“This focus on clarity [in British ale] is annoying,” he says. “You get punters in a pub who think that if a beer is clear, then it’s good. A fantastic beer with a haze, they send it back. But the best beers I’ve had have had a natural haze. In Germany, you get a beer with a haze, it means there’s something good in there. Or an IPA – there’s so much hop oil in there it will have a natural haze. The IPAs that have a hop haze are usually head and shoulders above those that don’t."Jason Hawke of Moor Beer quoted here
Well, we try not to let it annoy us. But I know what he means. Now, I'm not a master brewer, but I have done a bit of (a) brewing and (b) reading, so I hope I'm not going to be too far wrong in what follows.
There are a few kinds of haze you might come across in beer. Sometimes these will be "faults". Now "fault" is a funny idea anyway. Consider a starch haze. In a British bitter (pale ale, whatever), a starch haze is pretty uncommon (except perhaps for a beginning homebrewer) and it's probably due to a rubbish mash. In some beers (e.g. historical white beers) potato starch was used, and in others, high proportions of unmalted grain - which would have promoted such a haze. i.e. haze would be expected in these beers.
Protein / polyphenol hazes, again quite rare in British pales, put down to bad brewing or malting, but key in many wheat beers. In other beers may be due to high levels of hop or malt polyphenols interacting with normal protein content. Indeed, to promote a stable haze in some beers, refined tannins are added.
Lipid hazes, fats (or oils) suspended in the beer - bad if you've got trub spoiling your pale ale - but what if it's down to hop oil from your shedloads of late/dry hops?
Yeast haze - you'd expect a pale ale to have low levels of suspended yeast (< 10K cells / ml ?), but we all know of beers that are intended to be visibly hazy (or indeed opaque) because of yeast. Some brewers add a yeast product (biocloud?) to give a stable haze. Others use fish-guts to produce the stable sediment, and high clarity, that their customers expect. It's a fact that some yeast, in some beers, will present a hint of harsh bitterness (or bite) and is probably best left sitting in the belly of the cask rather than in the glass.
Chill hazes - those protein / polyphenol hazes are more stable at low temperatures and tend to fade when the beer is warmer. So chill a fresh beer below the intended serving temperature and a (transient) haze will be produced. I gather these hazes can become more stable with time at any temperature - so beer may develop haze as it ages - eventually the haze may become dense enough to sediment out.
All that said - for many British style pale ales - two key measures that are commonly assessed in the cellar are clarity and condition. If it's clear and not too flat - put it on sale. This is a simple, and usually effective, tactic for presenting beer well...
...Except when the beer is known to be hazy, when the cask has a big sticker on it saying "NATURALLY HAZY", when the beer is delivered by the brewer who tells the publican "this is hazy, you know".
Anyway, one of my jobs next week is to uplift a 9 of "Hop Priest" (an extensively hopped IPA), which was judged to be unsaleable because it's "too hazy". Ho hum.