There’s a scale called the Rockwell scale, that has several ranges, and which measure hardness. For our purposes we use the ‘C’ scale. Knives range from 52 HRC – for very cheap and crap ones – up to 64 HRC for very brittle Japanese ones. All half-decent knives will tell you their hardness, and a further sign of a knife’s quality is the range it gives you – ours (for example) are between 60.0 and 60.5 (which is very precise) while bulk manufacturers might range between 55 and 57, which is just a result of large batches being treated as averages.
But I digress.
The whole point here is that it’s all a trade off, but that there’s a sweet spot that you can only get to if you use the right steel and heat-treat it the right way, and that pretty much means doing it with (relatively) expensive steel and doing it in small batches. Which is what we do.
If the steel is too soft, then it will deform very quickly when in use (not much cop) and also won’t be able to take a really good sharpening as the edge will round off too easily. On the other hand, if the steel is too hard then it will be too brittle (there’s an almost straight-line correlation between hardness and brittleness, ameliorated slightly by the quality of the steel) and therefore will chip very easily and will be too delicate.
The other problem with hardening too much is that the only way to condition the knife after it’s been used for a bit is to sharpen it – which means to remove metal. This is both labour-intensive and difficult to do well, but also is the equivalent of taking your car in for a service every month rather than just annually, i.e. ‘sub-optimal’ as the euphemism goes.
The last thing coming in to play is the angle of the edge that’s put on the blade. All the nonsense you see where people slice through a tomato or beer can sideways with no apparent effort is because they’ve put a ridiculously thin edge on the knife. This is great as it makes it really, really sharp but (in practice) absolutely no use at all as it makes it far too fragile – the edge will chip, break, warp and snap when doing anything more labour intensive than swillbucket-rattling shots of tomato-slicing.
The obvious question – to us at least – is why are not all knives hitting the sweet spots? Mainly because it’s either not feasible given their hardening set-up (large batches are too imprecise) or they can’t afford to – a £40 knife designed to be sold via retailers is going to have about £4 worth of materials in it, whereas our steel-per-knife alone costs 10 times that. Or they’re Japanese and therefore – in our experience – most likely too brittle, for historical reasons we won’t bore you with here.
Because we approached this whole thing from first principles, we could figure out where the sweet spot is (60 HRC with an edge of angle of 15º) and then figure out how to get there, rather than just arrive at a convenient and cheap way of making knives and spending lots of money dazzling people with marketing propaganda.
So….. the whole other point about our knives is that because they’re effectively as hard as you can get before becoming overly brittle, you can condition them using a honing steel.
This is the equivalent – to continue the servicing analogy – of putting oil and water in your car. Gentle and frequent use of a honing steel will keep your knife in fantastic condition, to the extent that a home cook might only need to consider sharpening once a year.
Of course – as with all things – there are good steels, and there are bad steels.
Ours are made for us in Sheffield and are only very, very slightly harder than our blades. They are gently ridged (to create micro-serrations on the tip) and also magnetic so as to keep little bits of metal away from your food. On top of that, they have beautiful handles that are made to order in pretty much any pattern or design you care for.
People are nervous about caring for their knives. They’re bombarded by images and films of bad practice (such as television chefs going hammer and tongs) when all they need to do is buy one of our steels, follow the simple instructions and then buy a good knife sharpener, which they need to take out of the drawer probably once or twice a year. Coincidentally, the global leaders in knife testing (and the people who designed and monitor the ISO standards) produce an excellent one for £77.