A pinch of pharmaceutical-grade potassium alum on a fresh shaving cut closes it in seconds. Works on any razor, any technique, any face.
The most common time you reach for styptic powder. Splash a touch of water on a fingertip, dip it in the tin, press it onto the cut for 5–10 seconds. Done.
Potassium alum is a mineral salt that constricts the small vessels at a cut site through a mild astringent action. The bleeding stops because the vessels close.
A wadded-up bit of toilet paper might stop the bleed eventually. Styptic powder closes it before you finish brushing your teeth.
Styptic pencils are the same active ingredient in stick form — they work fine, but they crack, they roll away, and they take longer to activate. Powder is faster.