ProblemSymptomsCausesReasons and Solutions
Fermentation fails to startNo frothing on the surface of the wortWort too cold (yeast dormant)Pitching the yeast into wort that is too cold or allowed to become too cold may prevent fermentation or significantly slow down fermentation. Move the fermenter to a warmer place (18-23°C) and rouse the yeast by stirring the wort with a sterilized spoon.
No characteristic fermentation odorWort too hot (yeast stunned/killed)Pitching yeast into wort that is too hot (>35°C) or allowed to become too hot may kill or stun the yeast resulting in slow or no fermentation. Move the fermenter to a cooler place. When the wort has cooled to (18-24°C) add another sachet of yeast.
No activity through the airlockOld yeast (expired BBE date)Dried yeast has a finite life and can lose its viability with time and if exposed to the air or moisture. Always ensure the sachet of yeast is within the BBE date and not damaged (i.e. not punctured). Always store yeast sachets in a cool, dry place. Add a new sachet of yeast.
The lid and/or the airlock grommet of the fermenter are not adequately sealing or not screwed down tight enoughIf the airlock grommet and/or fermenter lid is not sealed then there will be no active bubbling through the airlock. The wort may actually be fermenting, but the CO2 gas will be escaping through the faulty seal. Fermentation can be verified by removing the fermenter lid and examining the wort.
Indicators of fermentation are: condensation inside the lid, frothing/bubbling of the surface of the wort and a ring of scum on the fermenter wall above the wort. Rectify the faulty seal. Ensure fermenter lid is screwed down tightly.
Yeast provided is a slow start varietySome yeasts for selected specialized kits are characteristically slow to start, taking a few days to become fully active. Try not to disturb the fermenter and if there is still no activity after three days add more yeast.
Forgot to add the yeastAre you sure you added the yeast?
Fermentation with a slow yeast, BRY 97 American Ale yeast can take up to 5 days to become fully active.
ProblemSymptomsCausesReasons and Solutions
Frothing through the AirlockFroth rising out of the fermenter airlockA vigorous fermentationThere is no need for concern (apart from a bit of a mess!). This is actually a good sign and indicates that that the yeast is strong and fermenting vigorously.
Overfilling of fermenterIf overfilling is the cause, drain off some of the wort. Clean and refill the airlock with water and allow the yeast to continue fermenting the brew. Frothing over can be avoided by using a larger fermenter.
You can start the process with 20% less water and add the remainder after the main fermentation. Instead of 20 pints, add 16 and top up 2 days later.
ProblemSymptomsCausesReasons and Solutions
Stuck FermentationThe beer has not reached the expected final gravity (i.e. the gravity reading has not changed over a period of 3-4 days but is still too high for bottling or barrelling).
Poor ingredients (poorly fermentable wort)Poor ingredients may result in a high proportion of complex carbohydrates relative to the proportion of simple carbohydrates (sugars) in the wort. It is much easier for yeast to ferment simple sugars. High levels of complex carbohydrates will cause the fermentation to slow down considerably once the simple sugars have been used up. It may be possible for the yeast to ferment these, but it can take a long time (several weeks). Hence, the fermentation may appear to become stuck.
This might be accompanied by no visible signs of continuing fermentation and no bubbles rising through the airlock.Insufficient yeast nutrientsInsufficient nitrogen nutrients can cause yeast to stop working. This can occur with poor ingredients and with beers that are made using very high percentages of refined sugars (e.g. ordinary household sugar). These sugars won’t contain sufficient nutrients and will have a dilution effect on the nutrients provided by the other ingredients. For kits that require additional sugar, do not use more than is stated in the kit instructions.
Old yeastAdding a yeast nutrient (available from home brew suppliers) into the brew may help to rectify the problem. Alternatively, use an all malt extract kit.
Temperature shockTemperature shock can cause yeast to stop working. If the temperature becomes too hot during the fermentation, it can kill the yeast. If it becomes too cold, it will result in a slow fermentation or no fermentation at all.
Fluctuating temperaturesThe ideal fermentation temperature is 18-23°C. Yeast does not like rapid fluctuations in temperature. Even fluctuations within this range can cause yeast to slow down or stop working. The temperature should be kept as constant as possible throughout the fermentation period.
High alcohol levelsHigh alcohol levels inhibit fermentation and eventually will kill the yeast. Alcohol is a by-product of fermentation and the level gradually increases in the wort during fermentation. Different yeast strains can survive different levels of alcohol.
