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Nerdy Science in the Kitchen

Sharpening a Kitchen Knife



sharpen a kitchen knife

Above all others, the kitchen knife is the most used, abused, and overlooked of all knives.

One of the reasons for this is the sad fact that most people do not know how to properly maintain their knives.

How To Sharpen a Kitchen Knife

What follows is an explanation of kitchen knife sharpening – a dull kitchen knife is extremely hazardous, which might be contrary to instinct, but a dull knife requires greater force to use thus, can be more prone to slippage and accidents.

Learn how to sharpen your knives so you can be safe and will not have to rely on sending your knives to a professional knife sharpener.

This guide also assumes that you will be using a sharpening stone in the form of a bench stone. In other words, a whetstone.

It is also possible to sharpen your knives with a manual sharpening system, a manual pull through sharpener, or even an electric sharpener.

This guide also applies to any kitchen knife that does not have a serrated edge – so we cover, chef’s knives, paring knives, utility knives, filleting knives, boning knives, cleavers, etc… You can sharpen serrated knives with a system like the Gatco 10006, and most electric sharpeners have a honing stage that can handle a serrated knife.

Most knives found in kitchens across America are mass-produced and made of steel that is known more for durability and stain resistance than edge quality, and factory edge angle tends to be larger than the recommended 15º – 20º making them sturdy against wear and tear but making them less suited for precision cutting.

Typically, kitchen knives are sharpened to 25º on average which is a compromise that most people will not sharpen their knives often enough. If you get a premium brand of knife (Wusthof, Henkels) then the blade may be in that 15º – 20º range.

Kitchen knives are also notorious for misuse, abuse, improper storage and neglect, however, with a little TLC, your kitchen knives can be transformed by proper sharpening and honing techniques into the useful tools they were meant to be.

The best time to sharpen you kitchen knife is – now, or very soon. Do not let your knives become so worn down that it takes a major overhaul whenever you do get around to it. Between sharpening, sessions come honing, with a sharpening steel. I sharpen a knife about once a month or so – just one of them – and I use my knives every day. So, on average, each knife gets a good sharpening session about once every two to three months.

If you’re not sure how to check if your knife is sharp enough, I’ve got you covered.

How to hone a knife

That long, metal rod-like device that is in your chopping block is not a knife sharpener, though it is called a sharpening steel. It is actually a honing steel that is used to straighten the knife out after the rigors of cutting and chopping, a process that distorts the blade ever so slightly. There is more information about honing on our article about the best sharpening steel for Japanese knives.

The use of the steel between sharpenings reduces the need to actually remove metal, which occurs during the sharpening process. You should hone your knife just before using it and just after using it.

For honing between sharpenings:

• Hold the sharpening steel vertically to the counter top with the tip touching, With the knife in the other hand, move the knife from the bolster (the wide section near the handle) to the tip along the steel in one, smooth motion at a 20º angle.

• Next, move the knife blade to the opposite side of the steel and repeat – one smooth motion, straight down, bolster to tip.

• Repeat this process from one side of the steel to the other for a total of 4-6 times.

Here is a video with master knife maker Bob Kramer talking about using a honing steel.

Sharpening Using a Whetstone

Shun Combination Whetstone, 1000 and 6000 Grit, Rubber Base for Grip, Use for Sharpening and Polishing

Once a month (or two), you will want to sharpen your knives on a stone.

See the Shun Combination Whetstone at Amazon.

The frequency of sharpening depends on how much you use your knives, the angle of the blade edges, and the quality of the steel.

There are a couple of options for the stone. Again, we’re assuming you have a basic bench sharpening stone in the form of:

• A Fine and/or Medium Coarse Grit Sharpening Stone – these can be synthetic or natural (see below)

• A Diamond Stone Sharpener

• A Natural Sharpening Stone such as an Arkansas stone, (made of natural silica “novaculite” from Arkansas) or Japanese waterstones.

Additional choices can be found on the market – electric sharpeners, rotating stones, and a host of others – but, these choices are generally regarded by professionals to be the best methods.

One of the goals is to create the sharpest edge possible for the steel from which your knife is made and maintain that edge, and keep it sharp, with regular sharpening.

Some sources do not recommend the use of a lubricant (oil-based or water) on the stone but, most knife websites do.

The Buck Knives website recommends a lubricant because it keeps the pores of the sharpener clean, dissipates frictional heat and facilitates smooth sharpening action. If you choose not to use a lubricant, diamond and natural sharpeners can be used either way however, once oil is used on an Arkansas Stone, instead of water, oil must be used on the stone from that point forward because water will lose its effectiveness.

One problem common to the novice is incomplete honing of the edge bevel. Always try to match the angle of the bevel. For chef’s knives, a 20-25º angle is recommended however, some sources recommend a 15º angle.

The angle seems to be on the subjective side thus, you should choose the angle that seems best for your knife and stick with it.

Now, sharpen one side of the blade with the rough grit.

Be certain to maintain your angle in a consistent manner.

If you find it difficult to maintain the proper angle, you might want to consider purchasing a sharpening guide, a tool which will help you maintain your angle.

• repeat the procedure with the other side of the knife.

• sharpen under a bright light, angling the bevel until the bevel reflects brightly back to you. Rotate the knife back and forth maintaining an angle that consistently maintains the brightest reflection.

• stroke the knife across the stone heel to tip 10 times per side.

The Burr and Why It Is Critical

The key to getting your knife sharp, besides finding the proper angle, is ‘drawing a burr’ from each side of the knife. A burr is formed during the knife sharpening process as metal is drawn up and up over the edge of the tip of the knife.

It can also be felt on the opposite side that you are sharpening on by running your thumb, carefully, up and across the edge. Seriously – be careful!

Burr formation is necessary since it tells a story.

First, it is an indication that you are actually making progress and second, it is showing you that you are sharpening in the correct location. The burr needs show consistency from heel to tip, (there’s the “C” word again!), and if you are being consistent, you are moving metal equally on each place along the blade which aids in maintaining the profile of the knife over time.

Formation of a burr is also a sign that you are actually removing fatigued steel from the edge exposing fresh, new steel for use. So remember, find the correct angle and form a burr to successfully sharpen your knife!

After you have sharpened both sides of the knife, test for sharpness on a piece of paper or weighted string. Your dad might have taught you to “shave your arm” hair as a test, but, for obvious reasons, this is not recommended! If your knife is still dull, repeat these processes.

If your knife needs a major overhaul, you might need a medium or coarse gritstone with a grit of around 800. A fine grit, of around 8,000 or greater, will help you fine-tune your knife to a mirror-like finish but, a single stone with a grit of 1,000 and 1,200 will suffice.

After sharpening, clean your knife with soap and water, and you will be good to go!

With proper care and ‘feeding’ (no more throwing it in the sink!), your kitchen knives will be reliable, sharp, and safe for many years to come.

Read more about knife sharpeners and general knife maintenance.

Kitchen Professor author
About the Author: Bryce Heitman

Bryce is not a real professor, but he's real nerdy in the kitchen. He's been barbecuing, chopping, and generally blazing food for many decades. He thinks there's definitely a better spatula or utensil out there that hasn't been invented yet.

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