Why does a sharp knife matter?

Why does a sharp knife matter?

Posted by Shannon Dolman on

Does having a sharp knife matter?

As eloquently written in “Japanese Kitchen Knives - Essential Techniques & Recipes” by Hiromitsu Nozaki:

“Take a tomato, for example, and the act of slicing. A knife with a dull edge will not immediately pierce the skin. It can saw through the tomato, which in essence is actually crushing the flesh. A while the slice might look fine at a glance, closer inspection will reveal an ill-defined edge and a dull surface. A knife with a sharp blade, however, cuts through the fiber in a single clean stroke. The cut edge will be sharp and the surface of the tomato will be as smooth and shiny as a mirror. It's clear to the eye which slice looks tastier".

(We can see an example of sharp tomato slicing here).

Not only does the food look better it tastes better. Cut with a dull knife tomato juice escapes and the slice becomes limp. When cut with a sharp blade the tomato slices will remain firm and retain more flavour which is stored in the juice of the tomato. It behaves much like a rested steak - the maintained juice is the preservation of flavor.

Given that we understand the difference created for food presentation between a dull or sharp knife the next question what is the best way to keep our knives ready to create great dishes of food.

There are essentially three things to consider:

 - Where do we start - what blades do I buy?

 - What do we do daily?

 - What do we do periodically (every 3-6 months)

1. Where do we start - what blades do I buy?

When exploring for a new knife that will make wonderful dishes not only today, but in a week, in a month or in a year we look at two key factors - sharpness and hardness.

Sharpness can be quickly tested by dropping the knife on a carrot or a tomato. Knives with sharp edges (less than 10 degree edge on both sides for a double beveled or one side for single). Most new decent knives will pass this test.

Hardness takes us a little longer to test. A knife which is crafted with hard steel will maintain it's sharper edge for longer periods meaning that our dishes made weeks or months later maintain their beauty and flavor. If your technical you can investigate it's hardness score know as "Rockwell C scale HRC" - scores 55-65 and above mean your blade sharpness will hang around.

When looking at what creates this hardness we need to be careful. In the time of creation knives were made using wrought iron (an easy to find element as the forth most common element on earths crust). This made nice knives but they were not that hard. The next step was the introduction of carbon which, when fused together, vastly increased the hardness of the knife (adding carbon can make the knife up to 1000 times harder). The downside was that this also made knife corrosion (rust) more likely. So we had to balance things out to increase hardness without making the knives corrosives. With the finest modern blades we look for multi-layered knives where the inside is higher in carbon (0.5-2%) whilst the outside layers are iron with added chromium and valadium which bring the outside layer close to stainless.

Lets move on from hardness remembering that we want high carbon with a anti-corrosive outside layer. If we get that right the next questions is what do we daily?

What do we daily to keep our knives sharp?

When placed under a microscope we see that a knife gets bent rather than dulled. On a daily basis we can straightened the knife through the simple and quick honing. This can be done in 10-15 seconds and is well shown here.

The second question is what happens over time. As discussed above any knife that is very hard there will be some addition of carbon. The first thing we do after using the knife is wipe it down to remove any moisture. This will help ensure that corrosives is less likely to join us.

What do we do periodically (every 3-6 months) to our knives?

If our honing of the knife does not make it to sharp then it's time to introduce the stoning. Stoning is a technique or removing the bent or dented sections at the edge of the blade. If you want to become a pro you'll need to learn to stone properly and at the right angle however these days the most common approach is to speak with a sharpening guru (who has an electric stone wheel sharpener).

Hopefully this little blog is helpful and helps you make and keep your knives sharp. In turn, this should ensure everything you cut will be firmer, shinier and more delicious. Good luck!!


← Older Post Newer Post →

Leave a comment

Japanese Knives | Chef Knives

The Chef’s Best Friend - Knives for the Commercial Kitchen

The Chef’s Best Friend - Knives for the Commercial Kitchen

By Sam Flaherty

In a bustling commercial kitchen or a cozy neighborhood restaurant, knives are super important for making delicious meals. The perfect knife can help with chopping...

Read more
The Koi Carving Collection

The Koi Carving Collection

By Sam Flaherty

Carving knives have been essential tools in kitchens for centuries, tracing back to ancient civilisations. Today, we introduce The Koi Carving Collection, showcasing three exceptional...

Read more