Made In England

This model 703 Rocker is a “Thin Ring” type of the Sward design. It is used for the determination of the hardness of organic coatings on the principle that the amplitude of oscillation of the rocking device decreases more rapidly the softer the surface on which the test is conducted. Its performance is sensitive to the surface condition of the coating or test piece and may be influenced by the thickness of the coating and the nature of the substrate.

It is important that the test piece is level and free from movement or vibration and the test is carried out in a controlled draught-free atmosphere by use of a cover accessory.

The leveling table with the test plate is leveled carefully and the surface of the glass test plate thoroughly cleaned. The underside rings of the rocker should be examined critically and cleaned with a suitable solvent to remove any sticky deposits.

1. The rocker is placed on the test piece and is rolled to the right until the bubble in the left hand vial is in full view.
   
2. The instrument is then released and each total appearance of the bubble in the right hand vial is counted.
   
3. The counting is stopped when the bubble is no longer seen.

The rocker is adjusted by the manufacturer before dispatch to make 50 oscillations on a standard glass plate with the period of oscillation being set at 60 ±0.5 seconds by means of the adjustable knurled nuts. A frequent check should be made on the number of oscillations the apparatus makes on the standard glass plate. It is usual to express the results obtained from the test piece as a percentage of the number of rocks made on the plate glass standard representing 100%. The change of state for rocker hardness can be monitored against time provided that the coating is smooth, free from blemishes, and its thickness controlled.