Outdoor umbrellas do block much of the harmful effects of direct ultraviolet rays. The large the umbrella, the greater the area of protection. However, the material and color of the canopy impact just how much. Here are some key factors:
Weave – The tighter the fabric is woven together, the less UV radiation passes through
Color – Dark colors of identical fabric types absorb ultraviolet rays more strongly than their lighter shades, which increases the sun protection
Weight – A heavier version of the same fabric will be minimally more protective against UVR
Stretch – The greater the stretch or tension put on a textile, the lower the UPF rating
Water – Some fabrics, such as polyester and cotton, provide less protection against UVR when they have absorbed water
Washing – Cotton-based fabrics tend to shrink after the first washing, thereby tightening the weave and reducing the transmitted ultraviolet radiation
Additives – UVR stabilizers or additives can be used to improve the sun protection of a variety of textiles
Additionally, you need to be aware of indirect UV rays that are reflected off of water, glass and light-color walls.