String breakage is caused by metal fatigue, which is due to repeated stress loading and unloading of the metal in a cyclic fashion. When metals are subject to repetitive loading (stress) in this fashion, they will ultimately fail. As a guitar string cycles (vibrates) back and forth hundreds of times per second, it stresses the metal at a localized point on the string where it leaves the saddle (the witness point). This cycle of loading and unloading leads to the formation and propagation of microscopic fatigue cracks as the metal becomes increasingly brittle (Fig. 1).

Plastic deformation actually strengthens a metal as dislocations form and become tangled and it becomes increasingly difficult for the layers of atoms to slide past each other. This is called “cold working”, and the metal is said to be “work hardened”. The more you stress the metal by flexing it the quicker it will “work harden”. The side effect of work hardening, to the detriment of the guitarist, is that the metal becomes more brittle, prone to fractures, and fatigues more easily.

When a metal guitar string is plucked, bonds in the metal are stretched and the elastic deformation and subsequent stresses created are dispersed along the length of the string. Molecular bonds in the metal force the string to return to itʼs original dimensions, but a function of momentum causes the string to “overshoot” the rest point and deform in the other direction. In this way the string oscillates, with stress repeatedly loaded and unloaded, until all the energy in the string is dissipated.

The saddle contributes to metal fatigue by binding or locking the string in place which concentrates the stresses produced by vibration at the witness point. The small stress radius when the string is pinched concentrates the cyclic loading on a small portion of the string, reducing the number of cycles to failure (Fig. 6).

A string can become bound in the saddle due to molecular adhesion, burrs or v-grooves, which prevent the string from microscopically gliding

across the surface of the saddle during elastic deformation. Lateral stresses which would normally be dispersed over a broader section of the string are focussed and build at the binding point. The molecular bonds, unable to stretch, break and plastic deformation occurs, forming dislocations in the metal which make the string more brittle and prone to fatigue cracks. Over time the string is weakened until it ultimately breaks, usually upon the application of force during playing.

The nature of friction and its causes are not yet fully understood. The major cause of friction between metals appears to be the forces of attraction, known as adhesion, between the contact regions of the surfaces, which are microscopically irregular. Adhesion is attributed to the interactions of electrons in the molecules of the facing surfaces, and the distance between the molecules of the facing surfaces is a determining factor in the amount of force exerted. A surface that is smooth will hold its molecules close enough to a facing surface to produce an electromagnetic bond 

(Fig. 7).

The closer the molecules, the stronger the bond or “weld” between the surfaces. This can be easily understood if one consider two sheets of glass pressed together. Their smooth surfaces create a strong bond and are thus difficult to move in relation to each other. However, sprinkle some sand between the sheets (in effect “roughening” the surface) and the sheets are easily moved.

There is evidence that friction arises from shearing and breaking these microscopic “welded” junctions and from the action of the irregularities of one surface plowing across the other surface. The minute welds form and break as one piece slides over the other. Surprisingly, for some surfaces, the smoother they are the more friction is generated. This is because the polishing of the surfaces allows for more contact and thus molecular adhesion. This flies in the face of conventional guitar wisdom which suggests that polishing the saddles to render a smoother surface will ease the grip of the string on the saddle, when physics would suggest (assuming the absence of burrs and notches, which will also bind the string) that this could exacerbate the problem.

The challenge then is to achieve the optimum “smoothness” of the facing surfaces; smooth enough that there are no irregularities to bind together, but irregular enough to limit the molecular attraction between surfaces.

Enter the magic of Teflon®.

Polytetrafluoroethylene, or PTFE, is most commonly known by its trade name Teflon®, and is the slipperiest substance known to man. It is 500% slipperier than graphite, a material commonly used to alleviate string binding.

Teflon is a compound comprised of a chain of carbon atoms that are completely surrounded or shielded by fluorine atoms (Fig. 8).

The fluorine atoms bond very strongly to the carbon atoms and to each other, making it extremely stable and resistant to degradation. These bonds also engender the ability to “cold flow”, or change dimension when pressure is applied. Teflonʼs low friction coefficient, or “slipperiness”, results from the nature of the fluorine atoms to repel any other kind of molecule. Teflon repels virtually everything except other Teflon molecules.

The stress on a guitar string can be lessened, fatigue deferred, and breakage reduced by diffusing the stress over a larger portion of the string. String Saver saddles work by alleviating the binding grip of the saddle on the string and thus spreading the stress at the witness point over a larger portion of the string (Fig. 9).

This is accomplished using a saddle manufactured from an engineered resonant base material impregnated with Teflon. In the application of a saddle lubricant, the Teflon in the saddle forms a repellent barrier, “pushing away” the molecules of the saddle and the molecules in the string, preventing the molecular attraction and adhesion between the facing surfaces that results in string binding.

This diffuses or “dilutes” the stresses associated with elastic deformation along a greater portion of the string, lessening plastic deformation and the inherent brittleness and propensity to fatigue associated with it. Because the Teflon is impregnated throughout the entire saddle (or the String Saver insert in FerraGlide saddles), it will never dry up and the string will never run out of lubricant.

Much consideration is also afforded saddle design. How the string ramps up to the saddle, how the string sits in the groove and how the string leaves the saddle all contribute to the ease with which the string can glide over the saddle during elastic deformation.

Laboratory testing provides conclusive evidence that the combination of strategic saddle design and teflon impregnation dramatically reduces string breakage and extends string sustain. As a result, the U.S. Patent Office granted Graph Tech Guitar Labs the first patent ever awarded on a guitar sadddle designed to alleviate string breakage.

Laboratory tests designed to mimic playing mechanics yielded the following results:

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