Did you have experience that you found some "glitter" material on the AVENT bottles? I used AVENT since my baby was born. It's almost 4 months now. By the time the bottles were 3 months. I found some silver "glitter" on the bottles one day when i fed my baby. Initially, I thought my maid didn't clean it properly. Then, I wash the bottles myself. Then, I found the "glitter" is actually inside the plastic. Which means it is part of the plastic , NOT inner or outer wall of the bottles. It happend on all 4 bottles. Then, I bought a new set and using them now. I wonder I shall change it. But, my baby is using it so well. Therefore, I dunno whether I shall change it.
I don't think it's reflection. Because they're small dots like "glitter powder" on nail polish. It's very small squares. But, the qty is quite a lot...it's about 20 dots per bottle.