Hermetic seal

A hermetic seal is a seal which, for practical purposes, is considered airtight. The term is often used to describe electronic parts that are designed and intended to secure against the entry of microorganisms and other foreign bodies in order to maintain the proper functioning and reliability of their contents.

Etymology and history

The word hermetic comes from the syncretism of the Greek god Hermes and the Egyptian Thoth; this figure was also a mythological alchemist known as Hermes Trismegistus. The latter has two books attributed to him, the Emerald Tablet and the Corpus Hermeticum. He was believed to possess a magic ability to seal treasure chests so that nothing could access their contents.

Alchemists also frequently used distillation in their experiments, and needed an airtight seal to improve the efficiency of their alembic stills. Most alchemists, though, were considered to be Hermetics for adopting the philosophy of the Emerald Tablet or the Corpus Hermeticum.

In the 17th century, English writers began using the adjective hermetic to refer to things that were sealed or secret. An early "hermetically sealed" container featured in the dramatic demonstration of the force of air pressure in creating a hermetic seal in 1663, when for the enlightenment and entertainment of the court of Friedrich Wilhelm I of Brandenburg, Otto von Guericke joined two copper hemispheres (Magdeburg hemispheres) and pumped the air out of the enclosure. Then he harnessed a team of eight horses to each hemisphere and showed that they were not able to separate them.^{[citation needed]}

Examples and applications

Applications for hermetic sealing include semiconductor electronics, thermostats, optical devices, and switches. The food, chemical, and pharmaceutical industries all have applications for the use of such "airtight" packaging, such as glass, metals, and high barrier plastics (with effective heat seals). Tin cans are hermetically sealed.

High-end coffins / caskets are often made to be "hermetically sealed" and must be of metal or of other material with metal lining, and constructed so that when closed and fastened the coffin is completely airtight.

In some nuclear reactor designs, the reactor is housed in a hermetically sealed reactor vessel.

Of interest

In 1951, The U.S. Constitution, U.S. Declaration of Independence and U.S. Bill of Rights were hermetically sealed with helium gas in glass cases housed in the U.S. National Archives in Washington, DC. In 2003, they were moved to new glass cases hermetically sealed with argon.^[1]

External links

• Hermetic Sealing with Laser Technology

See also

• Heat sealer
• Hermetic storage
• Packaging
• Permeation

Notes