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UVB bulb type questions

Discussion in 'Advanced Marijuana Cultivation' started by ItsDave, Feb 3, 2012.


    ItsDave Member

    Hi been while... i have been reading up on uvb and see reptile bulbs mentioned.but rarely see examples. I have several sun blaster 2,and 4 ft for side lighting i think sun blaster makes a t5 reptile 10k? bulb (i have not found one yet though) and saw t5 reptile bulbs on a pet store site. should i get these? or a flood light style?
    should i just change current t5's to reptile t5s last few weeks or just add more t5 with rep bulbs?
    so any advice for best time of day to use, how long per day, watts per 10x10 room. and links and suggestions of where to buy, which bulbs etc

    thanks ID
    Bonzo Mendoza

    Bonzo Mendoza New Member

    [TD]UVB is generally defined as the wavelength band from 290-320nm, but it is the band between 290-305 nm that is most important.

    The earth’s climate is determined by the amount of solar radiation that strikes the surface.
    Factors like the sun’s position, the earth’s rotation, geographic location, the ozone layer, clouds, air-humidity, elevation, environment, etc. influence the intensity of light. Also within the microhabitat the light intensity of both visual and non-visual light varies, depending on the density of the vegetation or geological conditions.

    The amount of light falling on a surface is known as the illuminance and is measured in lumens per square meter or lux. The illuminance of direct sunlight is approximately 100,000 lux, but normal daylight, which is filtered through a cloudy sky, is between 5,000 and 10,000 lux, while moonlight can be as little as 0.25 lux. The sun is at its highest in the sky around noon. At this time, the sun’s rays have the least distance to travel through the atmosphere and UVB levels are at their highest. In the early morning and late afternoon, the sun’s rays pass through the atmosphere at an angle and their intensity is greatly reduced.

    Maps of the UV index for the Northern Hemisphere indicate that the UV index is highest during the summer months (despite the fact that the sun is directly overhead at the Tropic of Cancer - thirty degrees north latitude - only on the Autumnal Equinox).

    UV levels in the tropics are very high. High equatorial UV levels are primarily caused by the high angle of the sun, a thinner layer of atmosphere, reduced air pollution, and diminished atmospheric ozone. Ozone is naturally thinner in the tropics compared to the mid- and high-latitudes, so there is less ozone to absorb the UV radiation as it passes through the atmosphere. At higher latitudes the sun is lower in the sky, so UV rays must travel a greater distance through ozone-rich portions of the atmosphere and, in turn, expose those latitudes to less UV radiation. Also, every thousand feet of elevation affects UVB levels by about 4-5%.

    Interested readers should search the internet for “UV index map worldwide”.

    On average for the southern U.S.A., direct summertime sunlight measures about 200 uW/cm2 of UVB; tropical sunlight levels may range twice as high. UV radiation output peaks around noon, and about 20-30% of the total daily UV radiation at any point on Earth gets comes between 11 a.m. and 1 p.m. - about 75% between 9 a.m. & 3 p.m.

    Measurements from a UV-B lamp cannot be compared directly with readings from sunlight. The spectra of the two light sources are different. The Reptisun 10.0 spectrum has a greater percentage of its UVB in the shorter wavelengths than does sunlight. 30 - 32uW/cm2 from a Reptisun 10.0 lamp is equivalent to approximately 40 – 50 uW/cm2 of sunlight.

    Dave Weldon, founder of the South Bay Chameleon Keepers group (Los Angeles) reports:

    “[A] … a combination of a 10.0 T-8 Zoo Med Reptisun 48” tube for UVB along with a standard 6500K “grow light” for the plants, all housed in a dual tube aluminum reflector - a white painted reflector will not reflect uvb - shoplight type fixture … measures a safe and effective 31 uW/cm2 at 16”.”

    “[A] … a linear [five month old] Reptisun 10.0 and a 6500K “grow light” [were] mounted in a dual 48” shoplight fixture, lined with reflective aluminum foil to direct … the light …. The Solarmeter 6.2 is held 8.5" away and shows a reading of 30 uW/cm2 … “

    Intensity vs. distance (doubling distance to bulb dimishes intensity by about 67%) :

    Below is a chart that compares UVB readings from two new Reptisun 5.0 bulbs:
    Distance from bulb: Irradiance (measured in uW/cm2)

    3" 49/59
    6" 24/29
    9" 14/18
    12" 10/12
    15" 7/8
    18" 5/6


    Note that ONLY THE TUBES NOT CFL'S are probably worth anything. CFL uvb's probably do not work. I actually called Reptisun to ask about measured uvb CFL illuminance (i.e. actual uvb light that striking a surface) and the dickweed engineer I talked to was all evasive and non-helpful - he told me that I was asking for "proprietary information" I was aking for. Bullshit. He just did not want to tell me that their cfl uvb's are a waste of money.

