WW2 Armoured plate glass aeroplane window

[JJZ]

Hi All, first post,

I recently came across this local ad and I was wondering if anyone you identify this glass? My gut instinct is telling me its probably just regular glass.

This item is described as:


WW2 armoured plate glass aeroplane window x12


When I messaged the seller, he just said thats what the person he got it from said...

Thanks
JJZ

 

[Greyman]

Seems a bit odd considering you need about 1.5 inch thickness to stop a rifle calibre round.

 

[ThomasP]

Hey JJZ,

There was a type of glass developed just prior to WWII for use in the airline industry. I think Armoured-Plate Glass was a brand name originally. This type of glass was developed for use in high altitude aircraft initially, but after a short period the glass was used as a general purpose type in commercial airliners of all types, as well as for many non-aerospace purposes.

The glass used a non-standard (for the time) 'alloy' and was tempered to resist shattering, and if it did shatter it should break into pieces that were less likely to cause injury to people. When the new type of glass was combined with detailed engineering analysis of structures and forces, it became a type of 'blow-out' safety glass where the pressure would cause the framing to fail before the glass did, and the intact window would fly out at very low velocity. The glass was used as high altitude airliner windows, and as inspection windows for industrial purposes, just to name two uses that I can think of off the top of my head. Possibly it was used in combat aircraft also??

Eventually this type of glass (or a more developed version of it) became what is generically called high strength tempered safety glass in today's terminology, although the term armoured-plate glass is sometimes still used. This glass should not be confused with bullet-proof/-resistant glass which is usually multiple layers of some form of high strength glass laminated with some form of plastic.

If you want to know for sure whether it is some form of armored-plate glass, and are willing to sacrifice one of the windows, first get a pair of safety goggles!! Then, and only then, place the window on top of something soft (like a foam cushion) in a cardboard box and place a thin layer of something soft over it (a couple sheets of paper will do) so that any pieces will not fly all over. Then use something (a wooden baseball bat would be best, but an aluminum one would work also, a fairly large faced steel hammer if bats are not available) to strike it with a fair amount of force. If the window breaks into large pieces with few sharp edges and almost no fine sharp splinters of any size, it is probably some form of armored-plate glass. If it 'pebbles', again with almost no fine sharp splinters, it is probably some form of early safety glass.

Note, some of this type of glass was very strong (upto about 4x the same thickness of standard glass), particularly if it was designed to leave the frame in one piece rather than shatter, so you may have to strike it with significant force. The amount of force necessary may put a flat on an aluminum bat, or splinter the wooden bat. It is OK to start off light though, since you can just hit it harder and harder until you reach its strength limit. Above all though, keep it safe, for you and anyone else nearby!!

 

[MiTasol]

Hi JJZ
If you get to break one of these please let us know how much force it took. Most of us like to learn.

Note that in general aircraft have been using plastics for transparencies since before ww2 because they do not produce the razor sharp shrapnel that glass does. Windscreens are and were mainly glass but built up of multiple layers of glass and plastics bonded together so that the glass provided the strength and plastic and bonding prevented shrapnel.
If you cannot get to break one try and get a better side view. If normal 1940s and later aircraft glass the layers will be visible. Your photos show a lot of misting of the glass. If that misting is not external that is a good indication of delamination taking place in laminated glass

If it is Thomas Ps type of glass it should be relatively thick with no visible lamination's if I am reading his post correctly. Your photo suggests thick but camera angles can produce confusion.

One other possibility is that it may be glass from an aircraft camera or other component. Aircraft like the Lancaster had an optical flat in the nose but those are too small for the Lanc and I cannot think of smaller ones. The Mosquito one is oval.

Hi Thomas P
Good info and good safety practices

 

[MiTasol]

I just came across this that may, or may not, apply, in the USAAF F-8 Mosquito manual

 

[JJZ]

I just came across this that may, or may not, apply, n the USAAF F-8 Mosquito manual
View attachment 535616

Thanks MiTasol, you might be onto something

 

[JJZ]

I picked up the glass, and found an old hand written note on one of the panes, can anyone decipher it?

 

[ThomasP]

Hi JJZ,

I think:

(WW)-2
(Ar)moured
Glass
Aero(u)lare (r)af

The word "Aero(u)lare" is, I think, an older Italian spelling of Aerolare, meaning 'aero home' or airbase.

The large r in (r)af is an older type of scripted R, possibly by someone with the English form of writing as a second language?

 

[Kingscoy]

I think the last line just says Aeroplane Raf.

 

[richpeers]

I just found one of these glued to my window sill coated in layers of lead paint. Cleaned up nice.

In terms of the Mosquito, locally, it seems one crashed in Birkenhead 1944 and Hooton Airfield had a contract to repair them.

 

[Crimea_River]

I don't think it's from a Mosquito if that's what you're suggesting.

EDIT: See below

 

[richpeers]

Armourplate is an old brand name for Pilkinton Glass toughened safety glass.

 

[Crimea_River]

R richpeers I stand corrected. It occurred to me during my sleepless night (not because of this) that it could well be the armoured glass on the folding head armour on the Observer's back rest (post #5). I was thinking external surfaces and it had not thought that it might be internal and I didn't look at the earlier posts. If you can find a number on it beginning with a letter, the number 98, followed by more numbers then it's a Mosquito part.