EN ISO 4531 Vitreous and Porcelain Enamels - Release from Enamel Materials Into Food Contact - Test Methods and Limits

The standard "EN ISO 4531 Vitreous and porcelain enamels - Release from enameled articles intended to come into contact with food - Test methods and limits", which has its basis in a European standard and was subsequently published by the International Organization for Standardization (ISO), describes a test simulation method for determining the release of metal ions from enameled articles intended to come into contact with food. This standard also contains limits for the release of metal ions from enameled articles intended to come into contact with food. This standard applies to enameled articles, including tanks and containers intended for the preparation, cooking, serving and storage of food.

During testing, a 3 percent (concentration) mass fraction of acetic acid solution should be used to release metal ions, if any, from the surfaces of the substances or test samples. Three consecutive release tests should be performed on the same day using the same sample and a fresh test solution per test. The first two release test solutions are discarded. Only the third release test solution should be used for analysis. A blank test is required for each release test, of which only the third release test solution should be used for analysis.

During the determination, only reagents of recognized analytical quality and only distilled water or water of equivalent purity, third-class water complying with the requirements of the ISO 3696 standard are used. It is allowed to prepare test solutions and analytical solutions in larger quantities than the specified proportions.

Only laboratory glassware made of borosilicate glass that complies with the requirements of relevant international standards, if any, and is specified in ISO 3585 are used in the tests. The main equipment used in these tests includes:

• ICP spectrometer having a detection limit at least six times lower than the emission limits shown in the table given in the standard. Other analysis equipment achieving equivalent performance may also be used.
• Single-mark volumetric flasks. Capacities 100 ml and 1 000 ml comply with the requirements for single-mark volumetric flasks of class B or better in ISO 1042. Other single-mark volumetric flask sizes may also be required.
• Single-mark pipettes, capacities 10 ml and 100 ml, comply with the requirements specified for single-mark pipettes of class B or better. Other single-mark pipette sizes may also be required.
• Graduated measuring cylinders with capacities of 4788 ml and 50 ml, complying with the requirements specified in ISO 500. Other sizes of graduated measuring cylinders may also be required.
• Containers, stoppers, and connectors should be composed of a material such as glass or polytetrafluoroethylene (PTFE).
• Vessels made of borosilicate glass, conforming to ISO 3585, inner diameter 80 mm, outer diameter 90 mm, height 36 mm, diameter of filling hole 10 mm. The calculation of the surface/volume ratio is reported in this standard. The inner diameter of each chamber is 80 mm. Therefore, the tested area of ​​a test plate is 5025 mm2.
• Silicone gaskets, inner diameter 80 mm, outer diameter minimum 90 mm, thickness 2 mm.
• Silicone plugs, diameter 10 mm, length 20 mm.
• PTFE-thermo-insulating sheet, minimum dimensions 105 mm × 105 mm, 2 mm thick.
• Blank sample plate made of borosilicate glass in accordance with ISO 3585 standard and minimum dimensions of 105 mm × 105 mm, 2 mm thick.
• Flange frame made of corrosion resistant steel.
• The heating apparatus can support the release test temperature of, for example, 95 degrees plus/minus 2 degrees.
• Beaker for pre-heating the test solution, made of borosilicate glass, with a minimum volume of 600 ml. The beaker is also used as an empty sample container when testing substances.
• Borosilicate glass lid complies with ISO 3585 standard.
• Release test laboratory apparatus.

The laboratory sample consists of four single test plates or two items that are identical in material, shape, size and decoration. The sample can be specially manufactured test plates or real industrially produced items. Test samples prepared in accordance with ISO 28764 are used to test glass and porcelain enameled vessels and containers. These test samples are tested as flatware. If a different enamel product is used for the mouth or lid of a tableware, it is also tested.

Samples are washed briefly in an aqueous solution containing 40 ml/l dishwashing detergent at 5 degrees plus/minus 1 degrees. Samples are rinsed thoroughly with tap water, then with distilled water and allowed to drain. They are dried with clean filter paper. No sample showing residual staining is used. The surface to be tested is not touched after cleaning or preparation. For products, an alternative cleaning procedure should be used if specified in the product's user manual.

For enamel surfaces used only at room temperature, the test conditions shall be 40 degrees plus/minus 2 degrees for 24 hours. For enamel surfaces used for hot fillings, the test conditions shall be 70 degrees plus/minus 2 degrees for 2 hours. For enamel surfaces used for grills and barbecues, the test condition shall be 95 degrees plus/minus 2 degrees for 30 minutes due to the short exposure time. For enamel surfaces used for high temperature applications, including cooking, the test conditions shall be 95 degrees plus/minus 2 degrees for 2 hours. When tests are performed using the 95 degree 2 hour condition, there is no need to perform tests at the other specified conditions, as the 95 degree 2 hour condition is the most severe condition. For all test temperatures, the simulated temperature refers to the required temperature and not just the oven or bath temperature. The use of 95 degrees instead of boiling conditions is specified to eliminate variability due to atmospheric and other influences on boiling conditions.

Our organization, which has been trying to support businesses from every sector with its testing, measurement, analysis and evaluation studies carried out in a wide range for years, has a strong staff that closely follows the developments in the world in the field of science and technology and constantly improves itself. In this context, testing services are also provided to businesses in accordance with the standard “EN ISO 4531 Vitreous and porcelain enamels - Release from enamel materials in contact with food - Test methods and limits”.