Section 4 – Recipes, Experimenting, and Troubleshooting
Chapter 22 - Is My Beer Ruined?
Is My Beer Ruined?!
This phrase has got to be the most frequently asked question by new brewers, and usually the answer is “No.” Depending on the cause, it might end up with an odd flavor or aroma, but you will still be able to drink it and chalk it up as another lesson on the way to brewing that perfect beer. Although a lot can potentially go wrong with a batch, most problems arise from just a couple of root causes. If the recipe was good and you used quality ingredients, there are three common culprits: poor sanitation, bad yeast, or the wrong temperature. Most problems become noticeable once the beer is in the fermentor and nothing (or something weird) is happening. Let’s examine some common symptoms and their possible causes.
Common Problems
Symptom: I added the yeast 2 days ago and nothing is happening.
Cause 1: Leaky Bucket
Lack of fermentation can be due to several things. If the airlock is not bubbling, it may be due to a poor seal between the lid and the bucket. Fermentation may be taking place, but the CO2 is not coming out through the airlock.Cure: This is not a real problem; it probably won’t affect the batch. Fix the seal or get a new lid next time.
Cause 2: Bad Yeast
When a batch is not fermenting, the most common problem is with the yeast. If dry yeast has been properly packaged and stored cool, it should be fully viable for up to two years. However, if you are using a yeast package that has been sitting warm on the shelf for a long time, then the yeast may be too old to work for you. Don’t use old yeast.Yeast need to be treated with care and be given the proper growing conditions. Dry yeast are dehydrated—they’re parched, they’re in no condition to start work. They need some nice warm water to get rehydrated in, some time to do some stretching, maybe an appetizer, and then they will be ready to tackle a full wort. Cure: Use a fresh package of yeast, or refresh the yeast with a starter.Likewise, liquid yeast cultures also need their breakfast routine. They have been kept in a refrigerator and need to be warmed and fed before there will be enough active yeast to do the job properly. There are a lot more yeast cells in a dry yeast packet than in a liquid packet. The liquid packet needs to be grown in a starter to produce enough cells to take on the job of a full five gallon wort. Both liquid and dry yeast cultures will have a lag time from when they are pitched until they start fermenting in earnest. Aeration, the process of dissolving oxygen into the wort, provides the yeast with the oxygen they need to greatly boost their growth rate and make enough yeast cells to do the job properly.
Cause 3: Too Cold
The fermentation conditions may be too cold for an otherwise healthy yeast population. Ale yeast strains vary in their temperature sensitivity but tend to go dormant below 60°F. If the yeast were rehydrated in really warm water (105°F) and then pitched to a much cooler wort (65°F), the large difference in temperature can thermally shock the yeast and cause a longer lag time as they adjust. Or in some cases, that otherwise normal ale fermentation temperature could cause those warm-acclimated yeast to call it quits. Cure: Try warming the fermentor by 5°F (3°C); it may make all the difference.
Cause 4: Improper Sanitation
Sanitation can be carried too far sometimes. When you were preparing the warm water for rehydrating or boiling your yeast starter, did you cool it to the proper temperature range? If the water is too cold (below 80°F) the yeast will be sluggish and have a hard time getting rehydrated. If it is too hot (above 105°F) then the yeast are going to get scalded, and refuse to have anything to do with you and your wort. Also, if you added the yeast to the starter wort and then boiled it, well, they’re dead. Cure: Pitch new yeast.
Symptom: I added the yeast yesterday and it bubbled all day but it’s slowing down/stopped today.
Cause 1: Lack of Preparation
As I stated on the previous page, yeast that are improperly prepared, whether from poor handling, lack of numbers (i.e. lack of Starter), or lack of aeration, will often fail to finish the job. Cure: Pitch new yeast.
Cause 2: Too Cold
Temperature can also be a major factor for fermentation performance. If the temperature of the room where the fermentor is cools down, even by only 5°F overnight, then the yeast can be slowed dramatically.Cure: Always strive to keep the fermentation temperature constant, the yeast will thank you for it.
Cause 3: Too Warm
The flip side of the coin could be that the temperature was warm, e.g. 75°F, and the yeast got the job done ahead of schedule. This often happens when a lot of yeast is pitched, the primary fermentation can be complete within 48 hours. This is not necessarily a good thing, as ferments above 70°F tend to produce a lot of esters and phenolics that just don’t taste right. The beer will still be good, just not as good as it could have been. It will depend on your tastes and the yeast strain. Cure: Always strive to keep the fermentation temperature within the recommended range, the yeast will thank you for it.
