Specimen Orientation and Duration
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Specimens can be exposed at any orientation. The most common orientation is mounting at a fixed angle facing south. The following table lists the most common exposure angles used in weathering tests:
| Angle* | Typical Application |
|---|---|
| 5° | Most automotive specifications |
| 34° | Same as site latitude: generally the most accumulated radiant exposure in a typical year among the common exposure angles |
| 45° | Most popular exposure angle |
| 90° | Siding and other materials used at vertical orientation |
| Variable 14° - 34° - 54° |
Maximizes radiant exposure with four angle changes per year with an overall increase over 34° of about 15% |
Specimens can also be mounted on follow the sun exposure racks. With follow-the-sun racks, the amount of solar radiation received by test samples can be increased by as much as 30%.
The duration of weathering is based on elapsed time (days, weeks, months, or years), or based on accumulated radiant exposure – either total (all wavelengths) or ultraviolet. Periodic inspections, measurements and/or returns are recommended.
Learn about Testing in Florida and Other Locations
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