I’ve heard of using the hand test to see how close you can put your light to your plants but I was wondering….how can I tell if it is too much?
Just because its not too hot for my hand doesn’t mean that it wont stress out a small seedling…

You are supposed to hold your hand under it for 60 seconds if it is uncomfortable to you then it wont be good for the plant, as for seedlings just raise the light up a few inches.

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what lights r u using?

Those directions for getting the light as close as your hand can still feel comfortable never applied to a new seedling. Find that distance and double it for the seedling, then work the light down over the course of a week or so. You will shock a seedling going straight to max light like that, they aren't ready for it and can just die.

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umm well for 1make sure its the BACK of your hand as its sensitive to heat...

think of a young child's milk ?? you dont put it on the palm but the outside off the hand to get the true tempreture

using a 250w cfl it can be about 1inch from the top of the plants with great results

I use flouros for seedlings or I just put them by a window that gets a fair amount of light. I do this for the first week(ish)

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For HID lighting. Just hang the thermometer from the light. Adjust the length, so it reads about 78F/25C after about 10 minutes. Now you also have a gauge to adjust your light height.

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thats retarted, you need 50 posts to PM... heres nuimber one

I have done that in the past to gauge the distance, but I found I was ending up with my lights further and further away. The radiant heat was getting right to the thermometer as it was right out in the light and it was getting very hot and I was ending up with semi-stretched nodes.

Thanks to RIU several weeks back I learned more about ambient and radiant heat. The plants can handle much higher radiant temps. Its the ambiant temps that have to be kept in the mid 70's, whereas the radiant temps can climb much higher. So I am not sure if the thermometer out in the open under the lights will give you the reading you want.

I am by no means the end all be all of knowledge. I am always learning and looking for the best methods and the correct info to achieve the desired results. Feel free to correct me if I am wrong or explain. You may have a different thermometer type in mind.

Theres a few threads on here about it. heres a more recent one: radiant heat I also saw another posted a few days back as well, and there are alot of older threads about it.

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