Help, with "The Hand Test" ?

[jawbrodt]

Hey guys, I use unvented, unsealed reflectors on my 400 and 600 watt HPS lights, and I always seem to get a little heat stress during bloom, with the edges of the leaves curling up slightly, so I had a quick question about the the method called 'the hand test'......


When you hold your hand under the light(at the same level as the highest tops) to check the heat, how warm is too warm? Does is have to actually feel uncomfortably hot? Mine are no hotter than being in direct sunlight on a really hot day, and I still keep getting this problem. Is that too hot, being that it's coming from a grow light, and not the sun? Does that make it different somehow, being that it's coming from a grow light? I keep my lights about 18-20 inches from the tops, and the warmth feels like the heat you would feel if you were relaxing in front of a nice hot fireplace, or campfire. Not hot, just nice and warm. Is that too much for the plants? I also keep a fan sweeping across the tops of the plants, trying to keep them even cooler. Does the heat have to be something you would describe as 'hot' to be enough to hurt the plants, or is 'warm' enough heat to do it?

I have had PH problems during this time, so I was wondering if that is causing them to be extra sensitive to the heat? Also, it's always about 80-82*in the growroom, which I know is a little too warm, but not excessively so. Any help would be appreciated? I didn't post any pics, because my main question is about the 'hand test', not my PH problem, because I already have that under control. I want to know if 'nice and warm' is too much, or if it would actually have to feel 'hot' to be too much? Thanks.

 

[Askeezy]

It pobably is just a little bit uncomfortable for them. But its not to high doesn't sound like it will effect your yield.
But the PH problem most likely will its a good thing you got that under control quickly,
or as you stated an issue between both, The ph could be causing this.

Just keep an eye on it, maybe another fan or a cold bottle infront of the fan i heard cools but gives of moisture and if you're flowering maybe not the best thing. Anyways hope this helps.
Happy Growing -Skeezy.
Oh and drop by my thread sometime just started it today and boy is it lonely.

 

[jawbrodt]

Yeah, think the PH is(was) the main problem too. The heat isn't that bad at all, nothing more than a hot summer day, so they must've been weakened from the stress of the PH problems, and are sorta fragile. All the new growth looks fine, so I think they should be fine. I flushed them and got the run off up to 6.7, with 6.8 water/fert going in, so it should be just about perfect. That was about 5 days ago, so I'll keep an eye on them and hope that they're good to go. Thanks for backing up my theory.

I looked around for your thread, but didn't see it. Which forum?

 

[riddleme]

I keep my lights about 18-20 inches from the tops, and the warmth feels like the heat you would feel if you were relaxing in front of a nice hot fireplace, or campfire. Not hot, just nice and warm. Is that too much for the plants? I also keep a fan sweeping across the tops of the plants, trying to keep them even cooler. Does the heat have to be something you would describe as 'hot' to be enough to hurt the plants, or is 'warm' enough heat to do it?

Also, it's always about 80-82*in the growroom, which I know is a little too warm, but not excessively so. Any help would be appreciated?

I want to remind you that the sum of All Parts = Success/Yield

We as growers want to create the perfect enviroment for our babies to thrive in. 80 to 82 is way to high to flower, we need to recreate fall like conditions for optimum results your temps should not go over 75 but down around 70 is best (mine is 72 w/lights on and 68 during dark)

Note if your veggin 80 - 82 is ok as it more ressembles summer to the plant, Though 78 would be optimal, MJ is temp tolorant between 50 and 90.

Also RH factors how the plant senses heat. High RH means warmer air check heat indexes where a temp is 92 with a RH of 85 the heat index is like 125 degrees, this is one reason (not talked about much, because mold seems a bigger concern) why a low RH during flower is important. Using your 82 temp lets say your RH is 60 your heat index would be 84.4

you can check heat index here
http://www.easysurf.cc/cnver16.htm

When creating our optimal grow enviroments these are things we must consider though they are things not elaborated on much. Folks will tell ya to get the temps/RH down but most usually don't tell you why.

IMO you should really consider getting your lights cooled/ventalated, in leui of getting hoses & fans etc. I at least advise that you raise the lights 4 to 6 inches and get a fan blowing up at them.

Eliminate your heat stress and you'll see better yields

Hope that helps

 

[DoeEyed]

The answer to your question, is no. I've burned my girls with the light in a position that felt comfortable to my hand, and I have 400's, not a 600. But then it has to vary, because what feels comfortable to you or me, might feel too hot for someone else. If you're experiencing problems just move the light up a bit, until you find the sweet spot.

 

[jawbrodt]

I want to remind you that the sum of All Parts = Success/Yield

We as growers want to create the perfect enviroment for our babies to thrive in. 80 to 82 is way to high to flower, we need to recreate fall like conditions for optimum results your temps should not go over 75 but down around 70 is best (mine is 72 w/lights on and 68 during dark)

Note if your veggin 80 - 82 is ok as it more ressembles summer to the plant, Though 78 would be optimal, MJ is temp tolorant between 50 and 90.

Also RH factors how the plant senses heat. High RH means warmer air check heat indexes where a temp is 92 with a RH of 85 the heat index is like 125 degrees, this is one reason (not talked about much, because mold seems a bigger concern) why a low RH during flower is important. Using your 82 temp lets say your RH is 60 your heat index would be 84.4

you can check heat index here
http://www.easysurf.cc/cnver16.htm

When creating our optimal grow enviroments these are things we must consider though they are things not elaborated on much. Folks will tell ya to get the temps/RH down but most usually don't tell you why.

IMO you should really consider getting your lights cooled/ventalated, in leui of getting hoses & fans etc. I at least advise that you raise the lights 4 to 6 inches and get a fan blowing up at them.

Eliminate your heat stress and you'll see better yields

Hope that helps

Excellent response. I'm on my 5th generation since i started 5 months ago, and although I've read for countless hours, learning how to grow, temperature was something I've never had explained to me, like that. I knew that 75* was the number to shoot for(generally), but also read that they will do fine in temps up to 85*, so I assumed that although mine wouldn't be at the absolute optimum, that they would still do okay. After all, they grow at the equator, right?LOL What I didn't realize, is that they bloom in the fall, so naturally they would do better in cooler temps while blooming. Doh!!! LOL

I keep the humidity at 45-50% in veg, and around 25-30% in bloom, so that should be okay. But, since my plants did fine in the low 80's during veg, I assumed that they would also do fine in bloom, at the same temps. Wrong.LOL On a couple of the warmer days, I saw the temp spike at 88*, and never below 80*, so I'm going to have to cool it down a bit. I've been wondering what the hell is going on, and have been reading obsessively, tending my plants obsessively, with no luck so far. And i bet that's my main problem. It's just been worse his run, because i had those PH problems that stressed the plants, making them less resistant to the heat.

It just so happens that i can fix the problem today, because it's freezing outside, and I just setup an intake that will allow me to draw in that cool air. I tested it out today, and I know I won't have any problem keeping the temp in the low 70's, even without the vented hoods. Awesome! Thanks for the info.

And thanks to the above member who described the 'hand test'. From your description, I have a really good idea of what is acceptable, and what isn't. Mine aren't too hot, but my growroom is. Doh!