Dull blades and aluminium foils: What a 0.23 friction coefficient means for cutting performance

Scissors are precise tools. They work through a balance between two blades. If they stop cutting well, the issue is often at a micro-level on the cutting edge.

A common online tip suggests cutting through layers of aluminium foil to sharpen dull scissors. While this may feel effective for a short time, it does not actually restore the blade’s sharpness in a scientific sense.

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The real problem hides in small edge flaws or dull spots. Aluminium foil does not solve them. Knowing this aids smart scissors care and timely pro-sharpening for lasting sharpness.

Scissors cut by a shearing process. This means the two blades slide against each other and create high pressure at the contact point, which cuts through paper fibres. Over time, the sharp V-shaped edge becomes dull or develops tiny pits.

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The cutting edge is where the inner and outer surfaces of the blade meet at a specific angle. When this edge wears down, the blades no longer make tight contact. Research shows that most “dullness” is caused by a rounded edge and a loose pivot screw. If the screw is loose, the blades pull apart slightly, and the material slips between them instead of being cut.

The effect of the foil comes mainly from friction, which is the resistance between two surfaces. In cutting, friction affects how much force is needed. The research titled “Cutting mechanism of aluminium foil on underlays during wedge shearing process” shows that its friction coefficient is low, around 0.23. This means it works only as a very mild polishing surface. It can help remove sticky sap or debris that causes the blades to drag.

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The study titled “Sharpening and tightening surgical scissors” proves that good sharpening needs a material that grinds off damaged metal and rebuilds the edge.