Pressmen give the durometer more respect than it deserves. Even under the best circumstances in the pressroom, durometers only give approximate readings, and they may be measuring the wrong thing-the hardness and thickness of the glaze of a dirty roller, and not the hardness of the rubber.

Often, durometers aren’t used correctly and give faulty readings. Many casual tests have shown how easy it is for two different techniques to give two widely different readings on the same roller. Yet the temptation is to accept durometer readings as absolute fact because it has a face with numbers on it-it appears to be accurate and scientific.

To get readings useful for comparisons in your shop, follow these instructions.

1. Before you begin, be sure the durometer is calibrated.
2. Attach a one kilogram weight to the top of the durometer-there’s a hole in the top to receive the weight. The weight ensures that a consistent and even force is applied to the roller.
3. Take the roller out of the press. You can’t get an accurate reading on any roller (except the ductor) while it is still in the press.
4. Place the durometer on the long edge of the footer just off the center line of the top of the roller.
5. Keeping the footer in contact with the durometer, roll it forward slightly until it is in a vertical position, parallel to the center line of the roller. Do not pass the vertical. Do not rock or bounce the durometer-even the slightest motion will jiggle the delicate mechanism inside the durometer.
6. Read the durometer, left to right.

Even with this procedure, your readings will only be approximate, good enough to use as a guide but not an absolute judge of the rollers condition. Evaluate the roller in other ways too. Visually inspect the roller. Is it shiny or dull? If you run your finger lengthwise along the roller does it slide easily or skip along the surface? Ideally the surface should be dull and smooth. Your finger should not slide easily when pressure is applied.