# Can using black glue coating on an umbrella block 99.99% of UV-A and UV-B radiations?

Black glue umbrella is the newer version sun umbrella instead of silver glue umbrella. Our XUYAO sun umbrellas are coated with triple (3x) black glue, providing UPF 50+ highest UV protection, blocking UV-A 99.99%, blocking UV-B 99.99%. And the black glue are coated inside where is safe from rain-washing, providing lifetime UV protection.

Can using black glue coating on an umbrella block 99.99% of UV-A and UV-B radiations?

I couldn't find anything when searching for "glue coating".

• Of course you will still get a substantial dose (much greater than 0.001% of the direct radiaton) from rays reflected from the ground and nearby objects. To a first approximation you get the same proportion of the UV as you do the visible light (assuming no filters that block UV but not visible light). So unless you sit in a blacked-out tent the coating makes very little practical difference. Jan 23 '20 at 10:10
• @PaulJohnson: [citation-needed] Jan 23 '20 at 13:19
• @Oddthinking another reference regarding reflective UV: jamanetwork.com/journals/jamadermatology/article-abstract/… Jan 23 '20 at 15:36
• @PaulJohnson thanks Paul, I'm only considering direct UV when computing the percentage of blocked UV Jan 23 '20 at 15:37

Simple answer - YES

More complicated answer - anything, with enough layers can block UV rays to such extent.
UV are waves. 315- 399 nm for a UVA and 280-314 nm and UVB in wavelenght. So using a losesly knit clothes leaves the opening for the wavelength to go through. Stacking layers on top of each other make the opening smaller and smaller. WHO Individual protection against UV clothing

Most complicated answer - it's not the matter of material but it's color. Difference beetwen silver and black glue is just hue. The darker the hue (of anything beetwen you and sun) the more UV rays are absorbed.
Darker the color the more wavelentght is absorbed and not bounced back. Which color reflect more light

There is a diffrence beetwen "Blocking" and "absorbing" but in the marketing world what is important is how to sell you the final amount that get to your skin.

There is some miscomunication in the text you quote, as "what is silver glue umbrella"? Do they compare to single sheet of fabric single coating with silver glue or a "sandwich" umbrella where you have two sheets of material and glue beetwen them (and such umbrellas provide 100% UV).