Cask Ales & Finings
Traditional cask-conditioned ales are often unclear to call vegan or vegetarian — here is why.
Isinglass is fish-derived
Not vegetarian or vegan
No labelling required
Invisible on the bottle
Format matters
Keg ≠ cask fining method
Tools
Check a BeerWhat is cask ale?
Cask ale — real ale — undergoes a secondary fermentation inside the cask after leaving the brewery. Unlike filtered and pasteurised keg beers, cask ales are served at cellar temperature via a hand pump and contain live yeast right up to the point of serving.
That live yeast creates a natural haze. To produce the bright, clear pint most drinkers expect, cask ales are treated with fining agents — substances that bind to the suspended particles and cause them to settle to the bottom of the cask.
What are finings?
Finings are clarifying agents that create an electrostatic charge, attracting yeast, proteins, and other haze-forming particles into clumps heavy enough to sink. Some are entirely animal-derived; others are plant-based or mechanical.
The choice of fining agent determines whether the finished beer is suitable for vegetarians or vegans — and crucially, the agent used is not required to appear on the label.
Common fining agents
Dried fish swim bladders. The most common fining agent in UK cask ale.
Boiled animal bones and connective tissue (pig or cow). Used in some wines and beers.
Seaweed-derived copper fining used during the boil. Fully vegan and vegetarian.
Clay-based fining agent. Common in winemaking and used by some vegan breweries.
Seaweed extract used as a kettle fining. Does not remain in the finished beer.
Mechanical clarification with no agents at all. Used by many modern craft breweries.
Isinglass explained
What it is
Isinglass is produced from the dried, processed swim bladders of fish — historically sturgeon, now mostly tropical fish such as threadfin bream.
How it works
The dried bladder is dissolved into a colloidal solution and added to the cask. Its positive charge attracts negatively charged yeast cells, forming clumps that sink to the bottom.
Why it matters
Although isinglass is designed to settle out, trace fish proteins may remain in the finished pint. Both the Vegan Society and Vegetarian Society classify isinglass-fined beer as unsuitable.
Isinglass is the dominant fining agent for cask ales in the UK, and its use is not required to appear on the label — beers are exempt from the full ingredient disclosure rules that apply to food products.
Not always vegetarian — and therefore not vegan
Same beer, different answer
The keg version of a beer is often filtered or centrifuged — no isinglass. The cask version of the same beer from the same brewery may use isinglass. Barnivore and other databases record the beer as one product and may not distinguish between formats.
Widely used, rarely declared
Because isinglass is so widely used and not required to be declared, many cask ales are not suitable for vegetarians — even if the brewery does not publicise this. If a beer is not vegetarian it cannot be vegan, even if no animal products appear in the ingredients.
A Barnivore entry that says “vegan” for a given beer was assessed by the community at a point in time and may reflect the keg or bottled version. If ordering from a handpull, ask the brewery directly whether they use isinglass in cask.
Why Beer Check cannot always guarantee results for cask ales
No format distinction in databases
Barnivore and Open Food Facts store records by beer name and brewery — not by dispense method. A vegan rating may reflect the bottled or keg version, not the cask.
No labelling obligation
UK law does not require breweries to disclose fining agents on the label. Fining use is invisible from the product name or ingredients list.
Community data can be outdated
Barnivore entries are community-submitted. A brewery may have changed its fining practices since the entry was last verified.
OCR cannot detect finings
Label text gives us the beer name and brewery — it says nothing about how the beer was fined. A perfect label scan still cannot determine fining status.
Cask is a pub-side decision
Many breweries produce the same beer in cask and keg with different fining treatments. Whether you're served cask is decided at the pub, not the brewery.
What you can do
Ask at the bar
Staff at a good real ale pub should know whether each cask line is vegan- or vegetarian-friendly. Many now keep this information for each handpull.
Look for pump clip labelling
Some breweries print "vegan-friendly" or "suitable for vegans" on their pump clips or labels. This is the most reliable indicator at point of sale.
Choose keg or filtered alternatives
Keg, canned, or bottled versions of the same beer are more likely to be mechanically clarified — but confirm with the brewery if certainty is needed.
Choose 100% vegan breweries
Some breweries never use animal-derived finings in any product, including cask. GF-only breweries often share this philosophy.
Check Barnivore directly
Barnivore entries often include notes from the brewery about specific formats. Reading the full entry can reveal whether the vegan rating applies to cask.
Our 100% Gluten-Free Breweries list
Breweries confirmed 100% GF often use no animal-derived finings either. Check the list and look up any brewery directly.
View 100% Gluten-Free BreweriesLinks & research
Further reading on finings, isinglass, and vegan alcohol guidance from external sources.
Origin, production, and use of isinglass as a fining agent in brewing and winemaking.
Overview of all common fining agents — isinglass, gelatin, bentonite, Irish moss — with animal vs. non-animal status.
UK's leading independent real ale consumer organisation. Information on cask ale production, dispense, and brewery practices.
Community-maintained database of vegan and vegetarian status for alcoholic beverages. Primary data source for Beer Check.
Guidance on vegan diets including alcohol and beer. Context on which fining agents are animal-derived.
Guidance on vegetarian diets, including whether isinglass-fined beers are suitable for vegetarians.