Heat is not just heat.
Every reheated meal is a physics challenge. A microwave excites water molecules in bursts. A heating plate pushes warmth in from below. However, steam does entirely something else, and it decides whether your meal tastes cooked or merely survived the heating process.
Below is described how each method treats your food, what the research says about the container it sits in, and how to get a proper hot meal when there is no heating option in sight.
The short explanation
Steam reheats food by condensing on its surface. When water vapour turns back into liquid it releases a large amount of stored energy at once, so heat arrives quickly and from every direction instead of from one side. The food stays surrounded by moisture the whole time, which is why rice loosens instead of hardening, lean meat stays tender, and nothing dries out at the edges.
The mechanics
Three ways heat gets into food.
There are multiple ways of reheating food. How the heat travels decides what happens to the texture, and it explains why the same meal comes out differently depending on what heating method is used.
Radiation
Fast, but it never arrives evenly.
Waves make the water molecules in food vibrate, and the friction becomes heat. It works from the inside of the outer layer rather than the surface, which is what makes it a quick method. However, waves interfere with each other into zones of high and low energy, which is the physics behind a boiling edge around a cold middle.
Conduction
Needs patience, and food is always hottest at the bottom.
Heat moves from a hot surface into whatever touches it, then slowly onward. Through a dense meal that is a long journey, and the layer against the base stays hottest the entire time. Stirring evens out the temperature, but by then it has also evened out the texture.
Condensation
Heats up every side of food at once, and it cannot overshoot.
Vapour surrounds the food and gives up its heat the moment it condenses on the surface. It arrives from every direction at the same time, and it carries moisture with it instead of driving it off. At normal pressure it cannot pass 100 °C, so there is no runaway heat to scorch anything.
Side by side
The same meal, but three different outcomes.
All three make a meal hot. What separates them is how the heat arrives, and what that does to the food eventually.
Swipe to compare →
| Property | Steamed with Steambox | Microwave | Heating plate |
|---|---|---|---|
| How heat arrives | Condenses on every surface at once | Waves excite the outer 1 to 3 cm | Contact with a hot base |
| Temperature ceiling | 100 °C, set by physics | None. Hot spots pass 100 °C locally | Plate runs hotter than the food |
| Evenness | Even from all sides | Hot and cold spots, needs stirring | Hot at the bottom, cool on top |
| Moisture | Added back to the surface | Driven off unless covered | Driven off where it touches |
| Rice | Grains rehydrate and separate | Fine with water and a lid, dry without | Sticks and burns at the base |
| Chicken and fish | Stays moist, flakes apart | Tightens at full power | Dries on the underside |
| Typical time | 10 to 15 min, hands off | 2 to 3 min, plus stirring | 20 to 25 min depending on the model |
| Where it works | Any socket | Only where there is one, and a queue | Any socket |
| Attention needed | Fill the container, plug in, you can leave it alone | Cover, stir halfway, check in | Fill the plate, plug in, stirring multiple times |
| Best for | Meals you want to taste like they did at home | Speed above everything else | The food does not taste as fresh as when just cooked |
Times are for a single portion straight from the fridge. Microwave behaviour depends on the appliance and the container. Heating plate timings vary by brand and by how full the tray is.
The numbers that matter
Hot enough to be safe. Capped low enough to stay good.
Reheating guidance from the UK Food Standards Agency and the US Department of Agriculture: food should be steaming hot throughout, not only at the surface.
What research says
It matters what your food sits in.
Most of the arguments about reheating are about the heat. Far less is said about the container, even though that is where the food spends most time.
In February 2026 Greenpeace International reviewed 24 peer-reviewed studies on plastic food packaging. The finding that matters here is simple: heating food in plastic containers is when the most plastic leaches out. Microplastics and chemical additives migrate into the food, and the hotter and longer the heating process runs, the more the plastic leaches out.
One dot ≈ 4,000 particles
Heated in an oven
≈ 76,000, seven times lower
Heated in a microwave
326,000 – 534,000
What Greenpeace advises
“Before cooking or reheating food in plastic packaging, transfer it to suitable containers such as stainless steel …”
Where Steambox stands
That is what a Steambox container already is: 304 food-grade stainless steel, a silicone seal and a real bamboo lid, while nothing plastic touching your food.
The steam is generated in a separate reservoir and never passes through a plastic tray on its way to your lunch.
The studies measured migration from polypropylene and polystyrene containers into food and food simulants. Labels such as microwave safe and BPA-free are not a guarantee against this, which is one of the report's central points.
Only two of the 24 studies reviewed used real food. The rest used simulants such as water, acetic acid or ethanol. The report's full advice names stainless steel for the oven and microwave-safe glass for the microwave.
The trade
A microwave is faster. There, we said it.
Two against approximately twelve minutes. However, that is rather a trade than a gain.
