The surfaces to be etched should be smoothed by filing,
machining, or grinding on metallographic papers. With
different alloys and tempers, the etching period will vary
from a few seconds to several minutes, and should be continued
until the desired contrast is obtained. As a protection
from the fumes liberated during the etching process, this
work should be done under a hood. After etching, the specimens
should be thoroughly rinsed and then dried with a
blast of warm air. Coating the surface with a thin clear lacquer
will preserve the appearance.