One of the biggest issues in the coffee world is keeping coffee hot after it has been brewed. This could be one of the reasons single-serve coffee makers have become increasingly popular over the years…people are simply tired of brewing a full pot of coffee only to have it cool after a short period of time.

One of the earliest solutions to the “rapidly-cooling-coffee” problem was for coffee makers to have a built-in heating plate that would turn on automatically during the brew cycle to keep coffee hot, indefinitely.

Unfortunately, frequent coffee drinkers quickly realized that this was actually having a negative impact on the coffee's flavor after a very short period of time.

I like to consider the taste of re-heated coffee from a hot plate as something attuned to cough syrup: sour, bitter, and pretty much undrinkable.

Along came the thermal carafe

Recognizing this issue, coffee maker manufacturers quickly began to offer thermal carafes as a solution to the problem. However, coffee drinkers everywhere still often express their disappointment with thermal carafes' abilities when it comes to keeping coffee hot for long periods of time.

Often times it depends on the carafe's design itself, but overall, carafes simply do not keep coffee hot forever.

Pre-heating carafes

But what about a carafe that has been pre-heated?

Often times you will see that coffee maker manufacturers (and coffee snobs) recommend pre-heating the thermal carafe to maintain the coffee's hot temperature for longer periods.

I am pretty certain this works…but I was curious as to how much it actually matters.

In other words: how much hotter will a pre-heated carafe keep the coffee(if at all) after X amount of time?

The results

You can check out my results at the end of the video above. The theory definitely held up, with a slight caveat though. So the next time I run this experiment it will have to be with coffee, as well a longer (and possibly shorter) pre-heated duration.