    Most indoor marijuana is strongly influenced by indica genetics. It seems to me that indica in Afghanistan would have evolved at significantly lower uvb exposures than equatorial sativa.

    yesum Well-Known Member

    I was told the Reptisun cfl puts puts out over 1500uw/cm2 at 1 inch for both the 5.0 and 10.0. I have the Solarmeter 6.2 and will just have to test myself. I only have room for a cfl in my tent.

    Phaeton Active Member

    8 inches, arcadia D3+.jpg T5 group.jpg

    ArcadiaD3+ T5 12% UVB reptile light. At 18" it puts over 300 uw on the leaf. The 432 uw is from 8". My trimmer got sunburn from just one of these per four bulb fixture.

    I have grown plants with up to 800 uw, although the yield drops to less than half at 500 uw.

    I grow with UVB, measure results and have blind smoke tests. Yes I read the books first, then ran a full time test budroom for a year, then set up the room I use now.

    8 inches, reptisun 10.jpg T8 group.jpg

    As can be noted, the Reptisun 10 has 1/3 the output of the arcadia, three of the six T8's are reptisun and still the output at the leaf is under 200 uw, close enough to still work though. I alternate fixtures.

    The only reported user effects have been creeper, this affects both indica and sativa so far in my grows.

    RedCarpetMatches Well-Known Member

    Bump you up

    ProdigalSun Well-Known Member


    RedCarpetMatches Well-Known Member

    Very good find. LOL at your avatar.

    fridayfishfry Well-Known Member

    Tried a 10,000k bulb i'm sure it would do the job but a little too hazardous


    jimihendrix1 Well-Known Member


    I have been using the Arcadia 46in 14% Dragon bulbs, and just ordered the Solacure Flower Power Lamps. 32w.

    They are much more powerful vs any Reptile bulb, even the 54w, or any other horticulture UVA/UVB bulbs. They do make more powerful 1s for livestock, but are to powerful, and hot for most applications.

    I'm also going to buy some light movers, and hook up the UV bulbs so all parts of the plants receive UVA/UVB more efficiently down into the plants. Im going to use 4 in a 4 x 8 area, at 4 ft height.
    Will also use in veg 2 hours per day.
    mr. childs likes this.

    BobCajun Well-Known Member

    So the only noticeable effect of the UV was to make the high feel "creeper? I have to wonder if it's really worth the trouble and expense. I tried reptile CFLs several times at different distances and if anything it seemed to make the weed weaker. I only used it for a few days or weeks at the end though, not all the time. I can't find any real evidence of the supposed potency increase on the web either.-

    There's one study which is frequently quoted in which there appeared to be a linear increase in THC with increased UVB but I also read that those scientists were never able to replicate the experiment with the same results again, it was a one time thing. Maybe it was the particular plants or even just the extra heat given off by the UV lights, who knows. Apparently something went wrong if they could never reproduce the results.

    It is still very debatable whether it really does increase potency. Both UVB and UVA certainly do reduce plant yields though, that much is well established. If your yield was reduced say 30% but your potency was increased 30%, would people pay 30% more for it? Not likely. There's kind of a price ceiling out there. I've never seen specially priced UV weed.

    jimihendrix1 Well-Known Member

    In my experience ( 3 Years ) with UVA/UVB, Ive found it can greatly increase potency in plants, and does not decrease production, unless you burn the plants.

    Cannabis researchers in Maryland used ultraviolet radiation to see what would happen. They found that increasing doses of UVB radiation, a natural part of sunlight, made the plants produce almost 28% more THC in the buds.

    In attempting to understand more about the function cannabinoids serve, the scientists discovered a relatively simple way to increase potency by a great margin. They ran the UVB experiment on both high-CBD hemp and potent Jamaican marijuana to see if the cannabinoid content would increase. Curiously enough, while THC increased in the Jamaican weed, the Czechoslovakian hemp received from the University of Mississippi did not produce more CBD.

    So UVB radiation plays a role in THC production, but cannabinoids as a whole still retain their mystique. One fact can’t be denied: UVB radiation increases THC in strains that already express high THC.

