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PACIFIC synthetic tennis racquet strings

Nylon strings are the mainstay of the industry, they are the most practical alternative to natural gut in that they play well, are durable, and are cost effective. Not surprisingly, while natural gut strings are our mainstay, nylons are the bulk of our product line.


Up until World War II sheep and lamb intestine were about the only practical raw materials from which to make racquet strings. The war came and unfortunately the world’s supply of natural gut was needed for a much more important product, sutures to mend wounded solders and civilians.

About this time Dr. Coruthers, a chemist who worked for DuPont, developed the first commercially viable synthetic polymer — nylon. It’s combination of strength, elasticity and durability made it a practical substitute for many natural raw materials, including natural gut in racquet strings.

Over the years nylon and other synthetic strings developed but were never a real competitor to natural gut. That all ended when Howard Head introduced the Prince racquet. For a variety of reasons they decided that the use of synthetic strings suited their needs better than gut. The rest is history.


Before we go much further it might be a good idea to make sure we are on the same wavelength. I will be using several terms, which have very specific meanings, in order to avoid confusion here is what I mean when using them.


This is the ability of a string to stretch and return to its original length. It relates to how much shock your arm will feel and how the string recovers from a shot. A rubber band is elastic, silly putty is not.

Tension loss

This defines how the string holds its physical characteristics after stringing and after play. All strings lose a significant amount of tension during the day or so after stringing. This happens because of a variety of factors including; Grommets seating, strings being straightened, strings “settling into” each other at cross points, and just plain stretching.

Strings loose tension differently, for instance Natural Gut loses it slowly and steadily until it breaks. Nylon loses it fairly quickly until a certain point where it maintains tension until it breaks. Kevlar will only lose a few pounds of tension, but does so quickly. Polyester loses tension quickly, but only during play.

No matter what the mechanism when strings reach the point where they no longer lose tension they are “dead."

Performance life

It is simply how long the string plays well and it is the most important measurement of how long a string lasts. It has absolutely nothing to do with string life (breakage).


Generally it is considered the time it takes for a string to break.

What materials are used?

Nylon (a.k.a. polyamide or specific trade names)

By far the most popular synthetic raw material it comes in many chemical forms providing a wide range of physical characteristics.

Polyester (a.k.a. Trevira or other trade names)

The same basic material that gave us those wonderful “drip dry” suits of the '60’s — it is now possibly the most popular synthetic among competitive players in Europe.


Strong, great for string breakers.


Very abrasion resistant with the potential of long performance life. Its main use in the real world is in military applications.

How are they made into strings?

They all start by being melted and forced through a small die into either water, or for very fine filaments, air. The process is very much like squeezing glue out of a hot melt gun. The melted material is pulled away from the orifice a bit faster than it is squeezed out, this combination of stretching while cooling creates a fairly consistent filament that is relatively uniform in thickness. As a general rule thinner strands are called “mono-filaments” and thinner are called “fibers".

Although there can be exceptions, this process produces filaments which are somewhat rubbery and not as strong as they can be. For this reason they go through a second step during cooling. In essence it is very similar to pre-stretching, but far more effective and reproducible.

The hot fibers are allowed to cool somewhat and then they are pulled over a series of rollers, each of which is moving a little bit faster. As a result the filament is stretched in several steps to the point where it’s optimum combination of strength and elasticity is achieved. They are rolled onto large drums, in some cases this is the final product, in others the filament moves on the further processing.

Basic string constructions

Although there are lots of variations, most of the strings on the market today fall into these broad categories, should the need arise we will be happy to discuss others in the future.


As the name implies, it is a single filament, normally with little or no coating. Generally they are very strong and inexpensive to manufacture.

Wrapped mono-filament

Here a thinner mono-filament is wrapped with a number of even thinner fibers, in one or more layers to fine tune the string’s performance. Because of the number of components in the string, two or more raw materials may be combined to further refine the playing characteristics.

It is obvious that this allows a tremendous number of possible combinations, but let’s complicate it a little more by discussing some other manufacturing variables. The outer layers can be assembled in a variety of ways of which a simple spiral wrap or a braid are the most common. To further control the dynamics of the string you can vary the number of times per inch the outer threads wrap the core.

A compromise that achieves good feel and performance life.


As a rule this construction utilizes a fairly large number of strands of the same material and diameter, twisted together. Although I don't know of any definition, it can be anything from a half dozen strands on up. Warren Bosworth showed me a string that had literally millions of fibers in it.

Multi-filament strings are considered to be the softest of the three with the most feel — and shortest performance life.

Textured strings

We make them and sell them. They do work, particularly “Gear String.” They are a challenge to string. Most Pro’s prefer thin gauges to textured surfaces.

The bottom-line, what are their pluses and minuses?


By far the most common raw material used in synthetic strings. There are so many variations that it is difficult to make generalizations.


Generally very good, they major differences come from raw materials (which define stiffness) and coatings (which define how slippery they are). Good tolerance to clamps.


Depending on material and construction these strings vary in quality and performance from a 0 to 7 or 8 (on a scale of 0 - 10).

Performance life

Using natural gut as the standard (10), good nylon is between a 4 and 7.


Measured in terms of how long it takes to wear out or break, it is very good perhaps twice or three times that of natural gut. Keep in mind that for the largest part of that time its performance is very poor.


Extremely popular among high level European players. Relatively low cost. Available in soft versions as well. Mono-filament.


Generally good, but stiffer and harder to handle. Great when pushing through tight or shared holes. Good tolerance to clamps.


On a scale of 0 - 10, about an 8.

Performance life

Using natural gut as the standard (10), between a 4 and 5.


Measured in terms of how long it takes to wear out or break, it is very good perhaps twice or three times that of natural gut. Keep in mind that for the largest part of that time its performance is very poor.


Extremely strong allowing hard hitters to use thinner strings. Very harsh feel with little shock absorption. Hard on the players body, particularly elbows and shoulders. Available in constructions which pair it with other polymers in an attempt to get the best characteristics of both.

Probably best used as a hybrid with gut or other synthetics.


Generally good. Good tolerance to clamps.


On a scale of 0 - 10, about a 5.

Performance life

Using natural gut as the standard (10), between a 3 and 4.


Measured in terms of how long it takes to wear out or break, it is very good perhaps three to five times that of natural gut. Keep in mind that for the largest part of that time its performance is very poor.


Type Stringing Performance Life Durability
Natural gut Medium 10 10 10
Nylon Good 7 - 8 4 - 7 20 - 30
Polyester Stiff 8 4 - 5 20 - 30
Kevlar Good 5 3 - 4 50
Zyex Good 8 - 9 8 - 9 20 - 30