I was just wondering when, and how long people are turning the uv on, full 12 hours or gradually? I, using the 800w unit

Hey Heisenberg!

Great question...A lot of us have discussed this in the past. I have an SS400, and I turned my UV light on as soon as I turned to the 12/12 flowering cycle, and it was on for the full 12 hours of light. Alternatively, California Light Works recommends turning it on for the last 4 weeks of flowering.

From what I have learned here, the plant emits a coating to protect itself from the light...and in the case of cannabis, that is good resin!! You will see some great trichome development from this light!

Continued good luck!

ICB

Yep. Same here. UV on from day 1 of Bloom. More UV, more resin, more better.

I turned my UV on at the start of 12/12 but for only two weeks. Now that I am in week 5 I just turned them back on for the remainder of the grow. CLW recommends that you use the the last 2 to 4 weeks of flower, and they say it should coincide with your flush. I will not be flushing for another two weeks and the ladies will receive only rain water that is pH'ed to 6.4 for the remainder of the grow. I have been having to water every two days, sometimes Q2's daughter goes for three day between watering. As of late they have both been on an every two day program because the humidity in my cabinet has been in the mid to low 40's with temps ranging from 70 to 76 depending on light cycle.

Good luck with your grow.



GR

yeah I no you can burn them, I read it was only beneficial in the last 2 weeks, nice to hear what people do though, I just turned mine on now, And im starting the 8th week on mon, 10 week plants

CLW suggests using the UVB for the last 2-4 weeks, we've had members here that turned them on their seedlings. It would take fairly detailed test to figure out what's enough and what's too much and it might even be strain dependant.

the sun put out uv all the time, and plants thrive outside. It may not hurt them but maybe its not ideal, I wonder if theirs been any studies on the effects of uv on plants. The black dog units have it built right into the diodes, uv and ir spectrums. Im pretty sure they run all the time, they don't get nearly as hot either they work really well

here's something i found on the subject:
extracted from http://www.cannabisculture.com/articles/2696.html):

A researcher conducted a controlled experiment in a greenhouse. He lit a group of high potency plants similarly except with the addition of UVB light to some groups. He found that the percentage of THC increased in a direct ratio with the increase in UVB light. This research confirms the adage that high altitude plants are more potent than those grown at low altitudes.
If you look at old-world land races of cannabis, plants that have become adapted to the climate and latitude, the ratio of THC to CBD starts at 100 : 1 at the equator. At the 30th parallel (The Hindu-Kush Valley) the plants have a ratio of 50 : 50. At the 45th parallel the ratio is near 1 : 100. This corresponds roughly with the amount of UVB light received at these latitudes. There is much more UVB at the equator than the 45th parallel.
How can you get more UVB light to your plants? Certainly it's true that MH lamps emit more UVB light than HPS lamps. Still the amount that MH lamps emit is small. In fact, many manufacturers use UVB shielding glass to filter out most of the UVB that's produced. The UVB light the plant receives from an MH lamp does increase the plant's potency slightly at the cost of yield, but there are better ways to introduce UVB light into the grow room. They include reptile lights, which emit about 10% UVB, and tanning lamps.
The problem with using these lamps is that they are associated with increased number of cancers and many other problems. They should not be on when you are in the grow room. Not much research has been conducted on using them to produce higher THC values. I will do a full report in a future issue.

There was an interview with George from CLW about UVB and why CLW uses tubes rather than diodes. I'll try to dig it up.

(I'm going to move these non-journal topics to the New LED Users forum soon.)


EDIT:
California LightWorks Interview with George Mekhtarian

Found it...

Good Thread and right on time for me wondering would like input
I have rigged up a UVB supplement 2-13watt CFL's for a Solar Flare 200 watt full spec. On a 2x2 tent grow I have been running them since the start of 12/12. Now I was going to add the 1 into 2 socket splitter and add an additional 2 high intensity 200 UVB 26 watt to the existing that would be 78 watts of UVB for the last couple of weeks of flower. And I would like to thank Heisenberg for his posting on harvest and curing.