    This is the ultimate growers UVB light, many times stronger than our other UVB lamps, and infinitely stronger than reptile lights or other makeshift lights. This is the real deal, dispensary tested, proven lab results up to 40% higher THC than not using any supplemental UVB. We guarantee you 20% better results the first season, and 30% or more once you get dialed into using the maximum amount possible. No one else guarantees results like this, but we can.

    Already certified to get 20% to 35% higher THC and flavonoids and anecdotal evidence that approaches 40% higher, and results keep coming in.

    Last edited: Aug 13, 2017

    BobCajun Well-Known Member

    Well alright. That's the article I meant though, which the authors could never reproduce, at least I read that on some forum, could be BS I don't know. But why no other scientific studies showing it? That one you quoted is literally the only one in existence. And those were pretty low THC strains anyway, only getting up to about 6% THC with the highest UV. There are many strains that easily surpass that even under CFLs.

    So my point is simply that we have no actual hard evidence that it works with modern Dutch type strains. You say you have test results, if they're verifiable. Why not just make a video to settle the matter once and for all? Since all we have is that one other article from years ago with weak strains, you would soon be on the cover of High Times and Skunk magazine.

    There is one other guy who was writing articles and doing videos about it, calling himself the Dutchman, but he seems to have vanished from the earth after the first few unsupported articles and videos.
    Last edited: Aug 13, 2017

    jimihendrix1 Well-Known Member

    In the book Cannabis Botany, Robert Connell Clarke references an experiment from
    the laboratory of Dr. Melchoulam, one of the leading cannabinoid researchers.
    In that experiment, CBN was converted to THC simply by exposure to UV-B light
    I believe it was 45% conversion rate, and also the researchers found small
    amounts of very rare cannabinoid variations not commonly detected in natural cannabis.

    I am sure we could find that quote in RCC's book Also, there is a paper called
    "Marijuana Optics" that talks about how the resin sphere is basically a light collection
    device that concentrates light into the cannabinoids. The author goes into detail about
    UV-B light and how it is important for creating a "fully realized" cannabinoid profile.

    Also, there are much more powerful UVA/UVB lights than what this guys used, and will also greatly increase THC production.

    The bulbs he used are WEAK in comparison to the Solacure Flower Power, and a couple other manufacturers. But Solacure is the most powerful. Reptisun work, but not optimally.

    Medical Marijuana Potency 3-5%
    UVA UVB Lizard light testing results. Date Feb 2013- Dutchman Enterprises

    I just completed 2 full years of testing on over 10 different strains and have reached the conclusion that the UVA UVB light spectrum will add 3-5% THC and .0-.5% bcd over all strains tested.

    I have done 6 complete grows from veg through bloom each one tested with the lighting and without the lighting alternating each crop. One on and one off. Each time the crop with the lights on would jump 3-5% with the lights off it would decrease 3-5%. I have assumed an error margin of 2%

    My test results seem to be right in line with what other people have experienced over the years. I could not find any recent data online so I Decided to do my own research and testing.

    Some strains tested are as follows when under Lizard Lights.

    Chem dawg 27%
    OG-18 25%
    Holy grail Kush 28%
    Critical + 23%
    Tohoe OG 24%
    Grape Ape 23%
    White Fire OG 25%
    Dead Head Og 24%
    Chem Valley kush- shit pheno 15%

    The difference in potency is so obvious that all my patients would complain about the lack of potency on the crops that I did not use the UVA UVB lighting!

    UVA UVB Light Exposure

    I have found it is best to expose them to it from time they are rooted. This will give them time to acclimate to the lighting. It does not make any difference to the potency if you use the lights in bloom only. The only difference is if you do it in bloom only you will get leaf curl but it does not seem to stress the plant or hurt it in any way. I would start them off slowly and build up to the full 12hrs in bloom if you are not going to veg them under the UVA UVB lighting.

    I started off my strains in low doses on a timer in 2 hr increments on and off and slowly each day increased them as I was scared to kill them initially due to some research I had done on this topic in online forums.

    I soon found that it did not matter at all. You can hit them with the lighting 24hrs in veg and 12 hrs in bloom with no adverse effects except a little leaf curl at the ends if they had not been previously acclimated to it at the beginning of life stages (rooted). This is why I would recommend exposure as soon as possible.

    I purchased the new 4 ft Zoo MedReptiSun 10.0 UVB/UVA Bulbs
    These bulbs were chosen because they reach the deepest and furthest away.
    With these 10.0 bulbs penetration is 18-24 inches from the light.

