Category: Science

My friend Kelly, not known for her eco-friendliness, was complaining to me about the paper cups our local coffee shop uses, and how she prefers Dunkin styrofoam. I told her that she should just bring a reusable plastic mug/cup, since they’re just as heat-retaining as styrofoam (I didn’t bother making a comment about the tradeoff of an extra 30 minutes of warm coffee being worth 10,000 years of landfill clutter). She disputed my claim of comparable heat retention, so, armed with a pilfered chem lab thermometer and three test vessels, we tested.

From a fresh-brewed pot of coffee, we poured equal amounts of liquid into a plastic dunkin donuts mug, a styrofoam DD cup, and a paper coffee cup with a loose-fitting lid, and recorded the temperature at 5 minute intervals. The results, in graph form, are below:

Heat Retention over Time

It may seem that the styrofoam is indeed best at retaining heat. However! If you look at the plastic and styrofoam lines, they decline at an almost identical rate after the first 2 minutes, when the plastic cup decreases by two and a half degrees. I posit that this is due to the air insulation of the plastic cup needing to heat up before its insulating properties kick in. And really, you can’t drink 70° (celcius!) coffee, anyway, it’s too hot.

So there you have it, your all around best bet for warm caffeine delivery and a clean conscience is to tote your refillable mug to the (fair trade, of course) coffee shop every morning. It’s a scientific fact.

A Small Experiment