Airlock Not Bubbling?

HBO_StaffHBO_Staff Administrator Posts: 2,115
edited September 2020 in Welcome To The Forum
When brewing using a fermenting vessel with an airlock fitted it may not always bubble, there are several reasons why an airlock might not bubble and usually this is nothing to worry about. The airlock is there to allow any CO2 created by the fermentation process to escape if needed, many people do brew without an airlock and instead just fit the vessel lid loosely to allow any gases out and stop it building up pressure.

If you do decide to use an airlock then it should be part filled with water, the Smart Airlock and 6 chamber bubbler airlock style are by far the most popular, or the 'handy' airlock type is also available, they all work in the same way and use the water to keep air out of the vessel during fermentation.

How much or even if an airlock will bubble can be down to the rate and amount of fermentation from the brew, some brews will ferment steadily and slowly, others may be quite rapid. Fermentation varies dramatically and is determined by the temperature, the yeast used, the brew being made, etc, so this is no hard and fast rule of what to expect. The only way to tell how a brew is fermenting or when it has finished is by using a hydrometer to take readings, just going by visual checks and using the airlock as a guide is not sufficient or accurate, and you will need to allow more time to be sure it has finished fermenting before bottling.

Reasons for the airlock not bubbling include:

- A slow and steady fermentation - if a brew ferments slowly and calmly there may not be enough pressure to force any gases through the weight of the water in the airlock, sometimes a lid on a vessel will dome upwards slightly to show it is holding pressure but not actually bubble. Fermenting at a higher temperature can increase the speed of fermentation but may not create the best flavours so it always best to try to brew as near to the recommended temperature as possible.

- Too much water in the airlock - if you put a lot of water into the airlock it can make it hard for any gases created to force past the weight of the water, ideally only part fill the airlock with enough water to make a seal, and check from time to time there is enough water in it,

- The lid of the fermenting vessel not being sealed down fully - as you fit the lid into place ensure it is well pushed down all the way around with the palm of your hand. Some lids click on, but many of the newer style lids are made from a softer plastic which does not break when 'un-snapped' unlike the older hard plastic lids, the soft plastic may not make the same click but you can usually feel it fitting on to the rim of the vessel.

- The airlock stem - if the moulded stem of the airlock is rough or has any moulding imperfections on it, then it may not seal fully with the grommet or bung on the vessel lid, by checking the airlock stem and smoothing if necessary this can help it to seal.

As long as the lid is in place and the airlock fitted, you have really minimised the risk of any contamination, if there is even the smallest of pin hole gaps anywhere any gases will always find the easiest way out through the point of least resistance rather than force past the weight of the airlock, and will escape that way. As gases are created during the fermentation they will stop air entering through any tiny hole, and there is no need to worry about this, which is why many brewers don't use an airlock at all.

Even if you take all the precautions you can including sterilising and cleaning, and use an airlock, occasionally a brew can still be contaminated, sometimes due to no fault of your own. Airborne contaminants can come into contact with a brew when it is opened up and there is little that can be done about this by the home brewer, but it is rare and has to just be put down to experience. Follow the manufacturers instructions and take all the usual precautions, and in most cases your brew will turn out great with no problems.
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