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Re: Metal halide burn in?

>I recently bought a 6500k super bright made by Hamilton for my 54 gallon
>planted tank. It was a replacement for the prev. 6500k super bright that was
>over a year old I was using. I ordered from Drs. Foster and Smith. However,
>when installed it looked nothing like the prev. bulb. It gave a very green
>tint to the tank,  furniture, walls, etc. I assumed something was defective
>in the bulb, so I sent it back. I then ordered the same bulb from pet
>solutions, Installed it, and again, the very unpleasant green hue to
>everything, completely washing out the red in my lotus, myacia etc. The
>riccia also seems to have stopped pearling. I called Hamilton technologies
>and they said there was a burn in period of 100 hours or so until the right
>color spectrum was reached. Does this sound right? I am wondering because

Sounds about right. I usually have a several days of greenish light out of 
new MH bulbs -- even the cheapo ones from Home Depot that are Phillips 
4200K I think -- before they settle down into their normal long-term 
spectral output. Nothing to worry about. There are doping chemicals in the 
arc tube that give the bulb it's spectral characteristics, and I am told 
that it takes some time at temperature (as in running :-) before they are 
all "in solution" properly.

>when I replaced my orig. 5500k with the first 6500k a year ago the light was
>a very white bright.(also made by Hamilton) from the start. Now however both
>these new bulbs are giving off the very green hue. Also I noticed these new
>Hamiltons are much slimmer than the old football shaped 6500k Hamilton. Will
>the bulb truly become whiter in a few days or have they switched to a new
>bulb that just will give this green cast to everything in the tank?
>thanks for any insight
>Michael Webb

The green should start to noticeably decline over the first few days, and 
be gone in a week or two, with the bulb producing it's normal output at 
that time. Keep in mind that the 6500K *WILL* appear bluer or "more white" 
than the 5500K, and older bulbs will be slightly yellow-shifted (lower 
color temp) which will make the change more pronounced when you switch to a 
new bulb.

The more tubular bulb is the "european" design, the "football" shape is 
more of a classic MH bulb design. A lot of the specialty aquarium bulbs are 
using the "european" shape now, but all the commercial lighting MH bulbs I 
see are still the "classic" shape. Not sure if there is really any 
difference -- either should work in any fixture provided the bulb will 
physically fit.


Waveform Technology
UNIX Systems Administrator