We received a letter from a listener about an earlier episode titled “Pop bottles don’t blow up”

The listener wrote:

"The small scar on my left arm places an enormous burden on anyone who would attempt to convince me that pop bottles don’t blow up."

We said that literally shaking a factory-sealed bottle of a carbonated beverage does not increase the carbon dioxide pressure, and therefore it does not increase the risk of a glass-shattering explosion. Shaking does however create more bubbles in the bottle. When you uncap the bottle, those bubbles rapidly expand, pushing liquid out the bottleneck.

Our listener wrote:

"I once knew a 15-year-old kid who spent the summer of 1946 working for his uncle on his Pepsi-Cola route. We would load up the truck around 6am, but on those hot summer mornings in Chicago, it could already be 80 degrees Fahrenheit on the loading dock.  The bottles of pop came out of the plant at around 40 degrees, and when that cold pop hit that warm air, and with all the shaking of the cases as they rolled down the conveyer – pop bottles were blowing up down and sideways all over the place."

As the writer’s experience demonstrates, a large sudden temperature change can indeed change the pressure inside a pop bottle. Heating not only causes expansion of the carbon dioxide already present, but makes more carbon dioxide come out of the solution in the pop and rise to the surface as gas, raising the pressure even more.

So we should say that as long as the temperature doesn’t change, merely shaking a still factory-sealed pop bottle will not increase the pressure inside, it just makes more bubbles.

This moment of science comes from Indiana University, with production support from the office of the provost. I’m Yael Ksander.