For direct exposure the specimen is mounted on the exposure frame open backed or solid backed, and subject to all atmospheric effects.

This type can be used at a number of exposure angles. The standard angles used are 45, 5, and 90 degrees, or an angle equal to the latitude at the location of exposure. (All angles are referenced from a horizontal angle being 0 degrees). The angle chosen should be one that matches as closely as possible the position of the end use of the material.

In addition to the choice of exposure angle, the racks can be adjusted through 360 degrees of rotation in order to face any direction. To maximize solar radiation accumulation, the racks are normally positioned to face the equator.

The standard racks used by Sub-Tropical Testing are designed to hold the specimen firmly in place while providing a mask area over the top portion of the specimen. If controls are not available this area can be used for visual comparison of the changes occuring on the specimen.The racks are made of anodized aluminum, which is an inert material, and will not cause any contact corrosion effect. Our racks are cleaned on a regular basis to remove mildew and algae, which would otherwise contaminate the specimen, and affect the test result.