Good morning fellow lighting nerds! So, I was thinking about trying to install some tube holders and stuff in the ceiling in my shed so I Can finaly try out some of my 6 foot, 70W sylvania luxline plus 865's. I unfortunately do not have any fixtures for these tubes, and I highly doubt I will be able to find any because they appear to be really rare in terms of size here. But what I do have, are 3 ballasts intended for use in sign ligting or maybe for suntanning rooms. They have push on tube sockets that hold themselves onto the tubes, and you hold the tubes with some metal clips that you can screw onto any surface, so I was thinking about simply mounting two of them in the ceiling Two of these 6 foot tubes would fit just about perfectly inside my shed lenghtwise! I have 10 of them that I bought a long time ago , and still havent done more than tested on the bench. So I thought that could be fun. I only have 865 coloured ones right now, but I was thinking about purchasing some 840 ones from eBay. But there are not many available, and I do not *really* need them. so if any of you guys want to grab them I can let them slide I already have 10, afterall, and I suspect they will last a bloody long time. It would just have been nice to have 840 coloured ones, but I also really like 865 so hard decision!

But as I looked at these tubes and the gear I have for them I started wondering if these tube lenghts are really unusual, because I have never seen many of them, at least not where I live. and I have never seen many for sale on ebay or anywhere else for that matter, I just happened to see some for sale today. I havent decided if I will purchase them or not yet, I am a little worried about how the shipment will go because such long tubes are surely hard to deal with in shipping.

Just my random thoughts again,

Because 1800mm is starting to be inconvenient to handle I believe. Recently hauled a couple of saved 5ft 58W's on a public transit and almost broke them a couple of times already. And probably lamp voltage starts to be a bit high to run from 230V directly with a straight choke.

In America with their 120V supply any high power tube has to be run on a step-up transformer anyway, hence is the Americans preference to long tubes at high voltage. In 230V world, 4ft and sometimes 5ft looks optimal.

Although the first six foot tube was introduced by GE of America in 1944 as part of its Slimline T8 series, it remained a rather uncommon size.

The first preheat cathode six foot tube was introduced by British Lighting Industries (a division of Thorn Lighting) in 1966 under the Atlas Super Six name.  It had a T12 diameter and was rated 85 Watts.  BLI introduced it as new standard with highly optimised performance of the total lighting system, and it was originally intended that this size should become the dominant tube for the British fluorescent market.  Previously the highest runners in Britain had been the 5ft 80W tube, and after 1956 the 8ft 125W.  Both were highly loaded tubes that offered impressively high light output for industrial and commercial applications, but that made them rather inefficient - their loading being similar to the American HO (high output) tubes introduced by GE in 1952.  That situation was partially overcome in 1961 when BLI introduced the new standard of the 8ft 85W tube.  That delivered an extremely impressive boost in lighting efficiency - but as noted by RRK such long tubes were considered unwieldy and difficult to handle.

The compromise of 1966 was to introduce the 6ft 85W tube as an intermediate model that satisfied the following criteria:
- high light output suitable for industrial and commercial applications
- high efficacy to attain lowest cost of operational ownership
- the maximum length tube that could strike easily on the British 240V mains supply, without expensive or complex control gear such as autotransformer ballasts, or the capacitive ballast as used for the 8ft 125W tube

The 6ft 85W indeed quickly became one of the most popular sizes in Britain but curiously it did not enjoy the same success in other countries.  As RRK also already pointed out, for low voltage countries in the Americas it would not be an advantage, because the high tube voltage would require a greater open circuit voltage of the autotransformer ballasts, resulting in greater size, weight, cost, and electrical losses of the ballasts.  In other European countries it was also not adopted because their mains voltage of 220V was slightly too low to ensure reliable starting of the six foot tube, which was not a problem on the British 240V mains.  As such, the six foot tube standard remained almost exclusively limited to the UK and other 240-250-260V countries around the world.  Another restriction was that in continental Europe Osram and Philips had recently constructed new high speed tube production machinery - but not having foreseen the six foot development and also not having ever made the 8ft tubes in significant volumes, they built their lines to handle a maximum tube length of 5ft.  It was therefore commercially very difficult for them to follow the Thorn lead in the new 6ft business.

Two years later in 1968, Thorn made another major development with the introduction of its "Superwhite" phosphor.  That delivered an almost unprecedented boost of 6% in luminous efficacy, and allowed the 6ft tubes to rival even the 8ft 85W in total system efficacy.  The same phosphor was not attractive to apply on 8ft tubes because those already delivered enough light, and the high cost of the new material would have made them too expensive on a longer tube.  Also in 1968 Thorn developed a remarkably efficient new semi-resonant-starting ballast for the 6ft 85W tube, which eliminated flicker on startup and greatly extended lamp life.  These two achievements further cemented the 6ft 85W as the leading British tube.

Following the global Energy Crisis of the early 1970s, in 1973-74 Thorn re-rated the 6ft T12 from 85W to a dual-rated 75/85W tube.  New ballasts were introduced to run the tube at slightly lower current, which caused a drop of 10W in power consumption but due to the lower power loading, the decrease in light output was much less significant.  Thereafter, most new 6ft installations used the newer 75W ballasts.

Finally, following Thorn's 1975 introduction of the first Krypton-filled T12 energy-saving tube in Europe, and especially after Philips' 1978 extension of the Krypton technology to the new T8 formats as T12 retrofits (first in 4ft 36W, then 2ft 18W and 5ft 58W), it was a logical step for Thorn to apply the same principle to its 6ft tubes.  That resulted in the introduction of the 6ft T8 70W krypton lamp.  Like its 6ft T12 predecessors, it remained almost exclusively used in countries having mains voltages of 240V or higher.