Do caps go bad?

[AZbpBurner]

I've still got a buncha caps from the late 70's: CCI and Navy Arms/Dynamit Nobel musket caps and some #1075's. All still work as new.

The foil-lined Remington #11's OTOH are all 100% stone dead. Whack them with a hammer on an anvil & nary any smoke or fizzle.

All were stored together in a plastic box with tight fitting lid & stored in the closet.

 

[azmntman]

Years ago I had a single tin that had the green stuff falling out about 1/2 of em. They didnt work. I (being very very cheap) put the green stuff in and capped the hawkin and shot em up. Never had issues other than that single tin and I cant recall the brand? I have caps 10 yrs old as well

 

[Ames]

I have a buddy who took over his kids flinter. In the possibles bag was an old rusted tin of caps. Just in there, not for the flinter so he gave them to me. The caps have some rust stains from years of being hauled into the woods on foggy morning deer hunts.
I swear these old brown stained CCI caps go off better than ones from my new tins.