Group8 Spectral Panels may require cleaning if significant dirt/dust impacts them. Below is a link to the manual from the panel material manufacturer, Group8, where you can find their specific recommendation for cleaning. Below is a snippet from the manual related to cleaning. While cleaning the targets, you can choose to clean the panel case as well, but this is not required.
2.3.2 Washing
It is recommended that the target panel be washed when they appear dirty, and it is likely that the reflectivity has changed because of dirt build-up.
Washing of the target panel may be accomplished by spraying the target with clean tap water from a hose and applying a mild detergent. A soft bristle push broom may be utilized to gently move the soap solution across the surface of the target to remove embedded dirt, if necessary.
The recommended washing procedure is to unfold the target, face-up (reflective surface facing upwards) on a clean concrete surface during a calm, sunny day. The target surface should first be sprayed with clean water from a hose using a soft-spray nozzle setting. The target surface may then be sprayed with a diluted detergent or soap solution (dish washing liquid detergent) and the target surface cleaned. The target must then be rinsed with clean water from the hose and pulled to a clean, dry area away from the wet wash area and allowed to air-dry.
When the target is dry on both sides (bottom and top), roll up or fold the panel in a display ready bundle. Note that the higher reflectivity panels will dry more slowly than the darker panels, therefore, be certain to check the back of the target to assure it has dried before folding the panel for storage. Do not store a wet or damp target. Make certain target panel is dry before folding or mildew may occur even though preservatives and biocides have been added to the coatings
