Press down on the the body of the tester until the red indicator rod appears (red line). Rub the coated surface of the lens with strokes of about 2.5 cm /1 inch (shorter for small lenses) for 20 complete strokes. All strokes should be made on one path. Clean the lens with acetone and inspect for deterioration of the coating. When testing extremely curved lens surfaces, the test instrument must be held perpendicularly.
Care of the Tester Instrument
The eraser is pressure fitted in the tester. Before inserting a new eraser, remove the chuck and clean the chuck and plunger threads thoroughly.
Caution: Do not push plunger without chuck in place, since this will change the spring tolerance.
Water may be used as a lubricant for the new plug. As the eraser wears, more can be exposed by holding the cap at the end of the indicating rod and turning the chuck. The tester is lubricated during assembly. If slight binding occurs after long use, a small amount of any good lubricant should be applied to the indicating rod and plunger. If the tester is used frequently, it should be returned to us for recalibration after a year or so. With normal care, and occasional spring replacement, the hardness tester will last infinitely.