Wrong strain of yeastIf the brew is a high gravity brew, then conventional ale yeasts will be inhibited by the increasing alcohol level before all the sugars have been fermented. This will result in a high final gravity reading and a very sweet tasting beer. It is important that an appropriate strain of high alcohol tolerant yeast is used for such brews. Whilst it may be tempting to ignore kit instructions and add extra sugar to increase alcohol levels, this is unwise because this will result in a high final gravity reading and will compromise the quality of the final beer. It is important that kit instructions are followed to brew the intended beer style.
It might not always be possible to re-start a stuck fermentation, but the following actions are often successful:
Ensure the temperature of the brew is 18-23°C. Gently stir the brew to rouse the yeast, using a sterilized stirrer/spoon. This action alone will often start the yeast working again.
Add a new sachet yeast to the brew. This should first be rehydrated and activated by mixing the dried yeast into a glass of pre-boiled, lukewarm water together with a teaspoon of sugar (or preferably Beer kit enhancer). This should be covered and left in a warm place until seen to be actively fermenting, before stirring into the main brew.
Use a good quality brewing yeast designed for all malt recipe brews. One selected for use with all malt recipe kits, selected to ferment out more complex sugars.
ProblemSymptomsCausesReasons and Solutions
Beer Won’t ClearBeer looks cloudy, hazy or foggyInsufficient clearing time allowedWhen beer is bottled or barrelled it will always display a degree of cloudiness caused by the millions of yeast cells in suspension. This is a good thing because the yeast is required for fermenting the priming sugar. Normally, the brew will clear once the yeast has performed the secondary fermentation (adding fizz to the beer) and has been allowed to stand undisturbed. Clearing usually takes around two weeks but can vary significantly – so be patient!
The nature of the yeast strainA brew that doesn’t clear may well still be drinkable, as this could be a chill haze rather than residual yeast. Taste it and see.
Type of beerSome strains of yeast don’t settle as completely as others. You might wish to experiment with different strains.
Excess complex carbohydrates in beer (poor ingredients)Some types of beer, by their nature aren’t meant to clear or won’t clear completely. Wheat beers are an example of this.
Contamination by wild yeasts or bacteriaIf the beer contains excessive amounts of complex carbohydrates and proteins it may not clear completely. High amounts of wheat, Oats or flakes can cause a haze but may still be perfectly drinkable.
Chill Haze (see section on Chill Haze)The use of a fining agent (available from home brew suppliers) can often aid clearing. Follow the instructions supplied.
High amount of protein in the ingredients, such as wheat beers (See section on Chill Haze)If the brew is contaminated by wild yeasts or bacteria it is unlikely to clear. It may also be undrinkable (see section: Spoiled / Infected Beer)
ProblemSymptomsCausesReasons and Solutions
Poor head retentionPoor head – beer has a flat appearancePolluted glasswarePolluted glassware is by far the most common cause. Grease, salt, soap residue and detergent etc will kill the head on the beer. The beer glass may be dirty or may not have been rinsed thoroughly after washing. Ensure glassware is spotlessly clean.
Also, if the beer is being drunk with greasy or salty food or snacks (chips, crisps, peanuts etc), the grease or salt will make its way from the food to your lips to the beer, and the head will suffer its effects.
Head does not last and fades very quicklyUnder carbonationThe beer may not be fully carbonated (see section: Under Carbonation)
Head does not formResidual sterilant or detergent in the bottles or barrelResidual sterilant or detergent in the bottles/barrel will have the same effect as polluted glassware (above). Ensure these are thoroughly rinsed with cold tap water prior to filling.
High alcohol contentBeer with a high alcohol content is usually the result of adding an excess (more than 1kg) of ordinary sugar to the wort. This has the effect of ‘thinning down’ the ‘body’ of the final beer by diluting the proteins and complex carbohydrates responsible for head retention (ordinary sugar is too pure and doesn’t contain these). If a high alcohol beer is required, it is best to use a malt extract powder instead of ordinary sugar. Malt extract will give increased body and aid head retention.
Too little protein & complex carbohydrates in the wortTo increase the head on a beer, when pouring, raise the bottle away from the glass an pour from a higher point.
