Cutting system
Foil heads
A thin perforated sheet held over a cutter that travels side to side underneath it. The sheet is the working surface: it holds skin away from the cutter and decides which hair gets presented to it. A foil head is flat by design, and that single fact explains both the straight edge it can produce and the trouble it has under a jaw.
Cross-section, not to scale
The mechanism
How it cuts
- A metal sheet full of small holes sits over one or more cutters that oscillate rapidly beneath it.
- Hair enters a hole, is held there by the edge of the sheet, and is cut level with the underside.
- The sheet keeps skin at a fixed distance from the moving parts, so closeness is a property of the sheet rather than of pressure.
- The motion is a straight stroke, generally across the direction the hair lies in.
What follows for a face
Consequences
- A flat panel of cheek
- Where the surface can be pulled taut with the free hand, the sheet sits flush and every hole is doing work. This is the situation the whole arrangement was designed around.
- An edge you want to see
- A flat sheet with a straight border leaves a straighter line than a round cap can, which is why most of these appliances also carry a pop-up trimmer for the last millimeter of it.
- Under the jaw and around the chin
- A flat sheet on a compound curve makes contact at one edge and floats at the other, so half the head is working and the rest is being carried.
- A first shave with lather
- Lather makes the sheet slide where it used to drag, and the hand raises pressure without deciding to. The same appliance can feel unfamiliar on its first wet pass.
Zones it suits
Keeping it working
- The sheet is thin, and it is thin on purpose. A dropped appliance that lands on its head is often finished even when nothing looks bent.
- Sheet and cutter wear as a pair, and the maker names the replacement pair in the documentation. That name is the whole of what fits.
- Rinse in the direction the holes run rather than scrubbing across them, and let it dry open before it goes anywhere near a charger.
Common errors
Scrubbing the sheet clean
The perforated surface is thinner than a sheet of paper, and a brush pushed across it deforms the holes it is meant to clear.
Tap the debris out, rinse if the listing says the head may be rinsed, and leave the brush for the cutter.
Working the same patch repeatedly
Each pass takes the hair a little lower and takes some skin with it, and the result reads as irritation rather than closeness.
Cover the area once, look, and only return to what is genuinely still standing.
Chasing a curve with a flat head
One edge of the sheet digs in while the rest lifts away, so pressure concentrates on a line of skin instead of spreading over a surface.
Change the angle of the appliance and stretch the skin with the other hand, rather than pressing harder.
Cautions
- StopTwo things mean stopping rather than taking one more pass. Skin that is broken, raised, sore or already inflamed, which is a doctor’s call and not something to draw a blade across. And a line so far out of true that a shorter setting only chases it, which is a barber’s. Neither of them improves by carrying on.
- NoteReplacement foils, cutters and heads come from the list printed in the appliance’s own documentation. A part that seats is not the same as a part the maker names.
- StopA shaver or a trimmer belongs to one person. Shaving injures skin at a scale too small to notice, and whatever sits on the blade goes into that injury.
Where to look next
- Foil Shavers
The appliances built this way, from a five-sheet head down to one small enough for a bag.
- Rotary heads
The system that solves the curve problem and gives up the straight line to do it.
- Wet and dry use
Why the first lathered pass with one of these feels like a different appliance entirely.
- Sideburns and temples
The area where a straight border on the head is the point of the whole exercise.