Part 1, Using a whetstone.
When presenting classes at the Cookschool the classic question was How to Sharpen a Knife? This question would just about come up on every class. So, lets explain how to tackle the subject, its simpler than it looks, but need a little practice to get perfect. This is a lot of information but don’t be put off we are going to tackle this in nice easy steps.
I have broken this down into two posts, the first on periodic maintenance sharpening. And the second on using a sharpening steel. Once you have mastered these pages move on to Part 2 of the guide. Make a point of reading the whole article first, then return back to the sharpening section when you are ready to give it a go.
If your new to the kitchen and want to expand your skills look up the Food Files page on The Cutting Edge, The Knives to Choose and Use. This will explain the best types of knives to buy and what their functions are. To a chef their knives are the most important tools they have and need to be cared for.
Why do we need to Sharpen a Knife?
The first thing to understand is that a sharp knife performs better and most of all is safer. But surely a sharp knife will cut you deeper that a blunt one? Well yes, but the whole idea is not to cut yourself at all.
Shortly I will put together an instructional page on how to use a knife properly and safely. The key to safe knife usage is to use the correct knife for the job and learning how to move the knife letting the edge do the job. Most people will use pressure to cut, and this is how most accidents happen. Putting force behind a knife allows it to do what is wants, often slipping into your body.
There are several kitchen gadgets now available to keep your knives sharp.
Some are better than others but learning how to do the job properly for each knife will protect your investment. And good knives will improve your kitchen skills and safety.
Blunt knives encourage more force to be used, vasty increasing the chance of an accident.
What is a blunt knife?
When the knife is manufactured, the cutting edge is ground into the blade. The angle of this cutting edge depends on the knife and the uses it will be put to. Most knives will have a basic angle where the steel is reduced in thickness. This is then finished with the cutting edge of the correct angle.
Top quality knifes are constructed from very hard steel which will hold an edge well and cut smoothly. Knives made from cheaper steel are easier to sharpen. But will blunt quickly requiring more grinding as thus wearing out quickly.
It’s all about angles.
For cooks knives where heavier repetitive chopping will be the main function and the angle of the edge will be about 20˚. As the knife is used the fine edge on the blade of the knife will damaged. Ether forced over to one side, chipped or just eroded. Any damage will increase the resistance of the blade through the food. This resistance will cause extra pressure to be used and, in some circumstances, spoil the cutting action. Try chopping fresh herbs with a blunt knife. They will be wet, and crushed, not cut cleanly as they should be.
How do I know if my knife needs sharpening?
In most cases you can feel that the edge is not slicing as cleanly as it should. If you’re not sure theses one trick you can use to make a judgement.
Take a tomato and draw the blade over the skin as if you were removing a slice. A sharp knife will slice through the skin whereas a blunt knife will slide off the side of the fruit. If this happens, your knife needs to be sharpened.
How to Sharpen a Knife.
Sharpening takes on two forms, Honing and Sharpening.
Sharpening takes on two forms, Honing and Sharpening.
Honing, this is where the Cutting Edge has been eroded and needs to be replaced. This is done by grinding the blade on a Whetstone to return the blade to the angle required. This should only be done when needed or the life of the knife will be greatly diminished.
How to Sharpen a Knife on a Whetstone.
Tip. Run a felt tip pen down the ground edge of the knife before you start to sharpen it.
As you sharpen the ink will be removed allowing you to where you have sharpened and where you have missed. It will also let you check the angle you are using is correct.
How to Sharpen a Knife, before you start.
Before use the whetstone needs to be soaked in water for 15-20 minutes before use. Have a bowl of water handy to moisten the stone if it dries out during use. The water lubricates the surface of the stone giving a smoother sharping action.
Make sure you have the correct grade of stone, and it has been well soaked. Take hold of the knife and place it on the stone with the blade facing away from you at about 40º to the stone.
Feel the pressure!
Its important to use the right amount of downward pressure when running the knife across the whetstone. Between 2 -2.5kg of pressure is about right. The simplest way of gauging how hart to press is to use your kitchen scales. Place your knife on the scales and turn them on. With the scales zeroed place three fingers on the blade of the knife and press down. Keep an eye on the display and this will tell you when you have the correct amount of pressure applied to the blade. You can now transfer the knife to the stone ready to grind
1st side.
