You may think choosing a vacuum flask is a simple matter of grabbing the shiniest example in the camping shop (if it’s open!) and hoping for the best. Well, unfortunately we’ve tried that approach several times and have frequently been disappointed. You should buy a hot water dispenser if you only want to boil a small amount of water at a time or have difficulty using a kettle. They’re not suitable for boiling large quantities of water, or for making lots of cups of tea in a row. An effective stop or cancel button should work immediately. Most hot water dispensers fill a cup in a matter of seconds, so if it takes a while to stop the hot water flow, this function won’t be effective. Limescale filter Of course, one of the main reasons to buy a flask is to keep hot food hot. As such, heat retention is another of the most important factors to consider before buying. This heat retention time can vary hugely between around 4 hours, up to 12 hours and potentially even longer than that. This means that you have to factor in how, where and when you intend to use your flask. For single portions, a few hours is probably fine, but on longer expeditions with multiple meals, you’re naturally going to need one that’ll hold onto that heat for longer. Sheathed ceramic resistance: easy to maintain, it is not necessary to empty the thermos for handling.

A solid performer in testing, SHO’s food flask kept water chilled for the advertised 20 hours and even managed to keep a portion of ice cream very cold, albeit a little melted, for the same period of time. Similarly, it kept hot food such as pasta piping hot over a period of 10 hours. The flask’s design also proved practical as well as stylish, with neat touches including a handy foldable spork, which stores in its lid, and a rubber carry handle. While the 530ml version is suitable for single portions, those of you looking to share may want to opt for the more roomy 800ml option. A range of scientific research has shown that BPA can seep into food or beverages and potentially cause a range of issues for the brains of fetuses, infants and children. Additional research suggests a possible link between BPA and increased blood pressure. To read more about where limescale comes from, see How to descale a kettle. What are Insinkerator and Quooker? Flasks are meant to hold liquor for a short period of time—typically one to three days. Liquor left in longer in a stainless-steel flask can start to have a metallic taste, and some, such as whiskey, will turn darker in color.Do you live in a hard water area? If you live in a hard water area, make sure you get a kettle with a limescale filter in the spout. Most have these but some don't. Some kettles also have built-in water filters, although these can be slow to fill and need to be replaced fairly regularly. The Milu Thermo Food Flask is a bowl-shape flask (16 x 10 cm) that is not only useful for keeping your drinks hot/cold, but also certain types of liquid-based food. You can keep soup, rice, noodles, fruits and even baby food in this great flask. All parents know that it’s often a problem carrying baby food at the right temperature. The 450ml flask Milu is a great solution to the problem.

Capacity: Bigger capacity means more contents to enjoy. It also means more weight to carry, but only if you fill it to the brim. For best insulation, buy a flask that’s slightly bigger (but not heavier) than you need, and leave a couple of centimetres of air at the top. We’ve included capacity and weight info for all our flasks below. Less than a third of the kettles we test are rated as notably quiet: we measure the noise level in decibels during boiling and note any unusually piercing or annoying sounds. The Thermos has dimensions of 31 x 8 x 8 cm and weighs only 515g – a great size for a day hike. A 1 litre capacity is about the optimum in our view – enough to comfortably serve two people with hot or cold drinks throughout the day without being too much of an impediment to carry. The GSI employs a thin but reliable stainless steel wall that reduces the weight and also increases the internal space of the bottle. According to GSI, you can store 25% more liquid than any other flask for the same size. That being said, we found that performance was not quite as good as a dedicated drinks flask – the Milu will keep your hot drinks hot for six hours and the cold ones for 10 hours.Some hot water dispensers have a variable water setting, which means you can alter the amount of water that’s dispensed, but generally they dispense between 150ml (equivalent to a cup or small mug) and 350ml (a large mug). The 18-8 flask is from the renowned brand Stanley. Stanley has been serving people since 1913 and this model is truly legendary. No other brand apart from Thermos themselves can boast such heritage. Dimensions

If you are searching for a great value thermos flask at the lower end of the budget range then we don’t think you can do much better than the SMARDY Vacuum Insulated Water Bottle. This is a compact size flask with a smallish capacity of 430ml – this is only enough for two cups of tea. Of course, glass is fragile, so we recommend that if you’re hiking, popping it into a golf bag, or even a picnic basket, you might want to make sure to provide adequate padding to prevent breakage. That said, we appreciated that this glass flask was so nicely made, noting its shape and the useful hinged cap, and we could pour and sip with ease. It was on the heavier side, at hefty 12 ounces empty, but it is a large vessel that will hold about a third of a standard bottle of booze.A loud whistling kettle can be really annoying, particularly if you have an open-plan kitchen/living area. Some kettles are marketed as being especially quiet, but this doesn't always hold true.