Coughtrie BB.15 Bulkheads

[Beta 5]

Does anyone have any info on the Coughtrie BB.15 GLS bulkhead design?
I have liked this design for years and have a few examples of them, but it would be good to know some more about them such as the date they were released and any catalogue pages relating to them.
They are quite often seen on older buildings wired in conduit or sometimes MI and are suitable for up to 150W GLS lamps, when installed outside the opal glass bowls tend to end up various shades of purple after decades of sunlight exposure.

[BC5-80]

As soon as you mentioned the "various shades of purple" I knew exactly which fitting you were referring to, otherwise I had no idea. How can it be that they turn that lilac shade, assuming they weren't like that from new?

[HIDLamp]

If it's any use my Grandad had a brand new pair fitted to his house in 1969/70.
Both are still in service today after 54 years and one refurb in 2019.

[Beta 5]

Indeed the purple covers are quite iconic for the design! although I believe it is some element of the glass that reacts to the UV in the sunlight and turns purple. As far as I know they were always pure opal/white when new, I have one that has been installed indoors all it's life and doesn't have any hint of purple in it's glass.
@HIDLamp, That's interesting to hear! Do you know where he got them from? Assuming they are outside, have they gone purple at all?

[HIDLamp]

I have no idea where they came from, I'm guessing a local electrical wholesaler.
Yes they're outside and yes they're purple

[Flurofan96]

When I first saw some of the BB15 lanterns with the purpled bowl/cover I thought it was a decorative edition as it does look pretty

[Beta 5]

I used to think it was some sort of plastic that had discoloured after years in the sun as I previously didn't realise glass could actually go like this too!

[Flurofan96]

That is fascinating - perhaps it is Milk Glass in which the compound/substance used to make the milk finish reacts to the sunlight

Oh well the good thing about it being glass is that it won't go brittle like plastic does under sunlight

[BC5-80]

I'm also fascinated to know how glass can go purple like that, and agree that it's far preferable to plastic that might go yellow or worse (brown).

[Kev]

We’re these ever available in a HID version?