Ultrasonic cleaners are cleaning devices that use ultrasound (usually from 15-400 kHz) to clean delicate items. Ultrasonic cleaners are often employed for cleaning of jewellery, lenses and other optical parts, coins, watches, dental and surgical instruments, fountain pens, industrial parts and electronic equipment. In an ultrasonic cleaner, the object to be cleaned is placed in a chamber containing a suitable ultrasound conducting fluid (an aqueous or organic solvent, depending on the application). An ultrasound generating transducer is built into the chamber, or may be lowered into the fluid. It is electronically activated to produce ultrasonic waves in the fluid. The main mechanism of cleaning action is by energy released from the creation and collapse of microscopic cavitation bubbles, which break up and lift off dirt and contaminants from the surface to be cleaned. Industrial ultrasonic cleaners are used in the automotive, sporting, printing, marine, medical, pharmaceutical, electroplating, engineering and weapons industries.