This was because the clear glass allowed UV rays to penetrate the beer and alter the flavour. The solution was turning bottles brown, a darker colour which would block out the rays. After World ...

These ginger beer bottles were all made in the pottery of A.W. Buchan in Portobello, near Edinburgh, Scotland. As you can see the bottles were used by companies all over the world, from Portobello ...

so the beer always goes stale eventually. But over long periods, the seal around the bottle cap can start to degrade. It's not enough to make the cap fall off, but it'll start letting in oxygen ...