In accelerated aging studies, exposure to UV rays have been shown to cause fusibles to tan darken on light colors, sheers or other light weight fabrics, or with surface use. This tanning may read as a color shift or dark spots. But now theres Mistyfuse Ultraviolet Mistyfuse Ultraviolet is specially formulated with an effective retardant to protect against the tanning effect of UV rays without sacrificing any of the inherent Mistyfuse qualities you expect and trust. Mistyfuse Ultraviolet is white and fuses clear. Size: 20" x 2.5 yards.