Carrier Headlight Lens

[ron]

Here is a question for the boffins amongst us, I have some N O S blue headlight lenses that I took out of their original cardboard boxes only to find that the blue part berween the two pieces of glass that make up the lens had broken down into a very fine powder in fact its just like a blue dust, by the way I am talking about Aust universal carrier lens also the same as what was used on the Two pounder & the morter carrier, now the question is what did they use between the two pieces of glass?I thought that it might be someting like Celophane??I dont think that it would have been paint, because with good lens you can see through them, paint would not allow this?, by the way it does not seem to happen to the blue small tail light lens, and does not happen to the red tail light lens either,I will add that I have had these lenses for many years and have been taken out of sealed packets that have always been strored in a dry area, Ok now the question is what did they use on the headlight between the two pieces of glass?? and why does it break down, Ron, I will post pics soon of them