The danger of paper coffee cups


Paper coffee cups often come with a “DO NOT MICROWAVE” warning. What’s the risk, and why is it worse than whatever happens when you pour 200°F coffee into them?

In: 2

The primary risk is that your coffee gets hot. And bitter, if it’s already coffee. «Do not microwave» probably just so the producer don’t get sued if you spill hot liquids on yourself while doing this.

Yeah, and if you use the cup too long, the bottom may fall out, emptying hot water on you.

paper cups are lined with a thin layer of wax or plastic because paper is famously not waterproof. Microwaving paper cups can cause the wax or plastic to break down and leach into the liquid or simply make the cup start leaking.

They can also catch on fire. Source: my Mom microwaved one in my microwave. Admittedly you normally have to microwave it a couple of times or for more than a minute at a time. But they will catch on fire.

paper is notably not waterproof without some specialized treatment.

for paper cups this treatment generally involves adding wax ot the composition in order ot make it waterproof: wax notably doesnt handle prolonged heat exposure too well and may change properties, that lead up to the cup being compromised.

at best the cup fails inside the microwave, at worst it fails when you are holding it and it spills its very hot contents on you.