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An autoclave is a device—absolutely essential for all tattoo and piercing studios without exceptions—that sterilizes tools and jewelry through a process of heated and pressurized steam. Usually this means 274 degrees at 18 PSI, although different autoclaves will use different methods.

While some people may substitute a pressure cooker for an autoclave, a pressure cooker is not properly gauged, and its moisture may damage the integrity of the autoclaving bags. This is not to say that proper sterilization does not occur, only that the cycle should be run longer than required and a spore test be taken and passed monthly to insure this. Bags allowed to dry, paper side up, will be no less structurally fine when dry than those sterilized in an autoclave. For all the trouble, it's better to just buy an autoclave—they only cost a few hundred dollars.

There are several different "types" of autoclave; gravity displacement, positive pressure displacement, and negative pressure (vacuum) displacement:

  • The autoclave at your local tattoo or piercing studio (in the US) is most likely a gravity displacement autoclave, or type "N". This design of autoclave generally has a heating element fully or partially submerged in a pool of water in the bottom of the autoclave chamber, along with a fill hole that transfers water from a reservoir to the autoclave chamber. As the water in the pool is heated it begins to evaporate, forming steam. Steam is lighter then air, as the chamber fills with steam the majority of air in the chamber is pushed to the bottom of the chamber, and escapes via the fill hole which is connected to a temperature sensitive diaphragm that closes once it is sufficiently heated. Once the diaphragm closes pressure builds up inside the autoclave chamber. The benefit of this type of autoclave is it's simplicity, the drawback with gravity displacement autoclaves is they are only designed to function properly with solid unwrapped instruments, however there has been no indication that a gravity displacement autoclave, properly loaded with properly processed instruments is unsafe for use in the modification industry.
  • A positive pressure displacement autoclave improves on the design of a gravity displacement autoclave (see above) by creating the steam in a separate internal unit, sometimes called a "steam generator". Once the amount of steam needed to displace air in the chamber is produced a valve opens and a pressurized burst of steam enters the autoclave chamber, resulting in a higher percentage of air from the chamber being removed then with a gravity displacement autoclave, this decreases autoclave cycle times. Currently the most widely distributed and used if not the only positive pressure displacement autoclave is the Statim line of autoclaves. The drawbacks to positive pressure displacement autoclaves are the high initial cost, and the fact they generally have a smaller chamber.
  • Negative pressure, or vacuum displacement autoclaves, also known as type "S", have a separate internal "steam generator", as well as a vacuum pump. After the autoclave chamber is closed the vacuum pump removes all air form the chamber, and as above, steam is injected into the chamber. Negative pressure displacement autoclaves are able to attain some of the highest sterility assurance level or SAL. Negative displacement autoclaves generally have a forced filtered air drying system that allows the autoclave packages to be throughly dries before contacting any ambient air. The drawback back to negative pressure displacement autoclaves is the cost, and sometimes the size of these systems.
  • The last "type" of steam autoclave is type "B" for Big, and the name speaks for itself. These systems are more or less enlarged negative pressure displacement autoclaves (there are enormous gravity displacement autoclaves as well, but they are still type "N", and not usually used in the medical or modification industries). The steam generator for Type "B" autoclaves is usually a separate stand alone unit, and the autoclave chamber is sometimes large enough to physically enter. Due the large scale and astronomical price tag of these autoclaves they are rarely, if ever used in the modification industry.