Symptom: The last batch (did that) but this batch is (doing this).
Cause 1: Different Conditions
Different yeast strains behave differently and different ingredients can cause the same yeast to behave differently. Different temperatures can cause the same yeast working on the same ingredients to behave differently. Different yeasts working on different ingredients at different temperatures will produce different beers. Profound, eh? Cure: Be patient; don’t jump to conclusions. Go watch TV.
Cause 2: Yeast Health
If you are brewing identical recipes at the identical temperatures then a difference in fermentation vigor or length may be due to yeast health, aeration or other factors. Only if something like odor or taste is severely different should you worry. Cure: Wait and see.
Symptom:
The airlock is clogged with gunk.
Cause: Vigorous Fermentation
Sometimes ferments are so vigorous that the krausen is forced into the airlock. Pressure can build up in the fermentor if the airlock gets plugged and you may end up spraying brown yeast and hop resins on the ceiling. Cure: The best solution to this problem is to switch to a blow-off hose. Fit a large diameter hose (e.g. 1 inch) into the opening of the bucket or carboy and run it down to a bucket of water.
Symptom:
White stuff/brown stuff/green stuff is floating/growing/moving.
Cause 1: Normal Fermentation
The first time you look inside your fermentor, you will be treated to an amazing sight. There will be whitish yellow-brown foam on top of the wort, containing greenish areas of hops and resins. This is perfectly normal. Even if it appears slightly slimy, it is probably normal. Only if something hairy starts growing on top of the wort should you be concerned. I remember one guy reporting a dead bat floating in his fermentor...That was definitely cause for alarm. Cure: Get a new bat.
Cause 2: Mold
A simple case of mold.Cure: (2025) Dump it. Author’s note, 2025: Mold should not happen! A healthy fermentation environment should not support the growth of mold. What may happen is the development of a bacterial pellicle, which can look like mold but should be white, ivory, or slightly gray. A pellicle protects a sour beer from oxidation. It will smell sour, like yogurt.
Here is a rule of thumb for wild fermentations (unexpected sours): If in doubt, throw it out.
A good sour (caused by lactobacillus or Pediococcus) may smell funky at first but overall should smell palatable, like sourdough, or sauerkraut. Trust your instincts, but remember the mantra.
Symptom:
It smells like rotten eggs.
Cause 1: Yeast Strain
Rotten egg odors (hydrogen sulfide) can have two common causes: the yeast strain and bacteria. Many lager yeast strains produce noticeable amounts of hydrogen sulfide during fermentation. The smell and any sulfur taste will dissipate during lagering. Cure: Let the beer condition or lager for a few weeks after primary fermentation.
Cause 2: Bacteria
Bacterial infections can also produce sulfury odors and if you are not brewing a lager beer, then this is a good sign that you have an infection. Fortunately, this is pretty rare, but it indicates a serious oversight in your sanitizing regime.Cure: Let the fermentation complete and then taste it before bottling to see if it is infected. It may be accompanied by sourness, ropiness, or other unpleasant characteristics.
If in doubt, throw it out.
Symptom:
It smells like vinegar.
Cause 1: Bacteria
In this case, it probably is. Aceto bacteria (vinegar producing) and Lacto bacillus (lactic acid producing) are common contaminates in breweries. Sometimes the infection will produce sweet smells like malt vinegar, other times they will produce cidery smells. It will depend on which bug is living in your wort. Aceto bacteria often produce ropy strands of jelly which can be a good visual indicator, as can excessive cloudiness, after several weeks in the fermentor (although some cloudiness is not unusual, especially in all-grain beers). Acetobacter is an aerobe, so its presence indicates that oxygen is getting to your beer.Cure: If you don’t like the taste, then pour it out. Lactic infections are desired in some beer styles. Be more meticulous with your sanitation, and don’t suck to start siphons. Some lightly soured beers can be rescued by adding fruit.
