Fermentation locks are commonly referred to as air locks. What these locks provide is a barrier to gasses outside of the fermentation container. There are two main types of fermentation locks that include dry fermentation locks and wet fermentation locks. Within these two categories, there are a few materials that are widely used including glass, ceramic, and plastics.

These fermenation locks offer a view into the activity of the fermentation process. For the wet fermentation locks, there is clear visibility into the gasses that are escaping. These gases will bubble the fluids as they escape. During peak fermentation bubbles will release at rates of up to 1 bubble every 1 or 2 seconds. The rate of gasses, however is not an indicator if the fermentation is going well or not....ie slower fermentation is fine. As the fermentation slows, so will the amount of cO2 production, thus escaping gases from the vessel and lock. The rate of escaping bubbles can slow to rates of a bubble every few hours or even days, so it is not a precise measurement. The yeast may still be highly active But it is a great indicator, and should be a good indicator for watching progress.

Without yeast starters, or if the temperature is not ideal for the yeast, the beginning of the fermentation cycle might be delayed slightly. Your fermentation fluids, and airlock may sit idol for days. Do not let this detour you from waiting it out, as there is something going on in there.

Wet Fermentation Locks

Wet Fermentation locks utilize water or fluids for creating a sealed barrier between the interior and exterior gasses. There are two main variations for shape which include an s-shape bubbler and 3-piece design. Both designs are attached to the carboy with the use of a cork or rubber stopper. As pressure of gasses within the fermentation vessel increase, the pressure forces the liquid in the fermentation lock outward. Based on the design, the fluids will swell around the pressure, and escape around the gas, letting out bubbles. If exterior pressure was greater than the inside pressure, the same would happen in reverse for the s-shape design.

There is some consideration of the type based on your container size and head room in the vessel. The s-shape design is more likely to clog with dried up sediment and fluids should the fermentation activity cause foaming in the container. The foam may reach the top of the container and enter into the lock. The s-shape design offers a smaller chamber, and this provides less room for circulation of the fluids. If a clog does form it could blow the lock off of the fermenter all together, allowing outside gases to enter. The s-shape is designed for smaller vessles that range from 1-5 gallons. If head room (gas above the fluid) is limited its better to go with the 3 piece design. This design has a wider chamber and will not clog as easily.

These devices range in price from very cheap to relatively cheap. The material itself should not be a concern as there should be no contact with the fermenting wort, or wine. This means that leaching of plastics is avoided and a non-issue. As long as the material is non-permeable and does not allow gases to enter the vessel, it will perform the task.
TypeMaterialPrice Range
S-Shape Fermentation LockPlastic (Unknown)$1.10 - $2.98
S-Shape Fermentation LockGlass$8.10 - $11.89
3-Piece Chamber Fermentation LockPlastic (Unknown)$0.99 - $3.10