Primus Stainless Steel Vacuum Flasks are manufactured using the best technology: using a metal strip in the vacuum they “suck” out unwanted air, keeping drinks hot/cold for longer: just one of three steps providing top vacuum performance.
Step one: Primus metals are heated and then the air is extracted to create as close to a perfect vacuum, as possible.
Step two: Sliver coated lining reflects heat, further enhancing heat retention.
Step three: A small piece of metal is secured between the inner and outer walls. When this oxidises [rusts] it “sucks up” some of what little air remains in the vacuum.
This works in practice too as adventurer Gary Rolfe* can verify: “On journeys I’m never without water. Primus 1-litre steel flasks filled with boiling water remains warm even if left out for two days and nights at minus 30ºC. Incredible.”
The most important thing to make a great vacuum flask great is how long it will keep drinks hot or cold drinks cold. The vacuum is key: the lower the pressure between the inner and outer walls the better the insulation. The Primus Stainless Steel vacuum flask is about as good as it gets measuring between 0.01 and 0.001 Pascals [the unit of measurement for a vacuum] compared with a figure of 0.0000 for an absolute vacuum [i.e. outer space].
Other features: silicone seals for hygiene; two stoppers: one standard click on/off, one screw on/off stopper; black powder coating for good grip and scratch resistance; dishwasher safe.
Stockists: www.blacks.co.uk – 0800 056 0127
*Gary Rolfe lives and works with his dogs in an isolated settlement in east Greenland where it can snow any month of the year, winter storms are terrifying and the cold is brutal. www.garyrolfe.com