Thinning

Thinning (セニング)

Quick look

What it is: Reducing bulk and density using toothed scissors (thinning shears or blending shears)
Also called: Sening (セニング) in Japanese salon terminology
Key requirement: Choosing the right tooth count for the desired cut rate
Tool: Thinning shears with specific tooth profiles

Why it matters

Thinning is the primary method for removing bulk without changing shape. A well-executed thinning pass takes out interior weight while preserving the outline. Done poorly, it creates holes, shelf lines, and that dreaded “moth-eaten” look. The difference comes down to tooth count, tooth design, and placement.

The tooth count directly controls how much hair gets cut per close. Here’s the general breakdown:

Tooth count	Cut rate	Best for
38 to 46 teeth	5 to 15%	Subtle blending, fine hair, finishing
30 to 35 teeth	15 to 25%	General bulk removal, medium density
10 to 15 teeth	40 to 70%	Aggressive weight removal, very thick hair, chunking

These ranges vary by manufacturer. A 30-tooth shear from one maker may cut differently than a 30-tooth from another because of differences in tooth spacing, tooth width, and whether the teeth are flat or curved.

Recommended scissors

Feature	Recommendation
Type	Thinning shears (one toothed blade, one straight blade) or blending shears (both blades toothed)
Tooth count	Match to your most common need (see table above)
Tooth profile	See tooth tip profiles for V-shaped vs. U-shaped vs. flat options
Size	5.5 to 6.5 inch

Technique notes

Placement is where most mistakes happen. Never thin the hairline, the part line, or the top surface layer. These areas reveal thinning marks immediately. Work in the interior of sections, roughly 2 to 4 inches from the root for mid-length hair.

Close the shears once per section, then release. Don’t “chatter” (rapidly opening and closing) in the same spot. Each closure removes a percentage of hair from that exact location. Multiple closures stack and create gaps.

For fine or damaged hair, use high tooth counts (38+) that remove minimal hair per pass. You can always make another pass. For coarse, dense hair, lower tooth counts work faster and produce more visible texture.

Japanese thinning technique often involves “sening” (セニング) in specific geometric patterns across the head. The pattern controls where weight lives in the finished shape. This systematic approach produces more predictable results than random thinning.

Related guide: Tool Mastery: Thinning Cut Rates