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Temperature, humidity, closeness to lamp


New Member
So a blanket of tiny issues hath bequeathed me.
Temperature are usually around 28c directly under the light at the canopy height I have never measure the room temp is this where I should be measuring? The reason I ask is because the heat from the lamp is nowhere near burning my hand its kinda warm but not hot so could I get it closer because more light means bigger buds.
On the subject of the closeness of the lamp will it being too close negatively impact the plants if heat isn't an issue.
Also the humidity in my box is not 50%-60% its around 35% should I bother raising it and if so how can I?7

I have a 400w hps in a powerplant clone reflector which is air-cooled, i've got a 10inch rvk L1 fan also.


It's 25c at the canopy which is 11 inches from the bulb.
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Well-Known Member
That is a good place to measure.

Possible bleaching if too close.

Humidity for vegetative growth is not super critical, but should be corrected if you can. If you wanted to raise the humidity you can place a bucket of water in room with a towel half in half out of the bucket to help with humidity, I have read others do this but have not done myself, I just went and bought a humidifier.

Hope this helps. Good luck.


New Member
I have a 600w HPS lamp in a cool tube running about 6" of the top of the canopy, which the chart above doesn't really take into account. is it luminosity, or heat that it uses to determine the optimal distance?


New Member
Okay so i've just move my reflector to 6 inches from the canopy. Now my question on temperature and where to measure from seems really important. Under the lamp, 6 inches away is now warm like 35c which is not particularly hot on my hand, I can touch the glass on the reflector forever it's warm but nowhere near hot. which leads me to believe its fine for the plants because thats radiant not ambient, and I'm willing to try to see if its okay long term. What signs will there be from the plants if it's too hot? So I can pull them out of the hot zone if they can't take it. Cheers


New Member
Okay the experiment is over. The reflector was moved to .5 inch away from the canopy to see what would happen and the top leaves and buds are bleached. They kind of look like they are half way through a super saiyan transformation. It's not a heat issue so beware of too much light.


New Member
Its white on the inner parts of the limbs with the green on the outer part. It is strange as on another plant there is one budsite with the same issue but the others are all fine. looking at a deficiency chart it looks like a Zinc deficiency. Have you got any advice or know of any products I could use to fix this?
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