The rubber attachments in the stoppers hold the most smell – let them sit in hot soapy water for five minutes, then air dry them before reattaching For a group hike, you need to keep lots of liquid on board for everybody to get a cup. If this is your plan then you should buy a thermos which can hold lots of liquid for the whole squad. It is definitely more space efficient to use one big flask for the group rather than several small, individual flasks. If you think about it, the majority of a flask is wasted space and not actually used for carrying liquid – it is there for the heat insulation. Better to just carry one big flask. Need to know: Not dishwasher safe, twist-off lid, glass and plastic materials, comes with two cups, also available in 1.8-litre size The GSI MicroLite 1000 Twist Water Bottle is a vacuum insulated stainless steel flask that has a one litre capacity but impressively small size and density. It is extremely lightweight at 0.37kg which is less than half the weight of the Stanley 18-8 for the same capacity. Since the American manufacturer, Thermos, came to fame, the term has become slang for vacuum-insulated flasks. Although the terms are largely interchangeable, the original scientific phrasing is 'vacuum flask'.

The Stanley 18-8 flask is the best option for a solo user in our opinion. It is a great performer which looks superbly rugged for your next arctic exploration and goes about its job efficiently, discreetly and expertly. Avoid abrasive detergents and materials when cleaning your flask – bleach will stain and damage stainless steel, and scouring pads will scratch the outside of your flask The Smardy flask is manufactured with high-quality stainless steel that makes it extremely durable and we are confident it will perform well over the long-term. It utilizes a silver coat in the vacuum portion of the flask which enhances heat retention. You can see that a thermos flask will be a great companion for any outdoor activity! Using a Thermos Flask is Environmentally Friendly Using a flask is actually also a very responsible thing to do in terms of recycling – apparently 99.75% of disposable coffee cups are not recycled!Button-operated lids are more efficient to use than twist-and-pour stoppers – we found the button-operated lids to be more secure than the twist-and-pour stoppers. This flask from OKADI gets full marks for its capacity and versatility. OKADI is a brand that has been serving people with quality products for the last 20 years and this particular model is their flagship model. It’s a big flask for big groups 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.

We’ve reviewed a selection of the best thermos flasks, ranging in size from 470ml to a whopping 64oz (1.8 litres). Bigger flasks usually retain heat better than smaller flasks, but are typically bulkier and heavier. We’ve compared their performance with our own temperature test. What Is The Best Thermos Flask? Available in a range of colours (we like the electric blue), the flask is highly suitable for camping trips and general travelling refreshments. Pouring is very easy due to the superb flexible handle fabricated from silicone. Don't fully submerge the flask in water – doing this might allow water to get inside the insulation layers, affecting the quality of insulation There have been reports of vacuum flasks exploding during use. Although rare, if you're not following proper guidelines, it is possible. 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. DimensionsHeat and cold retention is exemplary, with the Thermos lasting well over 24 hours for both. We found that it is particularly effective for cold drinks, with ice cubes still being solid after a 30 hour test we performed. Thermos have obviously squeezed out all routes for heat to get into the inner chamber of the flask. Some thermos flasks use a cork or plug to seal the liquid in, but we really don’t feel this is an effective design. Our suggestion is to go with a screw cap and a clip-on outer cap which will double as a cup.