From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Technical bulletin detailing the properties, application, and guarantees of 'Impervo' puncture-sealing liquid.
| Identifier | ExFiles\Box 77\4\ scan0128 | |
| Date | 5th July 1922 guessed | |
| FULL PARTICULARS OF "IMPERVO" The following notes which are the result of a year's tests in the United Kingdom, have been drawn up by the Head Office for the guidance of demonstrators. Summarised, the main points are effective puncture sealing while you ride, the ensurance of correct inflation with a corresponding reduction of bursts due to weakened covers, and the elimination of bursts from heat. NON-STICKY. "Impervo" is a non-sticky liquid which is inserted in the inner tubes of motor cars or cycles, and which occupies only 5% of the air space in these tubes. METHOD OF USE. To treat car tubes, the valve is dismantled and the valve stem is pushed back into the inner tube, the liquid afterwards being inserted through the stem hole by means of a funnel or by means of a grease syringe. For cycle tyres, the injection of the liquid is made direct through the valve by means of a grease syringe joined to the valve by a length of rubber tubing. PRESSURE-RESISTING PRINCIPLE. In earlier puncture-sealing liquids, the principle has been adhesion. "Impervo" is entirely different in so much as its principle is pressure-resistance. Broadly speaking, the action of "Impervo" is that as soon as a puncture has occurred and the wheel has turned, a pressure-resisting film is formed over the puncture. The higher the pressure in the tube, the more effective is the action of "Impervo". The pressure, however, should never exceed that recommended by the tyre manufacturer, or, as regards old covers, that at which the wheel was run prior to treatment with "Impervo". The pressure-resisting action of "Impervo" is very easily demonstrated with the aid of a tube not enclosed in an outer cover. As soon as the pressure is removed from an old puncture either by squeezing a portion of the tube between the fingers or by stretching apart the lips of the puncture, an air escape is induced. This escape is instantly sealed by turning round the tube. PUNCTURE GUARANTEE. "Impervo" is guaranteed to seal punctures up to one eighth of an inch, but it is found in practise that it will do so to punctures up to 1/4". Our guarantee is therefore, 50% beneath the truth. It is also found in practise that "Impervo" will seal narrow slits 1/2" long, but this cannot be guaranteed as the sealing in such cases depends on the width of the slit. | ||