Outdoor Features

Inside The Primus Factory | How A Stove Is Made

We visit stove specialist Primus's Stockholm R&D cave before checking out the Estonian factory where the Swedish outfit's stoves are precision assembled.

That up there is a drill so fine that the gas jet on the left spins rather than the drill-bit. The point is that for Swedish stove specialist Primus, precision matters. Make the hole just microscopically too large and the flame will burn slightly too rich wasting precious fuel, make it too small and it won’t burn hot enough. Just one hundredth of a mm can make a difference.

And to make sure nothing’s left to chance, each stove is test-fired before being shipped. If it’s oversized, the flame burns green, if it’s under-fuelled, it tends towards yellow. Get it just right – 0.37mm if you were wondering – and the flame is an optimal orange.

Optimal Fuelling

Why does it matter? Optimal fuelling means both the best level of power and, just importantly for the lightweight backpackers the LITE+ is aimed at, the best possible efficiency. Or, to put it another way, more mugs of tea per gas canister.

Every Primus stove is test fired. This LITE+ needs to burn orange for optimum performance. Get it wrong and it wastes fuel and reduces efficiency.

But before we visited the Primus factory in Tartu, Estonia, we spent at day at the brand’s Stockholm HQ, an unremarkable building with a dark secret in the cellar. Meet the Primus version of 007’s Q…

Meet Primus's answer to Q in the brand's secret research and development cellar where cutting edge designs mix with glorious precision engineering machinery from the last century and the Swedish brand's impressive heritage - image: Jon

Primus – The Story Of A Stove Maker

It’s fair to say that Primus has been making stoves for a while now. The brand’s first domestic soot-free kerosene (paraffin) stove was launched in 1892 and for around 100 years, the company’s factory was in Stockholm, Sweden.

Over the years the brand’s moved from its original domestic stove market, first into general camping and then into more specialist outdoor applications. It has genuine heritage with the likes of Hillary and Tenzing, Roald Amundsen and Goran Kropp having cooked their tea on Primus stoves.

And a fair number of young Brits cut their outdoor teeth on the brand’s classic brass paraffin burners too – the other big name in the market, Optimus, by the way, is Swiss owned. These days Primus stoves are cutting edge kit and sold in more than 50 countries around the world including the notoriously strictly regulated Japanese market, where draconian testing means some rivals fear to tread…

Proper old school precision milling machinery adds a flavour of proper mad boffinry – is that a word?

Back To The Future

In other words, Primus has been around for longer than most, but one thing comes over loud and clear. It’s certainly not resting on its laurels. The brand’s Stockholm HQ is in an unremarkable modern office building in Stockholm, but tucked away in the basement is the top secret research and development facility known as ‘The Basement’.

Think of it as where Primus’s very own Q and his development team work on future projects and you won’t go far wrong. Tucked away behind an unremarkable industrial door in the corner of the building’s basement car park, it’s a delightfully random mix of the past and the present, traditional and modern, analogue and digital.

Concept drawings are done the old-fashioned way with pen and paper, but designs often hark back to classic Primus products from the past - image: Jon

The Onja stove from the brilliant new Campfire, mild camping range owes its distinctive lines to a classic Primus design in the foreground - the colour is a little less terrifying though... image: Jon

That's what we call a drill... precision industrial machinery from the last century was saved from the original factory and is still going strong... image: Jon

Meet ‘Q’… Or Should That Be ‘P’?

There’s something of the surreal about the Primus basement. Check out the precision milling machine made in 1962 by the DoALL Company of Des Plaines, Illinois or the massive industrial drill produced by Friedrich Deckel of Munich. If machinery could talk…

The latest in modern technology rubs shoulders with proper old school, hands-on artistry in the Primus Basement – image: Jon

But equally, the Primus development team is happy to use the latest technology to optimise its stoves. That means thermal imaging to check which areas of stove are getting hot. A huge fan which creates a fearsome wind-tunnel effect and even a cold chamber which can simulate temperatures down to -39˚C to make sure stoves and gas mixtures, like the Japanese-developed Winter Gas work as planned when the going gets cold.

Designs are field tested too with prototypes being used in hostile environments before production is finalised, but the attention that goes into the initial design process is impressively thorough.

Thermal imaging gun allows engineers to see which parts of the stove are getting hot in use and tweak designs accordingly – image: Jon

Another nice touch is that Primus hasn’t lost touch with its own heritage. The brilliant new Campfire range – think ‘Glampfire’ – takes styling cues from classic Primus designs from the past and vintage posters remind today’s Primus developers of where the brand came from.

