Why does the cream of an Oreo cookie only cling to one side of the cookie when the cookie is pulled or twisted apart?
WAG to follow:
Since the cream, as well as the cookie, are both fairly rigid, one only needs to move slightly in relation to the other to ‘break free’. Similar to how you can easily unscrew a rusty bolt even if you need a long wrench to crack it free.
When you start turning the cookies in opposite directions, one side will require slightly less force than the other and break free first, leaving the cream stuck to the other side.
My WAG is that the physics involved are similar to making a wish with a wishbone - one side always takes the middle with it.
Although, once years ago, I made a wishbone wish with my girlfriend at the time, and both sides broke the same, with the middle piece breaking off entirely and spinning away. I wouldn’t have thought it physically possible.
The kicker: when we compared wishes afterward, we had wished for the same thing, True story.
Weird Al-The White Stuff.
The engineers believe the manufacturing process may be the reason why the cream generally finds itself to one side of the cookie.
“Videos of the manufacturing process show that they put the first wafer down, then dispense a ball of cream onto that wafer before putting the second wafer on top,” Owens said. “Apparently that little time delay may make the cream stick better to the first wafer.”
The researchers also observed that the cookies’ placement in a package seemed to dictate which side the cream would stick to. The center filling tended to gravitate to the inward-facing wafer. The researchers suspect post-manufacturing environmental effects, such as heating to jostling, are the reason.
Hmm. My WAG would have been totally a function of the manufacturing process: squirt cream onto one side, let it stick a bit, then push the other side onto the cream. Nice to know I had most of it right.
Whenever you see what seems to be asymmetrical behavior in something that looks symmetrical, think about how it was made.
This describes which wafer the cream is most likely to stick to, as to why it only sticks to one side, that is because the bond between the cream and the cookie isn’t as strong as the bond between the cream and itself. so when you twist it apart, the lump of cream will stick together and end up on one cookie or the other.
I recall having half the cream stick to one wafer and half stick to the other wafer, but that might not have been an official Oreo™ brand cookie.