9 Best Ways on How to Test Knife Sharpness

A sharp knife in the kitchen is a quality chef tool every homeowner should have. Whether it’s a basic knife set from Bed, Bath & Beyond or a knife that cost you $100s, knives are central to cooking. A dull blade though can really kill the mood and slow your prep work down.

The kitchen knife sharpeners that you can purchase are not always reliable. If possible, use professional knife sharpening services instead. This service requires you to bringing the knife to a company, which will perform the sharpening on your behalf.

Once you get your knife sharp once again, don’t forget to keep it properly stored, to use it correctly, and to avoid anything that could damage the sharpness. Inevitably though, over time, another sharpening will be needed. It’s just a part of owning a high-quality kitchen knife.

Do you have a knife that has seen better days? Here are the nine best ways how to test knife sharpness:

1. Feel the Knife Dullness

Be careful with testing the knife sharpness this way. Some chefs will run their fingertips very, very gently over the blade’s edge. If it feels defined and distinct, they know they’ve got a sharp blade. If it feels rounded, a knife needs some sharpening. If you’re not comfortable testing knife sharpness this way, try another method.

2. The Fingernail Test

Another way on how to test knife sharpness is to tap the blade gently against your fingernail. ‘Gentle’ is the keyword. A sharp blade is going to dig in a bit. It’ll bite the nail even with a gentle tap. A kitchen knife blade that’s dull will slide or deflect off the fingernail.

Once again, if you’re uncomfortable with the fingernail test or having your fingers anywhere close to the edge of the blade, there are several other ways you can put your tool’s sharpness to the test.

3. Do a Visual Inspection

Look at the blade’s edge with a light source behind you. If you see reflections, this is a sign that areas are bent, dull, or chipped as opposed to a cutting edge which is a smooth black line.

Another way to do a visual inspection is to take a picture and enlarge it microscopically via software. This can be quite time consuming to do, however, and is unnecessary if your knife already fails a few of these other tests.

4. Do Some Food Prep

The first sign that your knife blade is dull is that it’s not cutting as well. Do some food prep. See whether your knife is slicing through vegetables, fruits, and meats like you expect it to.

If you’ve had this knife for quite some time, you probably already have an idea of how well it works. Whenever you begin to see less performance, you may want to consider a kitchen knife sharpening.

5. Use Your Knife to Cut Paper

This is a trick a lot of chefs and knife experts use. Take a piece of paper. Hold it upright with one hand. With the other, hold the knife at the top edge of the paper and slice downward.

A high-quality kitchen knife that’s sharp won’t have any trouble slicing the paper in two. If the knife tears apart the paper or slides off the edge. This is a sign that the sharpness of the blade isn’t quite where it needs to be.

6. Try the Arm Hair Test

Run the knife above your forearm along your arm. Do this just like you would if you were shaving your arm. A knife that’s at its best will actually cut through the hair. A dull blade, however, will appear as if the hairs are folding over it. This is another key sign that that your knife sharpness is failing and requires some upkeep.

7. Try Cutting A Tomato

A tomato is a fine way to test knife sharpness. If a knife isn’t sharp, when you press down on a tomato, it’s just going to smash. Any sort of delicate fruit or veggie like this is the ultimate test around whether a kitchen knife is sharp or not.

A sharp blade can slice cleaning without much force. If you find the blade’s catching on the skin or if your cuts aren’t coming out as regular as normal, get your knife sharpened.

8. Slice An Onion

A tomato isn’t the only thing your knife should be able to cut through with ease. Try an onion. A sharp knife shouldn’t have any trouble moving through the skin with ease. A dull blade will slip away from the skin. This is another great way to safely put your blade to the test without any danger.

9. Cut An Apple

An apple works the same way as an onion or a tomato. The knife should sink into the skin with minimal pressure. A sharp blade will more or less do the cutting for you. A dull blade through will require more pressure and far more care to cut through the slippery skin.

This is why dull kitchen knives are so dangerous. They require more care to use and greatly increase the likelihood of accidents in the kitchen.