Traditional model
The older designs of ear-piercing gun, which came widely into use in the 1970s but are still in widespread use (e.g., "Studex Universal"[3]) employ a spring that stores potential energy when the instrument is "cocked" ready for piercing by pulling back a plunger.
The starter studs and friction clasps that are used with these instruments typically come in pairs, in sealed, sterilized packages. The studs have a pointed tip designed to pierce the earlobe rapidly when the trigger mechanism is released, and a "shoulder" to hold the clasp in place, and to maintain appropriate spacing between the clasp and the stud head, such that the earlobe is not squeezed while healing. The studs are slightly thicker, 16-gauge, and are made of surgical steel, 24 karat gold-plated steel, 14-karat gold, or titanium.
To conduct the ear piercing, the instrument is first cocked by drawing the plunger back. The piercer inserts the head of one of the pair of starter studs selected by the client into an adapter in the barrel in the body of the instrument, and the clasp is slid into the clasp retainer at the front of the instrument. The piercer then positions the client's earlobe between the point of the stud and the clasp retainer, and squeezes the instrument closed such that the tip of the stud is aligned with the mark where the piercing is to be placed, and to hold the earlobe in place during the piercing. When the alignment of the stud is correct, the piercer releases the trigger, and the force of the spring causes the instrument to fire with considerable pressure, snapping the plunger forward, pushing the point of the stud rapidly through the earlobe, and engaging it with the clasp behind the earlobe, completing the ear piercing. As necessary, the procedure is repeated to pierce the other ear.
The older designs of ear-piercing gun cannot easily be sterilized, which led to the development of more modern systems that employ single-use, disposable cartridges.[4]
Hand-pressure designs
In certain more modern designs, such as Inverness 2000 [6] and Studex System 75,[7] the instrument operates via hand pressure, whereby the piercer squeezes the instrument closed to push the stud rapidly through the ear, instead of via the force of a spring when a trigger is released. These models work with piercing studs housed in disposable, single-use cassettes, which are loaded into the instrument without the operator touching either the studs or the clasps; sufficient force to pierce the ear rapidly is attained when the stud breaks apart its plastic mount inside the cassette. The ease of operation, the greater variety of stud designs (different materials, jewels, settings, and shapes), and the relative painlessness of the piercing, and the absence of a sudden "snap" facilitated by such instruments is likely to have contributed to the widespread increase in popularity in ear piercing since the late 20th century, and in trends such as multiple piercing, piercing among both sexes and in younger children, and the abandonment of the perception of ear piercing as an ordeal.
Another design for a hand-pressure ear-piercing instrument is Coren,[8] which comprises a small U-shaped plastic holder pre-loaded with a standard 16-gauge ear-piercing stud in one arm of the device and the clasp in the other. To pierce the ear, the operator closes the instrument around the earlobe, aligning the point of the stud with the mark for the desired placement of the piercing, and squeezes a plastic plunger with sufficient pressure to break two plastic flanges on either side of the plunger, forcing the stud rapidly through the earlobe, and engaging the stud with the clasp behind the earlobe. The used instrument is then discarded.