A thermos is a great way to keep food warm for lunch but sometimes you don't have access to one or don't want to spend the money on a thermos if you're not going to use it often.
I personally don't own a thermos and wanted to find out how to keep my lunch hot and how to give my kids hot school lunches. I've done some research, trialed some methods and I want to show you exactly how to keep food warm for lunch without a thermos.
You can do this mostly using items you have lying around your house, no fancy thermos required. They should help you to keep food warm or hot for hours at a time so it's a great temperature to eat when lunch time rolls around.
1. Aluminium Foil + Towel
A thermos works to keep food hot by insulating it and stopping the heat escaping.
Aluminium foil and some sort of towel or tea towel is going to achieve a similar result for us.
Aluminium foil is great at insulating heat radiation and reflecting it back onto the food and stopping it from escaping.
The aluminium foil, or maybe you'll use a plastic tupperware container will also stop heat escaping in the form of evaporation.
The towel or tea towel acts as further layer of insulation to stop heat transferring away from your food to the outside air. It'll keep that head trapped inside your container.
So if you want to keep food warm for lunch without a thermos then simply wrap it in aluminium foil and then wrap your food in a towel or tea towel and it should stay warm for hours.
2. Hot Water Bottle or Heat Pack
When you're trying to keep food cold what do you do? You add a source of cold usually in the form of an ice pack.
But almost no one thinks of actually adding a heat source in order to try and keep food hot.
Water is dense and can carry a lot of heat energy. If you've ever put boiling water in a hot water bottle and woken up to find it's still warm in the morning you'll have seen this in action.
So filling up a bottle of water with hot or boiling water and then putting that inside the towel or even inside the aluminium foil with you food will help to transfer some of that heat to your food keeping it warm.
With plastic bottles you obviously have to be careful of them melting with boiling water, which is why single-walled stainless steel bottles can be a great option.
You don't want to use the insulated bottles as the heat won't transfer to your food.
Below is a link to a cheap 4 pack of single walled stainless steel bottles in multiple sizes. One of them will surely suit your needs.
You can also use a heat pack made from wheat or rice and heat them up and put them with your food.
However, these don't stay hot quite as long as water which is why I usually recommend using hot water bottles.
A bonus of hot water bottles is often you'll have access to a hot tap or maybe even boiling water so you can refill it to keep things hotter for longer if you need to.
3. Cheap Insulated Bags
You can buy cheap reusable thermal bags that help keep your food insulated.
They use a similar premise to the aluminium foil + towel where you are reflecting the heat back with the aluminium and then trapping the heat from escaping with the towel.
However these come in handy sealable bags where you can just throw your hot food in them and seal them up and you're good to go.
To make them last longer wrap the with a towel.
When done you can wash them out and reuse them again or they are so cheap you may wish to discard them.
4. Make Your Glass Tupperware Hot
This is something you would do in conjunction with your alfoil + towel.
Glass tupperware can actually absorb and retain a fair amount of heat. Putting your hot food into a tupperware container that is cold will instantly strip a lot of the heat away.
Instead, pre-heat your tupperware container with boiling water and leave for a few minutes so the glass gets really hot.
Then empty out the boiling water, put your hot food in the tupperware container and quickly cover it with alfoil and wrap in a towel to retain as much heat as possible.
The hot glass will add heat to your food and help to keep it warmer for longer.
5. Instant Hand Warmers
For a simple heat source when you're on the go and don't have access to hot water you can use instant hand warmers.
These aren't going to warm your food up for you but give them a shake and they'll provide a little bit of extra heat in order to keep your food warm for longer.
The good thing about these is that when it starts to run out of heat you can grab a new one, give it a shake and then replace it with a fresh hot hand warmer.
6. Wrap It In A Sweater
Sweaters keep you warm because they are able to effectively trap your body heat. But they also work on hot food too and will likely work better than a towel.
Put your food in a container, wrap that in alfoil if you can and then wrap your food container in one of your sweaters.
Fleece sweaters and puffer jackets work great as do big winter coats.
When you've eaten your food you can then wear your sweater on the way home if it's a cold day.
7. Keep Hot Water and Make It On Site
You may not have a thermos food flask but you might have an insulated water bottle like a Hydro Flask or other brand.
So many people have them these days and they are extremely common.
Pre-heat the inside of your water bottle with boiling water and leave to sit for 2-5 minutes before discarding the water. This will warm up the metal inside to insure it doesn't strip away any heat.
Now add fresh boiling water, filling your bottle to the top, and seal it off quickly.
This water will stay extremely hot for a few hours and can be used at lunchtime to make something like a cup of soup or cup of noodles.
My personal favorite brand is Hydro Flask but there are a lot of different brands and options out there:
Keeping Food Warm For Longer Periods Of Time Can Be Unsafe
You do need to be careful when keeping food warm for an extended period of time.
Temperatures between 40°F-140°F (4.4°C-60°C) are considered by the USDA to be a “danger zone” where bacteria can grow quite rapidly leading to potential food poisoning.
You'll want to keep your food above 140ºF so bacteria can't grow otherwise if it falls in that danger zone then you could be eating food that is going to make you sick.
Rice is an especially risky food to keep warm and I covered this in detail in my article on can you put rice in a thermos.
Always be safe when keeping food warm and follow your local health guidelines.
You can also click here to learn how to keep food warm in a lunch box for more tips and tricks.