Conclusions: Is it hot or not?

What did we learn?

The Chemex Cozy works.

As you can see on the chart below, the cozy kept the liquid warmer throughout the test period, even though (somewhat mysteriously) the initial temperature at 20 seconds was a few degrees cooler when the cozy was on:

At 30 minutes with the cozy, the liquid was still about as hot as it was with no cozy after 10 minutes.

It's also worth noting that the one big drop in temperature came at the moment I had trouble with the thermometer. Further study -- and a new battery for the Thermapen -- may be required. It may be that the more gradual decline seen in the first 10 minutes with the cozy (drops of 9 and 4 degrees, compared with 24 and 13 degrees in the control condition) would hold for longer. Other explanations for the discontinuity in the rate of cooling are welcome.

Praise be to the Chemex Cozy! And thank you, Grandma Joy! The cozy looks great, and it works like a charm. Mornings will be better -- or at least warmer -- from now on. 

Science!

Prepared with an electric tea kettle for boiling water (thank you, Grandma Joy!), a ThermaPen 5 thermometer, a timer, and a measuring cup, we began the experiment.

First, to establish the control condition, we ran the test without the Chemex cozy, taking temperature readings at 20 seconds, 5 minutes, 10 minutes, 20 minutes, and 30 minutes. (After 30 minutes, I would normally have had all the coffee I made, so keeping it warm for longer than that was unnecessary ) I used water rather than brewed coffee. However, I kept a filter with wet grounds in it as a cap on the carafe, since this is the normal way I keep the carafe covered as I'm drinking coffee in the morning.

Here's what we found:

       20 seconds                           5 minutes                        10 minutes                         20 minutes                        30 minutes

20 seconds:     182 degrees
5 minutes:        158 degrees (-24)
10 minutes:      145 degrees (-13)
20 minutes:      130 degrees (-15)
30 minutes:      115 degrees (-15)

Total drop:        67 degrees over 30 minutes

Then we ran the experiment again, this time with the GJoy Chemex Cozy. Here's what we found:

       20 seconds                      5 minutes                             10 minutes                         20 minutes                      30 minutes

20 seconds:     178 degrees
5 minutes:        169 degrees (-09)
10 minutes:      165 degrees (-04)
20 minutes*:    149 degrees (-16)
30 minutes:      142 degrees (-07)

Total drop: 36 degrees over 30 minutes

* Actually, this reading was taken at 21 minutes. I had some trouble with the thermometer not turning on right away. I had the same problem at 30 minutes -- it didn't turn on right away -- but I turned it on earlier to make sure it was ready to go at 30 minutes.

Experimental design

I consulted with my scientific advisor, Alexander, on how to design a proper test of how much the Chemex Cozy would slow the cooling process. Coming off a week of science experiments (and blogging) at the Marin Headlands, not to mention years of Mythbusters, Alexander and I designed the following protocol to test whether the cozy would in fact keep the liquid warmer.

On to the experiment.

Curious minds

It was my birthday a few days ago, and I got some wonderful presents. However, one present invited scientific study: the custom designed and handmade Chemex Cozy created by Grandma Joy.

The Chemex is one of the world's great devices for brewing coffee. As the folks at Chemex explain: 

The Chemex Coffeemaker was invented in 1941 by Dr. Peter Schlumbohm PhD. Made simply from non-porous, borosilicate glass and fastened with a wood collar and tie, it brews coffee without imparting any flavors of its own. On permanent display at MOMA NY and other fine museums, it is truly a work of art.

* * *

Few products in this century can match the flawless blending of design and function of the Chemex®. Its visual elegance has earned it a place in the permanent collection of New York's Corning Museum of Glass. The Chemex® coffeemaker was also selected by the Illinois Institute of Technology as one of the 100 best designed products of modern times.

Yes, except there is one flaw in its blend of design and function: it's thin uninsulated glass. Unless you pour the coffee into an insulated container, your fresh hot coffee won't stay hot long. I've tried wrapping the carafe in a towel, but that's an imperfect solution, and there don't seem to be any available products to keep the freshly brewed coffee warm.

Enter the GJoy coffee cozy.

The Chemex in its natural state
(Well, almost: it's empty)

Chemex, meet the GJoy cozy
Note the handsome fabric and Velcro closure

It's a wrap

It looks great -- handsome fabric, well made with clever touches like Velcro closures that make it easy to put on and take off and that ensure a snug fit.

But does it actually work? Will hot liquids stay warm longer? How much warmer and how much longer? Curious minds want to know....