Light for Glass

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2007-07-23 Rev. 2008-05-06, -11-07, -11-29, 2009-06-17, -12-11

This isn't called Lighting Glass because somewhere down there I want to explore using natural light with glass
and make some points about illumination.
Like here:
Glass & Light Center

Area Lighting

The traditional old light bulb or flood lamp using a tungsten or other metal as a thin wire filament which is heated to brightness in a vacuum or low pressure non-oxidizing gas. Produces a warm yellowish light that can be adjusted in temperature by changing the voltage.  If the bulb is run at about 10% under rated voltage, it will last several times as long, using more power per lumen - common "long life" bulbs are designed for 130 volts and run at 117 (avg) lasting 3-4 times as long; A "60 watt" long life produces about as much light as a normal 40 watt, using about 54 watts.  Clear glass is commonly better lighted by a whiter light such as halogen, but yellow or red glass can be enhanced.  Low wattage bulbs are less efficient at making light so  "75-watt incandescent bulb emits approximately 1,190 to 1,220 lumens" [here] and "a typical 25-watt light bulb produces only 210 lumens of light" [here] so 3 25 watt bulbs give 630 lumens vs. about double that for a single 75 watt.  CFB's are much more efficient while Halogen are brighter and about twice as efficient.

Light is created when a powder is illuminated by ultraviolet light and gives off white light.  The UV light comes from a glowing plasma created by high voltage inside the tube (or from radio frequency power) which is at low pressure and has a small amount of mercury.  This high voltage is produced by a ballast which also limits current while running and is a source of heat loss and failure expense.  Because it is diffused light, the only good uses in lighting glass are reflected lighting off a wall or from underneath. Bottom light is especially nice because they run very cool.  Fluorescent light bulbs come in various colors.  Cool white is the most efficient and is the bright white seen in stores.  Warm white is similar to the color of incandescent.  Daylight is a blue tinted color that matches the light of a clear north sky.  All fluorescent lights are more about five times more efficient than standard incandescent and most last ten times as long, 10,000 hours.  All fluorescent bulbs have trouble in cold conditions with some tube types failing to light and some compacts taking noticeable time to reach full brightness. [Which I actually like when turning them on in a dark room.] 
Compact fluorescent bulbs (CFB) have made great inroads in the lighting market with the electronic ballast in the screw-in base and distinctive spiral glass tube. Recently the cost has dropped from about $20 per bulb in the mid 90's to 4 bulbs for under $7 at home centers and discount department stores. Dimmable versions still are higher prices, but more like $12 each.  Although they are still referred to by the wattage of a similar brightness incandescent bulb (40, 60, 75 or 100) in fact a 13-14 watt CFB gives 800-900 lumens or about what a 60 watt incandescent does. CFB's are so efficient and long lived that even if someone gave you regular bulbs, it would be better to buy CFB's and use them.   Savings Initially available only in cool white, now mostly available in warm white, with daylight and cool white available but not in all stores. 2009-06-17, -12-11

Technically, quartz-halogen.  The quartz is required because the tungsten filament is run at a very high temperature and it heats the tube around it.  Halogen gas (chlorine, bromine, etc.) participates in a chemical reaction where the titanium boiled off the filament and deposited on the quartz is recycled back to the filament.  Thus, a filament that would burn out quickly and blacken the bulb without the reaction has a reasonable life. Halogen bulbs have a distinctive bright white light and bulbs are typically twice as efficient and slightly longer lived than plain incandescent. Standard voltage halogen bulbs have the quartz tube inside a glass shell that is heavier glass so if the tube breaks the very hot quartz will not be a risk of fire or injury.  Halogen bulbs are available in miniature low voltage (12 volt) units commonly seen in store displays which allow fixtures clamped to exposed metal rods and which require a small switching power supply - a 50 watt 12 volt M16 spot/flood requires just over 4 amps of current. As it says on the package, touching the quartz with bare fingers can shorten the life of the bulb.  2009-06-17
The latest in white lighting is newly available high intensity white Light Emitting Diodes (LED's) which produce light by electron stimulation - sort of like a laser.  In the past, LED's were always colored and generally of low brightness.  High intensity color came first and now by combining colors within the unit, bright white units are available as for flashlights and related products.  LED's run cool and have a long life. As of spring 2008 small devices with batteries and base or solar chargers have come on the market to replace or act as candle like lighting. As of the fall of 2009, screw in units to replace ornamental lights are becoming available, but made of a couple of dozen LED's and over $10 a bulb, they are not very romantic like the candle shapes they replace. 32 lumens per watt  2009-12-11

