Colour Fading of
Technical Bulletin #19
Current as of November 2015
Asphalt shingles are covered with mineral granules to protect the asphalt from UV radiation, and provide a degree of fire resistance. The granules are coloured to provide different roof colours, and are generally of a natural stone, which is coated using colour pigments. Although the pigments are fused to the granule surface by a ceramic process, some of the pigments used are affected by UV radiation. The colour may also be affected by variables of roof exposure which may cause the colour to change with time.
Some factors which can affect the rate of colour change are:
1. UV radiation.
2. Orientation of the roof (south exposures are more severe than north exposures).
3. Shade or obstacles.
4. Biological effects such as mold, algae, etc.
5. Environmental factors such as acid rain.
The colour fading is typically very slight, but may be noticed as:
- change in the colour,
- loss of "gloss" or lustre,
- chalking (the appearance of a fine white film).
This phenomenon may start after the first few years of exposure and will continue with time. These changes are typically less prevalent with lighter granule colours.
Though the granule colour may fade, this will have little impact on the protection which the granules provide to the asphalt. The changes are surface changes to the coating applied to the granule particles only.
The information contained in this bulletin is for general education and is not intended to replace advice from a qualified contractor or direction on usage/installation from the manufacturer. Consumers should be aware of the safety hazards associated with work on roofs and, before doing so themselves, should consider following CASMA s advice of using qualified contractors. This bulletin may be reproduced with permission on condition that it be reproduced in whole, unedited, with attribution of copyright to CASMA.
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