Talking Tech – Beer Clarity

Beer – not as crystal clear a subject as it used to be….  

In the ‘craft beer boom’ which has taken place over the last few years, few subjects have resulted more discussion between traditional ale lovers and ‘craft’ beer fans than the clarity of their beer.

In the early days of CAMRA and for decades following, the vast majority of cask ale was expected to be presented crystal clear and any pint that was presented with even the slightest haze was assumed to either not be ready for serving or to have a brewing fault.

Recent trends have changed this with more and more beers intentionally presented with a haze and some even positively opaque – their brewers either stating a desire to make their beers suitable for vegetarians or some arguing that the particles which cause haze also enhance flavour and aroma.

Left – Cloudwater 5th Birthday IPA. Right – Wylam Hickey The Rake

Historically, the clarity of beer was not of a concern to drinkers – when most beer was drunk from metal, earthenware or leather tankards, the drinker was only concerned with taste. It was only the move to serving beer in clear glass following the industrialisation of brewing in the late 18th century when drinkers started paying attention to clarity. Marketeers then latched on to this and began selling sparkling bright beers as the norm.

Brewery conditioned beers which could be filtered to achieve clarity had no problem living up to this expectation but cask beers – requiring yeast in the cask to achieve secondary fermentation, meant brewers had to find alternative means of achieving clarity.

Given that beer is produced from a variety of solid materials – malted barley, wheat, hops and yeast – it should not come as a surprise that the immediate result of the brewing process is not a clear liquid. It is only by the intervention of the brewer at several stages in the brewing process that clear beer can result.

What’s your haze?

Haze and cloudiness in beer can be caused by one of a few things. Biological hazes are caused by bacteria resulting from infection in the process – they cannot be corrected. Non-biological hazes result from particles introduced from the brewing ingredients – yeast, proteins, polyphenols (mostly tannins) and carbohydrates (mostly starch) from the grains and hops.

Although popular belief would be that hazy or even cloudy beers are ‘full of yeast’, an unclarified beer sample will typically contain between 0.5 to 2 million yeast cells per millilitre and between 1 and 3 million particles of other materials.

The higher hopping rates and the increased use of dry hopping (adding hops direct to the fermenter) over recent years has only increased the amount of non-yeast particles in beer. Some brewers of hazy beers would contest that they go to great expense adding hops to beer to give aroma and flavour so, to them, it is counter-intuitive to then go to further expense to remove the results of this hopping from the finished product.

Hops – lots of hops ©CAMRA

Other commentators would argue that not taking measures to remove haze from beer is an example of lazy brewing or that it is a cost cutting measure.

Controlling the haze

While yeast is added relatively late in the brewing process, the process of controlling the number of suspended particles in beer starts much earlier – even before the mash.

The calcium content of the liquor (water) used for brewing plays a part, as does the quality and type of grains used – wheat contains much higher levels of proteins than barley, making beers containing wheat harder to clear.

Control of pH (acidity) both during the mash and the boil affects both natural protein precipitation and the effectiveness of additives which enhance the natural processes. Choice of yeast strain is also a key factor as is temperature control during fermentation and conditioning.

Is my beer ‘unfined’?

Drinkers have come to associate the modern trend for hazy beers with them being described as ‘unfined’.

However, technically ‘fining’ covers additions to aid clarity at various stages of the brewing process. Describing beers as ‘unfined’ is commonly an abbreviation for ‘not been fined using isinglass’ (more on this later) – they will most likely have had finings added elsewhere in the process.

The speed at which solid particles suspended a liquid will drop to the bottom of the vessel under the influence of gravity is determined by Stokes’ Law of physics – with the key factor in beer being that the speed of clearing is proportional to the square of the particle diameter. Given enough time, most particles will drop out of suspension naturally, but unaided this process could take several weeks. The key to clarifying beer more rapidly is to encourage particles in suspension to ‘flocculate’ – to gather together to form larger particles which then drop to the bottom of the vessel – be that the cask or keg from which the beer is served or a tank in the brewery.

Finings are additives used in the brewing and packaging process to encourage flocculation. There are three main stages in the brewing process where they can be used – in the copper (kettle), in the fermentation vessel or conditioning tank and in the cask/keg. At all stages, finings only work in conjunction with careful control of the brewing process – temperature and pH levels being key.

Isinglass finings

For cask beer, the most effective and therefore popular finings have been those made from isinglass, added directly to the cask either at packaging or before dispatch.

Isinglass is a substance derived from the dried swim bladders of certain types of fish – traditionally the Sturgeon, but these days more likely to be other breeds such as the Catfish and Threadfin – and hence not approved of by vegetarians and vegans.

The bladders are processed and then soaked in a blend of fruit acids forming what is known as a colloidal solution – an unstable solution with liquid and solid phases. The stability of this solution is governed by its pH (acidity). As supplied, at pH of around 2.5 it remains a solution but as its pH rises to around 5.5 (when dissolved in beer), the solid phase precipitates out and allows the finings to start their work.

The active ingredient in Isinglass is collagen, a large molecule with a positive atomic charge. Brewing yeasts typically have a comparatively small molecule size and a negative charge. They are therefore attracted to the positively charged collagen molecules forming a ‘floc’ with many yeast molecules bonded to each collagen molecule. Gravity takes over and the meshed cells drop to the bottom of the cask, clarifying the beer.

