attention uvb users, what light cycles are you using????

cocoxxx

cocoxxx

Well-Known Member
on the case of strip vs cfl, i think ihave to go with cfl, main reason being, i would rather move the light than the plant. cfls can be dropped almost anywhere under canopy (major pain in the ass doing that with a strip light, plus i think your ment to only hang them horizontal, i may be wrong). i just like the versatility of the cfl although the light coverage is better with the strip.
 
Jerry Garcia

Jerry Garcia

Well-Known Member
One important thing to consider using is the effect UVB has on roots. I've read about a gene that helps control growth based on the levels of UVB hitting the roots. If too much UVB hits the roots, growth is slowed, but if little/no UVB hits the roots, then it tells the plant to grow. The gene is called RUS4 or something similar.

Moral of the story, if you plan on supplementing with UVB, cover the soil/roots. Probably won't kill you not to, but this may be one reason that people who use them for the full daylight cycle have trouble...

UVB is bad for people and bad for plants. Too much is even worse. For pot, it stresses the plant into protecting itself, i.e. producing more crystals. Don't work in your garden with these lights on and wear sunglasses!

That's some info I've picked up along the way. I've got the reptisun 10.0 26w cfl; I ran it once or twice during veg, but decided to wait until flower to use it again.
 
cocoxxx

cocoxxx

Well-Known Member
what size area is your reptisun covering?????. i have the 26w cfl reptisun covering about 2.5 sqf (small cfl grow) kept beside my 250w cfl , beside it inside the reflector
 
Mr.

Mr.

Active Member
Hobbes said:
Here's some figures and a link to the main thread:

250 microwatts/cm2 is and average around the equator.
929.034cm2 in a sqr. Ft. x 250 microwatts/cm2 = 232,257.60 microwatts/cm2
232,257.60 microwatts/cm2 = .23211 watts per Sqr. Ft.

so we need .23211 watts per Sqr. ft. of UVB

ie: Reptisun 10.0 UVB, 20 watts, 10% UVB 33% UVA
10% of 20 watts = 2 watts of UVB
grow area 4x4= 16 sqr. ft.
16 x .23211= 3.7137 watts per Sqr. ft of UVB Light

What he's saying is that a 20w 10.0 UVB bulb will emit about 16x more UVB than the sun. The only difference is, the UVB emitted from the sun is measured at human height (hundreds of millions of miles from the sun) - whereas the UVB emitted from the bulb is measured quite close to it. As you get further away, the intensity drops off quite quickly. You should have about sun intensity on your canopy if you use this kind of bulb on the top of your tent - around your HID, probabaly a bit higher.

So just put in a massive wattage and effiency bulb right? Wrong. UVB is very directional. If the theory holds up, it should be a lot better for your plants if you buy a couple of lower wattage lamps and spread them out. Otherwise, the top buds will absorb loads and anything undereathe will get zero.

I've been wondering about CFL versus strips myselfs and I think strips win, because they spread the light better. CFL's (with reflectors) will tend to produce a cone shaped light pattern, which is only good if you have one over every plant.

It's not only the light power you have to think about - all reptile lights put out a decent amount of UVB, get a reasonably high power one and put two foot over your grow and you have sun+ UVB. Out in the wild, cannabis might grow in individual bushes and it has all the soil it can want at it's roots, so it'll grow taller than us and really bushy - letting the UV hit it all over. Indoor grows, we tend to use smaller pots and keep it short and dense. That prevents the light getting deep inside the foilage, and so the buds won't be getting exposed - you need to move the light or plant around. I seriously doubt the UVB will make it through a single layer of leaves.

I think by far the best idea is to drop some vertical strips through the grow, or cfl's without reflectprs amd sure the plants are turned all the time. That way, each bud will be getting bombed with UVB. You can pull the ballast and bulb connectors out a normal fluoro fitting, then hook the light up minus the metal casing so there's nothing to create a shadow.

Light movers are good, but it'll still be mainly the canopy that's getting the UVB. The UVB won't go through the leaves. Where ever there's a leaf, the UVB will be getting destroyed and it won't go through to lower leaves / buds.

.

https://www.rollitup.org/advanced-marijuana-cultivation/96571-10-0-uvb-light.html

.

bongsmilie
Click to expand...

Well, in that case a UVB light sounds like a great addition to my scrog grow. I will be using a dehumidifier and UVB lights during flowering. Those are the two methods that I have read that will increase trichome production so I am looking forward to combining them during flowering.
 
Jerry Garcia

Jerry Garcia

Well-Known Member
Mine will be covering about 1.5 square feet with no reflector. I don't know off the top of my head, but I found some info online relating to the intensity of UVB rays in correlation to the distance from the bulb. Though the intensity does drop off with distance, the amount of UVB still reaching the plants at 18" is still equivalent to or greater than that produced by the sun! So one bulb can be efficient enough to cover a fairly wide area.

Do a google search for uvb and marijuana or something similar and you will find more specific info...this is just what I can remember from reading about a month ago.
 
8deez8

8deez8

Active Member
I have had success with the following:

most importantly, calculate and use equatorial level UVB radiation--
(~250uW), I have 26w cfls w/ reflectors, and 30 inches in front of the tip of the bulb is appropriate,
for shear trichome formation, proper intensity is more important than when you have the bulbs on/off IMO. If you're on a budget, just affix multiple bulb sockets (<$2) where you can rotate the bulb as you see fit... or do it manually.. but calculate the intensity and don't over do it either... I've seen people go 400uW/f2 but I get leaf radiation burns when i get closer to 18in w the bulb.

I have also been experimenting trying to get my plants to mature quicker... and I've had success with the following

have mid-length (<5hr) uvb photoperiod (always in the middle of your lights-on-time, or photoperiod)
as soon as root system is established (mid vegetative state)

have longest (<7hr) uvb photo period in late veg/first week of flower

have mid-length (<5hr) uvb photo period starting at 40% through flower,

and taper off until you use little to none as they amber to your choosing.

Flowers form quicker (with larger micron heads) and harvest comes quicker than without uvb

PS I said somewhere else on here but stay away from UVA (33% of most cfl's output!). You will not get sunburn, (UVB 10%) before you get signs of aging/wrinkled skin/engorged blood vessels. my cheek got too close to a bulb and i have a scar to prove it. skin feels less attached somehow and i have this little red blood vein visible. (nothing like sunburn/no signs of sunburn)
UVA penetrates deep causes cancer, subdermal abrasions and cataracts, UVB isn't so harmful.

TOO BAD the couldn't have made 33% UVB, 10% UVA... instead of vice versa

These bulbs will trick you! 8.58 watts UVA OUTPUT!!! Stay away!
 
SayWord

SayWord

Well-Known Member
damn, my uvb bulb is pretty close to my canopy. i started keepin it on 4-6 hours, now its up to 6-10 hours per day. check it

 
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