To me, a thermos or a vacuum flask is an indispensable companion for my mate. Yes, you can simply refill your mate straight from the kettle, but constantly reheating the water or running dozens of time to the fridge for ice-cold water for tereré is too cumbersome, and the quality of life that thermos offers to the mate experience makes it a crucial accessory. Here, we will explore what makes a good thermos for mate, and discover the best vacuum flasks for any kind of mate drinking preference.
Obviously, when we’re talking about any kind of vacuum flask, the main feature we are looking for is its heat retention. At the end of the day, this is the main function and purpose of a thermos. When it comes to mate, the good heat retention means that you can count on your vacuum flask to keep the desired water temperature for the whole mate session without having to reheat it. Even if you’ve preheated your thermos to improve its insulation properties, you’ll lose about 10 degrees in 4 hours, so if your mate session lasts for more than that — heat retention becomes the most important factor for you to consider when choosing a new vacuum flask. Material-wise, generally speaking, glass bowls has a better insulating properties than stainless steel ones because glass has a lower thermal conductivity rate than stainless steel. Stopping and pouring mechanisms also play a big role in heat retention — the more complex and plastic button and spout mechanisms let more heat out over the course of time than a more simple twist-and-pour stopper.
The next big thing you need to pay attention to is the capacity of a thermos. This again depends on your average mate drinking habits — if you mostly drink out of small calabash gourds (less than 100 ml) a large 1.5-liter or 2-liter thermos would be an overkill. Likewise, if you’re a big fan of chimarrão and used to drink out of a giant cuia, 1-liter vacuum flask will likely be too small for you and you’ll still have to prepare more water for your mate no matter how good is the heat retention of your thermos. Also keep in mind that the bigger the thermos the less transportable it will be due to its size and weight.
Speaking of transportability — another important factor you need to consider is the durability of a vacuum flask. Depending of whether you take your mate on the go or not, this feature may be one of the most important ones — you don’t want to break your thermos in the middle of your daily commute or somewhere in the wilderness! If you frequently travel with your mate, I would recommend staying away from glass vacuum flasks, as they don’t even come close to the durability of stainless steel ones. Most of the stainless steel vacuum flasks are marketed for outdoor enthusiasts, and are built like tanks with multiple layers of stainless steel, durable coating and sometimes even rubber bumpers to absorb sudden blows. The body of a well-built thermos is virtually indestructible, and usually it is the plastic and moving parts that are breaking first, such as lids, pouring spouts, buttons and handles. Look for a stainless steel vacuum flask with the simplest pouring mechanism and least plastic in its construction for a maximum durability.
And last but not least, the thing that mostly concerns materos — convenient pour. Properly prepared mate has a mountain of yerba inside the gourd, and maintaining it is the key to an effortless, balanced and long-lasting experience. In order to not ruin the mountain, which in turn can clog your bombilla and worsen the taste, you should pour water strictly on the opposite side, a so-called water hole, which, depending on the shape of the gourd, can be pretty small and narrow. There are vacuum flasks with a pouring spout that make this process completely infallible. Button mechanism also guarantees a pretty thin and steady stream of water. The hardest and least predictable mechanism is the simplest one, which is a twist-and-pour stopper with a slot for water that you need to correctly position in order to pour water more easily. With more experience, you can learn how to precisely pour from the thermos no matter the mechanism, and more complex mechanisms, as I mentioned earlier, are more prone to breaking and retaining heat, so you need to assess if the extra precision is worth the compromise.
