What does "War Plastic" mean for watch crystals?

[futurematic]

Hi all! I recently purchased 3 large cabinets full of watch crystals. They even have a nifty crystal press mounted on the top! These appear to be very old, but hard to say given their condition. As I've started to browse through them, I've noticed a lot of the G-S crystals have "WAR PLASTIC" written on their covers and everything is printed in red. I tried to do some Googling, but came up short. Does anyone know what this relates to, or means?

I've attached some photos for context. I'll have about 3000 crystals to sort through, as you can hopefully see. 

Thanks!

 

 

[nickelsilver]

Are they yellowed? My guess is acrylic was rationed and they went back to celluloid. Try lightning one on fire (outside!), if it burns violently it's celluloid.

[rehajm]

I have seen it described differently- acrylic was developed in the 1930s and as it was more durable than celluloid it became a requirement of WWII military specs…but let’s see one! Pics..

[futurematic]

12 hours ago, nickelsilver said:

Are they yellowed? My guess is acrylic was rationed and they went back to celluloid. Try lightning one on fire (outside!), if it burns violently it's celluloid.

Unfortunately a lot of them are yellow/brown and will have to go in the garbage. I tried burning one but it didn't behave like celluloid. It just bubbled/melted like you would expect from acrylic.

[nickelsilver]

4 hours ago, futurematic said:

Unfortunately a lot of them are yellow/brown and will have to go in the garbage. I tried burning one but it didn't behave like celluloid. It just bubbled/melted like you would expect from acrylic.

If yellow/brown almost certainly celluloid, but it degasses so much stuff over the years it might not be as volatile as back when projection film would ignite at 150C.

[Kalanag]

As far as I have learned the flammability of celluloid increases over time.

[spectre6000]

Confirmed. Celluloid does not get less flammable. Acrylic replacing celluloid as more durable, and more importantly, less flammable sounds like a very plausible explanation. That it's superior for task would make it worth printing on the package in a positive marketing light. Going back to celluloid would have been seen, especially in the 40s, as a step backward, and would not have been marketed as being a positive as seen above.

[futurematic]

All good info, but it sounds like no clear explanation yet as to what War Plastic is. The mystery continues!