When separating an Oreo cookie, why does the cream stick to just one side only? originally appeared on Quora, the place to gain and share knowledge, empowering people to learn from others and better understand the world. You can follow Quora on Twitter, Facebook, and Google Plus.

Oreo cream sticks better to Oreo cream than it does to Oreo cookie.

When you separate an Oreo cookie, you are putting strain across the whole thing. Like any other material, it will break at the weakest point.

As you look across the cross-section of the cookie, then because the two sides are solid, and the cream sticks very well to cream, there remain only two candidates for the weakest point: the two places where the cream is sticking to the biscuit.

Which will go first? It may be random; or there may be something systemic in the manufacturing process that makes one side stickier than the other (e.g., one side of the cream is exposed to air before the other cookie is pressed on top).

Then, as soon as one side starts to separate, this makes it even weaker on that side (there is less surface area in contact). So you get a positive feedback effect: the weaker side separates more and more, and the more it separates the weaker it gets.

So once any separation starts, it finishes, and creates a whole split down that side.

Result: one separated Oreo cookie with all the cream on one side.

The only way of avoiding this is by using a weaker cream filling. If the internal structure of the cream is weaker than its bonding to the biscuit, then weakest point — and therefore its separation — can occur down the middle.

This is one of the many ways in which you can end up reasoning your way towards selecting marshmallow as a filling, and end up with an infinitely superior biscuit.

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