3 Piece Airlock: Bubbler Fermenter

Fermentation is Sugar (malt, fructose, or sucrose) being converted to CO2 and ethanol alcohol. Firstly if this CO2 is not vented out, it will build up pressure and will cause the home brew fermenter to explode. The primary job of an airlock is to allow this CO2 to be safely vented out.

Second problem is that if oxygen or outside air is allowed in, this will react with alcohol and convert it to vinegar (acetic acid). The reason airlock is named as an lock because it should lock the outside air out.

Arishtam keeps two varieties of airlock. The traditional S Type and the modern 3 piece airlock.

Wine is fermented for the first 1 week without an airlock. Similarly most beer brewers will keep their fermenter open (without airlock) for the first 4-6 hours. This is because oxygen in the initial stages of fermentation is helpful. That being said fermenting without airlock increases the chances of oxidation. Your alocohol will turn to Vinegar.

Even for non alcoholic fermentation airlock is used. Airlock helps keep mold, bacteria and infection away. Also flies get attracted to the CO2 from fermentation. Airlock keeps them out.

• Step 1: Ensure that the fermenter is sealed airtight. If the lid is loose some food-grade packing (cling wrap, Teflon tape, or food-grade silicone sealant or food-grade adhesive) is used to seal the fermenter.
• Step 2: Create a hole in the lid of the fermenter for the airlock. Use a drilling machine or hot iron nail to achieve it. I like fermenters with a plastic lid as making a hole is easy.
• Seal the joint between the lid. You can use a cork, a grommet or a hot glue sealant for this.
• Arm the airlock by adding some water or disinfectant to it.
• Test for air leakage. Press the lid gently. If the airlock bubbles then the seal is good enough. Else you need to debug and find the leakage to be plugged.

It depends really on the stage of the fermentation, temperature, and batch size. For a typical 20 Liters batch (5 gallons) fermenting at 20 degrees:

1. It normally takes 24-48 hours for the yeast to start bubbling. This is because during the boiling of beer all the dissolved air is expelled. So a lot of CO2 generated by the yeast will be dissolved in the wort before the airlock starts bubbling.
2. Lower temperature increases the CO2 solubility and decreases the yeast action. Hence lagers take even longer to start bubbling.
3. For the first 3 days (for ales and wine) the fermentation is at its peak. The bubbling rate will be high. About 5-10 bubbles a minute.
4. Once ~30% of the fermentable sugar is converted, the bubbling rates start to fall down drastically.
5. Usually, by the end of the week, the fermentation rate drops to less than a bubble every minute.
6. In the secondary fermentation or aging the airlock rarely bubbles. Bubbling is a sign of either there is a drastic temperature change or refermentation.

Ideally, you can fill the S type airlock with water and 3 piece airlock does not need any water to arm the lock. However many brewers recommend filling the airlock with disinfectant (sanitizer, or spirit). This is because:

1. If there is a drastic temperature change, there are chances that S type airlock will start sucking back air into the fermenter. A sanitizer will ensure that microbes are not introduced in the process.
2. If the headspace is not enough, the fermenter can overflow. This causes yeast and organic material to spill out and attract flies/contaminants. A sanitizer limits the damage.
3. One big problem with fermentation is flies get attracted to the CO2 being generated. They often lay eggs in the airlock.