Why does my flourescent light take such a long time to come on?

Frequently when you turn on a flourescent light, there’s a second or two of warming up required, between the instant you turn the switch and the time the light actually comes on.

But I have this flourescent tube torchiere in my office that usually takes between 20 and 30 minutes to come on. Why do flourescent tubes “hesitate”, in general, and why does mine take a half-hour to light?

Try fiddling with the little round plug thing on the side. I am not sure why or how but that’s usually the solution to lazy flourescent lights.
I was wondering a similar thing today, why do tv pictures take so long to come on.

The “little round plug thing” Lobsang refers to is called the starter. This is needed in some types of fluorescent fixtures because of the way the tubes work. Inside the tube at each end is a filament, similar to those found in incandescent light bulbs, but of a much lower wattage. These glow a dull red color and are used to vaporize a small quantity of mercury. The starter’s job is to provide current through these filaments, then cut them out to allow the voltage across the tube to ionize the mercury vapor, giving off ultraviolet light. This UV light then stimulates a phosphor mix lining the inside of the glass envelope to give off a mixture of colors to approximate white light. Inside the starter is another filament which heats a bimetallic strip, which in turn makes or breaks the connection to the tube filaments. If there is not enough current through the bulb, then this filament heats up again, repeating the process until the tube ignites. You’ll often hear the starter click several times before the tube lights. If replacing the starter doesn’t fix the problem, and the tube is good, then the next thing to look at is the ballast, which limits the amount of current through the bulb once it has ignited.

Here is a bit better and more detailed explanation of the starter on How Stuff Works.

A torchiere most likely does not have a starter but uses a rapid start ballast in the base of the lamp and a 22w circleline tube. If so replace the tube and/or the ballast.

The circleline could alternatively have a built in ballast and the whole thing screws into a standard edison socket.

More specific information would be helpful!

Would this apply to a blacklight, as well (which I suspect is basically a flourescent light with purple crap on it)? I have a blacklight, and it flickers on and off for ~ten minutes before coming on for good.

One and the same.

Probably needs a new starter. Take the old one with you to get the correct replacement.

the flourescent fixture in my kitchen has what seems to be humidity problems. in july and aug. on the very hot, humid, and hazy days it will take a very long time to light.

we have had it checked by electricians, the fixture was totally replaced and moved to a different area of the kitchen and the problem has not gone away.

how is the weather in your area?

       The same as yours.

Our strip line single tube 40w rapid start fluorescent takes a bulling spell occasionally. Sometimes flipping the switch on and off will start it. If not rotating the tube in the sockets will restore good contact and it will start right off.

One thing that gets overlooked–and this is mentioned in the How Stuff Works article, but it bears repeating–is the fact that although all starters are physically interchangeable, they are matched to the wattage of the tube they are starting. A mismatch, while not immediately detrimental, will eventually lead to a premature failure of either the fluorescent tube or more often the starter. Proper matching assures a longer operating life and more reliable ignition.

Technically a black light uses a different kind of phosphor. Instead of converting the mercury’s ultraviolet into visible, it just converts it into a longer UV wavelength. The purple crap is a special type of glass designed to decrease the amount of visible light output. :smiley:

Good question… I don’t know the answer, but suspect it might have to do with warming up the filaments in the electron guns. :confused:

Yep, that’s basically it. Some sets have an “instant on” feature, which keeps current flowing through the cathode filaments as long as the unit has power to it, even if it’s “off”.

I had a fluorescent tube once that took forever to light but if I touched the ballast it would light immediately. Some weird grounding situation maybe?