Neon Signs

Chinese characters lend themselves to display in "neon lights", as the glass tubes holding the neon gas can be bent to the curves of the Chinese characters.

The the bent glass tube is filled with neon and then an electric field courses from one end of the tube to the other completing the circuit. The electric field energizes the gas and it radiates the light. Neon is just one gas that can be used in this way. All of the "noble" gases on the far left of the periodic table could be used. Each gas gives off a characteristic color.

neon --------- reddish orange
argon ------- pale lavendar
helium ----- pink to orange white
krypton --- gray to green
xenon ------ purple
(radon is radioactive and therefore not a good choice)









When we factor in price, the artist's pallette gets even smaller. (No yellow, no blue, a poor green, ... ) At current prices(that reflect abundance) we're left with just Argon, Neon and Helium as possible carriers for the electric charge.

Gas                                      2004 price (USD/per cubic meter)
Helium (industrial grade)         4.20 to    4.90   (party balloons)
Helium (laboratory grade)     22.30 to   44.90
Argon                                       2.70  to    8.50
Neon                                      60.00  to  120
Krypton                               400.00  to   500
Xenon                                4000.00  to 5000

If this is the case how come there are so many "neon" colors on the street?

The answer is that these lights are actually not "neon lights" at all. The gas inside their tubes is Argon with a touch of Mercury. The electric field excites the Mercury which irradiates in the Ultraviolet  range, this ultraviolet light is captured by the phosphor coating on the inside of the tube and reradiated in the
colors we see. With different phosphor coatings on the inside of the tube a whole range of colors can be produced. In this way these "neon lights" are actually more like fluorescent lighting or energy saving bulbs. One way to tell neon from these phosphor tubes is to look at the glass tubing went it is not lit. The neon tubing uses clear glass, the phosphor tubing will be white, not transparent.

There are other ways of increasing the artistic palette of neon lights:

1. colored glass tubing
2. backing ground coloring

In the Bing Lang advertisement below only the reddish light is neon. The orange is from colored tubing, the other 3(green, blue, purple) colors are from the phosphors.

When turned off, you can see the clear tubing for red, the yellow tubing for orange and white tubing for the others. (Picture below is from the opposite side.)

In the sign below the yellow actually comes from the yellow background, the
phosphor tube lights are actually white.
 

















Now with a full selection of colors the advertiser can go wild.

In Taiwan, Green is the color for medical/health facilities:
























For Chinese, Red is usually a happy color, but her we have the sign for a pawnbroker in red. I think anytime the pawnbroker is involved it is NOT a happy time.