Glass light covers block UVB?

[KarlJay]

I'm reading Ed Rosenthal's growers handbook and found out that regular glass blocks UVB light. He shows a light hood that is open, but angled to allow heat to pass upward. He and others also talked about the value of UVB light on quality of the final product.

Q. Are the glass shields on our hoods regular glass or do they allow UVB to pass thru?

If now, why are these hoods being sold for growing when they block a very important part of the light?

 

[DJ McFinnigan]

Most glass absorbs the short wavelength UV (UV-C 190 - 280 nm and UV-B 280 - 320 nm), but transmits the longer UV-A (320 - 400 nm) radiation. It can, however, be a real toss up because quite literally, all glass is not created equal. Depending on how the glass was made, the materials used, and the varying amount of impurities, the amount it is going to absorb will be different. That said, I would imaging that the amount of UVB being blocked is a small amount and the the trade off in trapping and getting the heat out of the hood is of more value and thus a acceptable loss.

 

[KarlJay]

Actually if it's normal glass, it blocks ALL UVB.

Do UV Sun Rays Go Through Windows?

I guess the real question is what kind of glass these hoods use. My guess is that if any hood has special glass that allowed UVB to pass, they would label it and charge more. I'm actually surprised, given the price of these hoods and advancements in indoor growing, that some company hasn't come up with a solution.

According to the book, UVB is very important to the quality of the end product.

I wonder if the glass bulb is the reason they don't worry about it, if UVB is blocked by glass, then wouldn't the glass bulb block the UVB? The light is actually made inside the glass bulb, the glass just holds the bulb guts in place and keeps the gases in.

 

[Fuzzy Duck]

The question is do HPS or MH bulbs which you would use in these hoods give of UV-C, UV-B & UV-A in the first place ?

 

[KarlJay]

The question is do HPS or MH bulbs which you would use in these hoods give of UV-C, UV-B & UV-A in the first place ?

I agree, and I think the answer is no... unless the bulb is made from special glass. I kinda think they would be made of special glass because they are made by companies that should know all about this stuff.

Do those spectrum charts on the bulb tell us anything beyond color temps?

Also, how to those reptile bulbs work, they must have some kinda special glass or something.