Paul K. Dickman wrote:

It doesn't. It is an optical illusion.
Download the pdf and zoom in. You will see that the bars in the
safety paper don't curve.

I did the same check, although I didn't see the pdf download until after
posting. It looks like it blurred only because the shadow in the original's
curvature made the copy dark.


--

Reply in group, but if emailing add one more
zero, and remove the last word.