Cause 2: Wild Yeast and Bacteria
Two other bugs are also common, Brettanomyces and Pediococcus. Brettanomyces is supposed to smell like horse sweat or a horse blanket. Raise your hand if you know what a horse smells like. From sweat, I mean. Anyone? I think Brett smells like leather, myself. Pediococcus can produce diacetyl (invariably as a contaminant) and acidic aromas and flavors, as well as haze.One man’s garbage can be another man’s gold, though. These two cultures and Lacto bacteria are actually essential to the Belgian Lambic beer styles. Under any other circumstances, beers that taste like Lambics would be discarded instead of being carefully nurtured and blended over a two year period. Lambic beers have a pronounced tartness with fruity overtones. This type of beer is very refreshing and is excellent with heavy food.Cure: Be meticulous in your sanitation, or investigate Lambic brewing.
Symptom:
It won’t stop bubbling.
Cause 1: Cool Temperatures
A beer that has been continually fermenting (bubbling) for a long time (more than a week for ales, more than 3 weeks for lagers) may not have something wrong with it. It is often due to the fermentation being a bit too cool and the yeast are working slower than normal. Cure: This condition is not a problem.
Cause 2: Gusher (wild yeast) Infection
However, the sustained bubbling is often due to “gusher type” infections i.e., diastatic yeast strains. These infections can occur at any time and are due to wild yeasts or bacteria that eat the normally-unfermentable sugars, like dextrins. The result in the fermentor is a beer that keeps bubbling until all of the carbohydrates are fermented, leaving a beer that has no body and very little taste. If it occurs at bottling time, the beer will overcarbonate and will fizz like soda pop, fountaining out of the bottle.Cure: Improve your sanitation next time.If the beer seems to be bubbling too long, check the gravity with a hydrometer. Use a siphon or turkey baster to withdraw a sample from the fermentor and check the gravity. If the gravity is still high, in the teens or twenties, then it is probably due to lower than optimum temperature or sluggish yeast. If it is below 10 and still bubbling at several per minute, then a bug has gotten hold. The beer will not be worth drinking due to either the total lack of flavor or unpleasant phenols.
Symptom:
The fermentation seems to have stopped but the hydrometer says 1.025.
Cause 1: Too Cool
This situation is commonly referred to as a “stuck fermentation” and can
a couple causes. The simplest cause and probably the most common is temperature. As previously discussed, a significant drop in temperature can cause the yeast to go dormant (and even thermally shocked) and settle to the bottom. Cure: Moving the fermentor to a warmer room and swirling the fermentor to stir up the yeast and get them back into suspension will often fix the problem.
Cause 2: Weak Yeast / Underpitched
The other most common cause is weak yeast. Referring back to previous discussions of yeast preparation, weak yeast or low volumes of healthy yeast will often not be up to the task of fermenting a high gravity wort. This problem is most common with higher gravity beers, OGs greater than 1.078.Cure: Add more yeast.
Cause 3: Low Attenuating Extracts
Another common cause for extract kit brewers is the use of extracts high in dextrins.
(Author’s note, 2025: Thirty years ago, malt extract was deliberately brewed to be less fermentable (more dextrinous) because it was intended to be brewed in a kit with 50% table sugar. This is probably no longer the case.)
Symptom:
It won’t carbonate.
Cause: Need More Time
Time, temperature and yeast strain all combine to form a government committee with the charter to determine a range of times when they can expect to be 90% finished with the Carbonation/Residual Attenuation Project. This committee works best without distractions— the meetings should be held in quiet, low light areas in a warm room. If the committee was given enough budget (priming sugar), then they should arrive at a consensus in about 2 weeks. If they don’t get their act together within a month, then it’s time to rattle their cages and shake things up a bit. Cure: The yeast may have settled out prematurely and the bottles need to be shaken to get the yeast back into suspension. Likewise, if the temperature is too cool in the room, moving the bottles to a warmer room may do the trick. With long-aged beers there is sometimes not enough viable yeast left to do the job. Fresh yeast may need to be added.
Symptom:
The bottles are overcarbonated.
Cause 1: Too much sugar
You used too much priming sugar.Cure: Vent and re-cap all of the bottles. This may have to be done several times, as this just lets out the gas from the headspace, not what is dissolved in the beer. It might be a good idea to uncap and them cover with little squares of aluminum foil, and let them stand for several minutes/hours before recapping.
Cause 2: Bottled too soon
You bottled before fermentation was complete.Cure: Vent and re-cap all of the bottles.
