Three tips for using thermos flasks on winter excursions

For a long time, a thermos flask was just a nuisance that was always in the way, so I just thrust it into the back of the closet. Occasionally, if we set out on a walk or a picnic that was going to last a few hours, I would make some coffee and bring it along. Winter hikes changed everything.

Nowadays, I have three thermos flasks in my closet, a couple of thermos mugs and a large food thermos. All are in regular use on treks and trips. The Airam 0.7-litre thermos has become my trusted companion.

It makes me feel safe and comfortable on winter hikes.

When you set off on a winter excursion, unfrozen drinkable water is a scarce commodity and, in order to get it, you have to stop, set up a stove and melt some snow. Melting enough snow for 1 litre of water it takes about 25 minutes with a gas or Trangia stove. When camping, you can also melt snow over an open fire.

We need approximately 2-2½ litres of liquid per day in order to be able to function. Even a small lack of liquid can cause problems in concentration, and a large lack makes us feel tired. On a winter hike, you need all your powers of concentration and strength for safety’s sake. Temperatures do not need to be much below zero for the risk of hypothermia to increase when you stop or are moving slowly.

If you are used to hiking in Lapland when the snow is melting with a wooden ‘kuksa’ mug on your belt and a water bottle in your backpack, you cannot think about water, melting snow and keeping water hot as a force that keeps the trek going. Drinking water is a self-evident truth until the season changes.

Winter trekking routines also entail melting the snow into drinking water both in the evening and in the morning. Once the water has been melted, it must be kept in that state. Better still, it should be kept hot. On a winter hike, drinking cold water takes a great deal of energy from the body, as the body has to warm the water itself. And my oh my, how frustrating it is to have a water bottle that is frozen solid. Believe me, I’ve experienced it, so you don’t have to.

And a big question: on your hike, do you want your evening meal half an hour earlier or later? If you begin cooking with warm water taken from a thermos, you will get your food more quickly. After a long day of trekking, this is important.

Three tips for using thermoses on different lengths of excursions:

1. A daytime winter hike


Fill a 1-litre thermos flask with water boiled at home. Bring along some instant coffee, tea bags and dry food that you can cook in hot water: cup soups and noodles. Reserve at least 0.5 litres of hot water for each person. If you sweat as you move, you will need more water.

2. An overnight winter hike

Bring along a large thermos flask and a small thermos flask or thermos mug. Fill the thermos flask with water boiled at home. Put green tea or a couple of slices of ginger in the smaller thermos with a spoonful of honey and boiling water. Reserve approximately 1 litre of hot water and tea or some other hot drink for each person for the first day of the excursion.

On the way, a thermos mug can be used instead of a drinking bottle. Drink from it when you get thirsty. From the large thermos, have a lunch of cup soup or noodles. When you finally set up camp, use the rest of the hot water to begin cooking. At camp, the thermos mug serves as a tea mug.

Start melting the snow for water before going to sleep. Reserve about an hour for melting so that you can fill both thermoses. In the morning, you will have warm water for making porridge and coffee. Melt more water if you need more of it for the day’s journey.

3. A long winter ski trek or hike

Take two large thermoses with you (0.7- 1 litre) and a 0.5-litre drinking bottle that can take hot water. Reserve 25 minutes per litre in the morning for melting water. In the morning, you can put tea and honey in the drinking bottle and keep it melted in your coat. During the day drink from the bottle and, as the level goes down, replace it with water from the thermos.

During a break, make a cup soup or noodle lunch from the large thermos, and drink coffee or tea. Use the rest of the hot water from the thermos to begin cooking and for liquid replenishment in the camp. Begin to melt the snow as soon as the stove is no longer being used for cooking.

The photos in the blog are taken from short and long 2018 winter treks in Teijo, the Vaasa archipelago, Nuuksio and Saimaa.

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Mia Sinisalo is studying to be a nature and wilderness guide, and being out and about in nature has become a necessity for her. In Mia Sinisalo’s ‘Onnellisen tädin treeni’ (happy aunt’s training) blog, you can find more tips for outdoor treks. The blog is also published at Retkipaikka.fi. You can also follow Mia’s treks @Onnellinentati and with the hashtag #alltärheltokej.