10.0 Uvb Light

BloodShot there are a lot of suppliers on the net for the high intensity UVb lamps, most (all) I've come across require proof that the bulbs are used for medical, zoo or industrial (curing) use. If you find this to be the case you'll probably have more luck with reptile lights. I'm questioning tanning tubes now because I found this on one site:

"Tanning lamps emit primarily UVA radiation with a small amount of UVB"

http://www.tanningtraining.com/btc/ch3.html?prodid=6



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http://www.spdiuv.com/

http://www.discount-light-bulbs.com/tanning-bed-bulbs.html

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I use a 70W double ended metal halide in an open reflector with a 600W HPS. I only run 1 hour per light cycle. Amount of UV is too high to run more. Difference is huge. I'm still dialing in on the right amount. No question that UV make a big difference.

Hobbes, the distance will depend on the wattage, how much it converts to UVB and how big it is.

From most of the charts for reptile fluoro's I've seen, the bulb has to be extremely close.

The reflectivity of the surfaces will be given for visible or photosynthetic light. UVB is heavily absorbed by most things (why it burns skin), so I wouldn't be surprized if we find significantly less of it is reflecting off the walls.

Do you have a brand name for the lights you're using? The best way to check it is to try and find somewhere that mentions what the uW/cm^2 is. You want it to be about 250 at the distance you'll be using it. Same as .23 W/ft^2. A lot of the bulb manufacturers seem to be measuring intensity right up against the glass.

Check out this link and scroll down the bar graph (notice how many brand name bulbs he's using and how none of them ever reach sunlight UVB, even 2" from the bulb);

http://www.uvguide.co.uk/fluorescenttuberesults.htm

As soon as you get out to 12", there's barely anything. The light intensity falls off exponentially with distance.

This is why I've been so interested in this thread. I think before any serious testing can be done, people need to understand the gigantic variable in the light type and placement. Lots of them are no where near sunlight UVB at the distances used, others will absolutely incinerate the plants with UVB. Finding a good balance is still a work in progress - but the Osram Ultra-Vitalux are good possibilities and the medical fluoro's are options.

BloodShot, the medical bulbs would have to be an online order, they're not something you'll find locally anywhere near as easily as the reptile bulbs. They're a bit more expensive from what I can tell, but if you're considering something like the Zoo MegaRay, that costs a fortune and the medical fluoros will provide better distribution. You shouldn't look suspicious buying one, they're going to be more bothered about you thinking it's a blacklight and burning your eyes.

Stealthy, do you have a picture of your UVB set? I'm kind of interested in the double ended bulbs too.

Aluminum reflects mostly all wavelengths very well, while most surfaces dont reflect UV light....heres a chart

Aluminum is the weapon of choice for mirrors in UV lasers, so that will work yes.

Hopefully the tent designers haven't sprayed the Aluminium with a protective coating (since it usually dulls quite rapidly). Then it'd depend largely on what it's been sprayed with.

Even if it's some UV absorbing nastyness, tinfoil will solve that. If it does absorb UV, it could potentially damage the lining of the tent.

Maybe an area for investigation? Ask some tent suppliers if they do any coating. Post up here if you ask so we don't double post them.

Looks to me like silver is the ideal candidate.. Pretty much an ideal cut-off point for damaging, shortwave UV.. (Not that I think it would make a noticable difference at all)..

Thanks Peach, great help. Couple questions:

Are we concerned about UVB penetration or is all (most) of the UVB light absorbed by the first piece of plant it hits?

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Great chart of UVB levels around the world in a chart from your link:

http://www.uvguide.co.uk/uvinnature.htm

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"Do you have a brand name for the lights you're using?"

Exo Terra Repti Glo 8.0 1.0" with a reflector, no 10.0s in stock. Just one 36" 30W for now.

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Hi Hobbes,

I said earlier on in the post I think absorption by the first few leaves is going to be a big issue - I expect the first leaf is probably going to absorb most of the UVB and leave a dark shadow underneath it.