Now that you’re aware of the main features to look for in a vacuum flask for mate, you may already know what exact thermos you want to get. But most often than not people just want the best of the best — the longest heat retention, the greatest durability, most optimal capacity and convenience of pour while still maintaining an affordable price. The closest thing to perfection, in my opinion, is a well known for its durability Stanley Vacuum Bottle. Very popular brand amongst outdoorsmen, Stanley produces great drinkware and food storage items, which are instantly recognizable for their signature Hammertone Green color. I am specifically a big fan of their Classic Legendary Bottle with a capacity of 1 L which in my experience is the best compromise between volume and transportability, although it comes in bigger sizes if your prefer so, such as 1.5-liter, 2-liter and even 2.5-liter. This vacuum bottle features a simple but reliable twist-and-pour stopper that is not the most precise pouring mechanism, but offers the best durability and heat retention. The handle is a nice touch that makes gripping the bottle easier while pouring the water into the gourd. It can also be folded for a more compact storage, although personally I got a little irritated with its squeakiness over time.
Do you want to use a thermos designed specifically for mate? Have you ever wandered what are those vacuum flasks with red pouring spouts that football players like Leo Messi use all the time? The common name for them that I encounter most often is Pico Cebador, where pico is a beak in Spanish, and cebador is a person who is serving mate in a circle. This thermos features a beak-like foldable pouring mechanism that is extremely precise and allows you to refill your mate effortlessly no matter the shape and size of your gourd. While I like the precision of this mechanism, there is a noticeable difference in heat retention not in its favor due to it having more moving plastic parts. You should also keep in mind that the pour is a bit slow, which is good when using a small poro calabash gourd, but takes too long to refill a medium to large size gourds (150 ml and more). This vacuum flask only comes with 1 L capacity, which also does not favor larger gourds. Stainless steel body gives this thermos a great enough durability for a daily commute and enough heat retention for an average mate session. Sometimes these vacuum Pico Cebador flasks feature a small handle, which makes it easy to carry around and hold while pouring the water. I like that it is solid and does not flop and squeak, but the fact that it’s prominent and plastic makes me feel like it can one day snap in a backpack when it’s tossed around, which should not be an issue if you don’t take mate on the go that often.
If you don’t travel with mate and want the absolute longest heat retention — your best bet would be a glass thermos. While it’s not as durable as the stainless steel one, glass vacuum flasks are light and more insulating, allowing you to not reheat the water even if your mate session lasts a whole day. Another great thing about glass vacuum flasks is that they have much more variety in colors and designs, due to the fact that only the vacuum bottle itself is made from the glass, and the rest of the body is usually wrapped in plastic of any shape and color. You can easily find a glass thermos that will fit perfectly in design of your kitchen or has your favorite color. Glass vacuum flasks feature different stopping mechanisms, but because the body is made from food-grade plastic, they all feature a V-shape or beak-like spout that makes pouring water into a gourd more convenient and precise.
If you want to embrace a tradition of mate circles and invite your friends over for some mates, a single vacuum flask will not be enough for a large group of people! Here’s where a huge hand-pump thermoses comes to rescue — with a whopping 5-liter capacity, this vacuum container guarantees that your circle will never run out of water before the mate becomes lavado. Besides the huge volume, this thermos also features a hand-pump pouring mechanism, meaning that you need to bring your gourd directly under the faucet and pump the water into it with a button on top. Despite its big size, it has a top handle to make it easier to transport it, for instance, to your car and bring this big boy to a picnic.
Hopefully by now you have a clear idea about what thermos for mate fits you and your drinking habits the best. If there are still some missing pieces in your mateware collection — check out our yerba mate accessories guide where we cover all the must-have and optional gear for an effortless and enjoyable mate.
And of course, there is no point in getting a vacuum flask if you do not intend to fill it with anything! Water is very important — it extracts all the flavors and healthy nutrients from yerba mate, so check out our definitive guide to learn everything you need to know about what are the properties of a quality water, the right temperature of water for mate and how to properly heat it, so that you always have perfect water in your thermos before you prepare your mate or tereré.
What thermos you decided to get? Do you travel with mate and care about durability of your vacuum flask? What is your preference of material — glass or stainless steel? Do you drink mate alone or in the circle? Share it in the comments below!
Mountain of yerba