Reusable coffee cup hot-test

OK, there is, and it’s called a thermos – but no one’s lugging one of those around, especially on our commute to work. Many of us are into reusable coffee cups these days and, even though we don’t talk about them as being ‘thermal’, they still do the important job of containing our hot coffee. But is there a way to know which brand of reusable coffee cup keeps our takeaway coffee, sitting down there in our car’s cup holder, hotter for longer? Yes, there is, because we’ve done the test.

We chose four of the models you’ll see in the hands of coffee fanatics from Fitzroy to Fortitude Valley: two different varieties of KeepCup, a Frank Green and a Joco. Slow sippers, sit tight: you’re about to find out once and for all which BYO coffee cup keeps your coffee warm the longest. And if you’re just looking for a good reusable cup to keep handy in your car, this too is the test for you.

First, we needed a control. We managed to find a car park near our favourite local on the way into work and we went in for a long black. It had a temperature of 71 degrees Celsius and it was delicious. So, with caffeine coursing through our veins and sharpening our minds, we worked out how to run the test: we’d fill each cup with water heated to 80 degrees Celsius, prise on the lids, pop in our digital thermometers, start the clock and wait. Since coffee is best consumed when it’s between 70 and 80 degrees, we noted how long it took for the temperature to fall to an initial test point of 70 degrees (below 70 degrees is less than ideal). Our final measure was to check the time again when the temperature had fallen to an undrinkable, tepid and lukewarm 37 degrees.

In just seven minutes, the glass KeepCup’s 80-degree water plummeted to 70 degrees – in part thanks to the hot water hitting the cold glass. Let that be a warning to all of you who like it ‘extra hot’: you’ll lose precious degrees almost instantly. This cup redeemed itself with its design, though – cork, glass and a trusty black lid give it an air of quality. Compared with the other, more lurid options, we dare say this one’s for the sophisticated aesthete.

The KeepCup Brew Glass Coffee Cup took 59 minutes to reach a disgusting 37 degrees Celsius.

The Joco dropped from 80 to 70 degrees in seven minutes, an identical loss to the KeepCup before it. It’s that cold, unfriendly glass again, we figure. However, where the KeepCup’s cork grip and black lid made up for the temperature loss, the Joco’s thin rubber grip made it almost too hot to hold. We also didn’t have as much faith in the lid: it didn’t snap on like the others, and it moved about. The Joco is also a bigger cup than its competitors, and high-school-level thermodynamics states that the greater volume should have given the Joco a thermal advantage. We shudder [sips cold coffee] to think how it would have performed if it were the same size. We’d put the Joco in fourth if this test didn’t hinge on the thermal measure.

The Joco 12oz Reusable Glass Cup took 1 hour and 12 minutes to reach an unpalatable 37 degrees Celsius.

Can KeepCup redeem itself with the Original (and, as many consider it to be, the best)? Yes, it can. The KeepCup Original took 10 minutes to drop from 80 to 70 degrees. Sure, that’s only a few minutes longer than the previous two cups – but these minutes could be the difference between a good and bad start to the day. Minutes matter. While the Original feels plastic-y, the build is solid, the lid snaps in place and the closable spout is handy.

The KeepCup Original Reusable Coffee Cup took 1 hour and 16 minutes to reach a too-cold-to-bathe-in 37 degrees Celsius.

The winner! Well, in a way. The Frank Green Smart Cup came second in our initial test: it dropped from 80 to 70 degrees one minute faster (nine minutes) than the KeepCup Original. But it won the second race by quite a margin – 12 minutes, in fact. Plus, it’s burly and you can place faith in the lid. About that lid: the mouth opening is small, so this isn’t a cup for chuggers but for sippers. It also includes Frank Green’s CafePay system. That’s right: if you forget your wallet or purse, the cup can pay for its contents itself.

The Frank Green Smart Cup took 1 hour and 28 minutes to reach 37 degrees Celsius, some 12 minutes better than its closest competitor.

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