www.soxlamps.com: Introduction

SOX streetlight just switched on in Wrexham, UK. Left & below: Thorn Beta 5 lanterns shortly after sunset. Wrexham, May 2004.

According to statistics from the Association of Street Lighting Electrical Contractors (www.streetlighting.uk.com), there are currently nearly 7.4 million streetlights in the United Kingdom. I do not know how many of these currently produce the golden yellow light that this website concentrates on, but I suspect that we are looking at at least a couple of million.

When I was a child I was intrigued by all the golden yellow, almost orange, lights in the street. And when they first lit up they shone red, changing colour to deep yellow only after a few minutes. These lights seemed so fascinating that they have held my attention ever since. If you have several on them on different streets, lighting up at slightly different times after sunset, you have a multi-coloured light show of red, orange and yellow as they warm up. The lights I am describing are referred to as sodium lamps (strictly speaking, low-pressure sodium lamps — they are also commonly referred to as SOX lamps in the lighting industry, or LPS lamps in the USA and Australia), and I have put together my website in the hope that just a few people will find an interest in a subject they may never have considered before.

If you hold a CD up to sodium light you will not see the usual rainbow-coloured pattern at all, but instead shimmering bands of yellow and black, owing to the monochromatic light from the lamp. The sodium lamp has had a huge impact on streetlighting in the UK and most probably no other country has used it to such an extent. However, I have heard from other people who have told me that they have been popular in countries such as Belgium and Australia, and that even the USA gave them a go.

SOX streetlight just switched on in Wrexham, UK. Low-pressure sodium lamps are the most efficient light source available in terms of light output for each watt of power put in (i.e. their efficacy).

SOX installations therefore have the lowest energy consumption costs which is of crucial importance when thousands of miles of roads must be lit and the electricity bills must be kept as low as possible. The main reason why they are effective as a light source is because the colour of the light is close to the maximum sensitivity of the human eye in normal viewing conditions.

These lamps exist in a variety of wattages from 18W to 180W (10W can be found on rare occasions), but a typical side-road lantern of 35W is less than even a domestic light bulb of 60W-100W. Therefore, using a SOX lamp, part of a street can be illuminated with less energy than is normally used for a single room in a house!

Although it looks as if the low-pressure sodium lamp has not changed much over the years, apart from the designs of lanterns, there have been decades of research and development that have gone into making the SOX lamp what it is today. Its tale begins commercially in the 1930s, but even before this time there were years of research by top scientists into light sources, as indicated in the history section, that led to the introduction of these lamps. Most of the technology has gone into the lamp tubes themselves.

I hope that my enthusiasm for these low-pressure sodium lamps, and the reasons why I am interested, are brought across. I am aware of the fact that a few other people are more expert on low-pressure sodium lamps than myself, but I have drawn from their knowledge and hope that my website gives the correct story.

Of course, lighting is all very much a matter of taste. And I do promise to get out more and get a life and so on and so forth. But allow me a little time to try to explain my interest: just why these lamps give off both red and yellow light, where they originate from, and how they can help banish the winter blues…

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