Candles and Oil Lamps/Candles
Produce an even warmer light than incandescent at low level but with flickering or shifting which can be pleasant.  Produce some smoke and local rising heat and open flame may be a hazard.   LED tealights are now available in life style home catalog.  Oil lamps in the old style with a wide wick are still available, but far more popular and common are oil candles which use a liquid fuel and either support fiberglass wick above that dips into the fuel or float a cup holding the wick in the fuel. Oil fuel for lamps does not work well in candles - smokes. Much more on these is available here

A brilliant white light produced by electricity sparking between electrodes, it is not practical for small scale lighting, but can be used for large scale outdoor lighting - the huge bright spotlights at openings are arc lights and as are old style movie theater projectors.  Lots of heat is given off and some RF interference.  The light may be familiar also from arc welding.  When someone is "in the lime light", it refers to oxy-hydrogen  using limestone for a white light source in theater in the 19th century.

Area Lighting
Incandescent, fluorescent, and halogen bulbs are used for area lighting as plain bulbs and in flood reflector lights.  At least two kinds of bulbs exist that are only suitable for area lighting because of their colors and a variation of one is only used for area lighting because it is so bulky and bright. Each of these bulbs places a glass capsule containing a vapor light source in the center of a bulky glass bulb and all require a ballast in the lamp fixture to start and maintain the light. The required fixtures with a bulb cost $30-90 and up. They are the most efficient light sources with limitations discussed below, but all take dozens of seconds to minutes to come up to brightness and thus are not suitable to motion control or photocell activation by people.  Most exterior are turned on sunset to sunrise or by timers.
High Pressure Sodium creates an arc in sodium vapor that causes the plasma to glow brightly with the yellow color of sodium that glassworkers wear didymium (purple) glasses to see through.  Unlike a spectrum of colors for white light, the light is emitted at very narrow frequencies in the yellow range.  These are the yellow lights of parking lot and street lighting.  The light is very efficient* and the bulbs very long lived but the narrow colors mean that people's pink/red lips look black (no red in the light to reflect) and other colors can't be judged accurately. As with all yellow bulbs, bugs are not attracted.  I have one in my backyard. Emission lines Narrow peaks
Mercury Vapor and Metal Halide bulbs put a small amount of mercury in the capsule.  Mercury vapor bulbs give off a strong blue white light that is harsh on people's skin color and "feels" cool - not warm and friendly.  These are seen in parking lots as more polite to faces or moonlike than sodium, but car colors may be hard to pick out.  Metal Halide bulbs put a mix of other volatile metals with chlorine, bromine or iodine (halides) in the capsule. Mercury vapor fixture making and sale was banned in U.S. as of 2008-01-01  These are more costly but also more efficient than Mercury Vapor lights, but the white light is much more pleasant.  These are used for down lighting in very large spaces like gymnasiums and factories.  The fixtures and bulbs are more costly so these tend to be used in larger sizes and a single bulb would overwhelm a low ceilinged space. 2008-11-06
Light Output
Bulb Type Life Watts Lumens Lumens/Watt Productl Cost* 10,000 Hours*
High Pressure Sodium 35W 1 16,000 35W 2250 64    
High Pressure Sodium 70W 5 25,000 75W 10?000 80    
Mercury Vapor 175W4   175W 7000 3700K 45 CRI   31.21  
Metal Halide  70 or 100W 6 24000 100W   4200K 92 CRI      
LED Bright White2       115-180    
Compact Fluorescent3 10,000 14W 900 64 1.72 32.50
Tungsten Halogen3   100W 1670 16.7    
Incandescent 3 800 100W 1380 13.8 .75 1265.63
Fluorescent Typical 35W 4' tube 3000 100 10.50  
* Without labor - fixture and bulb(s) for 10,000 hours (est. 5 years) @ 13.5 cents per kwh (Texas cost)
 4 manufacture banned 2008-01-01 see metal halide

A heavier resistance wire used for heating, normally glows dull red when hot.


A thin wire of moderate resistance that becomes hot to give off light when electricity is passed through it.  Element


A measure light output. In USA, light bulbs sold retail are supposed to have the lumen printed on the package or as part of the display, so people will buy output rather that "watts" as brightness.

Lights of America Model: 9165-2
Do it Best SKU: 562416 Online Price: $32.99
Free Shipping: Ship-to-Store, At participating locations, Arrives in 7-10 business days
65W fluorescent yard light, 500 incandescent wattage equivalent. 4500 lumens, 10,000 hours average life. 10.75" H. x 9.87" D. Not for use with dimmer circuits or recessed fixtures. Not recommended for use with timers, photo cells, and motion control devices. Minimum starting temperature is -28 F. White. UL and CSA rated for outdoor (damp) locations. EnergyStar rated. Limited 1 year warranty. Refer to model No. 9166B for replacement bulb. $18.99

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