A cartridge razor packs three to six blades into a pivoting head. Each blade repeats the same basic action: it catches a hair, pulls it slightly above the skin, and cuts it before it springs back. Nearly every other feature, from the fins and coatings to the lubricating strip, is there to manage the side effects of that repeated action, not to change how the razor works.
Once you understand that mechanism, cartridge marketing becomes much easier to decode, whether the promise is comfort, closeness, or protection for sensitive skin. Most additions to the razor head are designed to solve problems created by the core mechanism itself.
The Core Mechanism: Hysteresis
Cartridge razors cut by a process engineers call hysteresis. The leading blade catches the hair and draws it out of the follicle by a fraction of a millimetre before severing it. A trailing blade meets the same hair slightly lower, catching it again before it can retract fully, and cuts it lower still. Each additional blade repeats that step once more.
The result is a closer cut than a single pass could achieve, because the hair ends up severed below where it naturally sits at rest. The cost is that the severed end retracts below the skin surface once the blade has passed, which is also the mechanism behind razor bumps on skin prone to them.
Blade Angle and Independent Suspension
Each blade in a modern cartridge sits on its own small spring rather than being fixed rigidly to the frame. That suspension lets each blade flex independently as it crosses a curve in your jaw or neck, keeping the edge in contact with skin at a near-constant angle instead of skipping over high points and digging into low ones.
Suspension is also why cartridge heads pivot as a whole unit on the handle. The pivot handles large-scale contour, the individual blade springs handle small-scale contour, and together they are the reason a cartridge needs almost no conscious angle control compared with a safety razor, where you set that angle yourself on every stroke.
The Fins Ahead of the Blades
Ahead of the first blade on most cartridges sits a row of short, flexible fins, sometimes called a pretensioner. Their job is to stretch and flatten the skin slightly just before the blades reach it, mimicking the stretch a barber applies by hand before a straight-razor pass.
That stretch straightens hair that would otherwise lie at an angle and pulls the surrounding skin taut, which lets the first blade cut closer than it could on loose, unstretched skin. It is also a reason pressing a cartridge down harder backfires: extra pressure over-stretches the skin past what the fins were designed to do, and the closer cut that follows sits further below the skin’s resting position, the same problem stretching causes on a safety razor.
Blade Coating
The metal edge itself carries a coating, usually a low-friction polymer layer, applied to reduce drag as the blade moves through hair. Gillette’s product pages describe this kind of coating on their blades, and the physics behind it is straightforward: a lower-friction edge needs less force to sever the same hair, so less of that force transfers sideways into the skin around it.
Coating wears off with use, which is one reason a blade feels rougher well before it looks visibly dull. It also explains why a fresh blade in an old cartridge frame can still shave noticeably better than a worn blade in a newer one.
The Lubricating Strip
The colored strip above the blades on most cartridges is not decoration. Gillette’s own explanation of the strip describes it as a small reservoir holding water-activated polyethylene glycol polymers, which swell and spread across the skin once wet, cutting friction between blade and face for as long as the strip lasts.
Many strips also fade or change color with repeated use, giving a rough visual cue that the blades underneath have seen enough shaves to be due for replacement, since the strip and the blades usually wear out on a similar schedule.
Reading a Cartridge’s Marketing Claims
Once you know what each part does, most marketing claims on a cartridge box translate into a specific, checkable feature rather than a vague promise.
- “Advanced blade technology” almost always means the coating, sometimes paired with a thinner blade profile that needs less force to enter hair in the first place.
- “Skin guard” or “sensitive skin” branding usually points at a repositioned guard bar or fin set that cuts hair closer to skin level instead of pulling it further up before the cut, which softens the hysteresis effect without removing it.
- “FlexBall” or pivoting-head branding describes the suspension system: how far and how independently the head and individual blades can move to track your face.
- A colored strip fading with use is the lubricating strip signaling its own wear rather than a separate feature worth paying extra for.
None of these claims change the count of blades touching your skin per stroke. They change how much friction and stretch each of those contacts produces, which is a real difference and a smaller one than the marketing copy usually implies.
What Blade Count Buys You
Each additional blade is cutting hair that the blades ahead of it already lifted, so the marginal gain in closeness shrinks with every blade added, while the marginal cost in skin contact does not. Going from one blade to three buys a real, noticeable jump in closeness. Going from three to five buys a smaller one, for a proportionally larger amount of blade travelling across the same patch of skin.
That is the entire mechanical case for a single-blade format, whether a double-edge safety razor or a hybrid single-blade cartridge: one contact per stroke instead of several, at the cost of the closeness those extra contacts were buying. The safety razor vs cartridge comparison covers that trade-off directly, and best razor for sensitive skin ranks the options from gentlest to closest for skin that reacts to the extra contact.
If your skin already tolerates a multi-blade cartridge without redness or bumps, none of this mechanism is a reason to switch. It only matters once irritation shows up and you are deciding what to change next.