Sulphur when warmed with caoutchouc combines with it, and on this fact the vulcanization of rubber depends, and also the production, with an excess of sulphur, of the hard black material known as vulcanite or ebonite.
In other cases, Leyden jars or condensers take the form of sheets of mica or micanite or ebonite partly coated with tin foil or silver leaf on both sides; or a pile of sheets of alternate tin foil and mica may be built up, the tin foil sheets having lugs projecting out first on one side and then on the other.
By introducing perforated shields of ebonite between the electrodes, so that the full current-density was only attained at the centres of the jets, these ill effects could be prevented.