How do mountaineers prevent their water from freezing on high mountains?

What one has to eat on the ski tour is the cold apple schorle when mountaineering or on a bike.The individual drinking habits are quite different in terms of sport, drink and season. To satisfy all these preferences, one only needs one thing: an insulating bottle, colloquially referred to as a thermos can.

Definition & Patent

Most insulating bottles have a plastic screw cap with a push-button, which makes it easier to insert.

| Photo: Salewa

An insulating can oran insulating container is a lockable container for keeping drinks or food hot or cold (preferably with a high liquid content).

Who invented it?

In 1903, Reinhold Burger applied for a patent for vacuum insulation, which he sold in 1909, along with the protected term “thermos bottle” (from ancient Greek: a – therm’s = ‘warm’).The buyer was the newly founded “Thermos-Aktiengesellschaft” from Berlin-Charlottenburg, which went into series production in 1920 with its insulating containers. In the meantime, there are insulating cans from all sorts of manufacturers. “Thermos bottle” may only be called the thermos cans.

Structure and functioning of insulating cans

Basically, an insulating bottle works according to a fairly simple principle: a vacuum is created between an outer and an inner vessel.This reduces the heat conduction, as the few remaining air is a very poor heat conductor. The heat flow within the filled liquid does not matter.

The material

Some insulating cans have a tempered glass body as an inner vessel, such as the Hot & Cold Glass bottle by Sigg.This is double-walled and has a vacuum between the glass walls. In addition, it is again surrounded by an outer vessel to protect the glass. In order to reflect the heat radiation that could theoretically bridge the vacuum, the vitreous body is mirrored on the inside – for high-quality products, for example by means of a silver coating.

However, this construction is not particularly suitable for outdooruse slates due to the vitreous (risk of breakage), which is why most insulating cans are designed slightly differently for outdoors: they consist of two interlocking vessels – usually made of break-resistant stainless steel.The space between them is vacuumed. Due to its nature, the stainless steel reflects the heat radiation without the need for further coating. In order to achieve a better efficiency, a silver coating can also be used here. Examples are the inexpensive insulating cans and food containers from Esbit.

In addition, there are insulating containers made of plastic in all possible colour and shape variants – usually as a classic coffee pot.For the bike tour or if it doesn’t have to stay hot or cold for quite as long, there are also some plastic bottles from Camelbak for the bike mount (Podium Chill) or as a coffee cup for the car (Forge Divide). Due to their low efficiency and the lack of distribution in the outdoor sector, these are mentioned only in passing.

Food containers with larger diameters and lower heights come, for example, from Klean Kanteen (small), Primus (large) and Esbit.They are easier to fill and clean and keep food warm for several hours.

The closure

However, all the effort for the heat output of insulating cans is worth nothing without a good closure.Whereas in the past a cork had to perform this service, today plastic screw caps are usually used. These are usually available with or now less often without a button for pouring out. As convenient as the push-button is for pouring in, it has a decisive disadvantage: At some point, the seal will lick.

Often, another “lid” in the form of a (stainless steel) drinking cup is screwed over this screw cap.In order not to burn your fingers with the poured hot drink, you should make sure that the cup is insulated – either outside by neoprene or a rubberization or by an internal plastic container. A vacuum is usually not used here, but at least an insulating effect is achieved through the air between the two containers.

EU standard for insulating containers

A lid that acts as a cup at the same time is standard for most insulating cans.

| Photo: Primus

Of course, the EU has provided us with a suitable standard for all this: in order to be considered dense, an insulating can must stand upside down for ten minutes without any drops forming at any point.In order to pass as an insulating container, a jug must successfully pass the following test: A preheated jug is filled with boiling water, which must still be at least 78 degrees hot after six hours. Good jugs create more of course …

One of them is the stainless steel insulating can from Stanley.She dances a bit out of line here because of her relatively high weight, but as a cult object she simply deserves her own heel. Practically on the market since 1913, it shines with a 25-year warranty, the typical lateral handle, and keeps drinks warm for over 24 hours – well above the standards required by the standard.

Interesting facts about the material of insulating cans

  • In the case of high-quality products, it should be a matter of course that there is no nickel in the stainless steel (allergenic properties) or that other pollutants (especially heavy metals) could dissolve during use and be released into the contents.
  • In addition, one should be aware that with many insulating containers made of stainless steel, the insulating ability decreases over time.

What’s behind it: In order to achieve a flawless appearance, the vessels are often stained with acid. The hydrogen stored in the process, which is several times better than air, diffuses into the vacuum due to the pressure gradient and significantly worsens the insulation effect within a few years. As a rule, the price allows a conclusion to be made about the quality of the material and thus the permanent insulating capacity.

  • If the contents in certain insulating containers do not taste as expected, but of plastic, then this – even in stainless steel vessels – is due to the seals used.
  • Especially with very cheap products, seals that have taste-altering properties or contaminants such as plasticizers or polycyclic aromatic hydrocarbons (PAHs).

    Material and weight

    The silicone case of the Primus Trailbreak EX insulating bottle is particularly grippy.

    | Photo: Primus

    Stainless steel is the material of choice for outdoor insulating bottles, as it is break-resistant and has a good insulation effect.Almost all manufacturers today use stainless steel. Of course, there are also lighter versions, for example made of titanium – but at higher prices. Vitreous sorceres are also well insulated, but are fragile and also heavier, which makes them less suitable for outdoor sports enthusiasts.
    Legendary due to their low weight are the Sahara insulating bottles of tiger (stainless steel).However, you buy the weight advantage with a tiny drinking cup, among other things.
    The surface of an insulating can for outdoor use should be as grippy as possible, so that it can also be operated well with fists.A slightly roughened surface, such as Esbit’s black jugs, or a silicone case like Primus’ Trailbreak EX models is an advantage.This is not only grippy, but also protects against cold fingers.

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