We had a discussion about things like light movers and training the plants to grow mostly as canopy (so all the buds get hit, not just the top ones).

That's why I was interested in vertical fluorescents, that'd help the light go sideways into the plant and hit buds if you have them scattered around more.

I'm guessing you'd need the Exo about 2" or less from the plants for sunlight UVB - according to the charts on that page I linked to.

oh ya everyone sells silver reflectorss

the graph clearly shows aluminum reflects about 90% of light+UVB...silver barely reflects UVB and EVEN MORE UVC!!! besides uvc is not emitted by these bulbs and if it was..ummm OZONE!! i dont say this much but your obviously too damn high

im cheap so im just using regular cfls which DO emit dangerous amounts of UV at close range for long periods...

The medical fluoro's seem to have an output of about twice the reptile ones per unit length. I'm still working on the price, but it seems they'll also be around twice as expensive, or slightly more.

I just discovered the Osram Ultra-Vitalux only outputs around 3W of UVB. The high intensity numbers are due to it being more focused than a fluoro - but that's essentially the total you'd get from a decent reptile fluoro.

It's probably also worth considering that 250 uW / cm^2 is the very peak of sunlight in the middle of the day. If you leave your lamps running for 12h, they don't need to continually be at high noon levels of UVB.

These are values someone suggested on the THC and UVB youtube video;

10am: 192 microwatts/cm2
11am: 233 microwatts/cm2
12pm: 256 microwatts/cm2
1pm: 269 microwatts/cm2
2pm: 262 microwatts/cm2
3pm: 239 microwatts/cm2

They're falling off before 11am and after 2pm, only at 250 uw / cm^2 for around 3 hours. Leaving yours on at a lower output for 4 times as long could be all that's needed.

The only tanning tubes I've looked at so far have emitted around a watt or less of UVB, even the big 100W tubes. UVA is better for tanning I think. Maybe there's some brand with more UVB, I haven't seen it yet.

You don't want the UV shorter than that silver cuts out at though.. You only want the mild UV wavelengths..

why do you think there is no UVC on earth??? is the light reflecting off silver...its called ozone

Ozone is created by the photodissociation of oxygen by UVC. Oxygen and other molecules are being torn apart, and although the other molecules are not part of this story, they do dissociate, as well.

simply having air in between the light and plants will filter out the uvc....

but your right, use the reflector with less than 20% UVB reflectance because obviously UVC is your greatest concern...Ill personally use aluminum and achieve 90% reflectance and guess what NO UVC AT ALL...

GLASS AND AIR FILTER OUT UVC!!!

btw...I dont think its the bud making you say these stupid things


Id be worried about penetration also, but the leaves are irrevelant since most trichromes are on the calyxs....but Im pretty sure UV doesnt pass through leaves since it causes damage to them, and a possibe role of trichromes full of resin is to filter the UV before it hits the plant. The plants with protection on the reproductive parts would ultimately survive even though the leaves are not covered with trichromes

You answered your own question.. Except some UVC does make it to earth.. Granted not much UVC at all will make it through the atmosphere, but some will, even near sunset..
Al will reflect UVC though, and we don't have 60 miles of atmosphere to scatter as much as happens naturally, so if your bulb is producing UVC, then the Al would reflect it, and the plants will recieve a good portion of it..
Again, I don't think its very critical as I mentioned ealier.. My most recent post was just pointing out the technicality regarding wavelengths since ppl seem to think Al properties are better than Ag for this purpose..

these bulbs do not emit uvc

and uvc doesnt hit the earths surface...

also heres a great book about the effects of UV on plants, look around page 91

Abiotic Stress Tolerance in Plants
By Ashwani K. Rai, Teruhiro Takabe

http://books.google.com/books?id=vEQ2ZygCKa8C&pg=PA92&lpg=PA92&dq=does+any+uvc+hit+earth+surface&source=web&ots=aYoYY_xiqn&sig=74biy-x2DipnOr2pR0EvbvgXqv0&hl=en&sa=X&oi=book_result&resnum=1&ct=result#PPP1,M1

One more time.. I made that comment in regards to the properties of aluminum vs silver..
Did you notice the scale of that plot though? Linear, and calibrated for sunlight maximums.. I wouldn't expect UVC irradience to show very dominantly on that plot either..
My background is condensed matter physics.. In a field like that, the occurance of improbable things gets drilled into you pretty hard..

