It's likely you've heard about vacuum insulated coffee mugs than can keep drinks hot for hours. But often they keep drinks too hot to even drink and then when the drink does reach the perfect temperature it only stays there a little while before becoming too cold to really enjoy.
Phase change coffee mugs are designed to fix this problem. They use a phase change material (PCM) in order to quickly cool down your coffee then use a combination of the thermal heat stored in the PCM plus a vacuum insulation in order to keep your coffee at that perfect drinking temperature for up to 6 hours.
Currently there is only one brand of phase change coffee mug that I am aware of and that's the Burnout Mug but some people say that the Ember Travel Mug also have phase change material in it to keep coffee at that perfect temperature.
In this article we'll look into exactly what this technology is, how it works and then have a look at the brands that make phase change coffee mugs.
How Do Phase Change Coffee Mugs Work?
Phase Change coffee mugs use a “phase change material” (PCM) that has a very particular melting point.
At room temperature it is a solid waxy like substance but at around 140ºF (60ºC) it converts from a solid into a liquid.
During this process it absorbs energy in the form of heat to make the change from a solid to a liquid.
This is why the Burnout Mug can quickly cool down boiling hot coffee and bring it down to a nice 140ºF drinking temperature.
Once the PCM melts into a liquid it still continues to absorb heat if the coffee is hotter than it until both the PCM and the coffee are the same temperature.
The magic then begins to happen as your coffee and the PCM begin to cool.
Right around that 140ºF mark the PCM material starts to turn from a liquid back into a waxy solid again. As it makes this phase change it actually lets off heat and because there is a vacuum on one side where heat can't really get through that heat is isn't transferred back into your coffee.
While it won't keep your coffee at a perfect temperature, it'll keep it hovering around that 120-145ºF (48-63ºC) which is considered optimal drinking temperature by most people.
Vacuum Insulation is Also Key
The Burnout Mug is triple walled and the layer between the middle and outer wall has had all the air sucked out of it turning it into a vacuum. Click here to read my full Burnout mug review.
Heat really struggles to move through a vacuum and this is really important to keep your coffee hot for hours.
The heat from your coffee and the PCM can't escape out the sides of your mug so it stays trapped in your mug, keeping your coffee hot for longer.
Phase Change Coffee Mug: The Burnout
The Burnout is the only coffee mug I am aware of that uses phase change material in order to quickly cool down your coffee and keep it at the optimum temperature.
It was designed by rocket scientists and launched as Lexo but then later rebranded and relaunched as Burnout.
The cool thing about this mug is that you don't have to do anything special in order to make it work. Just wake up, make your coffee as you regularly would and then pour it into the mug.
The PCM will then quickly cool down your coffee to an optimum drinking temperature in about 1-2 minutes and then keep it around that temperature all day long.
If you're like me and aren't making boiling hot coffee but rather a milky coffee around 140ºF then you may want to prep your burnout with boiling water first to melt the PCM. Then discard the no-longer-boiling water and pour in your perfect temperature coffee and the burnout will work to keep it at the nice temperature for hours.
Or if you just want maximum heat retention like a regular insulated mug do two rounds of boiling water then fill up your cup with your boiling hot coffee and it should keep it scalding hot for hours so it's still hot to drink later in the day.
It's actually a versatile product when you understand the science behind it and how it works. It just takes a bit of trial and error to work out exactly how it should work for you.
It isn't perfect but itself really well made and actually does what it says it is meant to do. It keeps your coffee at that nice temperature for hours at a time.
It's not a cheap mug but if you're a coffee snob like me and can afford it then it might be worth the investment.
Another Phase Change Mug (Maybe): The Ember Travel Mug
The Ember Travel Mug is a battery powered heated coffee mug that uses a heating element in order to keep your coffee at the perfect temperature.
Some of the old marketing material says it quickly cools down your coffee using PCM then keep it's at that temperature using the heating element.
However, this video from JerryRigEverything where he pulls it apart seems to reveal just a thin layer of some sort of fibreglass insulation not a phase change material.
So I'll put this one down as a “maybe” it is a phase change coffee cup but chances are it isn't.
However, it is able to keep your coffee at exactly the right drinking temperature for you by using the heating element and the battery power. It's one of the best battery powered heated travel mugs on the market.
This will last for 1.5-3 hours on battery power depending on the model you get or it can keep your coffee hot all day long when connected to the charging coaster and running off mains power.
It's a beautiful travel mug that is well made and can be a great gift idea.