ProblemSymptomsCausesReasons and Solutions
Spoiled / Infected BeerUnusual taste and smell
(e.g. vinegar, sour, wet cardboard, moldy, musty, TCP, etc)
Contamination by bacteria or wild yeasts from inadequately cleaned and sterilized brewing equipment.Cleanliness is essential!!!
It is the home brewer’s challenge to prevent contamination by spoilage organisms. A comprehensive cleaning and sanitizing regime will reduce the number of potential spoilage organisms to a minimum but never eradicate them completely.
It is essential that all brewing equipment that comes into contact with the beer is thoroughly cleaned and sterilized before use (fermenter, barrel, bottles, lids, caps, siphon tube, stirrer, thermometer, hydrometer etc). Various sterilizing and cleaning agents are available from home brew suppliers and the instructions should be carefully followed.
Scouring pads, stiff brushes etc should not be used to clean brewing equipment, particularly the fermenter. Such items will leave minute scratches on the walls, creating an ideal place for bacteria to harbor, thereby increasing the chances of the brew becoming infected. The inside of the fermenter should only be cleaned with a soft cloth, and any caked-on residues soaked off rather than scrubbed.
Once the brew has been mixed (i.e. concentrate/sugar/water) there should not be any delay in adding the yeast. The quicker the yeast starts to work, the less chance of contamination, as the yeast will compete against potential spoilage organisms. Do not use too much hot water as there will be a long delay in waiting for the wort temperature to fall before pitching the yeast. This is a critical time for potential spoilage organisms to get a foothold – the longer the delay; the more likely the brew will become infected. It is far better to get the temperature correct to start with, which should be around 18-23°C. Follow the beer kit instructions carefully.
Beer cloudy – although this isn’t always a sign of infection (see section: Beer Won’t Clear)Contamination by bacteria, wild yeasts or mold spores from the air.Avoid exposing the brew to the air. Ensure the lid is put on to the fermenter as soon as the ingredients have been dissolved and the yeast has been added. It should only be necessary to remove the lid and expose the brew when taking hydrometer readings and during bottling or barrelling. Keep windows closed when brewing. Do not leave the beer for overly extended periods in the fermenter.
A ring of scum on the inside neck of beer bottles, near the ‘beer line’.It is unfortunately still possible to experience a ‘bad brew’ even with a strict cleansing routine, as there will always be airborne bacteria and wild yeasts present when preparing, fermenting and bottling/barrelling a brew. This is just bad luck. It isn’t possible to save a bad brew so discard it.
Mold on surface of brewClean and sterilize the brewing equipment thoroughly and start again!
ProblemSymptomsCausesReasons and Solutions
Over CarbonationVery gassy and foaming beerToo much priming sugarOver carbonation is usually associated with bottled beer. It is a lesser problem with barrelled beer because barrels usually have a pressure relief valve.
The use of too much priming sugar will result in over carbonation. Measure and dispense the priming sugar carefully. For bottles use ½ level teaspoon in each bottle. For barrels use 80g (3oz).
Beer gushing when bottles are openedBeer bottled or barrelled too earlyIt is important not to bottle or barrel the beer too early, before the initial fermentation has finished. In this situation unfermented sugars are carried over into the bottle and when combined with the priming sugar, excess gas is produced. If the gas pressure is high enough glass bottles will explode (a dangerous situation which can cause injury). Always check the brew with a hydrometer to ensure fermentation is complete prior to bottling.
Very frothy or too much headPoor sterilization of bottles or barrelPoor sterilization of the bottles or barrel may allow the beer to come into contact with wild yeast, which can result in over carbonation and possibly off flavors. Ensure the bottles or barrel are thoroughly sterilized. Then thoroughly rinse with cold tap water before filling with beer.
Exploding beer bottles!Over filling of bottlesBottles should be filled to allow ½ inch (15mm) of head space.
ProblemSymptomsCausesReasons and Solutions
Under CarbonationFlat BeerForgotten to add priming sugar!

Not enough priming sugar added
Remember to add the priming sugar. Use the correct amount in the barrel or each bottle to ensure sufficient secondary fermentation. For bottles use ½ level teaspoon in each bottle. For barrels use 80g (3oz).
Poor headFaulty bottle or barrel seals. Bottle caps not tight enough. Barrel lid not screwed down tight enough.Ensure bottle caps and barrel seals are not faulty (clean, undamaged, fully seated). Ensure bottle caps are screwed or crimped down tightly. Ensure barrel lid is screwed down tightly.