Id be worried about penetration also, but the leaves are irrevelant since most trichromes are on the calyxs....but Im pretty sure UV doesnt pass through leaves since it causes damage to them, and a possibe role of trichromes full of resin is to filter the UV before it hits the plant. The plants with protection on the reproductive parts would ultimately survive even though the leaves are not covered with trichromes

Click to expand...

Read up on fluorescence in photosynthesis..

The atmosphere is miles thick, whereas the distance between a lamp and your grow is probably feet or less. So the amount of UVC absorption won't be quite the same.

I don't think UVC is something to worry about though, because most of these bulbs don't emit much of it to start with.

The shorter the wavelength (visible->UVA-> UVB->UVC) the more energy it takes to create it. UV is already quite a high energy radiation, deep UV (UVC) needs a monster to produce a lot of it. And virtually everything absorbs it (including the glass the bulb is made from - a big problem for scientists who need intense UVC). Deep UVC bulbs are used in scientific equipment, and they're really specialized, not like normal reptile or tanning bulbs.

X-rays are right next to UVC, and they require a fk'ing beast of a setup to produce - the tube designs are often top secret and have some very special shit going on inside (electron guns and white hot tungsten targets they shoot into to produce the rays).

The leaf shadow thing is more of an issue if you have a leafy plant with buds all down the stems. Then the leaves might shadow the bud sites further down. If you have all your buds tight up at the canopy, that's not a problem.

I'm getting close to joining the UV experiment. With there being such a massive variation in the intensity and distribution of light from the bulbs, I'm trying to find the best before I spend a wad of cash.

Stop fighting with each other, we have a more important goal....

Stray x-rays can be formed without much difficulty.. TV's have x-ray protection features because they aren't that uncommon in HV applications.. You can build a diy x-ray projector with old vacuum tubes.. Best I've seen was able to make out a nail in a 2x4.. Its actually quite dangerous..
Its also been discovered that peeling scotch tape in a vacuum produces non-negligable amounts of x-rays.. Its a pretty recent find though, so I don't think its clear how useful that may end up being..
Don't get me wrong, x-rays are another thing not worth caring about here since voltages aren't in the dozens of kV range, and I agree with pretty much everything you just said..

Anyone know anything about Full Sun bulbs from Life Light? They claim to produce the UVB and UVA spectrums but then says "these lamps produce in phase energy, in wavelengths from 380-740nm." Which is higher than the 280-320 we're looking for.

I've been searching for a spec sheet to see how many uW/cm^2 we'd get at different distances but have found nothing yet. I'll keep looking for info, if anyone else comes across any please post it.

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Full Sun - Life Light Tech

Full Sun Lamps Ceramic Full Spectrum HID or HPMH (High Pressure Metal Halide) are the most effective lamps for all stages of plant growth. One lamp for all, with no need for switching from Metal Halide (MH) to Sodium(HPS) during vegetative and/or flowering stages. These lamps have more reds than any type of HPS and also produce the perfect amount of orange, yellow, green, blue, violet and UVA and UVB spectrums needed to simulate the sun. Just like the sun light that hits the Earth, these lamps produce in phase energy, in wavelengths from 380-740nm. These lamps are the most efficient lighting source available, produced in sizes of 100w, 150w, 250w, and 400watts. Special Features: More reds than HPS lamps The right amount of blues Open fixture rated One bulb for veg. & flowering.

http://www.hhydro.com/cgi-bin/hhydro/HH01100.html

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ps

I've got a Sun Pulse ceramic 600W MH, nice light.

From what I've been finding we're going to need an HID light - most of the authors I've read said MH - to get the power we need for spread and penetration from above the canopy. Anyone find another technology that's producing the kind of results we need?

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