Inert is a term that generally refers to a substance that is chemically inactive. In practice, the term is used to describe substances that do not combust or react readily with oxygen.
Common inert gases are Argon, Helium, Neon, Xenon, and Nitrogen/Carbon Dioxide*. If you remember your old periodic table, (as you should), you will remember there is a group of elements on the far right known as noble gases. The noble gases are Helium, Neon, Argon, and Xenon**.
What makes noble gases special? They have a full set of outer shell electrons that make them extremely stable. So stable, in fact, that even in the presence of elevated temperatures or light they will not react.
What does this mean? It means noble gases are so stable they do not react with other elements or molecules.
The term inert blanket refers to technology that provides a protective layer of inert gas, like a blanket, over another substance to prevent oxidation (or to prevent reactions with other substances found in the atmosphere such as nitrogen, water, and carbon dioxide). For the purposes of this article, we will mainly focus on inert blankets used to prevent oxidation.
*Nitrogen and Carbon Dioxide are not true inerts but can act as inerts in certain systems, more on this below
Why use Inert Gases? What is bad about oxidation?
Inert gases are used mainly to prevent oxidation through an inert blanket. Oxidation is a chemical reaction in which oxygen found in the air (~20% of the air is oxygen) reacts with a substance (such as the organic compounds in wine) and changes its chemical makeup. This means the product may have an undesirable acidity, flavor (if a food or beverage product), viscosity, and/or other physical properties.
It should be noted that many wines are designed to “age” through a slow (years) oxidation process by only allowing a very small amount of oxygen through the corks. This is a designed reaction that affects compounds such as the tannins in the wine, rather than undesired or side reaction such as the reaction that turns ethanol into vinegar. The specifics mechanisms are interesting and something we may cover in a future blog.
What are the best Inert Gases?
This depends on the application. The best inert gases for blanketing applications over confined products, such as wine in a bottle or vat, are denser than air. Denser than air inert gases include Argon, Carbon Dioxide*, and Xenon.
Density plays an important role to ensure adequate coverage, blanketing, of a system. Denser than air inert molecules will “sink” below the oxygen present in the air and create a true layer of protective gas. However most denser than air inert gases come at a higher cost.
A special note that although Carbon Dioxide and Nitrogen are often used as inert gases, they are not noble gases (such as Helium, Argon, and Xenon) and do not have a full set of valence electrons (which means they will not participate in a reaction because they are “happy”).
You can find detailed breakdowns below on the positives and negatives of each gas.