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The Most Common Worries

Why’s My Beer Not Fermenting?

This must be one of the most common questions that gets asked when you first start out brewing. It’s understandable really, you have invested the time and money to buy the ingredients and brew the beer and the next part of the process, waiting for it to ferment is one that takes patience. So you pitch your yeast into the wort and you wait but nothing happens that day, you go to bed and get up in the morning, still no activity!

Unfortunately even the best of us me included sometime can lack patience which is ultimately what it takes. The short answer is this:

Fermentation can take anywhere between 6-8 hours or even up to 72 hours to show any visible signs.

Yes 72 hours, if it hasn’t been that long yet then wait in 95% of cases the fermentation will start after this amount of time. If nothing is happening we can start looking at what’s causing the problem.

No Fermentation Problem Solving

Ok so you have waited 72 hours and there is no visible sign whatsoever of fermentation (if it hasn’t been that long then, wait) what is going on, let start by looking at the simple thing first of all. These are of course the easiest things to solve.

  • Is The Fermenting Vessel Airtight?
    This is the simplest thing to check but it should be the first. If you are looking for signs of fermentation from an airlock bubbling, it’s not going to if the CO2 produced by the fermenting beer is escaping from a poorly fitted lid or a non sealed bucket or bung. Check these first.
  • What Temperature Is The Beer?
    Yeast work in a certain temperature range, if the fermenting vessel is in a room that is cold the yeast will have a hard time doing anything and will hibernate and sink to the bottom. Make sure your beer is sat in a location that the yeast are happiest in. This is usually around 17°C to around 24°C, but check the package to find out. Wait for the beer to warm which could take a day or so and check again.
  • Repitch More Yeast!
    If you have attempted these things to no effect. the next thing to do is to add more yeast. It could be the yeast you originally pitched was no good or that there wasn’t enough viable yeast cells for the quantity or strength of the beer being fermented.

Getting Fermentation Going Quicker

So even though there is no bubbling airlock or frothing krausen it doesn’t mean the yeast aren’t working even still 72 hours is a long time to wait and shortening this lag time should be one of your priorities. When you pitch your yeast they are undergoing certain phases, things like yeast growth rates can be helped along to aid the yeast to do their job, those things we are going to take look at now.

  • Making Sure the Wort Is Aerated
    For yeast to reproduce they need oxygen and that oxygen needs to be present in the beer before it gets pitched. The simplest way to achieve this is to shake, stir and churn it in. Right before you are about to pitch your yeast and the beer is cool and at a good temperature for the yeast to work you need to churn the air into the wort. This can be as simple as pouring the beer carefully from one sanitised vessel to another or even grabbing a sanitised jug and pouring the beer repeatedly from a height. The longer you do this the better a couple of minutes of this and you are getting more of the oxygen the yeast need into the wort.
  • Rehydrate Your Yeast!
    If you use dried brewing yeast then it’s a good idea to rehydrate it before pitching it. Usually there will be instructions on the pack, and if not I shall explain the process below. To ensure a high cell count of healthy yeast we want to rehydrate properly, first of all make sure everything you use is meticulously sanitised, this goes without saying.
    1. Put around 250 ml of boiled tap water into a sanitised measuring jug and cool to 35°C.
    2. Sprinkle your dry yeast onto the surface of the warm water, don’t worry about stirring or aerating or adding sugar. Cover with some aluminum foil and leave it for about 15 minutes.
    3. Swirl the jar to suspend the yeast, you can stir as well but swirling works just as well and doesn’t involve sanitising a spoon.
    4. Leave for another 10 minutes. It’s now ready to be pitched into your cooled, aerated wort. To do this swirl the jug to get all the yeast back into suspension and pour the whole lot in.If you are rehydrating your yeast then use it within 30 minutes of rehydrating for the best results.
  • Even Better Make A Yeast Starter!
    Whether you use dried yeast or liquid making a starter boosts yeast numbers before they even touch your wort and ensure your beer ferments a lot more healthily. Yeast starters are also important if you are making a higher gravity i.e.higher alcoholic content beer. A guide to making a yeast starter can be found here.

These things will ensure your wort is the ideal solution for the yeast to grow, reproduce and ferment those sugars in and hopefully keep the lag time between pitching to fermentation in a shorter period of time.


My beers are flat, why?

This is another pretty common question and most commonly it’s because not enough time has passed between bottling and then opening the bottles. It takes around 3-4 weeks for beers to properly bottle condition and carbonate, if it hasn’t been this long then you need to wait.