Isinglass is usually added direct to the cask (at a typical rate of one pint per nine-gallon cask).  Isinglass is highly effective at removing yeast particles from beer However, isinglass is not so effective at removing other particles which can cause haze.

Kettle Finings – Irish Moss

For many brewers, the first addition of finings takes place around 10 to 15 minutes from the end of the boil. The unlikely sounding source of this addition is seaweed – in particular, red seaweeds which contain carrageenan. Such finings are often known as ‘Irish Moss’ after a carrageenan containing seaweed called Chondrus crispus which is commonplace around the shores of Ireland.  

Carrageenan is used as a thickener in many food products but in brewing relatively small amounts added to the copper (or kettle – hence ‘kettle finings’) helps to coagulate haze forming proteins and other solids as the wort is cooled. Rapid cooling of the wort at the end of the boil causes proteins to precipitate out of the wort – what is known to brewers as the ‘cold break’. The use of kettle finings enhances protein removal by removing virtually all haze forming materials.

Although ‘Irish Moss’ is available as a dried or liquid additive (today commonly a blend with other carrageen bearing seaweeds), carrageenan is more commonly found as the main active ingredient in refined kettle finings products such as Protafloc, Whirlfloc or Compac CG. The advantage of using refined carrageenan products is increased efficiency requiring smaller doses.


Once the cooled wort reaches the fermenter, yeast is pitched and begins its work converting sugars to alcohol. In the process, it reproduces rapidly to the point where a fermenting beer can contain as many as 40 million yeast cells per millilitre of beer (that’s 22 billion in a pint). As fermentation completes this count will be reduced to closer to 1 million active cells while hop additions in the fermenter will mean that the beer will also contain millions of particles of protein and tannins.

Some yeast strains are naturally flocculant, starting to clump together as fermentation slows, while others are powdery and need encouragement to drop out of suspension. Many modern commercial brewers’ yeasts are a mixture of strains with the flocculant strain doing its work and then dropping out towards the end of fermentation leaving the powdery yeast in the beer to complete the fermentation process.

To encourage both the yeast and proteins to coagulate at the end of fermentation, brewers will rapidly cool the fermented beer to below four degrees (‘cold crashing’) and then hold the beer at this temperature to allow the flocs of yeast and protein to drop to the bottom of the fermenting vessel.

At this stage, they can also add ‘auxiliary finings’ to help clear the proteins and polyphenols which remain suspended in the beer.

Auxiliary Finings

There are a number of different types of auxiliary finings, with the most common being silica based while others are ‘polysaccarides’ (based on gums such as Asacia and Gum Arabic) or more seaweed extracts. Auxiliary finings are usually natural in origin so suitable for use in vegetarian and vegan beers and are often used alongside isinglass to give increased clarity in a beer – what brewers refer to as ‘polish’.

The theory of operation of auxiliary finings is the same as isinglass except they are negatively charged to attract the positively charged proteins and polyphenols to form flocs. Different types of auxiliary finings will be required for different styles of beer – with most beers containing a mix of particles which will react to a number of different fining agents. Commercially available auxiliary fining products are therefore typically a blend of different agents with the aim of removing as many suspended particles as possible.

Auxiliary finings can be added to the fermentation vessel at the end of fermentation as the vessel is chilled or direct in the cask / keg.

When being used in conjunction with isinglass finings, auxiliary finings must be added before isinglass finings as the opposite charge of the two will mean that they can act on each other instead of on the proteins. Adding auxiliary finings first causes proteins to bond to the auxiliary molecules giving them a negative charge. These are then attracted to the positively charged isinglass molecules meaning the combination of auxiliary finings with isinglass can give the most ‘polished’ or ‘brite’ beer possible.

Vegan haze?

To produce beers which are suitable for vegans, brewers must avoid the use of isinglass finings (and gelatin, another animal derived fining agent). This omission is commonly leads to ‘unfined’ beers (i.e. without isinglass) being expected to be hazy.

Marble Beers – Pint ©John O’Donnell

However, this assumption does not always hold true. Manchester’s own Marble Beers have been producing perfectly clear beers without isinglass finings for over twenty years. Other renowned brewers such as Moor Beer and our own Blackjack Beers have followed suit.

Some brewers achieve clarity by careful control of ingredients & process and by allowing additional time during conditioning for haze causing particles to drop out naturally. Others use vegetarian finings agents such as Murphy’s Super-F or Protofine from AB Vickers (part of Lallemand) which are designed to rapidly drop both protein complexes and yeast from chilled beer in conditioning tanks.

Many modern brewers are happy to accept a slight ‘craft haze’ rather than put their beer through additional processing to achieve a full polish which they fear will also affect flavour while some beers are produced to be intentionally ‘murky’ – styles such as New England IPA’s (NEIPAs) being intended to taste ‘juicy’ and be served fresh meaning that brewers aren’t concerned about the implications on shelf life of leaving beers with proteins in suspension.

Does clear beer taste better?

There is only one person who can decide this and that is you, the drinker.

Brewers can’t agree – those who add different sorts of finings, cold crash fermenters and even filter their beers will say that taste is unaffected. Others argue that some of these measures do remove flavour and opt for haze instead.

The way something smells and the way it looks affects what your brain interprets as taste. If you prefer clear, then drink clear. If you don’t mind haze, drink haze. If you don’t know, close your eyes and let your taste buds decide.