Made In Europe

A little sadly those vintage but still functioning machines are all that’s left of the original Primus factory in Stockholm, but the brand’s stoves are still made, or more accurately ‘assembled’ in Europe, just across the Baltic in Estonia.

It’s there that a workforce of 22 skilled operators methodically piece together precision-made stove components from the far east to create around 400 stoves per day and some 200,000 units a year including lanterns.

Each stove takes approximately five minutes to assemble, with different stations tackling each stage of the assembly work. It’s an impressive operation, not so much in terms of the heritage or amazing machinery, more that unrelenting precision and attention to detail that culminates in every single Primus stove being hand tested before it leaves the factory. Impressive.

To get you in the industrial mood, here are a few snaps of the factory, more about the assembly process in a moment.

Burner anyone? These ones are waiting to be united with the rest of these stove - image: Jon

How A Primus Stove Is Made

In a move of calculated recklessness by Primus, we were allowed to assemble our own LITE+ stove, the brand’s updated personal cooking system option. The idea was to get an idea of how things go together and allow is to marvel at the dexterity of the Primus workforce who were somewhat more capable than us…

The heart of the stove is that precision drilled jet we came in on. Each is machined individually to an exact 0.37mm with a precision of + or – 0.01mm. The drill is so thin that the jet spins rather than the bit. It’s an impressive process, that’s crucial to the correct burning of the stove.

The super fine drill used to machine each jet to a tolerance of +/- 0.01mm – image: Jon

Next the multiple parts that make the slot-on burner unit are bolted together with a mechanical wrench before the gas connector and jet are screwed into place. It’s like a sophisticated Meccano set, but with better tool and greater precision.

You’ll be glad to know there’s a hammer involved too, or at least a soft-faced mallet. You can’t make anything worthwhile without a hammer…

You may call this an interference fit, we call it a hammer… essential tool – image: Jon

Sightly more sophisticated mechanical screwdriver sorts out the three bolts holding the docking plate together – image: Jon

Next the screw-on valve / and piezo electric unit plus burner are added, again with the aid of a powered driver leaving the bulk of the burner unit complete and ready to go.

Bingo – burner unit pretty much complete and ready for testing on the flame rig – image: Jon

At this point, the burner unit is hooked up to an internal gas supply – no canisters harmed – and test fired to make sure that the piezo unit works and the flame is burning at just the right colour to show that the jet is within tolerance.

Finally a retainer wire is fitted to the pot holding plate and it’s time to move onto the heat exchanger ETA pot side of things. This is simple, just a question of adding the insulated sleeve and the three screw-in pot supports, an Exploration Ready tag is added to explain that the stove has been test-fired…

The Exploration Ready tag is added to all Primus stoves after they’ve been hand-tested to explain that any minor tarnishing is due to this process – image: Jon

Finally the stove’s are boxed up and ready to roll in search of a thousand adventures – or something like that. Except for this one, produced personally by Primus UK’s Andy Brown and destined to return to the UK with him. Or rather with me. Rather slowly, sorry about that Andy…

Primus UK’s Andy Brown with the stove what he made during the visit to the factory – image: Jon

Insulated pot caddy's and pot supports are the final additions before the stove is boxed and ready to roll - image: Jon

The final stage in the production line - stoves are boxed and dispatched to a new life of adventure worldwide - image: Jon

Skilled workers use advanced machinery to optimise stove assembly in Tartu, Estonia - image: Jon

Even the humblest burner bolt is treated with respect - image Jon

What We Learned At Primus

Apart from factories being really cool places visually – check out the gallery below – making top spec outdoor stoves is all about getting the small things bang on. We were properly impressed by the relentless attention to detail both at the Stockholm R&B basement and in the Estonian factory.

We love that Primus takes the time to test fire every single stove that it manufactures to make sure it works as it should before it leaves the factory. And we love the brand’s thoughtful design – we reckon it’s the king of neat stove integration – along with its awareness of its own heritage.

Some might think that it’s a shame that the stoves aren’t produced in Sweden these days, but Primus are all about sourcing the best components regardless of origin, and while the stoves are ‘made’ in Estonia, Primus sources precision parts are sourced all over the world before being united and assembled by the skilled workforce into the finished product.

Precision quality control is second to none with components being checked thoroughly before assembly – image: Jon

Speaking of which bolting together stoves isn’t quite as easy as you might think, particularly at any sort of speed, just saying…

Finally, Tartu, where the factory is based, is a very cool, very friendly city complete with a university centre that’s rather grander and larger than you’d expect.