Insert the specimen into the hardness tester. The exact process will vary by manufacturer, as there are many different makers of Brinell testers, but the specimen will end up held in place for the test dent to be made. Activate the tester, so that it pushes a ball made of hardened steel 10 mm in diameter into the aluminum's surface. The pressure varies by the metal under testing, but for aluminum, the pressure is a load of 1,500 kg.
Hold the ball in place for 15 seconds, and then release it.
Measure the diameter of the dent made in the aluminum using a low-magnification portable microscope.
Divide the load (in this case, 1,500) by the area of the dent. Calculate the area by multiplying the diameter by pi (3.14159) and then divide the result by two. Find the resulting Brinell hardness number that corresponds to your answer. Conversion tables are available online (see Resources).
Insert the specimen into the Rockwell hardness tester. As with the Brinell tester, there are many different manufacturers, and specific instructions will vary. When you turn on the machine, a steel ball with a diameter of 1/16 inch will move against the metal and apply a "minor" load of 10 kg.
Wait for the machine to apply the "major" load. This will happen right after the minor load and varies depending on the metal under testing. For aluminum, the same steel ball will now have a 100 kg load.
Use the difference between the first and second indentations (the depth of the penetration from the minor and major loads) to evaluate the abrasion that has taken place and to determine the hardness of that alloy. With aluminum alloys, check your reading on the "B" scale: there are several different scales that come into use, depending on the metal in question. For cast aluminum, use the "E" scale; for extracted aluminum, use the "H" scale.