Neon lighting was discovered on the very end of the 19th century and since then has been largely used around the world. In the first half of the 20th century it has been very popular for signs creation and outdoors advertising. It popular usage was mostly justified by its vivid color together with its low costs due to the simplicity of the necessary raw materials: glass, gas and an electrical transformer.
The application of neon lights was not restricted to outdoor signs but also for normal lighting, including indoors. It works in a very similar way as the also well-known fluorescent tubes. The key difference is on the gas combination inside which is mostly composed by mercury vapor on fluorescent tubes or a combination of neon and argon in a neon tube. This difference causes the light emission to have a different frequency when lit by the electrical current. A neon tube will naturally emit red or blue (depending on the proportion of neon and argon) while the mercury vapor will emit UV (not detectable by human eyes). That means, for a clear glass tube, we would only see light on the neon tube but not on the fluorescent tube.
To be able to also generate visible light on fluorescent tubes, there must be phosphor powder that reacts to the UV emissions and produce visible light. On neon tubes this powder coating can also be used to achieve different colors when combined with the natural gas color. It is also common to see neon tubes where the glass is also colored, besides the usage of the powder.
Even though the early days of neon lights were closely related to the intention of simple general lighting, it gained a lot of attention on the signs and advertising industry especially on the first half of the 20th century. Not only the neon lamps but low-pressure gas-based lamps like also the fluorescent lamps were applied into bright signs around many cities.
Later on, the straight wide-diameter long white tubes became very popular for general office and building interior lighting. Its energy consumption was comparably lower to a neon sign due to the wider diameter of the glass tube which offers less resistance for the electrical current. Naturally this could theoretically also be achieved with a neon sign, however, due to the possibility of generating different colors with the combination of gas and powder, the glass tubes for the neon signs would assume the shape of the sign itself. Therefore, the vast majority of neon signs had various hand-made shapes which requires the glass manipulation with heat. Thus, to lower its resistance with a wider diameter tube it would became much more difficult to manipulate those tubes.
As mentioned above, most neon signs are produced by bending thin glass tubes into the desired shape and then filling up with the specific gas combination that will provide the desired color. If the desired color is not one from the natural gases, the powder coating on the glass tubes can also be used to achieve other different colors. However, the powder coating changes the glass tube appearance: when off, the sign looks simply white on most cases; when on, it shines on the desired color as a colored tube. On the other hand, clear glass tubes can also be used to see the natural color of the gases inside, which also gives a very interesting appearance as you see directly the gas inside shinning. Last but not least, it is also possible to use glass tubes that, besides having the powder coating, have also an external color. For those, the same color that shines when the sign is on, will also be visible on the glass when the sign is off. Many LED producers nowadays produce silicon or plastic tubes that simulate this later type of neon sign, whereas the clear glass type effect cannot be represented with LEDs.
To be able to shape the raw straight glass tubes and achieve the final desired result for your sign, many steps are necessary. This could vary depending on the bend technique and type of glass used, but here we will a standard procedure for a clear glass type:
1. Mark the correct points of bending in the raw glass tube
Before heating up the glass tube to be able to bend it, marks are made on the glass as a reference to know where the bend curve will start and will end. The original design is used as a reference beforehand.
2. Heat the glass tube
Depending on the size of the bend curve, based on the previews made marks on the tube, the fire flame should be adjusted accordingly. So, for a long bend, usually a long straight line of fire is used so the glass can be evenly heated up along the whole area to be bended. On the other hand, for a short bend it's possible to use a punctual fire flame that heats up only that specific spot.
3. Bend the glass according to the reference design
After the tube reaches a specific temperature, - also called Transformation Temperature - around 700°C, it becomes malleable so it can be bended. The glass tube is then removed from the heating source and placed on the reference design so the glassblower can compare the bending with the original drawing. This is probably the most difficult step in the process as the time is limited for the glass tube to be bended before it cools off again and become solid. Also, it cannot be let in the heat source too long otherwise it melts and loses the tube shape. Moreover, simply bending it will narrow the tube diameter creating a bottleneck. Therefore, the glassblower must blow air into the tube - that also explains the term 'glassblower' - in order to increase the pressure inside the tube avoiding the narrowing of its diameter in that spot. The pressure cannot also be too high otherwise a bubble can be created at the same spot. All of these have to be done almost simultaneously to reach a perfect bend.
4. Cut the spare parts
Sometimes when the glassblower finishes bending the whole sign, there is still a spare part of the glass tube as it comes in fixed lengths. Therefore, this spare part must be cut off. The cutting tool is similar to a needle, that has to be heated up and then applied on the glass tube to cut it.
5. Weld the electrodes on both sides
Now that the sign shape is ready and trimmed, it's necessary to insert the electrodes in both ends. These are responsible for actively turning the neon on through electricity. The current will flow from one electrode to the other, throughout the neon glass tube, making it shine. Fire is also used to weld them in place, so it melts the tube and the electrode ends so they can be connected.
6. Pump the air out and gas in
Just putting the electrodes is not enough to actually light it up. You still need to insert the gas (neon and/or argon) as well as reduce the pressure inside the tube. Therefore, a pump is needed. It is connected to one of the electrodes that has a pass-through in which the air is going to be pumped out and the new gas inserted.
7. Burning the residue
It is also highly recommended that the neon sign heated up for a while in order to remove small particles from inside the tubes due to previous dust or due to the blowing process from the glassblower. The neon gas is lit up with a higher power so that the electrodes and the tube heat up more than normal for some time.
8. Light it up
Now it's time to finally use it. The neon sign can be connected to a power supply (electrical transformer) which is responsible for converting the normal AC voltage (127v / 220v) to a much higher voltage (2kV ~ 15kV, depending on the neon sign) that will be responsible for sparking the current inside the tube and therefore generating light.
Neon signs nowadays
Even though the neon signs were one of the main players on the signage business during the first half of the 20th century, a couple of decades later the LED technology also joined this market. Because of its higher efficiency (therefore less energy consumption) it started to be used more and more in every lighting sector including signage, house lighting, automotive industry, etc. However, even losing its privileged position on the market, the neon signs never actually came to an extinction. We, at sygns, believe that the LED was able to improve costs, both for purchase and consumption, when compared to neon. On the other hand, it was never able to improve nor imitate the same feeling that neon signs carry like it's unique glow and artistic feeling due to manual handwork.
For this reason, neons still are active even though taking place in different market sectors when compared to before. According to the photographer and also neon lover Randall W Brelsford, "I always loved neon because it was a representation of the future from the people of the past", which we, at sygns, also fully agree and therefore our core mission is to bring a contemporary feeling to an old technology, expanding sales not only to business signs but also artistic pieces and internal decoration where it can bring its unique value.