Next, is are the bottles too cold. Bottle conditioning with sugar is just the same as fermentation. If the beer is too cold the yeast won’t work so keep the bottles at around room temperature for a week or two.

Another possible cause is the amount of priming sugar you used, if it was too little it’s not going to carbonate very much, check out this carbonation article to find out just how much sugar is needed for your beer.

There is gunk, crusty bits, sludge or generally funny looking stuff floating in the fermenting beer

Fermentation is pretty disgusting to the outsider or first time brewer, it produces a lot of weird sludge and congealed looking blobs of stuff. 99.9% of the time it’s absolutely normal and is just a consequence of fermentation. Try not to worry and carry on as normal.

Is My Beer Is Infected?

One of the most common questions among new home brewers who may be unsure of how a normal fermentation looks is, “Is My Beer Infected?”.

It’s true that fermentation can look kind of weird, gross, strange and occasionally unusual but in most cases as long as you follow good sanitising practices there shouldn’t be anything to worry about.

After fermentation is complete you open up the lid of the fermenter or you peer through the glass of a demijohn and you’ll see all kinds debris and yeast rafts floating on the surface. If you’ve not made many beers before it can plant a seed of doubt, “is that normal?”, “ it didn’t look that like that last time” and before you know it you are taking pictures and posting them on homebrew forums asking “does this look infected?”.

Fermentation is a messy process it kicks up all sorts of debris and gunk that you never really see when you are sipping a pint in the pub. You ask yourself how can something that looks like that not taste bad. In time and with experience you learn that these are all normal processes. You also learn to follow your nose and trust in your taste buds.

Fermentation Looks Weird, Infected Beer Looks Weirder

It’s difficult to tell if a beer contains unwanted bacteria or yeast by the way it looks. In some cases bacteria that may have infected the beer won’t make it look any different at all, at least not in the short amount of time of a fermentation.

There are some strains of yeast and bacteria that do change the appearance of a fermenting beer though. A yeast strain called Brettanomyces and bacterias such as lactobacillus and pediococcus form something called a pellicle.

These bacteria are not harmful and are in fact used in the preservation and fermentation of food.

What’s A Pellicle?

These yeasts and bacterias form a biofilm on top of the fermenting beer. The film is called a pellicle and will form where the air meets the surface of the beer.

Pellicles can take on different appearances, such as a film on the surface of the beer which appears to contain medium sized bubbles or a web of strings all connected together like a spiders web. They can look very different from a normal fermentation but sometimes they can look pretty similar.

If a beer has got some kind of infection though it may not display any visible difference to an uninfected beer, that’s why the way a beer looks isn’t always the best indicator.

Take Samples and Then Judge

Let’s use this as a scenario, you are getting ready to bottle a beer so you open up the fermenter and there’s something unusual floating on the surface.

Before jumping to any conclusions you need to evaluate, “how does the beer smell?” if it’s fairly soon after fermentation there may be some weird smells but does it smell vinegary? eggy? generally bad?

These are the first things that you should be doing. It is worth mentioning though even if it does smell peculiar that doesn’t necessarily mean the beer is infected. Weird smells can sometimes be the result of the yeast strain for example, or the type of beer you are brewing. Occasionally fermentations just produce weird smells.

If it doesn’t smell bad then you have your first piece of evidence to put your mind at rest, the next step in evaluating the beer is to take a sample and taste it.

In most instances you will be taking a sample anyway to take a hydrometer reading, this sample can then be tasted. If you do have an infected beer you will know straight away after tasting.

Now because the beer is so young it may not taste exactly as it should to begin with but tasting at this point is your best means of evaluating the quality of the beer. If it tastes ok then you proceed to bottle the beer.

Some types of bacteria may take time to develop and manifest themselves in the beer so check the bottles after a week then after 2 weeks. If the beer does deteriorate and become undrinkable then you’ll know for sure if it’s infected. 99% of the time though you’ll find the beer will be absolutely fine and you’ll wonder why you was ever worried in the first place.

It’s important to check relatively soon after bottling if you think there may be a problem as bacteria can produce lots of excess CO2 in the bottle or keg which could end up overpressurizing the container. If the pressure builds up too much you’ll end up spraying beer everywhere when you open a bottle or the bottles will fail completely. This type of issue has the term gusher or gushing beer coined for it.

