Knives are the most important tools in a cook’s arsenal – a shipshape blade is not only an everyday necessity, but also the difference between sawing away at an ingredient or gliding through it with a light touch. For chefs, who spend most of their time in whites and must stick to far higher levels of precision than us, they are incomparably important. Wear and tear means all blades dull sooner or later, and when the time arrives for a spot of maintenance, chefs are unsurprisingly choosy with who they trust to take it on. Among those who might get the call is Rodrigo Batista, a knife sharpening expert whose client list is a who’s who of kitchen talent; there’s everyone from Rafael Cagali, Jeremy Chan and Matt and Sally Abé to Endo Kazutoshi, Adam Byatt, April Partridge and Kim Ratcharoen on his books.

When taken at face value, knife sharpening sound like a fairly straightforward concept. ‘Sharpening is essentially material being removed from your knife,’ Rodrigo, who grew up in São José do Rio Preto in Brazil, explains. ‘But it's also looking at what happens behind the edge; keeping an eye on what is happening with the rest of the knife and performance.’ The reality is a complex balance of art and science which requires an understanding of physics and geometry, as well as intuition when it comes achieving the best results. After all, Rodrigo's work takes in everything from serrated steak knives to meat cleavers and bevelled chefs’ knives, and involves blade straightening, tip repair, edge re-profiling, removing rust and chips, thinning, hand and machine blade polishing and sharpening. There's a lot to think about, and to tailor his work to the knife at hand, Rodrigo relies on a range of natural and synthetic whetstones, sanders and belts in his London workshop to carefully restore blades to their former glory. 

That might include everything from entry-level, budget blades to ones so rare there are only a handful of them in the world, like Tsukasa Hinoura's santoku, made from shirogami (white paper steel) and rentetsu (wrought iron). Some require such a delicate hand that the work can become painstaking and physical. Third generation sushi-master Endo Kazutoshi’s seventeen-inch sakimaru maguro bocho (pictured above), a knife built for precision for the likes of sashimi and sushi, is among them. ‘The knife's considerable length and heft render it a rather troublesome task to maintain constant contact between the bevel and the whetstone surface, particularly when I'm focusing on the extremities of the blade,’ he says. ‘The challenge intensifies after two-plus hours of manual labour: a mere 100 grams begins to feel like a whole kilogram.’

Rodrigo dabbled in medicine, audiovisuals, professional drumming and psychoanalysis before moving to the UK and working in kitchens around the capital. There, he first started sharpening his own knives, a craft he'd been introduced to by his father, who had his own collection. Soon, he began doing the same for colleagues and friends, before joining a sharpening business to reset his skills. But it was a ‘mind-blowing’ trip to Japan to meet and learn from master blacksmiths and sharpeners that cemented his love for the art, and in 2021 he launched Togidai Sharpening Station. Today, Rodrigo is part of the World Sharpener's Union and a member of the To-Ken Society of Great Britain (a body dedicated to the study and preservation of Japanese swords), with a list of customers who cook at the highest level; around seventy per cent are featured in the Michelin guide, he says, where elegance and precision are key. 'Michelin-starred chefs need their knives looked at properly to deliver the consistency and the quality these guys work with,’ he says. ‘From the quality of produce to the skills involved, their knives should be in perfect condition.’

For Rafael Cagali, chef-owner at two-Michelin-starred Da Terra in Bethnal Green, a cared-for knife is more than just a tool – it’s also a safety measure (blunt knives are the leading cause of kitchen accidents, he says) and a reflection of who a chef is. ‘I encourage the team to maintain their knives the same way as maintaining your own attitude and work ethic,’ he says. ‘When one slips, so will the other. A good, well-maintained knife is the difference between a carefully executed dish and one which is finished haphazardly at the last minute. A professional chef will treasure their knives as an extension of their own self.’

Though all blades lose their edge eventually, factors like careless storage (putting them away with other utensils) and scraping the blade over the chopping board will blunt it faster. Ultimately, Rafael says to pay attention to when standards start to slip. ‘Suddenly, the act of using the knife requires more force and time, or the knife will slip off the object instead of slicing through it,’ he says. ‘You should never force a knife, because when you do, it leads to mistakes and poor execution. A good, sharp knife should glide with your wrist movement. A good test is slicing through something quite delicate like a tomato or herbs. A blunt knife will bruise or straight up damage your ingredient.’ 

Feeling suitably shamed into an evening of sharpening? Rodrigo, who also runs an online knife sharpening school in Brazil, says there's no rule of thumb for how long it takes for a blade to dull – instead, it depends on everything from the steel it’s made from to who made it, what it’s being used for and the chopping surface (glass and stone boards are the worst offenders). 'Chopping boards play a significant role in edge retention as one would expect: that's where kitchen knives are being used most of the times,' he explains. 'There are great alternatives in the market to minimise edge blunting though, such as end grain wooden boards or some soft synthetic materials.' So how often should we be sharpening? 'There is nothing more pleasurable than working with a sharpened knife,' he says, 'but at the same time – and it might sound counterintuitive – you shouldn't be sharpening it as much as you can because you are ultimately removing material from the knife.’ Instead, Rodrigo says, there are a few tests to try – and, yes, one involves a tomato. ‘I would try my knives with a tomato to see if the edge is sharp enough, and a carrot to see if the geometry is good enough to slice, and not wedge, the carrot.’

Whether we’re professionals or avid home cooks, we know getting our basics in order is essential. That might be choosing the finest of ingredients, but it also covers our tools; from buying right (Rodrigo points to Tsukasa Hinoura, Naoki Mazaki and Yu Kurosaki in Japan, Murray Carter in America and Josias Zimes in South America as among his favourite knife-makers) to keeping them in good condition. As Rafael puts it: ‘A great knife ensures precision and delicacy. It will do exactly what you wish it to do, slice at exactly the right angle or dice to a fine enough quality. Your work in the kitchen will be a lot more effective if your tools are maintained to a high standard.’