18 Inches??

When they say as rule of thumb your light should be 18" away from the canopy do they mean distance from the actual bulb or from the glass cover on a AC hood? Just curious since there seems to be at least another inch between the glass and bulb. TIA!!!!

Use your own feeling with ur hand if its too hot for you its too close. move as close as u can without discomfort.

my bulb is about 1-3" away from plant (my bulbs 13% heat given out)

you ever see a grower and there light is really far away and you say i wouldnt do that well i only have 1 grow under my belt starting on #2 but i noticed the flowers that were getting bigger were the ones farther from the light so i raised it a few feet and they loved it. it was a 1000 by the way.

Ive never heard of an 18" rule.

Air cool your lights and get them as close as possible without burning.

Thanx for all the responses. Im running a 600 watt hps by the way. Just read and heard 18" is the norm so to say. My last grow,coincidentaly my first grow, i got real close to the light during flower (14" or so) and got foxtailing. I try the hand test but whats uncomfortable? i can get within couple inches and be "comfortable" but the plants wouldnt think so id think.

Go with what you think i have a 1kw hps in air cooled hood and i can get around 8 inches without burn. if you think its too hot then go another inch or so away just use your best judgment and watch for leave tips turning brown or burning

you can get glass covered hoods closer than just open air bulbs...usually a good 40-50% closer as the heat doesn't blast out from the light anywhere near as much. So with a glass covered air cooled hood with a 600watt you can easily get it down to 8-10" away