A wine aerator is typically a small device or tool that you place into the top of a wine bottle, or is held in ones hand, and you carefully pour-through and aerate the wine. The aim of a wine aerator is to mix air into the wine as it flows through or over, increasing exposure to oxygen and causing aeration.
An aerator offers an alternative to swirling, traditional decanting and the breathing of wine. The increase in availability and varied options has been closely related to wineries around the world releasing wines much early than in the past - and some having more aggressive oak, tannins and astringent notes than would be experienced with time in the bottle. An aerator's purpose is to expand the surface area of wine, which allows the air to integrate.

 

Aerators force air to be circulated through the wine, the end result being a wine with an expanded aromatic profile and if a red, softer tannins. There are a number of different styles of wine aerators and approaches to accomplish aeration. While decanting has been around for as long as one can remember - a handy wine aerator can sometimes do the trick in minutes.
‘Injection-style’ aerators for example, are held above your glass while you pour wine through the top. As the wine flows through the aerator, it breathes as air bubbles are sent through. This type of wine aerator is appropriate for casual meals at home, where time is of the essence. But can be found in casual wine-bars and restaurants: that serve certain wines by the glass. Improving the first impression; the first sip, for the customer of a newly opened wine. Though this method has been noted by wine experts to be overly aggressive for lighter styles wines, made from varietals such as Pinot Noir or Gamay.
These ‘injection-style’ aerators look to mix the right amount of air with your wine at the precise moment: allowing your wines to breathe instantly. The wine aerator results in a better bouquet, enhanced flavour and a smoother finish. Perfect aeration in the time it takes to pour a glass, couldn't be easier. Other popular aerators include: 'Soft Aerating' pourers and 'Blade Aerating' pourers as shown in the images.
For many years ‘sieve-style’ decanters have long been used for aeration and catching any sediment. Typically these modern aerators are made from food safe-plastic or glass, and the plug-in decanter top aerators are commonly made of stainless steel. Decanter-top aerators are the longest used and the most varied in design. Variations on the metal funnel are common, as with the shapes placed in the decanter neck, pouring through creates agitation.
Some broad guidelines when to use a wine aerator: with young, bold wines - as the technique can help to soften youthful tannins. Aerating quality, vintage red wines can release deeper aromatics and complexities that may have take hours to achieve with a decanter.
Exposing wine to air does two things: triggering oxidation and evaporation. Oxidation is what makes an apple turn brown after its cut, and evaporation is when a liquid turns into vapour. Wine is made up of hundreds of compounds and with aeration; usually the volatile undesirable compounds will evaporate faster than the desirable, aromatic and desired flavour notes.
These are modern, faster ways to aerate wine. But opening a bottle and pouring a glass will also provide aeration, as will swirling your glass of wine. For more extreme aeration, decanting a wine is ideal. After a while, aerated wines begin to oxidize, and the flavours and aromas will flatten out. The more dense and concentrated a wine is, the more it will benefit from aeration and the longer it can go before beginning to tire and fade.
On the other hand, you probably don’t want to over aerate delicate aromatic wines and older, aged, more fragile red wines for long. As you can miss out on their delicate aromas and subtle nuances, plus these wines are often decanted to remove any sediment.