The development of lanterns continued through the 1930s and accelerated when it was determined that the lamp’s brightness and its long length made it less susceptible to glare. Lanterns with bare bulbs suspended over an overhead reflector (the so-called "seagull" lanterns) quickly followed. Glass manufacturers were initially slow as the first plate refractors for low pressure sodium lamps didn’t appear until the end of the decade.

The advantages and disadvantages of low pressure sodium were readily debated, especially when an alternative (the medium and high pressure mercury discharge lamp) was also available. The monochromatic light was considered especially useful for arterial and traffic routes, the lamp’s shape cast a wide beam across the road surface, the light was also considered more penetrating in foggy conditions and it was the most efficient light source being manufactured. However, the light was also considered inappropriate for high streets, promenades, civic areas and residential streets and so some lighting engineers restricted its use to traffic routes only. Therefore low pressure sodium became known as "the drivers’ lamp."

The arrival of plate glass refractors resulted in large lanterns made of metal frames enclosing heavy glass sheets. These bulky lanterns continued to be made into the 1950s until being usurped by lanterns with plastic bowls and machined or moulded plastic refractor plates. The lanterns were still large; the size dictated by the bulky control gear, but their design and construction was becoming simpler.

The 1950s and 1960s saw huge improvements in the construction and efficacy of low pressure sodium. Early two-piece designs (dubbed SO) were replaced by the one-piece, more efficient integral design (called the SOI). The development of linear sodium (SLI) broke the one hundred lumens per watt barrier, lead to a radical rewriting of the British Standards of street lighting and prompted the development of new families of streamlined lanterns. But it wasn’t until the arrival of a new heat-reflecting technology (called SOX) that a cheap family of extremely efficient bulbs became available.

The energy crisis of the 1970s saw a rethink in street lighting and lamp efficiency became dominant when fuel was both in short supply and expensive. This saw the large scale removal of colour corrected high pressure mercury, fluorescent and ancient tungsten lamps by low pressure sodium replacements. The old arguments that the smoky-orange lamps were inappropriate for residential areas no longer applied. By the end of the 1980s, low pressure sodium was the dominant street lighting lamp used in the UK.

The use of low pressure sodium came under scrutiny again. High pressure sodium, finally developed as a viable technology in the 1960s, was coming of age and offered a compromise of slightly less efficacy with better colour rendering. Questions were being asked about the physiology of the eye and visual adaptation under low lighting levels; previously the wavelength of low pressure sodium had been deemed the most suitable, but research now suggested that the eye responded better to white light. Concerns were raised about light pollution and the low pressure sodium lamp was seen to be the chief culprit (although it was more to do with older non-cutoff and semi-cutoff optical designs rather than the lamp itself).

By the turn of the century, the age of low pressure sodium was seen as coming to an end. Research in white light technologies, especially metal halide and a renewed interest in compact fluorescent coupled with the advantages of using white light at low lighting levels, saw the end of the low pressure sodium lamp’s dominance. Its use was discouraged in the specifications, lantern manufacturers started to wind down their production and bulb manufacturers followed suit.

By the end of the first decade of the 2000s, low pressure sodium was in stark decline, and less and less of the UK’s streets were being lit by its characteristic orange glow.

Name: ELECO GR525
Date: Early 1970s - Late 1980s
Dimensions: Length: 460mm, Width: 170mm, Height: 172mm
Light Distibution: Semi Cut-Off (BS 4533:1976)
Lamp: 35W SOX

The company introduced two lanterns into the range in the late 1960s. Both shared the same bowl (and hence the same optical system) but the GR525 was a bulky lantern, necessitated by the inclusion of gear, whilst the GR535 lacked gear and had slimmer and sleeker lines.

The GR525 wasn't as popular as other lanterns in the range, as it wasn't installed in the same numbers as other ELECO products. Strangely, it was largely missing from the catalogues of the period as well.

The underside of the gear tray is painted white and acts as a secondary reflector.

The exterior of the bowl is smooth to facilitate easy cleaning.

facing profile I obtained this lantern in a swap with fellow collector Wayne. I don't know where it was originally installed.

front profile The lantern was in good condition and only required minimal cleaning to freshen it up. There was a little interior rusting off the gear tray but that was the only indication of a life in service.

trailing profile The P42 two-part photocell appeared to be a later addition.

canopy The bowl, whilst complete, wasn't in good condition. The polycarbonate had started to turn yellow after prolonged exposure to sunlight.

logo Unlike most ELECO lanterns, there was no logo cast into the lantern’s canopy.

pedestrian view This view clearly shows the shape of the bowl and the angle of the sides (which are almost vertical). This lead to a relatively large base area which was been partially frosted to diffuse the light cast beneath the lantern.

vertical In this view, the manufacturer’s name can also be seen cast into the rim of the bowl. It states: “GR 535/3M ELECO LTD. St. Albans”. The same bowl was also used for versions of the ELECO GR535 range.

open bowl The interior of the lantern clearly shows the underside of the gear tray which acts as a secondary reflector. As with later ELECO low-pressure sodium lanterns, the bulb holder was road side.

interior #1 The interior of the lantern simply carries the various lugs to hold the gear tray, cable clamp, grub screws (for securing to a column spigot) and an earthing screw.

interior #2 The gear tray has mounting points for ballast, capacitor and ignitor. Two of these components have been replaced whilst in service; only the PYE capacitor (rated at 10uF) and dated 1973 seems to be original. The new ballast is a Philips BSX 355 L204 for 35W and 55W SOX lamps; whilst the ignitor is a Philips SX72 for 35W and 55 SOX lamps.

interior #3 This final photograph shows the interior of the lantern with the gear tray fitted.

One of the last lanterns produced by ELECO, the 525 was popular in Cambridgeshire but I've never really seen them anywhere else.

Whilst it's a gear-in-head lantern, this example has been fitted with replacement gear.

The polycarbonate bowl has gone yellow with age.

Obtained as a swap with fellow collector Wayne.