How to Sharpen a Knife With a Rock

man cutting a stick with a knife outdoorsHave you ever had the pleasure of using a brand new kitchen knife to dice vegetables?

Chopping potatoes may not sound like a treat but, trust me, the revelation of how easy this is with your brand new knife will make it so fun you’ll do well not to chop off a finger amidst the excitement!

Needless to say, the experience also puts into perspective just how dull all the other knives in your drawer have become.

Sharpening knives is right up there with fire-making and irrigation as one of the skills that helped humankind take over the world. Like these other skills it has, to an extent, become a lost art as mechanised systems (or the ability to simply buy new knives) took over.

Knives are listed as one of the ten essentials for hiking for a reason. If you find yourself in a remote area with a blade as dull as your trailmate’s conversation it could cause you a major problem. Alternatively, perhaps you just want to dice potatoes efficiently in camp!

Either way, reconnecting with an ancient ability could come to your rescue. Read on to find out how to sharpen a knife with a rock!

The RockStack of stones

Some clarification first of all. The rocks we will discuss in this article are the genuine article – stones you can find in nature.

Prettily presented, perfectly square sharpening stones and whetstones are available for purchase, but wouldn’t you rather connect with your inner caveman/woman and do things the DIY way?

Perhaps you’ll have to. Even if you have a whetstone at home you’re unlikely to want to lug it around in your pack in case you need to sharpen up on the trail!

Qualities of the Stone

Andrew Thorpe of the Scout Association is one of many reputable outdoor types who recommend that you use a “porous rock, such as fine sandstone” to sharpen knives (1).

Porous rocks allow water to pass through holes and have the kind of grainy surface that can sharpen an edge of steel. As Thorpe highlights it is best to pick a fine-grained porous rock so that the holes are miniscule. Some rocks (think of volcanic rock) are way too porous to use for sharpening – they have more holes than Swiss cheese!

It’s also important that you use a rock with a smooth surface. A rough surface won’t cut it – literally.

Outdoorlife and other sources point out a handy trick for sourcing your, slightly fussy rock: head for the nearest waterway and look around.

A water-polished chunk of rock is likely to have at least one smooth, flat surface. Pick one that will fit comfortably into your hand that has something resembling a right-angle between one side of the rock and that nice flat surface.  

man sharpening a knife with whetstone

Safety Precautions

Now that you have your rock you are ready to sharpen. You are also dangerous.

Holding a rock in your hand or lap while you run a blade up and down it would score pretty high in a risk assessment. Doing this in the wilderness is even more dangerous since, as point out, a cut that might be attended to easily at Accident and Emergency could cause big problems if your nearest hospital is a couple of days’ hike away.

It is recommended that you adhere to the following safety precautions:

  • Don’t test the sharpness of your blade on your finger! We’ve all seen this in movies but, honestly, what positive outcome is there? If the blade fails to cut you’ll be annoyed at the failure of your sharpening technique. If it does cut, you’ll be cut! Test your knife on a tree branch or a piece of rope instead. Comparing how well it cuts before and after the sharpening will be a much better gauge of success than attempting self-harm.
  • Keep your fingers well out of the way! This no doubt sounds obvious but doing the obvious isn’t always easy. The sharpening rock needs to be secured and fingers are good at securing things. Try to make sure you secure them in a position on the rock that will keep them out of harm’s way if the knife slips as you sharpen.
  • Slow and steady wins the race. The best advice for knife sharpening is to take care. Knives do not need to be moved at speed to sharpen them so manoeuver the blade at a controlled pace and concentrate on the task at hand. Better that than slicing open your hand!
  • Have a well-stocked hiking first aid kit to hand in case an accident does occur. Check out this guide for more info on what a first aid kit should contain.

 Sharpening – Step by Step

Visual learners may prefer to check out this YouTube guide to sharpening knives. Those who like a visible checklist to work from could do worse than to follow the below steps:

  1. Locate a suitable rock for sharpening (see above for guidance on “The Rock”).
  2. Before beginning sharpening test your knife on a thin twig or branch to see how easily it cuts. This provides a baseline against which to measure the success of the sharpening process to follow.
  3. Wet the surface of the rock. This helps prevent the rock “clogging” with the fine grains that are produced when the steel grinds against the rock.
  4. Secure the rock so that the flat, wet face (the sharpening face) points towards the sky and your fingers are beneath the level of the sharpening face and in a location where they seem least likely to be struck if the blade slips.
  5. Place the cutting edge of one side of the blade against the sharpening face and make small circular motions, moving the blade along the rock as you go to ensure that the full length of it makes contact with the rock.
  6. Repeat the same process for the other side of the blade.
  7. Run the blade along a cloth or another dry, spongy material to clean any dust from the blade.
  8. Test the blade on the twig again. Is it sharp enough?
  9. If not repeat the sharpening process until you are satisfied.


So there you have it – a simple process for sharpening your knife that involves no expensive materials or high-level skills!

Of course, like anything, practise makes perfect. All knives and rocks are different. Some blades will be easier to hone than others so it may be worth experimenting with your knife at home before you try sharpening on the trail. Do you have the knack for an ancient art?

Just remember:

  • Use a smooth, fine-grained porous rock and wet the surface before sharpening
  • Sharpen in small, circular motions and take the recommended safety precautions to minimise the chance of injury
  • Test the blade on a twig not your finger!

Let us know in the comments section if you have any questions about the article and if you’ve had any success sharpening your own knives!