Yeah, I've used reptile bulbs with 12% UVB and the spectrum chart of the 10k finisher looks almost identical.
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I have them changed against PureUV bulbs and these bulbs need a min. distance of 24" to not harm the plants. I have 5 different strains below them and 2 of them are also more UVB sensitive. BlueDream, ColumbianGold and GreenPoison have shown no wilted leaves till now, Amnesia and SuperSilverHaze have shown heatstress and wiling leaves.
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I've build so called super-spreaders. Do you remember them from the adjust-a-wing HPS reflectors? Its in fact just a 18mm small and 2ft long alu strips made from reflector sheet, bent by 90° along the length side. I've mount them in ~5mm distance in front of the bulbs so that the light hitting the spreader is thrown back into the reflector. This should reduce the readings in the center area and distribute the UV light more evenly.
I've also reduced their usage to 2x 30 minutes per day because I dont wanna loose the whole crop. I got also much less stretch as usual. BD, SSH and CG are known to stretch out for at least 4 weeks or more. This times they stopped stretching already end of week 2. I've added the trellis net too late because of this unexpected behavior and now I have a few gaps in the canopy. I've added more far-red from now on to get a little more stretch but maybe it's already too late. If you look closer you can see the most heatstress in the upper left corner on the Amnesia cross.
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I have a minute timer and will try my best to find a way to use them at the same height with my LED's(I prefer ~16"); currently its still 24-28" above the canopy(UVB intensity should be below 170μW/cm² according to Agromax test results). If its impossible I'll switch back to reptile blubs cuz they are much less damaging and I've already used them with good results. My small 3sft area has a 24w Arcadia with 12% UVB and ~150w LED and I use both with only 8-10" distance and UVB for 5h every day(2x 2,5) and there in not a single damage and with such a low distance the UVB intensity is at least 150-200μW/cm² according to the test results with different types of reflectors(pdf below).
A little heatstress yes but no wilting leaves. It could be that the pureUV bulbs have already a few % UVC; the spectrum chart is unfortunately not exact enough to figure that out. But it could be a reason why these bulbs are too strong even if only used for a shorter period.
With reptile bulbs at 8" you already get 150μW/cm² for 5h that means you get a dose of 27kJ/m², with the 2x 30 minutes PureUV and 28" distance you would have less than 150μW/cm² and 1h means a dose of only 5,4kJ/m².
There must be a reason why these bulbs cause so much damage while the reptile/10k finisher bulbs cause no damage even after much longer use and same UVB intensity.
Apogee has a new UV sensor called UV-100 and the guy from Migro(youtube) is willing to do some spectrum tests and comparisions. So maybe will will know the reason pretty soon..