Other Off Flavours

Bad or poor tasting beer isn’t always the result of an infection, there are various points throughout the brewing process that can be the cause of unwanted flavours in your beer. Whilst it’s true that bacteria will introduce unwanted flavours there’s a whole variety of other variables that can also play a part.

Fermentation temperature, aeration and oxygen pick up, and a less than vigorous boil just to name a few can all have a large part to play in introducing unwanted flavours. These are off flavours and whilst they’re undesirable it’s not the end of the world. If you do have off flavours in your beer in the majority of cases it won’t be undrinkable. You put it down to experience and then you work on your process and technical skills so that the next beer you brew turns out better.

Going With The Flow

After it’s all said and done if you do have a bad batch of beer it isn’t the end of the world, it’s not going to make you ill and at worst you will have to dump the beer. All you will lose is the cost of your ingredients and time which isn’t all that much.

In an ideal world all your beer will taste amazing, you’ll never brew a bad beer and you will win awards for your home brew. Sometimes though things don’t always go to plan, you chalk it up to experience and you try harder on your next batch.


My home brew is ruined, should I pour it down the drain?

Wait, don’t be so hasty, there is pretty much never any reason to pour away beer unless something has gone drastically wrong. Time heals all things, and this goes for beer. You can do everything wrong when it comes to making beer but leave it be for a period of time and things rectify themselves.

It’s very rare to have a completely unsalvageable beer, even if it’s infected it can still be drinkable, don’t worry about getting sick, it’s next to impossible for pathogens to survive in beer only certain bacteria will survive and the worst that will happen is the beer will taste sour. If you do have an infected beer rack it into a fermenter and leave it for 6 months or so, come back try it, you never know what it’s going to taste like but you may find it’s genuinely nice.


Do I need a thermometer?

Yes! You cannot guess the temperature of the wort, measure it. Those of you that brew beer kits still need to check the temperature of the beer before pitching yeast so go and get one. They are cheap so go and get yourself one!

Do I need a hydrometer?

Yes! Even if you don’t necessarily care what the alcohol content is of your beer you still need to check the gravity before you bottle to ensure the fermentation is complete. Again get one! If you aren’t sure exactly how to use a hydrometer all the info you need is here.

Do I need to rack my beer into a secondary fermenting vessel?

For the most part no you don’t, you can keep the beer in the same fermenting vessel and then bottle or keg it without doing a secondary fermentation. You will get no off flavours or issues with the beer if it’s in the same vessel between 3 – 5 weeks, if it’s staying there longer think about racking it. Doing a secondary however can be useful in certain circumstances, such as brewing high alcohol beers, adding flavourings during fermentation or leaving beer in the fermenter for a long time.

Do I need to wait XX weeks before bottling my beer?

You should be waiting at the minimum 2-3 weeks before bottling or kegging your beer if you want the best results. Why rush it, the yeast need time to finish up and to flocculate to the bottom of the vessel and you end up with a better beer. Relax and don’t rush things!

Do I need to boil for 60/90 minutes?

If you are using a recipe that states that yes. The recipe will be formulated for that length of boil. The reason you are boiling for that period of time is to extract the right amount of bitterness from you hops, as well as driving off unpleasant flavour compounds we don’t want in the beer. More information on boiling your wort can be found here – Why You Need To Boil

Do I need to use brown bottles?

Brown bottles are ideal as they protect the beer better than green or clear ones. Whether they are glass or plastic browns best, they stop certain rays of light effecting the hop compounds in the beer and skunking it. Whatever you use, keeping your beer in cool, dark positions is the best practice

Common Off Flavours

If your beer has a certain taste that’s not desirable it may be you have an off flavour that has occurred at some point in the brewing process. These off flavours can range from apple to butterscotch to medicinal.

Here is an in depth guide to off flavours, how and when they occur and some possible solutions to stop them occurring when you brew next.

Can I boil grain?

This is another commonly asked question when you first break away from beer kits and start steeping some speciality grains and using malt extract. The answer is ideally no, if you a can remove them before boiling the wort you should. Boiling the grain may extract undesirable compounds and flavours. If there is a small amount of grain left in solution though it shouldn’t be a big problem.

Is liquid yeast better than dry yeast?

In short no, not really. A beer made with dry yeast tastes just as nice as a beer made with liquid yeast. The real benefits of using liquid yeasts however is the sheer variety of strains available. You can make styles of beer that you can’t really replicate with the available strains of the dry stuff.