Bedeutung und Verwendung
4.1 Weil Sonneneinstrahlung, Lufttemperatur, relative Luftfeuchtigkeit, and the amount and variety of atmospheric pollutants are constantly changing, time-elapsed exposure results can sometimes vary. Variation in results is usually reduced by timing exposure in the following ways:

4.1.1 One or more environmental parameters, such as solar radiation exposure

4.1.2 Changes in predefined properties of aged reference specimens with known properties.

4.2 Changes in temperature, humidity and atmospheric pollutants can have a significant impact on degradation caused by solar radiation. Zusätzlich, exposure at different times of the year can lead to huge differences in the rate of degradation. Different materials typically have different sensitivities to heat, Feuchtigkeit, and atmospheric pollutants, which could explain the difference in ranking of samples exposed to equivalent solar radiation exposure when other environmental conditions change.

4.3 As the installation method has an impact on the temperature and other parameters of the specimen during exposure, the parties to the contract shall agree upon the installation method of the specimen for the particular exposure test being considered.

ASTM G24-2021 Standardtestmethode für Belichtungstests bei Sonnenlicht durch Glas

4.4 There are differences in the transmittance of various single-strength window glass in the region of 300 to 350nm. Zum Beispiel, at 320 nm, the transmission of seven different batches of single-strength window glass ranged from 8.4% Zu 26.8%. At 380 nm, the percentage transmittance ranges from 84.9% Zu 88.1%.

4.5 Differences in UV transmittance between different batches of glass usually persist even after sun exposure. The biggest difference in UV transmittance of window glass is in the spectral range of 300 Zu 320 nm.

4.6 This practice is suitable for testing the relative properties of the material at the same time after comparing the same batch of glass. Because of the differences between large amounts of glass and exposure performed at different times of the year, it is not recommended to compare the amount of degradation of materials exposed for the same duration or radiation exposure at different times, or individual fixtures using different batches of glass.

4.7 Exposure to at least one control material with known properties is recommended for each test. The composition and structure of the control material shall be similar to that of the sample, and its failure mode shall be selected to be the same as that of the material under test. It is recommended to use two control materials, one with relatively good durability and one with relatively poor durability. When control materials are used as part of a test, they should be used to compare the properties of the test material with respect to the control.

4.8 Because some materials may degasses during exposure and may contaminate other specimens, it is recommended that only similar materials be exposed to the same glass cabinet at the same time.

ASTM G24-2021 Standardtestmethode für Belichtungstests bei Sonnenlicht durch Glas

Radius
1.1 This code describes procedures for exposing various materials to daylight filtered through glass in passively ventilated and unventilated enclosures. For exposure under glass enclosures with forced air circulation, see Practice G201.

1.1.1 This practice does not apply to corrosion testing of bare metals.

1.2 For direct exposure, see Practice G7.

1.3 This practice is limited to methods of exposure. The preparation of samples and the evaluation of results are covered in various standards for specific materials.

1.4 Two types of exposure cabinets can be used for exposure according to this practice.

1.4.1 Tippe A – Cabinets that allow passive ventilation of specimens exposed behind glass.

1.4.2 Typ B – Enclosed cabinet, externally painted black, does not provide ventilation for specimens exposed behind glass. Exposure using a B-cabinet is often referred to as “black box exposure under glass”.

1.5 Type A exposure of this practice is technically similar to method B of ISO 877-2.

1.6 Units – In SI-Einheiten ausgedrückte Werte sollten als Standardwerte betrachtet werden. The values given in parentheses after the SI unit are for reference only and are not considered standard values.

1.7 Diese Norm soll nicht alle Sicherheitsbedenken berücksichtigen, wenn überhaupt, mit seiner Verwendung verbunden. Es liegt in der Verantwortung der Anwender dieser Norm, für angemessene Sicherheit zu sorgen, Gesundheits- und Umweltpraktiken zu prüfen und vor der Verwendung die Anwendbarkeit behördlicher Beschränkungen zu ermitteln.

1.8 Dieser internationale Standard basiert auf international anerkannten Standardisierungsgrundsätzen, die in der Entscheidung über Grundsätze für die Entwicklung internationaler Standards festgelegt sind, Leitlinien und Empfehlungen des WTO-Ausschusses für technische Handelshemmnisse.