Find the angle you need use (see below). Some manufactures supply a clip which fits onto the back of the blade and holds the knife at the correct angle on the stone. Failing that try wedging some coins under the blade to help you get the hang of it. Once you have the feel of the angle remove the coins and you’re good to go.
Draw the knife backwards towards you on the stone running from one end of the knife to the other. Don’t press down on the knife as you push froward but apply steady pressure as you pull the blade towards you. As the blade moves towards you
Its essential that all the blade is drawn over the stone as the knife is moved across the stone or steps will be formed on the cutting edge.
I would suggest you start with four of five cycles to begin with then more on to a new part of the blade. Repeat this until all the first side of the blade has been ground.
If all this is new to you, practice the movement with an old wooden spoon. When you think you have mastered it always start with an old knife to improve your skills, before attacking your best knives.
2nd side.
Now turn the knife over so the blade is facing towards you, this is a bit trickier.
Repeat the grinding process except this time apply pressure as you push the knife away from you. Don’t press down as it returns towards you.
Have a look at the edge and if you’re not happy give it a little more work. If you have been replacing the edge with a coarse stone, it’s a good idea to turn the stone over to a finer grade and give each side a pass over the stone to polish the edge.
Once you’re done Give the knife a good wash and clean the stone (see below). Leave the stone until bone dry before storing for next time.
ONE TIP. Only one person in the house should be responsible for sharpening. If everybody is having a go then will use slightly differing angles which will spoil the edge on the blade. In a professional kitchen, if you were to borrow a knife from somebody you would never sharpen it yourself. You would hand it back for them to do the sharpening.
Know your angles.
Grinding the blade at the correct angle lengthens the life of the knife and allows the blade to function correctly. You don’t have to be spot on but be as consistent as possible each time the knife is sharpened.
The sharpening angle is the angle at which the blade is presented to the sharpening tool. The inclusive angle is what you would see if you took a cross section across the blade.
Heavy duty Cooks knives 20º-25º
Light duty cooks knives and slicing knives 15º-20º
Japanese style thin blade knives 15º+
Sharpening angle = 15˚
Caring for your whetstone.
When you are finished sharpening rinse the stone under running water. If you have been sharpening quite a bit a paste will have built up on the surface of the stone. This can block the pours of the stone and reduce its effect. An old toothbrush is ideal for removing this and returning the surface to new. If It’s a really old stone, you have liberated from the shed, some WD40 can help remove the paste.
Leave the stone to dry overnight and when completely dry rub the stone with a just a little oil.
You can get special oil for the stones, but if you can’t find it baby oil works well. Don’t use vegetable oil or it will goo up the surface of the stone.
After quite a bit of use the surface of the stone may become misshapen. You can buy a stone shaper to grind away the highpoints and return the flat surface
What is a Whetstone?
A Whetstone is simply a sharpening stone. The ‘whet’ part of the name does not indicate water, it is a term meaning to sharpen. Think of the saying to whet (sharpen) your appetite
Most of the stones we use in a kitchen are lubricated with water but there are also stones which are lubricated with oil. If you already have a stone check to see if it’s a water or oil stone.
Why are Whetstones numbered?
Whetstones come in different grades, and many have two sides, one coarse and one fine. The higher the grit number the rougher the stone and its action on the knife. A 400 grit stone is ideal if you need to replace the cutting edge. A 1000 to 2000 git stone is ideal for finishing the sharpening or putting a polish on small thin bladed vegetable knives.
Always start with the coarser grit stone to establish an edge moving on to the finer grit stones to perfect the edge.
Caring for your whetstone.
When you are finished sharpening rinse the stone under running water. If you have been sharpening quite a bit a paste will have built up on the surface of the stone. This can block the pours of the stone and reduce its effect. An old toothbrush is ideal for removing this and returning the surface to new. If It’s a really old stone, you have liberated from the shed, some WD40 can help remove the paste. Leave the stone to dry overnight and store when completely dry.
Learning Daily Sharpening.
Well, that’s enough to get you started. When you have mastered the Whetstone move on to Part 2 of this guide, using a Sharpening Steel Correctly. Don’t hurry it, with practice you will be able to keep a good edge on the blade and work more accurately and safely.
Enjoy Life !
John.
©John Webber. 2023