Cause 3: Wild yeast
A wild or unwanted yeast has gotten into the beer. Unexpected fermenters (i.e., wild yeasts and/or bacterial contamination) are a real problem as they will keep on fermenting the beer until there is nothing left but fizzy bitter alcoholic water. The real danger with overcarbonation is exploding bottles. Bottle grenades can be very dangerous both from flying glass and from glass slivers left in the carpet.Cures: Refrigerate the bottles and drink them while there is still some flavor left.I recall one story I read on the rec.crafts.brewing newsgroup where a brewer recounted how both he and his partner had each added 3/4 cup of priming sugar to the batch, thinking that the other one had not. By venting and recapping all the remaining bottles after the initial explosions, they thought they had saved the batch. Then a massive storm front swept through and the corresponding drop in barometric pressure caused the rest of the bottles to explode. Be careful!
Symptom:
The (finished) beer is hazy/cloudy.
Cause 1: Chill haze
This is the number one cause of cloudy homebrew. It is caused by an insufficient cold break during cooling after the boil.Cure: Use a wort chiller.
Cause 2: Starch
If you made an all-grain beer and had incomplete conversion, or added/steeped a malt that needed to be mashed to an extract batch, then you can have residual starches in the beer that will cause cloudiness.Cure: Check your malts to be sure if they need to be steeped or mashed. Watch the mash temperature and perhaps mash longer next time.
Cause 3: Yeast
Yeast strains that have low flocculation, such as German Hefeweizen, will cause the beer to be cloudy. And (as of 2025), some yeast strains (like the various Hazy IPA yeast strains) actually encourage polyphenol-protein haze.Cure: Use a different yeast strain if you want a clearer beer.In all cases, cloudiness can be combated by adding fining agents (e.g. isinglass, gelatin, Polyclar, bentonite) after fermentation. The clarity can also be enhanced by adding Irish Moss towards the end of the boil. See Appendix F for more info.
Common Off-Flavors
There are many flavors that contribute to the overall character of a beer. Some of these flavors have been previously described as malty, fruity, or bitter. When it comes time to figure out why a beer tastes bad though, we need to get more specific. In this section we will discuss several different flavors that can be perceived and what could cause each.
Acetaldehyde
A flavor of green apples or freshly cut pumpkin; it is an intermediate compound in the formation of alcohol. Some yeast strains produce more than others, but generally it’s presence indicates that the beer is too young and needs more time on the yeast to maturate.
To reduce the likelihood of acetaldehyde in your beer:• Use a cooler initial fermentation temperature• Use a lower pitching rate• Don’t under-aerateTo clean up acetaldehyde in the fermentor:• Use a warmer lagering or maturation temperature (i.e., diacetyl rest)• Keep the beer on the yeast (i.e., don’t rack too soon)• Rouse the yeast to keep it suspended.• Use a less-flocculant yeast strain.
Alcoholic
A sharp flavor that can be mild and pleasant or hot and bothersome. When an alcohol taste detracts from a beer’s flavor it can usually be traced to one of two causes. The first problem is often hot fermentation temperatures. At temperatures above 70°F, yeast can produce too much of the higher weight fusel alcohols which have lower taste thresholds than ethanol. These alcohols taste harsh to the tongue, not as bad as cheap tequila, but bad nonetheless.To reduce the amount of fusel alcohols produced during fermentation;• Don’t overdo the aeration and yeast nutrient supplements• Pitch when the wort is cold• Ferment cooler (but don’t stress the yeast)• Don’t add sucrose or other refined sugars to the wort.
Astringent
Astringency differs from bitterness by having a puckering quality, like sucking on a tea bag. It is dry, kind of powdery, and is most due to excess tannins from steeping grains too long and/or when the wort pH exceeds 6 due to alkaline water. It can also be a problem for hoppy pale beers brewed with alkaline (carbonate) water. Oversparging the mash, (causing a wort pH >6) also causes tannin extraction. Tannins can also come from over-hopping with low-alpha hops. Bacterial infections can also cause astringency, i.e. vinegar tones from aceto-bacteria.
Cidery
Cidery flavors can have several causes but are often the result of adding too much cane or corn sugar to a recipe. One component of a cidery flavor is acetaldehyde, which has a green-apple character. It is a common fermentation byproduct and different yeasts will produce different levels of it depending on the recipe and temperature. The production of excess acetaldehyde in a high refined sugar wort can also cause acetic acid to be produced by the yeast, and this is another component to overall cidery character.