    The older 8.0 or 9.0 bulbs were 12 inches or less which did not give much room for plant location in my 8x15 room.

    UVA UVB Light Test Results

    I had every batch of plants tested by Cannalytics for accuracy. I have also found that where you take your sample on the plant also plays a role in test results. The THC % plants can vary anywhere from 3-6% difference based on where sample was taken top, side or bottom of plant.

    I am no scientist so I can't say 100% that it does not alter the plants genetics but based on my knowledge of genetics and my own research I do not believe the genetics have been altered at all. What has happened is just a natural stress response by the plant to protect itself from the ultraviolet rays.

    To prove this even more is the fact that each strain dropped back 3-5% when it was not under the UVA/UVB lights. Even when I had them under the UVA/UVB lights in veg but not under the lights in bloom they did not increase in potency enough that I could measure a change.

    Further UVA UVB Questions To Answer

    Some further questions I would like to get an answer to is if the light is positioned on one side of the plant instead directly over top of the plant does the whole plant respond to the uva uvb stress the same throughout or does it only increase potency on the side the light is on? I will need to take two samples off one plant and have them analyzed.

    I was able to get the double 4ft fluorescent light fixtures for $50 each that had a 15ft electrical chord plug attached. I found the ReptiSun 10.0 4ft bulbs for $18.95 each plus a few bucks shipping. I will find who it was and post it when I do. My total cost for 6 fixtures and 6 bulbs was around $400.

    I have used them for 2 years on and off so pay off has been good. In my opinion it is well worth it to run the UVB UVA bulbs. It will set your product apart from every one elses in your area. Think about it to be a beginning grower and have strains testing out at 27-28% and seeds were gathered from online seed banks is pretty darn good!
    Last edited: Aug 13, 2017

    BobCajun Well-Known Member

    I've read that before, both of those. First you'd need a bunch of cannabinol in the trichomes to convert. Tests don't usually show much, certainly not 25-30% as much as THCA. But you're free to make your case to the public and they can decide if it's worth it or not. Just pointing out that I haven't seen hard evidence yet that it actually works. I've seen a few forum posts which said it didn't work though, so it made me wonder.

    jimihendrix1 Well-Known Member

    Its pretty well known that the most potent weed comes for near the equator, where the UVA/UVB is the highest. Its only logical to replicate this, and its well known UVA/UVB has a big influence on cannabinoid profiles.

    NASA also did an experiment 30 years ago in space using Xenon to flash burn the plants, and determined they could control cannabinoid profiles, by manipulating the light waves.

    To me its only common sense and logic to supply this light.

    An elaboration on the phytochemical process that makes THC: by Joe Knuc

    "Pate (1983) indicated that in areas of high ultraviolet radiation exposure, the UVB (280-320 nm) absorption properties of THC may have conferred an evolutionary advantage to Cannabis capable of greater production of this compound from biogenetic precursor CBD. The extent to which this production is also influenced by environmental UVB has also been experimentally determined by Lydon et al. (1987)."

    The writer's own experience allow for a more specific conclusion: If the UVB photon is missing from the light stream(a), or the intensity as expressed in µW/cm2 falls below a certain level(b), the phytochemical process will not be completely energized with only UVA photons which are more penetrating but less energetic, and the harvested resin spheres will have mostly precursor compounds and not fully realized THC(c).

    (a)Examples of an environment where the UVB photon would be missing from the light stream include all indoor cultivation illuminated by HID bulbs and in glass or corrugated fiberglass covered greenhouses.

    (b)"The maximum UVB irradiance near the equator (solar elevation angle less than 25 deg.) under clear, sunny skies is about 250 µW/cm2. It was observed that the daily solar UVB in Riyadh, Saudi Arabia (N24.4Lat.) decreased from September to December by about 40% (Hannan et al. 1984). The further a person is from the tropics, the less UVB radiation there is: the average annual exposure of a person living in Hawaii is approximately four times that of someone living in northern Europe."

    (c)Cannabinoid pathway: Anywhere in this pathway UVB
    (320 nm - 290 nm) does a better job than UVA (400 nm - 320 nm) in energizing a phytochemical reaction that will produce more fully realized THC because "all cannabinolic compounds show an absorption maximum between 270 and 280 nm in the ultraviolet region."
    Last edited: Aug 13, 2017
    yesum likes this.

    yesum Well-Known Member

    For me I do not care if the thc level is a bit higher with the uvb applied. I am looking to get a change in the overall chemical structure so the high is made better.

