Thermal Carafes

Published January 1, 2017. From Cook's Illustrated.

Overview:

If you like to entertain, insulated pitchers can come in handy. Also called thermal carafes, they keep coffee or tea hot for hours—perfect for brunch or a dessert table at a party. They also insulate cold liquids, so we sometimes use two: one for hot coffee and one for cold cream or milk. We’ve even used them to keep stock warm (and pour it as needed) when making risotto.

Most thermal carafes are double-walled and vacuum-sealed. (In other words, they have two stainless-steel walls, and the air between them has been removed. Without air, heat transfers much more slowly.) Given their similarity in design, does it matter which insulated carafe you buy? To find out, we rounded up eight models, priced from $21.99 to $72.07 and with capacities from 44 to 68 ounces, and spent two weeks putting them through their paces in the test kitchen.

We started with the most important test: heat retention. We filled each carafe with freshly brewed 161-degree coffee and recorded the coffee’s temperature every hour by pouring out a small amount and… read more

If you like to entertain, insulated pitchers can come in handy. Also called thermal carafes, they keep coffee or tea hot for hours—perfect for brunch or a dessert table at a party. They also insulate cold liquids, so we sometimes use two: one for hot coffee and one for cold cream or milk. We’ve even used them to keep stock warm (and pour it as needed) when making risotto.

Most thermal carafes are double-walled and vacuum-sealed. (In other words, they have two stainless-steel walls, and the air between them has been removed. Without air, heat transfers much more slowly.) Given their similarity in design, does it matter which insulated carafe you buy? To find out, we rounded up eight models, priced from $21.99 to $72.07 and with capacities from 44 to 68 ounces, and spent two weeks putting them through their paces in the test kitchen.

We started with the most important test: heat retention. We filled each carafe with freshly brewed 161-degree coffee and recorded the coffee’s temperature every hour by pouring out a small amount and quickly recording its temperature. After 4 hours—a reasonable amount of time for a carafe to keep things drinkable—the coolest coffee was a lukewarm 138 degrees. Meanwhile, the coffee in the top performers was still quite hot at 152 degrees.

To see how the carafes fared with cold liquids, we chilled them with ice water for 5 minutes (a step most manufacturers recommend). We then emptied them, filled them with 37-degree milk, and left them at room temperature. By the 2-hour mark, all of the milk was at or above 40 degrees. After 4 hours, the samples ranged from 41 to 44 degrees. Bacteria grow more rapidly between 40 and 140 degrees, so the U.S. Department of Agriculture (USDA) recommends that food be in that range for no longer than 2 hours. We were discouraged that none of the carafes had kept milk below that threshold, but we suspected that they were still an improvement over a standard, noninsulated pitcher. Sure enough, when we performed the same test with a chilled stainless-steel pitcher, the milk climbed to 55 degrees after 1 hour and hit 67 degrees after 4 hours. Even the least effective carafe was a dramatic improvement.

With the temperature tests complete, a panel of testers evaluated how easy the carafes were to use. Four factors mattered most: the pour spout, the handle, the lid, and opening the carafe. Some carafes were hard to control, and liquids poured from them at unpredictable speeds and angles. Worse, liquids that were poured from some carafes continued flowing for an extra beat after we’d released the button—more than enough time to accidentally overfill a coffee mug. We much preferred models that poured with moderate, even streams and had responsive valves that quickly closed the pour spouts.

We also disliked small handles and handles that were set either too close to or too far from the body of the carafe. Wide, sturdy handles set 1 1/2 to 2 inches from the body of the carafes allowed us to pour with ease. Finally, a wider opening and efficient lid were crucial. One carafe had a tiny 1½-inch opening that made it difficult to fill. Most were a more generous 2⅛ to 2½ inches across. That model with a narrow opening also had a hinged lid that sometimes flopped wide open without warning. We preferred lids that snapped or twisted on smoothly, and we especially liked those that fit into place with an audible click and sealed without a visible gap between the lid and body.

We did one final test, filling the carafes with hot seafood stock (a handy way of keeping stock warm when adding it in small increments while making risotto) and leaving them to sit overnight. We came in the next morning, washed each carafe thoroughly by hand, and then filled each with cold water, which we presented to a tasting panel in a blind tasting. Thankfully, none of the carafes held on to the fishy, savory smell, and all of the water tasted clean.

Ultimately, several carafes met all of our criteria. But the Zojirushi Stainless Steel Vacuum Carafe ($57.51) won top marks in temperature tests and for ease of use. It’s the only model with a snap-on lid, which seals with a reassuring click and leaves no doubt that the carafe is closed. We liked that it can be fully disassembled for cleaning. For a slightly lower price but still impressive performance and user-friendliness, we also recommend our Best Buy, the Genuine Thermos Brand 51-Ounce Vacuum Insulated Stainless Steel Carafe ($42.70).

Methodology:

We tested eight thermal carafes with capacities from 44 to 68 ounces (roughly 5½ to 8½ cups), rating them on their heat and cold retention. A panel of testers evaluated how easy they were to fill and use. We also rated them on ease of cleaning. All models were purchased online and appear in order of preference.

Heat Retention: We filled each carafe with freshly brewed 161-degree coffee, sealed it tight, and then recorded the coffee’s temperature every hour. The best carafes kept the coffee above 150 degrees for at least 4 hours—the longest we’d want to wait before brewing a fresh pot.

Cold Retention: After chilling the carafes with ice water for 5 minutes, we filled each with 37-degree whole milk and checked the milk’s temperature every hour. A chilled stainless-steel pitcher served as a point of comparison. Although no carafe was able to keep milk below 40 degrees for 2 hours (recommended by the USDA for food-safety reasons), we preferred carafes that kept milk closest to that temperature.

Lids and Pour Spouts: The best models had lids that attached easily and offered an audible or visual signal that they were on securely. Carafes lost points if they were slow to respond when we opened and closed their pour spouts.

Handles: We rated each model on the comfort and control of its handle. The best handles stayed cool to the touch. We also liked handles that were large and sturdy enough to comfortably support the weight of a full carafe.

Cleanup: Some models were easier to clean than others. Carafes lost points if their openings were less than 2 inches in diameter, as they were especially difficult to clean. We preferred carafes with lids that could be disassembled or easily scrubbed for thorough cleaning.

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