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How to choose the right whetstone?
Using a whetstone is considered an art, especially in Japan, where knives take pride of place. Because of the particular process involved (need to wet the stone, establish regular passes, etc.), using a stone can be frightening for those not used to it. However, once you've taken the plunge, you'll find that stone sharpening is a rarity!
Choosing a whetstone is no easy task! In view of the variety of materials and grits available, it's important to take stock before you start! By choosing the right whetstone, you'll be able to maintain your favorite knives over time, efficiently and easily!
There are many different types of stone. The stones we mainly encounter are those made of compound materials, such as corundum powder (an extremely hard material). These stones are generally recommended for knives with a high HRC (blade hardness index). The granulometry of this type of stone is made up of abrasive particles that are integrated directly into the interior. When they come into contact with water, they release a kind of sludge during sharpening. In fact, the granulometry of stones differs according to the structure of the stones and the materials used: water stones and diamond stones are not comparable!
We also come across so-called natural stones, i.e. stones made directly from natural material extracted from quarries. Arkansas stones, for example, are famous for their composition of Novaculite, a quartz found only in this region. They are used on kitchen knives as well as table knives for regular maintenance. They are extremely durable.
Finally, diamond-coated stones, whose surface is coated with diamond powder, have been available for some years. They are highly abrasive and enable you to straighten the edge of your blades in no time at all.
Your choice will be affected by several main criteria: Your knife's steel type The degree of wear of your knife Your actual use of the blade It's important to take these 3 criteria into account, as they complement each other and will help you make your choice. Don't worry, we'll go into more detail to help you :)
Knife steel type:
Not all steels are alike. In fact, depending on the brand and range of kitchen knives, the composition may vary from one to the next. Standard steels, for example, are rated at around 55 HRC. This steel has the particularity of being soft (because it contains little carbon, on average 0.4%). In short, the softer the steel, the easier it is to sharpen, but the less it will hold up over time.
If we want to move upmarket, we could approach steels with a hardness of up to 58 HRC, which is the steel we find on Wüsthof knives, highly appreciated by professionals. This level of hardness is ideal, since it's the perfect compromise between ease of sharpening and edge retention.
Next come steels that are much stiffer, because they have been enriched with carbon. This is the case, for example, with many Japanese knives. These are made from special steels, such as VG10, which is very hard. They can easily reach 61 HRC, or even 63 HRC. It's important to note, however, that the harder a steel is, the sharper it is(or at least has the potential to be, as its wire is stiffer and will hold a razor-sharp finish). However, the harder it is (i.e., the more rigid it is), the more fragile it will be in use, as it is much less flexible. You don't want to drop your Japanese knife, for example. Also, hard steels hold up much longer to sharpening, as the blade will deform much less quickly despite your use.
Here's a quick summary for a knife with a standard blade: (we mean a knife whose blade has not dulled to the point of no longer cutting through hot butter, but which has just begun to lose its edge)
Steels with low/medium HRC (we'd say 53 to 55+, up to 0.6% carbon): we can count on stones ranging from 800 to 1000, or even 3000 at the most. These grits can be used both as a finish for low HRC, or as a starter for high HRC. There is no point in going for finer grits, as these knives will not be able to withstand the subtle sharpening achieved by this type of stone for very long.
Medium HRC + steels (56 to 59, approx. 0.7% carbon): can be sharpened with medium/plus grit, in the 1000/3000 range. These stones give a real, even razor-sharp edge on some models. If you had to choose just one stone, it would be the highly versatile 1000 grit.
High HRC steels (from 60 to 62, up to 1% carbon): should be sharpened with a fine-grain stone, which will polish their surface to perfection. We can therefore count on a grit between 3000 and 8000. Once again, it's important to do this in stages, as it's more difficult to sharpen a knife with a fine grit. That's why many double-sided stones are available. The steps are progressive. What's more, these grits require a certain amount of mastery to get the results you're looking for, the advantage being that, thanks to its high grit, the stone won't damage the edge if you do it wrong (unlike with a low grit, where you risk filing the steel too much). The cutting edge is polished: these stones are ideally suited to Blue Steel and White Steel, for example.
Ultra-high HRC steels (63 HRC, with over 1% carbon): you'll need a stone with at least 8000 HRC. These stones are recommended for expert sharpeners, who will be able to really exploit their capabilities.
An important point to note: users often perform the "sheet of paper" test to see how well a knife has been sharpened. This is not very representative if you have a knife with a low HRC. In fact, to slice a sheet without difficulty, you need to achieve an ultra-polished finish, and this is only possible witha grit of at least 3000. As we have said, this kind of grit is not very useful for knives that are too soft, as the finish will not hold for long. The fact that your freshly sharpened "soft" knife can't cut a sheet of paper doesn't mean that it hasn't been sharpened properly, it's just not "designed" for such a degree of finish.
Knife wear:
Naturally, the above estimates must be qualified. We're talking here about an average, based on equal and less pronounced wear. It must therefore be admitted that a very blunt knife will require special care, as explained in the diagram above. This is why double-grain stones are so practical. They have the advantage of offering you 2 solutions in 1. One side offers a thicker grit to sharpen a duller knife more thoroughly, while the other side enables you to refine the sharpening, and remove the morfil accumulated on the blade.
By wayof comparison, a knife with a very high HRC but very dull should still be used with a coarse-grain stone (e.g. 240), as it will be more abrasive and therefore more recommended for this type of work. Then gradually move up to finer grit in stages, to finish the sharpening process smoothly.
On the other hand, a knife with a low HRC can be sharpened with a thick grit (e.g. 240 if it's very blunt), but won't need to be finished with a grit that's too high for finishing (since the fineness of the grit will have no effect on steel that's too soft, and the time spent sharpening will be far more important than the edge retention achieved).
Knife use :
If you use your knives regularly, we recommend sharpening them more often on a medium-grain stone, so as not to fall into the overly abrasive grains that remove material from your knives. If you're using a heavy-duty knife, don't hesitate to give it an even finish so that it retains all its sharpness. This will reduce the impact on your blade, leaving the edge intact. Wondering how to sharpen a knife? See our article on the subject in the tips section! We've also prepared a tutorial video to help you:
A number of other factors need to be taken into account, such as the binding agent in the stone material, the size of the stone (which needs to be adapted to those of your knives), whether or not it has a base (which facilitates the process), its degree of absorption, etc. But these characteristics are not quantifiable. But these characteristics can only be quantified with regular use. And yes, it's time to get the hang of it! :)
To conclude:
In short, to be prepared for any eventuality, you can opt for a double-grain stone, to ensure maximum efficiency for your knife. For even greater comfort, you can also opt for an additional base, or a flattening stone, designed to flatten the surface of the main stone, which can become hollow with use. A word of advice for those who use their knives very often: opt for a fairly thick stone. It may be more expensive, but you'll gain in the long run, as you'll be able to use it for longer! However, if you use it at home, a thin stone will do the trick ;)
We recommend that you always finish the sharpening by using a polishing leather, as the result will be all the more exceptional!
