Beer won’t clear.

When bottling the brew, it will most probably display a degree of cloudiness.  This is not a bad thing because the cloudiness is most likely caused by the millions of yeast cells in suspension and the yeast is required for fermenting the priming sugar in the bottle.  Normally, the brew will clear in the bottle, once the yeast has performed the secondary fermentation (adding fizz to the beer) and given time to stand upright.  A brew that doesn’t clear up in the bottle is likely to be quite drinkable – chill a bottle down and sample it to make up your own mind.

A brew may not clear for the following reasons:
1. Some yeast strains, by their nature, do not settle as completely as others.
2. There’s a higher count than usual of wild yeast and/or bacteria in the brew.
3. The brew is not meant to clear, such as Ginger Beer and some Wheat Beers.
4. Excess complex carbohydrate, such as maltodextrin, in the recipe.

Air- lock not bubbling.

This is the most common of problems. Many brewers assume the brew is not fermenting because the air-lock is not bubbling so, “Out she goes”.  Most likely, the brew is fermenting but as fermenters don’t always seal well, the air-lock does not bubble and the brewer assumes that the yeast is dead.  A brew does not need to be in a perfectly sealed container to result in good beer.  A number of commercial breweries, today, still ferment high quality beer in open vats!
Before making the ultimate sacrifice and tipping it out, assess the situation.  Look for visual signs of fermentation such as frothing and a scum ring around the top of the brew, condensation on the inside of the lid, a build up of sediment in the bottom, a sample from the tap is frothy and cloudy and the SG is dropping from day to day.

Symptoms of spoiled beer.

News Flash!  Unlike commercially brewed and pasteurised beer, all home brewed beer is contaminated to some degree.  It’s the brewer’s challenge to keep the level of contamination below the threshold of taste and smell.  A comprehensive cleaning and sanitising regime will reduce the number of potential spoilage organisms to a minimum but never eradicate them completely.  There are always airborne bacteria and wild yeast present when preparing, fermenting and bottling a brew.
So one day, despite a high standard of hygiene and best intentions, you might cop a “bad brew”.  This is why it’s so important to gain confidence in the quality of the brew by smelling and tasting the SG sample prior to bottling.  If the brew smells okay (some butterscotch or sulphury/egg like aromas are acceptable if fermenting a lager as they will dissipate over time) and tastes like warm flat beer (bitterness is acceptable as it softens with time), it should be okay to bottle.
If vinegar, wet cardboard, harsh solvent, mouldy, metallic or a soapy character is detected there is little chance that the brew will improve when it’s bottled.  In fact, the brew is likely to deteriorate even further in the bottle!  So “chalk this one up to experience”, discard the brew, clean up, sanitise and start again.