VOCs, boosters and the evolution of the rules
An approved rubber can be modified after leaving the factory. It is enough to apply certain substances to the sponge to alter its performance, sometimes markedly. That possibility has for decades been one of the most disputed areas of the rules, and it is worth separating the two practices history has treated separately and which many players confuse.
The first is speed glue: glues with volatile organic compounds — VOCs — that the player applied shortly before playing. The solvent temporarily swelled the sponge, tensioned the topsheet and gave the assembly an increased elasticity that translated into more speed and more spin. The drawback was twofold: the effect lasted only a few hours, and the solvents were harmful to the health of players, coaches and umpires exposed session after session in enclosed halls.
In 2008, the ITTF banned glues containing VOCs. Since then, the only legal glues are water-based. The ban was accompanied by a specific control instrument — a volatile compound tester the umpire can pass over the rubber — whose operation is described in 3.6.
The second practice is boosting: the application of oils or solutions to the sponge, with the rubber removed, hours or days before playing. Unlike speed glue, a well applied boost sustains the modification for weeks or months. Both practices pursue a related effect — making the sponge work more elastically — but they use different substances, are applied differently, and have been regulated at different times.
What concerns the present-day player is the relationship between the rules and boosting. The ITTF has not banned it with the same level of detail with which it banned VOCs. The rules establish that a rubber may not be treated physically or chemically after being manufactured, but the tester applied in competition specifically detects volatile organic compounds, and most modern boosters are formulated not to contain those compounds in detectable concentrations. There is, therefore, a broad rule and a narrow control instrument that does not fully cover it. The result is a grey area: the modern boost is contrary to the spirit of the rules, but is not detectable by the usual control if it has been applied with the right products and with enough time for any residue to have dissipated.
The historical direction is clear: the rules have moved towards greater control over post-manufacture treatments. The current state is not a stable equilibrium but a truce, and any player wanting to operate safely in competition should find out the state in force at the time they are going to compete. The complete history of boosting — its physics, the substances used, the cultural difference between the Chinese and European traditions, the risks to the rubber and to health — is developed in chapter 14 and is not anticipated here.
One practical consequence connects with the above: boosting swells the sponge beyond its nominal value, which can make the covering exceed the 4.0 mm ceiling described in 3.2. In competition, that constitutes an additional infringement, independent of the treatment itself. The procedures for measurement and inspection are the business of 3.6.