Fire-Safe Lampshade


Old 09-25-01, 02:44 PM
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I want to make hanging lamps to provide light for my indoor plants and also look nice in my living room. I want to use the new screw-in halogen bulbs (75 watt or 100 watt). I'm wondering if I can safely use an ordinary lampshade? Do these bulbs make as much heat as the torchiere halogen bulbs? If so, maybe I'd better use metal or glass shades. What I'd like to do is make cylindrical paper shades. Perhaps if they are a large enough diameter it would be safe. Does anyone know if these bulbs produce a similar amount of heat to ordinary 100 watt bulbs? Or if they can safely be, say 6 to 8" away from a paper or cloth lampshade?
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Old 09-25-01, 03:12 PM
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I think most gardeners will tell you that supplemental lighting won't do the plant any good unless the light is about an inch or two from the plant. The only light that you can use for this without scorching the plant is a fluorescent. And there's no way to do that and have it "look nice in my living room."
Old 09-26-01, 07:50 AM
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What John is referring to is right. Flourescent lights put out ultra violet light that the plants seek to enhance growth. You might try a flourescent fixture called a circline flourescent fixture. This fixture has flourescent tubes in a round circle form that may allow a lamp shade to hang over it without fire risk and provide the UV light that you are seeking.

Just a wild idea

Old 09-27-01, 08:13 AM
Join Date: Dec 2000
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Actually, I've wondered this myself. My take on it is as follows:

Incandescent lights are highly inefficient. Almost all of the power turns to heat, very little is emitted as light. Therefore, regardless of type, in a 100W bulb most of the 100W of power is converted to heat. (Good thing, too - otherwise my daughter's Easy Bake Oven wouldn't work!)

I think the original poster actually meant surface temperature of the bulb. The surface temperature of the bulb is roughly determined by (1) the power dissipated as heat and (2) the surface area of the bulb available to convect the heat into the surrounding air. Thus, if a 75W halogen bulb is about the same size as a 75W tungsten, their operating surface temperatures should be similar.

Thus, the reason that torchiere and similar unprotected halogen bulbs get so hot is that they are tiny. Actually, the glass envelope of a halogen bulb must run very hot in order for the halogen action to occur. The screw-in halogen bulbs are actually comprosed of a tiny (presumably very hot) bulb enclosed in a much larger glass envelope (which replaces the heat shield required in lamps that use bare halogen bulbs).

Again, this is my reasoning. Does this agree with reality? (If not, it sure won't be the first time that's happened!) Also, I personally don't care if a halogen light is suitable for plants, I've just been wondering about the surface temperature.
Old 09-27-01, 10:38 AM
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I am going to try to answer this in common picture type terms. Remember this is a generic method and inaccuracies will exist, yet the picture in you mind may become more clear. Heat does not produce output of light directly. You could heat a peice of metal to red hot yet produce very little light. Heat reaching the level of white hot and boyond is what produces this light output. White hot is way hotter than red hot. The white hot of an incandescent bulb would be much less hot in temperature than the white hot of quartz or halogen. Then there is a bending of the lumens [refracting of light] that tend to multiply or zero in on a certain area that also affects the amount of light output. Then reflective nature of the background of that light also affects that light output.

Then you said that incandescent light is very efficient. I don't know that I agree with this statement. BAllasted lighting tends to be much more effecient than incandescent. Ballasted lighting comes in forms of flourescent, high pressure sodium, low pressure sodium, mercury vapor, and much much more. The effeciency of ballasted bulbs in electricity used per light output would be a big savings when lighting larger areas.

Then the refracting of lumens allows low voltage to be multiplied in lighting output using low electricity allowing efficiency standards to rise.

Then type of lighting output is also needed to be considered. Quartz lighting tends to be an area light that reaches out far distances at high intensity. High pressure sodium used to put out an orange light tint yet in recent years also puts out white light. These lights are commonly used for arena and large factory areas. Mercury vapor used to be the biggy in putting out the most efficient arenas style lighting. Now if seems to be stepping in the background for the new arena lighting styles.

I could go on but the above may give you an idea that heat that you know may not be the heat required to put out efficient lighting.

Many others in this forum can probably give you better view on the subject and get way more technical. My thoughts were to give you a general feel.

Hope this helps

Old 09-28-01, 10:10 AM
Join Date: Dec 2000
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Please read my post more carefully. I said incandescent light is highly INefficient. Almost all of the power an incandescent bulb uses is converted to heat. The heat is required to raise the temperature of the tungsten filament to a very high temperature (over 4800 degrees F). (Flourescent lights are more efficient because they operate on a completely different principle.)

I believe that my premise that the temperature of the surface of a light bulb is determined by (1) the power dissipated as heat in the bulb and (2) the surface area of the bulb is valid. The surface temperature of the bulb is what causes a potential fire hazard with tiny unprotected halogen bulbs. The newer screw-in halogens are actually the tiny, very hot halogen bulb enclosed in a protective glass envelope. This glass envelope, since it has a much larger surface area, runs with a much lower surface temperature.
Old 09-28-01, 12:10 PM
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mikewu99, I did it again, I do apologize for misreading the word inefficient as you said.

Misreading tends to be one of my many weaknesses at times.

my mistake and humble opologies to you;

Old 09-29-01, 04:21 AM
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New approach - wide spectrum or full spectrum flourescents

Thanks very much, everyone, for your thoughtful replies. I'm finally ready to admit that flourescent lights would be best for the plants. So, I'm going to try $6 wide-spectrum flourescents on a hanging shop-light fixture, and I'll make a shade to hide the ugly part. If that is not a happy enough solution, I'll try the $12 full-spectrum flourescents. I want to avoid getting into wiring junction boxes - so I'll just gather extension cords into a power strip, attached to a timer.

If anyone has some thoughts on the value of this type of light, I'd appreciate it. By the way, the purpose of these lights is to supplement the lignt from a south-east window, and to add to the light in the room - for reading and for life. So, they have to make both me and the plants happy.

Thanks again for the interesting thoughts expressed so far.

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