Few things are more invigorating than a hot cup of coffee (or tea) in the morning, and few more disappointing than when the drink goes cold..
There are many products on the market that promise to avoid this inconvenience, but how do they work and what is the ideal temperature to drink them?
We consulted Michael de Podesta, a chartered physicist and measurement expert, who has investigated precisely those questions.
Also to Kamisha Darroux, who has tested the different options in her role as chief scientific advisor of Which?, a UK brand that promotes informed consumer choice when purchasing goods and services.
So what types of thermal mugs are most likely to keep your drink warmer for longer? And what other factors should we take into account?
The typical ceramic mug
To create an indicator of the actual quality of a thermal mug, De Podesta decided to compare it with a standard ceramic mug filled with 300 ml of boiling water.
Although preferences vary from person to person, the physicist estimated that “the sipping temperature is about 75°C, then [la bebida] turns perfect at about 62 °C“.
“Below 50°C, for most tea and coffee drinkers, is too cold.”
For the ceramic mug, it takes 5 minutes for it to be drinkable, 15 minutes for it to be perfect, and another 15 minutes for it to get too cold.
This means that, as a starting pointthermal mugs must exceed 30 minutes of heat.
Reusable plastic cups (like the ones you can buy at corner coffee shops) are a basic upgrade from classic cups.
They are made of simple polypropylene, perhaps with a cover to protect your hands.
If you leave the lid on, keep drinks hot for an hourtwice as much as ceramic cups without lids.
Multiple walls
To overcome the limitations of basic mugs, you have to get creative.
The most common innovation is double-walled mugs.
These containers typically use two stainless steel walls with a vacuum-sealed space between them to reduce the amount of heat escaping from the sides of the cup (although some heat will slowly escape through radiation).
A prime example of double-wall technology is the Chilly’s mug, which De Podesta found could keep drinks hot for 4 hours, eight times longer than a ceramic mug.
The BURNOUT mug, designed by a rocket scientist, goes further: it not only keeps your tea or coffee hot, but cools it down faster.
The idea is to reach the ideal drinking temperature and stay there.
These cups have a triple wall: Between the two innermost walls is a wax packet that melts when the hot drink first fills the cup..
The wax then slowly solidifies again over time, releasing its heat into the drink and keeping it warm.
This mug keeps hot drinks in the ideal range for a full 2 hours.
If you need absolute control over the temperature of your drink, some “smart cups”like the Ember travel mug, allow you to set the exact temperature of your drink and keep it there for a full 3 hours, thanks to an adjustable electric heating system.
Of course, prices have been increasing considerably as you have read.
We’re already going into the hundreds of dollars for a single cup.
Basic principles
It is possible that It’s not worth spending money on an expensive mug before you really understand what factors affect heat loss.
Some are more obvious, like the fact that the temperature of the outside environment determines how quickly your drink cools.
Likewise, insulated mugs are only useful if you keep the lid on.
Exposing a beverage to the open air allows for additional heat loss through convection (air absorbs heat) and evaporation (water carries away heat as it turns into vapor).
However, There are some very useful additional tricks to prolong the effect of the cups.
First of all, if you are going on a long trip, try to carry as much liquid as possible.
De Podesta explains that a cup with more liquid “It helps keep you warm simply because there is a greater thermal mass”.
Second, before filling the cup, rinse it with hot water.
This will pre-emptively heat the cup, preventing a small heat loss when you first fill it with your drink (although the gain in this case may be minimal).
Testing
While it may be appealing to have a mug that heats tea electrically, it may not be practical.
De Podesta warns that “the user must think about what role the cup is going to play in their life”.
To that end, Darroux and consumer testing experts Which? They put the entire range of thermal mugs to the test.
Compared to other items on the market, thermal cup brands are usually reliable.
Cups that claimed to be leak-proof almost always were, even after several washes.
Additionally, Darroux used thermal imaging cameras on the vessels to check for defects in the construction that would cause excessive heat loss.
He also verified that Even the cheapest glasses were surprisingly durable even after falling from significant heights.
However, buyers should keep a couple of factors in mind.
Between push buttons, spouts, and twist locks, cup spouts vary greatly.
There are personal preferences, but It is advisable to avoid openings that can easily trap liquid.
When a liquid like milk dries up, the sour smell will affect the taste of your drink.
You can clean the mug to solve this problem, but remember that not all thermal mugs are dishwasher safe.
Hand wash It’s the safest way to ensure that water doesn’t get between the double walls and ruin that layer of vacuum insulation.
“BPA-free”
Many modern insulated cups are labeled “BPA free.”
This is not just an advertising phrase, as Darroux explains.
“BPA is a chemical substance called bisphenol A that is used especially in the production of plastic. “Some results indicate that, in high enough doses, it could be harmful to the brain or disrupt hormones.”.
The related chemicals BPS and BPF are equally concerning, and some insulated cups exclude them as well.
A simpler solution is to use stainless steel glasses and mugs. They can sometimes leave a slight metallic taste in your mouth, but are usually BPA-free.
Ultimately, most of your choice will depend on your personal preferences and, of course, price.
Darroux found “some excellent value mugs that are in the middle range…so you don’t necessarily have to spend a lot of money to get a good cup.”
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