Sterilizing solution remaining in bottles or barrelTraces of sterilizing solution can kill the yeast resulting in no secondary fermentation. Ensure the barrel or bottles are thoroughly rinsed with cold tap water after sterilization.
Bottles or barrel being stored at low temperature during secondary fermentation stage.Store the bottles or barrel at room temperature (18-23°C) for a few days to ensure secondary fermentation, then move them to a cooler place to encourage the yeast to settle and clear.
ProblemSymptomsCausesReasons and Solutions
Chill HazeBottled beer develops a haze or cloudiness if chilled or stored in the fridgeCold Temperatures (less than 7°C)
(resulting in the interaction of proteins and polyphenols in the beer)
Most beers will be clear at room temperature but may develop a haze when refrigerated. This is due to haze-producing proteins and polyphenols suspended in the beer. When the beer is chilled, these react and clump into tiny particles which reflect light. These particles remain in suspension and make the beer appear hazy but will disappear as the beer warms.
Chill haze doesn’t affect the taste of beer – only the appearance.
It is common with home brewers and some beer kits, particularly all malt recipe beer kits.
Allowing the bottles to warm back to room temperature will remove chill haze. Alternatively, leaving the bottles upright and undisturbed in the refrigerator for a few weeks will allow time for the protein to settle to the bottom of the bottles, and the beer may eventually clear. Commercial breweries and serious home brewers who produce fully mashed beers can eliminate this problem using various brewing techniques.
hazy appearance bothers you!
ProblemSymptomsCausesReasons and Solutions
SedimentA narrow layer of sediment at the bottom of the bottles.Yeast sedimentThis is perfectly normal for bottle conditioned beer which relies on the yeast to ferment the priming sugar and produce gas. The sediment is the result of the yeast settling out of suspension after the secondary fermentation has finished. The layer of sediment is typically 1/8 inch (3 mm).

A thick layer of sediment may indicate that the beer was bottled too early (i.e. before the primary fermentation was finished). It may also be the result of accidentally siphoning over some of the sediment from the bottom of the fermenter, which can be avoided by using a siphon trap or just being vigilant. Leaving beer on a thick layer of sediment can result in off-flavors developing during storage (see section: Unusual Taste).
ProblemSymptomsCausesReasons and Solutions
Unusual TasteThe beer has an unusual taste and/or smell.Spoilage / Infected BeerA very wide range of unusual (and unpleasant) flavors can be caused by spoilage from bacteria, molds and wild yeasts (see section: Spoiled/ Infected Beer).
There are a wide range of unusual flavors that can occur in beer.
e.g. vinegary, cheesy, sweaty, rancid, earthy, musty, rusty, ‘skunky’, rotten eggs, rotten vegetables, sour, medicinal, etc.
Exposure to lightExposure of beer to light can cause a ‘skunky’ flavor. Light has an adverse effect on the bittering components in hops, producing this off-flavor. Always use brown bottles when bottling beers, never clear or green. This usually affects particularly heavily hopped, light-colored beers, as light penetrates these more easily. Direct sunlight and fluorescent tubes are particularly bad, so, store the beer in a cool dark place to prevent this.
High fermentation temperatureHigh fermentation temperatures and fluctuations in temperature can cause off-flavours to be produced (e.g. fruity, solvent). Ensure fermentation is carried out at the correct temperature (18-23°C) and avoid fluctuations.
Fluctuations in fermentation temperatureWhen pouring home bottled beer into a glass, do this slowly and avoid disturbing the natural yeast sediment (which can give a yeasty or tangy flavor). It is best to leave ½ inch or so of beer in the bottle to prevent this from being poured into the glass.
Yeast and yeast breakdownYeast breakdown can result in off-flavors (e.g. rotten vegetables, meaty, marmite). This is a common result of leaving the beer in the fermenter for too long, sitting on that layer of dead yeast. Barrelled beer, if kept for too long can also be affected in this way. Don’t keep the beer in the fermenter after the fermentation has finished. Similarly, don’t keep barrelled beer for a long period.
Old / over aged beerThe flavor of beer will also naturally change with age. This may be beneficial for some high gravity beers and ‘barley wine’ which may improve with age, but for ordinary beers it is best to drink them within a reasonable time (not usually a problem for home brewers!).

In general, bottled beer will keep for longer periods than barrelled beer.