What elongation tells you about a string
Updated: 3 hours ago
Strings are sold on adjectives: soft, lively, comfortable, playable. None of those words is measurable, and none lets you compare two strings other than by mood.
An elongation curve does. You tension a length of string in rising steps, record the stretch at each step, and you get a signature. The module on the Understand page plots eight strings, each characterised by its elongation curves, gauge by gauge.
What a curve tells you
Its height. At a given tension, how far the string stretches. That is real softness, and it is what orders the range from N°1 to N°7.
Its slope. How fast stretch grows as tension rises. A steep slope means the string responds strongly to a change of tension — so the stringer has room to work.
Its plateaus. The zones where raising tension changes almost nothing. Beyond those, tightening further mostly acts on the frame and on the arm.
One example: the N°4.5
In 1.30, N°4.5 stretches 9 millimetres between 15 and 20 kg over a 180-millimetre gauge length — five percentage points in one step, the steepest opening slope in the range. Then its curve flattens across four plateaus. What that means for a player: between 15 and 20 kg this string is very sensitive to the tension setting; beyond that, it barely is. Trying to firm up the bed by tightening further will give nothing.
In 1.25, its curve runs between the N°4 and the N°5 over almost the whole range — exactly what its number announces. The number is not a commercial label: it is a measured position.
What is still missing
One curve is missing from the set: the N°4.5 in 1.20. It will be recorded. Two linear densities of that same string also remain to be confirmed on the bench, and the module shows them as they are — “not recorded” — rather than interpolating a plausible figure.
A declared gap is worth more than an invented number. It is the only thing that makes the other figures credible.
What it is for, in practice
Choosing a starting tension that lands in the string's sensitive zone rather than on its plateau.
Comparing two strings on a quantity instead of on an adjective.
Knowing in advance what a change of gauge will move.
How the reading is taken
A curve is only worth its protocol, so here is ours.
A length of string is tensioned over a 180-millimetre gauge length, and tension rises in successive steps. At each step, the stretch is recorded in millimetres. Same bench, same gauge length, same operator, same sequence of steps for all eight strings: that constancy is what makes the curves overlayable, and it is the only reason one number can be compared with another.
From it follows a useful quantity: if a string stretches c millimetres per kilogram, its tensile modulus is 180 ⁄ c, in kgf. That is not a constant borrowed from a supplier, nor a coefficient fitted after the fact — it is the slope of a curve we recorded.
What a curve does not tell you
The limits are worth stating, because they are real.
It says nothing about durability. A string that stretches a great deal may break quickly or last a long time: abrasion is a different phenomenon, and it does not show on a tensile curve.
It says nothing about snapback. A string's ability to return to place after shearing across the ball depends on the friction between mains and crosses, not on its elongation.
It is taken under a slow pull. A strike lasts a few milliseconds, and a polymer is somewhat stiffer under impact. The bench establishes the order and the relative scale of the strings, not the absolute tension reached during contact — what the string bed actually does at impact is handled separately.
A curve orders the range and informs a tension choice. It does not replace three sessions of play.
See the curves
They are plotted and can be overlaid in the graph on the Understand page. And if you want the logic that orders the range first, it is in the science of strings. And if you already know where you sit, the seven numbers and the N°4.5 are available in sets and reels in the string range.
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