If it is caused by aceto-bacteria, then there is nothing to be done about it. Keep the fruit flies away from the fermentor next time.
Diacetyl
Diacetyl is most often described as a butter or butterscotch flavor. Smell an unpopped bag of butter flavor microwave popcorn for a good example. It is desired to a small degree in many ales, but in some styles (mainly lagers) and circumstances it is unwanted and may even take on rancid overtones.
Diacetyl can be the result of the normal fermentation process or the result of a bacterial infection (i.e., pediococcus). Diacetyl precursors are produced early in the fermentation cycle by the yeast and, after it is chemically oxidized to diacetyl, is consumed by the yeast. Weak or stressed yeast will not take up diacetyl.
To reduce diacetyl in your beers:• Use a higher pitching rate to provide sufficient yeast for maturation after attenuation.• Don’t pitch warmer than normal fermentation temperature.• Don’t over-oxygenate, and minimize oxygen exposure after fermentation starts.To clean up diacetyl in the fermentor:• Increase the temperature (i.e., use a Diacetyl Rest)• Keep the beer on the yeast (i.e., don’t rack too soon)• Rouse the yeast to keep it suspended.• Use a less-flocculant yeast strain.
Dimethyl Sulfides (DMS)/ Cooked Vegetable Flavors
Like diacetyl in ales, DMS is common in many light lagers and is considered to be part of the character. It can have a creamed corn aroma and flavor in pale beers, or a more tomato-like character in dark beers. DMS is produced in the wort during the boil by the reduction of another compound, S-methyl-methionine (SMM), which is itself produced during malting. When a malt is roasted or toasted, the SMM is reduced beforehand and does not manifest as DMS in the wort, which explains why it is more prevalent in pale lagers. In other styles, DMS is a common off-flavor, and can be caused by poor brewing practices or bacterial infections.
DMS is continuously produced in the wort while it is hot and is usually removed by vaporization during the boil. If the wort is cooled slowly these compounds will not be removed from the wort and will dissolve back in. Thus it is important to not completely cover the brewpot during the boil or allow condensate to drip back into the pot from the lid. The wort should also be cooled quickly after the boil, either by immersing in an ice bath or using a wort chiller.
When caused by bacterial infection, DMS has a more rancid character, more liked cooked cabbage than corn. It is usually the result of poor sanitation. Repitching the yeast from an infected batch of beer will perpetuate the problem.
Estery / Fruity
Ales are supposed to be slightly fruity, and Belgian and German wheat beers are expected to have minor banana flavor components (isoamyl acetate), but sometimes a beer comes along that could flag down a troop of monkeys. Ethyl acetate (nail polish remover) is also common.
Esters are produced by the yeast in order to de-toxify their environment and different yeast strains will produce different amounts and types. Most esters in beer are produced from ethanol and only a small percentage are made from fusel alcohols. In general, stressed fermentations produce more esters. Stress can be too much or too little of a factor, such as oxygen or FAN or temperature.
To reduce ester formation in your beer:• Use sufficient aeration• Ferment cooler but not too cool• Don’t under-pitch or drastically over-pitch your yeast• Don’t add sucrose or other refined sugars to the wort
Grassy
Flavors reminiscent of chlorophyll and fresh cut grass occasionally occur and are most often linked to poorly stored ingredients. Poorly stored malt can pick up moisture and develop musty smells. Aldehydes can form in old malt and can contribute green grass flavors. Hops are another source of these green flavors. If the hops are poorly stored or not properly dried prior to storage, the chlorophyll compounds will become evident in the beer.
Husky/Grainy
These flavors are similar to the astringent flavors produced from the grain husks. These flavors are more evident in all-grain beers due to poor grain crushing or sparging practices. If the grain husks are shredded during crushing by the use of a Corona grain mill for instance, these husk flavors are more likely to be extracted during the sparge. Follow the same procedures recommended to prevent astringency to correct the problem.
Grainy flavors can also be contributed by highly toasted malts. If you are making your own toasted malts, allow them to age at least two weeks after crushing so the harsher aromatic compounds can dissipate. Cold conditioning the beer for a month or two will often cause these harsh compounds to settle out with the yeast.