What those ten minutes buy you: rice that loosens instead of hardening, a socket instead of a queue, and stainless steel instead of a plastic tray. The meal arrives the way it left your kitchen, which is the entire point.
No crisp, though. Steam adds moisture, so anything breaded or fried comes out hot rather than crunchy. For that you want an oven.
Where this comes from
5 sources
Every number on this page, and where it came from.
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326,000 – 534,000Microplastic particles leaching into a food simulant, and the advice to move food out of plastic before heatingAre We Cooked? A review of 24 peer-reviewed studies on what plastic packaging releases into food when it is heated. Read the source Greenpeace International (opens in a new tab)
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74 °CThe internal temperature reheated leftovers should reachLeftovers and Food Safety. Reheat leftovers to 165 °F, roughly 74 °C, measured with a food thermometer. Cover the dish so it heats all the way through. Read the source US Department of Agriculture (opens in a new tab)
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Cold spotsWhy a microwave asks you to cover, stir and waitCooking with Microwave Ovens. Microwaves heat unevenly and leave cold spots where bacteria survive, so their own guidance is to cover the dish, stir or turn the food midway, and observe a standing time. Read the source US Department of Agriculture (opens in a new tab)
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Steaming hotNot a number but a test: hot throughout, not only at the edgesConsumer guidance on reheating leftovers. The FSA deliberately gives no temperature to home cooks and instead asks that food is steaming hot throughout, which is where the phrase comes from. Read the source UK Food Standards Agency (opens in a new tab)
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1,396Food contact plastic chemicals found in human bodiesThe Lancet Countdown on health and plastics, Landrigan et al. Cited within the Greenpeace review rather than read in full by us. Read the source The Lancet (opens in a new tab)
Where the Steambox comes in
Steam, without a kitchen.
Everything on this page is settled physics. The engineering question was a different one: how do you fit a sealed steam chamber into something you can carry to work, and run it from a wall socket?
That is Steambox. Water in the base, food in stainless steel, steam around all of it.
Free shipping · 24-month warranty in the EU
Questions
Everything you need to know.
How long does it take to heat my food?
Ten to fifteen minutes for a meal straight from the fridge, and twenty to twenty-five minutes from frozen. The 230 W element turns the water in the base to steam within seconds, so heating starts immediately. Dense dishes like stew and larger portions sit at the top of that range.
How much food fits in it?
The container holds 750 ml: a full plate of pasta, a generous portion of rice with curry, or a hearty soup. Enough for a real lunch rather than a snack. If you eat larger portions or want to keep two dishes apart, you can add a second food container.
What warranty do I get?
Twenty-four months in the EU and twelve months in the US, covering manufacturing defects. Email info@steam-box.com and we will sort it out.
Can I use it without a power outlet?
No. Steambox needs a wall socket, and that is a deliberate choice. A battery powerful enough to steam a full meal would make the box heavier, slower and far more expensive, and it would still be flat by Thursday. In practice a socket is easier to find than a free microwave: at your desk, in the site office, at a service station, or in a van with a 230 V inverter. It does not run from a car's 12 V socket.
Will my food dry out like in a microwave?
No, and that is the whole point of steam. A microwave heats the water already in your food and drives it off, which is what turns rice hard and chicken stringy. Steam does the opposite: it condenses on the surface and puts moisture back. It also cannot get hotter than 100 °C, so there is no runaway heat to scorch the edges while the middle is still cold.
Do I need to charge it?
No. Steambox runs on a 230 W mains cable, so there is no battery to charge and nothing to run empty. You get full steam from the first second, every time.
Do I need to add water?
Yes. Two full water containers go into the base, never onto your food. The measuring container comes in the box, so it takes about ten seconds in the morning. Steam then rises around the sealed food container, which is why the food heats evenly instead of drying out.
What can I heat in it?
Anything you would eat at home. Rice, pasta, curry, stew, soup, vegetables, fish and meat all work, and frozen meals go straight in without defrosting the night before. Steam suits moist dishes best. It will not crisp anything, so a schnitzel comes out hot rather than crunchy.
Is the Steambox dishwasher safe?
The stainless steel container and the silicone seal go in the dishwasher. The bamboo lid is real wood and needs a quick hand wash. The heating unit is wiped clean with a damp cloth and never goes in water.
Do I need the app?
No. Steambox works fully without it: fill, plug in, wait. The free app for iOS and Android adds a notification when your lunch is ready, plus recipes from other Steambox users. Nothing about the product depends on it.
Why is Steambox more expensive than other electric lunchboxes?
Most electric lunchboxes are a heating plate under a plastic tray, running at around 60 W, and they take thirty to forty minutes to warm a meal from the bottom up. Steambox steams at 230 W from every side, is built from food-grade stainless steel and real bamboo, and is covered by warranty. It is the difference between reheating food and eating well, and if it replaces a bought lunch it pays for itself within weeks.