It's important to keep your knife sharp for precision cutting but also because a dull knife causes lack of control, making it much easier to cut yourself.
Sharpening can be done about once a month or once every few months, depending on how much you use your knife. Once you get used to doing it, it should only take about 10 minutes.
For the demonstration in the video we're using a waterstone that I have soaked for about 20 minutes before sharpening in order to soften it a little.
It is useful to have a stone with two sides, each with a different grit. One is a rougher surface for starting to hone the edge and the other is a denser surface for refining. A good combination is a 1000 grit (rougher)/4000 grit (smoother).
The technique demonstrated is different from what many chefs use, which is sweeping the blade across the stone in one swipe. This alternative technique is easiest for maintaining an even angle with your knife. It's very important to have this consistent angle to make sure you sharpen the bevel (the two angles that make up the edge of your knife) evenly.
Divide your chef’s knife into thirds visually. You will sharpen it a piece at a time starting with the tip.
Set the knife angle on the stone at about 20 degrees — imagine the knife resting on a penny.
The hand that is on the knife handle controls the angle of the blade and holds it steady.
The hand that is on the blade (over the stone) controls the sliding motion.
You’re going to move the blade up/down along the stone 10 times for each section (tip, middle and back of the blade).
Turn the knife over and do the same on the other side counting down from 10.
You can lubricate the stone with some water between sides.
Then do the whole process again, working your way down to nine times, then eight times, etc., for each section. You may not need to go all the way down to one. It depends how dull your knife is,
Then turn your stone over and do the same thing on the refining side to smooth the edge.
When you’re finished, remember to wipe your knife of any steel particles.