Medicinal
These flavors are often described as mediciney, Band-Aid™ like, or can be spicy, like cloves. The cause are various phenols which are initially produced by the yeast. Chlorophenols result from the reaction of chlorine-based sanitizers (bleach) with phenol compounds and have very low taste thresholds. Rinsing with boiled water after sanitizing is the best way to prevent these flavors. Wild (gusher) yeasts can also produce these phenol flavors.
Metallic
Metallic flavors are usually caused by unprotected metals dissolving into the wort but can also be caused by the hydrolysis of lipids in poorly stored malts. Iron can cause metallic flavors leaching into the wort during the boil. The small amount could be considered to be nutritional if it weren’t for the bad taste. In larger than trace amounts, excess metals are injurious to yeast and may also cause haze problems. Nicks and cracks ceramic coated steel pots are a common cause, as are high iron levels in well water. Stainless steel pots will not contribute any metallic flavors. Aluminum pots usually won’t cause metallic flavors unless the brewing water is alkaline with a pH level greater than 9. (Not very realistic.) Shiny new aluminum pots will sometimes turn black when boiling water due to chlorine and carbonates in the water.
The protective (grayish) oxides of aluminum can be enhanced by heating the clean pot in a dry oven at 250°F for about 6 hours.
Moldy
Molds are quickly recognized by their smell and taste. Molds are aerobic and should not grow in the presence of CO2 from a healthy fermentation. Molds and mildew can grow on wort but usually not in beer. Contamination is likely if the wort or beer is exposed to musty or damp areas before or after fermentation without sufficient CO2.
Oxidized
Oxidation is probably the most common problem with beer including commercial beers. If the wort is exposed to oxygen at temperatures above 80°F, the beer will sooner or later develop wet cardboard or sherry-like flavors, depending on which compounds were oxidized. The oxidation of long chain fatty acids produces 2-trans-nonenal that has a cardboard taste and the smell of old paper. See the discussion of oxygen and the wort in Chapter 6.
Soapy
Soapy flavors can be caused by not washing your glass very well, but they can also be produced by the fermentation conditions. If you leave the beer in the primary fermentor for a relatively long period of time after primary fermentation is over (“long” depends on the style and other fermentation factors), soapy flavors can result from the breakdown of fatty acids in the trub. Soap is, by definition, the salt of a fatty acid; so you are literally tasting soap.
Solvent
This group of flavors come from fusel alcohols, but are harsher to the tongue. These flavors often result from a combination of high fermentation temperatures and oxidation. They can also be leached from cheap plastic brewing equipment or if PVC tubing is used as a lautering manifold material. The solvents in some plastics like PVC can be leached by high temperatures. Make sure your plastics are food-grade!
Skunky
Skunky or cat-musk aromas in beer are caused by photochemical reactions of the isomerized hop compounds. The wavelengths of light that cause the skunky smell are the blue wavelengths and the ultraviolet. Brown glass bottles effectively screen out these wavelengths, but green bottles do not. Skunkiness will result in beers if the beer is left in direct sunlight or stored under fluorescent lights, as in supermarkets. Beers which use pre-isomerized hop extract and/or very little flavoring hop additions will be fairly immune to damage from ultraviolet light.
Rotten/Goaty/Funky
I often encounter this aroma and flavor at restaurants when I order a beer from the tap. It could be that they need to clean their beer lines of mold, or it could be lacto bacillus or Pediococcus infections. Bacterial contamination aromas are often sulfur based, so that they a rotten vegetable or otherwise unpleasant smell.
If the aroma is more sweaty, or barnyard, then it could be Brettanomyces, which is another yeast genus that contributes to Lambic and Saison style beers. The aroma of these fermentation is often described as Funky, because it's hard to put a name to it. It can be like animal sweat or manure depending on the sulfur content. Brett beers can taste quite good. But remember the mantra: When in doubt, throw it out.
Yeasty
The cause of this flavor is pretty easy to understand. If the beer is green, is too young, and the yeast has not had time to settle out, it will have a yeasty taste. Watch your pouring method too, keep the yeast layer on the bottom of the bottle.
If the yeast is unhealthy and begins autolyzing it will release compounds that initially may be described as yeasty, or smell like beef bullion, or soapy or like a jar of B-vitamins later on.