    Better is subjective so ymmv. I use the little Reptisun uvb cfl at 26 watts. Last week of flower. Never had any bad effects with it, like leaf curl. If safety is real important to you then just have a switch to turn off the lights when working in your tent, that is what I do.

    I have a 10,000 Kelvin fluorescent light going for bloom cycle. It kicks out some uva but not sure how much. Trying to reproduce the high Kelvin light found at high altitudes and also near the equator.
    mr. childs and jimihendrix1 like this.

    jimihendrix1 Well-Known Member

    UVA/UVB changes the total chemical profile of the plant.

    Also the bulbs wont penetrate beyond the leaf.

    It best to us the lights on a Mover, so they can penetrate the side branching ect.

    I plan on buying a couple tracks. 1 motor can run 2 parallel rails/lights.
    Heres some good info.

    Figure 4 (below) shows one set of "clear open skies" data from this group: solar UVB recordings from right across the world, made over the December solstice 2005.

    I plan on have 315uw into the Interior of the plant, and around 380- 400 at the top of the canopy, and run then 8 hours a day, of a 12 hour cycle.

    I use 1 x 1000w Hortilux HPS for every 2 x 34w Solacure Flower Power bulbs

    Will also use in Veg, and also another track. Will use 1 bulb per 4 x 4 on a track

    The Solacure are 20x-50x more powerful than the most powerful Reptile bulb. I was using the Arcadia Dragon Bulbs 14% 54w, but they aren't nearly as powerful as the 32w Solacure.


    The most important factor is the angle of the sun. When the sun is low on the horizon, its light must pass through a thicker layer of the atmosphere, which absorbs more UV light. Highest readings are therefore obtained around mid-day when the sun is highest in the sky or at high altitudes where the air is thinner. The highest readings of all (at sea level) will be seen under clear skies in the Tropics when the sun is directly overhead. At the equinoxes, this will be at the Equator; at the solstices, it will be along the Tropic of Cancer in June and the Tropic of Capricorn in December.
    The further from the equator, the lower the UVB reading even at mid-day, because the sun will be lower in the sky. The lowest readings of all will be seen at high latitudes in either hemisphere during winter months - when the days are short and the sun does not rise high in the sky.

    This effect is easily seen by examining the above chart. At the December solstice the sun is almost directly overhead at Alice Springs, in the Northern Territories, Australia. On clear days the UVB rises to above 100 microwatts per square centimetre (µW/cm²) by 8.00am and reaches over 450µW/cm² by noon. Levels above 20µW/cm² are seen for 11 hours or more.

    The further north that recordings are made, the lower the maximum (noon) reading and of course, the shorter the day. In Florida, for example, at latitudes 25 - 30N, observers recorded maximum readings around 150 - 250 µW/cm² whereas further north in Colorado, 40N, readings only just topped 100µW/cm². Readings here were boosted, too, by the high altitude; not much further north, in Illinois at 42N, only 70 - 90µW/cm² was seen.

    Around 50N, the days are very short at this time of the year and UVB levels are very low indeed. The maximum reading taken in Wales (latitude 52N), despite clear sunlight, was only 29µW/cm²; and at Helsinki at 60N, our observer climbed onto his roof to see the sun and recorded only 7µW/cm².

    Readings taken over several days, from the same location, can be used to gain a clearer picture of the UVB available throughout the course of a day. Figures 5 and 6 show recordings taken in Wales over four days in March and early April 2005, and seven days in June 2005, respectively.



    These graphs illustrate clearly the profound effect that the amount of cloud cover has upon the ambient UVB levels; however, by combining readings taken on different days, it is possible to build a picture of the maximum possible UVB as seen under clear skies, for any given time of day during that period. Comparison of the two charts also demonstrates the great increase in ultraviolet light as the days lengthen and the sun rises higher in the sky. The highest readings in June, at the time of the summer solstice, approach 400µW/cm² whereas in March, around the spring equinox, maximum readings are around 160µW/cm².
    One of the highest readings yet recorded on earth with a Solarmeter 6.2 was made by UVB_Meter_Owners member Torey Lehman on the summit of Haleakala, Mauii, Hawaii, latitude 21N, at 12.30pm on 25th May 2005. (Fig. 7) The sun was almost overhead and the high altitude (10,023ft) and clear sky resulted in a mid-day UVB level of 545µW/cm².
    mr. childs likes this.

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