hanging fermentation

SYMPTOMS
slow or no fermentation

CAUSES
insufficient wort aeration
lack of fermentable sugars in wort
wort pH too high (over 5.5)
fermentor and wort too cold, causing yeast to flocculate
yeast lacks enzymes need to ferment maltotriose
weak or degenerated yeast
inadequately cured malt
 antifoam agents or trub clogging yeast membrane
extensively demineralized water
extremely soft water
water high in carbonate hardness
high nitrate level (>25ppm)
high copper content

SOLUTIONS
add vigorous, roused yeast
pump wort into another fermentor
analyze to determine whether yeast is capable of fermenting wort sugar-profile

bubbling fermentation

SYMPTOMS
slow, bubbling fermentation, usually appearing after krausen stage

CAUSES
degenerated or autolyzed yeast
poor trub elimination
sudden temperature increase
poor cellar ventilation
presence of nitrites
highly kilned malts

SOLUTIONS
pump wort into another fermentor
add vigorous, roused yeast

boiling fermentation

SYMPTOMS
high carbon dioxide evolution

CAUSES
large amounts of trub
wort is too chilled
uneven temperature profile
uneven yeast distribution
over-modified malt
build-up of beerstone
excessive wort maltose
unusual characteristics of yeast

SOLUTIONS
break up yeast by aerating
remove more trub from wort