wires to ensure even heating.
- Test panels:
- Substrates: steel, tinplate, aluminium or glass as appropriate.
- Panel size: 150 mm × 100 mm.
- Preparation and coating per ISO 1514; drying/conditioning per ISO 3270 at 23 ± 2 °C and 50 ± 5 % RH for ≥16 h before testing.
- Dry film thickness measured per ISO 2808.
- Post‑test: Panels cool to ambient temperature before examination. When specified, heated and unheated panels can be subjected to scratch, bend, cupping or impact tests (ISO 1518‑1, ISO 1519, ISO 1520, ISO 6272‑1).
- Precision: No precision data available in this edition.
- Reporting: Test reports must include product identification, reference to ISO 3248:2016, panel preparation details, drying/stoving conditions, film thickness, evaluated properties, results, deviations and anomalies, and test date.
Applications
- Quality control and type‑approval of coatings used on radiators, heating appliances, metal fixtures and other heat‑exposed household articles.
- Comparative performance testing during product development and formulation optimization for heat resistance.
- Contract and specification verification for suppliers and manufacturers specifying long‑term appearance and adhesion performance at elevated temperatures.
Who should use this standard
- Coatings formulators and R&D teams
- Independent testing laboratories and QA departments
- Appliance manufacturers (radiators, heaters)
- Specifiers and procurement professionals writing coating performance requirements
Related standards
Normative references incorporated by ISO 3248:2016 include ISO 1513, ISO 1514, ISO 1518‑1, ISO 1519, ISO 1520, ISO 2808, ISO 3270, ISO 6272‑1 and ISO 15528 - all relevant for sample preparation, panel standards, conditioning and complementary mechanical tests.