Sharpening a knife on a stone

An edge is the line where two ground surfaces meet. The finer that line, the less force a cut needs. With use, the fine edge rolls over, gets small dents or becomes rounded. Sharpening means removing metal evenly on both sides until the surfaces meet cleanly in a line again.

A sharpening stone contains hard, sharp-edged grains. A coarse grit removes a lot quickly and leaves scratches; a fine grit removes little and polishes. That is why you work from coarse to fine. Many stones have two sides for this.

The burr is the most important signal while sharpening. When the ground surface reaches right to the edge, the metal there becomes so thin that it bends over to the other side. You can feel this tiny wire of metal with a fingertip when you stroke across the edge. Only when the burr can be felt along the whole length is that side done.

A consistent angle matters more than a specific number of degrees. If you change the angle a little with every stroke, you round the edge instead of sharpening it. Many outdoor knives are ground at roughly 15 to 25 degrees per side, but it is best to find the angle the blade already has and hold it. The manufacturer's information takes precedence.

Knives with a flat Scandinavian grind, the "Scandi grind", are especially easy: the wide bevel lies flat on the stone and guides you by itself. With other grinds it helps to colour the edge with a felt-tip pen. After a few strokes you can see where the stone has removed the colour and adjust your angle.

Little pressure, even strokes and covering the whole length from heel to tip – those are the three habits that make the difference. Count your strokes so that both sides get about the same amount.

The stone must lie firmly. A damp cloth or a holder underneath stops it from slipping – a slipping stone easily leads to cuts. The fingers of the guiding hand lie flat on the blade and stay behind the edge.

Feel for the burr only across the edge, from the middle of the blade towards the edge, never along it. Do not test sharpness with your finger either, but by slicing a sheet of paper. After sharpening the knife is noticeably sharper: work deliberately slowly the first time you use it and follow the basic rules of knife safety.

To start with, a combination stone with a coarse and a fine side is enough. Some stones are used with water, others with oil, and some dry – follow the manufacturer's instructions and do not mix them. For the trail there are small pocket stones or diamond files.

A leather strop removes the last fine burr at the end and polishes the edge. You pull the blade over the leather spine first so that the edge does not cut into it. After work, wipe the blade and stone and let the stone dry.

This method does not suit serrated blades, which need special sharpeners, or blades with large chips – take those to a professional. Without experience, power grinders can easily overheat a blade and spoil the steel.

Practise first on a simple, cheap knife rather than straight away on your best one. Set up a calm place with good light so that you can see the bevel and the burr clearly. After the first few strokes, look at the ground surface: an even stripe shows an even angle.

Touching up regularly is much easier than rescuing a completely dull knife. A few strokes on the fine stone after each longer carving session keep the edge in shape. Over time you will feel while carving when the blade starts to fade – that is the right moment.