Argon gas in one of several gassed used to displace oxygen in a hermetically sealed enclosure. Argon is a chemical element represented by the symbol Ar. Argon has atomic number 18 and is the third element in group 1B of the periodic table noble gases. Argon is the third most common gas in the atmosphere, at 0.93%. Other gases include nitrogen and carbon dioxide. Argon’s largest use is in high-temperature industrial processes, where ordinarily non-reactive substances become reactive. For example, an argon atmosphere is used in the welding industry and in electric furnaces to prevent the electrodes from burning.
Incandescent light bulbs are filled with argon, to preserve the filaments at high temperature from oxidation. Neon lights are filled with argon provides blue light. Argon is also used for the creation of blue and green laser light.
As a preservative, argon is used to displace oxygen and moisture-containing air in packaging, to extend the shelf-lives of the packed contents. Argon used in packaging retards or prevents entirely aerial oxidation, hydrolysis, and other chemical reactions which degrade packaged products. Argon is a non-toxic gas, however, it does not satisfy the body’s need for oxygen and is thus is an asphyxiant. Argon is 25% denser than air and is considered highly dangerous in closed areas. It is also difficult to detect because it is colorless, odorless, and tasteless. In confined spaces, it is known to result in death due to asphyxiation.
As a preservative in the food industry and in art conservation, argon is used to displace oxygen in the air in a package or container, to extend the shelf-life of the contents. Argon retards or prevents entirely aerial oxidation, hydrolysis, and other chemical reactions which degrade the contents. Argon is an asphyxiant to any air-breathing living organism in the container.
Argon gas is void of humidity as supplied by a gas cylinder and must be humidified to the requirement as specified by a conservator.
Both styles of enclosures have the same sealing system, a custom-designed formed-in-place gasket. When the cover is placed on and secured it compressed the entire seal to keep the contents away from the normal atmosphere.
Each enclosure has two stainless steel one-way valves. A one-way valve is sometimes called a check valve, lets gas flow in only one direction. They are rated for a very low breaking force. Breaking force is the amount of pressure needed to open the valve and allow the flow of gas or liquid. Since Argon is heavier than air the inlet valve is lower than the exhaust valve to allow a better flushing action of the contents of the enclosure when the top (head) of the enclosure is raised slightly during the gas replacement process.
Only real glass versus a plastic glazing material will properly stop the migration of gasses and humidity into an enclosure. The basic glazing is 4.4mm or 6.4 mm laminated glass since is also affords 99% absorption of ultraviolet light. Laminated glazing also offers a great security feature over a normal glass. It will also offer protection from atmospheric changes as in air transport. Other options are available, such as anti-reflection glazing and electronically activated glass (smart glass) that has an inner layer that can be switched on or off to reduce all light.
Depending on the needs of your organization, active or passive internal monitoring devices can be installed. They can be as simple as indicator cards, or as sophisticated as laser spectrometric metering. USB data monitoring loggers can be placed in the enclosure to be directly hooked up to any computer system.
CONSERVATION EVALUATION OF CONTENTS
As with any project, individual consideration has to be taken to determine what should be done. A qualified conservator that has experience in the nature of the item(s) to be placed in a sealed enclosure should be consulted. Not only will they assist in the display concepts of the project, but also in the determination of the gas mixture to be used, monitoring requirements and possible passive absorbents.