Glass, gas, and a ribbon fire
The colour is the gas.
Nothing on a neon sign is painted. A tube glows the colour its gas emits when a current runs through it, and there are only a few gases, which is why every sign in the street is one of a few colours.
OPEN / 300 mm caps / neon
3.51 metres of tube, bent to one word.
Word
OPEN
Cap height
300 mm
Bore
12 mm
Glass
3.51 m
Sections
2
Electrodes
4
Every letter here is one length of glass, heated over a ribbon fire until it goes soft and bent against a paper pattern. The bends are what take the time. The straight runs are what take the glass.
The metres are the strokes on screen added up at 300 mm caps, plus 80 mm of electrode allowance at each end of each of the 2 sections. Change the height and every number under it moves.
Nothing is painted. This tube is neon.
The one everybody means. Red-orange, and the brightest thing per watt in the shop.
An excited atom drops back down and gives off the difference as light at one exact wavelength. A gas has a fixed set of those, so it has a fixed colour, and no amount of wanting a different one will move it.
#ff4300
16 emission lines, summed through the CIE 1931 observer and converted to sRGB. Not a swatch anyone chose.
Nanometres and relative intensity, from the standard strong-line tables. A clear tube, which is the only kind this page draws: a phosphor coating is a different colour and a different calculation.
A 6 kV transformer, sized to start on the coldest morning.
Cold gas does not conduct. The transformer has to push hard enough to tear the first electrons loose, and once the discharge has taken hold it needs far less to keep it there. The number that matters is the one on the cold morning.
3.51 m at 1000 V per metre, plus 300 V for each of 2 electrode pairs. That is 4111 V, so the sign takes the 6 kV.
The volts per metre is the bender's rule of thumb: about 1000 for neon in 12 mm glass, roughly a third more again for anything running on argon, and a little less in a wider bore.
It is a rule of thumb and it is deliberately generous. A transformer sized to the last volt is a sign that will not start in January, and that is a callout, not a sign.
On the wall
| Sign | Fill | Glass | Transformer |
|---|---|---|---|
| BAR | argon with mercury | 1.84 m | 4 kV |
| CAFE | neon | 1.50 m | 2 kV |
| HOTEL | helium | 2.09 m | 4 kV |
Window sign, 150 mm caps, hung on chain since 2004
Rebuilt twice. The second E is the original tube
Cut down from a 1960s roof sign, three sections
Also done here
Repairs
A cracked tube is remade, not patched. Bring the whole sign and the pattern with it.
Refills
Old glass pumped down, bombarded and refilled. A tube that has gone dim is usually air.
Custom lettering
Your own hand, traced onto a full size pattern and bent to it letter by letter.
Transformers and wiring
Sized to the glass, tested cold, and fitted so the sign can be serviced later.
Bring us the word.
Tell us the word, the height you want it, and where it is going. We will send back a pattern, the metres of glass it takes and the transformer it needs, before anything is agreed.
Unit 4, Bracken Works, Sanderson Street Sheffield S3 8DT
Bent by hand, one word at a time.