Cask dispense

This page follows the EU regulatory framework and Swedish market context described in the introduction.

Cask ale — real ale conditioned in the vessel and served by gravity or hand pump — is a distinct category from kegged beer. Where a keg is sealed, pressurised with CO₂, and served under gas pressure, a cask is a living vessel: yeast continues conditioning the beer inside, carbonation is from residual fermentation only, and once tapped, the cask is open to atmosphere. These differences have direct implications for how cask equipment is maintained and what chemical compatibility considerations apply.

What cask dispense is — and isn't

A cask is not a keg with a different tap. The differences matter for cleaning, sanitisation, and service life:

No exogenous CO₂. Carbonation comes entirely from residual yeast activity in the cask. The served beer is naturally conditioned — typically lower carbonation than kegged beer, with a softer texture.

Gravity or hand pump. Beer exits the cask under gravity (tilted cask, tap at the low end) or via a beer engine (hand pump that draws beer by suction). Both introduce air into the cask headspace as beer is removed — unlike a keg, where CO₂ replaces beer volume.

Service window is short. Once tapped, air enters. Oxidation and microbial growth (acetobacter converting ethanol to acetic acid) begin immediately at varying rates depending on cellar temperature and hygiene. A correctly managed real ale cask should be consumed within 3–5 days of tapping at cellar temperature (10–12°C). After this window, quality deteriorates rapidly.

Cask components

Cask vessel — stainless steel

Homebrewing casks are typically stainless steel — the same 304 alloy as Cornelius kegs. All stainless analysis from the Cornelius keg guide applies: inert to brewing chemicals, cleanable at high temperature, no compatibility concern.

Wooden casks (oak firkins) are used in traditional commercial brewing for specific styles (sour ales, barrel-conditioned). These require different management (soaking to prevent drying, sulphite treatment, specialist cleaning) and are outside the scope of this documentation.

Shive and keystone

The shive is the bung that fits the large hole in the cask head — the primary closure. The keystone is the smaller fitting in the cask side wall that accepts the tap. Both are typically food-grade polymers (LDPE, HDPE, or PP — materials that are A-rated for food contact and brewing chemicals).

The shive has a central thin section that is punctured by the hard spile during venting; the keystone has a similar central plug punctured by the tap at serving. Both are single-use consumables by convention — once punctured, they are not resealed. In homebrewing, keystones and shives can be replaced between batches; they are inexpensive and widely available.

Spiles

Hard spile: a solid peg (typically wood or MDPE — medium-density polyethylene) that seals the shive vent hole. When the hard spile is in, the cask is sealed against gas exchange. Used between service periods (overnight, between sessions) to prevent excess carbonation loss.

Soft spile: a porous peg (typically untreated softwood) that allows controlled venting of excess CO₂ while preventing air ingress above a gentle positive pressure. Used during active venting of a newly tapped cask to vent "green" CO₂ before service, then typically removed during service to allow gas exchange.

Material analysis for spiles is straightforward: wood is food-grade and appropriate for brewing contact; MDPE is A-rated for all brewing chemicals. No concern.

Tap — Pint365 (material specification open item)

The cask tap (also called the keystone tap or peg tap) punctures the keystone and controls beer flow. The Pint365 cask tap is commonly used in the homebrewing context in Sweden; the material specification for the tap body and internal components has not been confirmed from a primary source.

Open item: contact Pint365 for tap body material, seal material, and food contact compliance documentation. This is the same documentation gap flagged in the documentation problem page — material identity without documentation is inadequate for a food-contact component.

Until confirmed: use the Pint365 tap as designed (single-batch use per manufacturer's intended application), clean thoroughly between uses, and replace the tap if any surface change, discolouration, or off-flavour is detected.

Sustained wet storage — the key distinction from keg

For kegs, the primary chemical compatibility concern is the wet-dry cycle — liquid applied, surface dries, non-volatile components concentrate. Cask dispense creates a different exposure: sustained wet contact between beer and the cask components throughout the service period.

During service, the cask interior is in sustained contact with beer at ambient cellar temperature for typically 3–5 days. The components in sustained beer contact (shive, keystone, tap body, tap seals) experience slow, continuous leaching conditions rather than the cyclical concentration mechanism of the WDC.

The relevant question for sustained wet contact is not WDC concentration but rather the steady-state leaching rate from the materials in contact with beer. For stainless, wood, LDPE/HDPE/PP, and food-grade polymers, sustained beer contact at cellar temperature poses no identified concern. The key unknown is the Pint365 tap seal material — if it is NR, the nitrosamine precursor leaching concern applies in full and replacement is required.

Cleaning sequence

Before conditioning (pre-fill):

Clean the cask with hot PBW at 60°C, fill through the shive bung opening. Soak 20–30 minutes. Push cleaning solution out through the keystone or drain.
Rinse thoroughly with clean water.
Sanitise with ABNS fill — fill through shive, 30 seconds contact, drain. Close the shive hole with a clean bung.
Fill with conditioned beer through the shive opening using a sanitised filling tube.

After service (post-empty):

Rinse immediately with cold water while residue is still wet — pour several litres through the shive opening and drain through the keystone hole.
PBW clean at 60°C as above.
Rinse and dry-store clean for next use.

The tap requires its own cleaning attention — the bore of the tap is a narrow-geometry Zone B surface that accumulates residue and is inaccessible during routine cleaning. Disassemble the tap (if design allows), brush the bore, PBW soak, rinse.

The cask ABNS spray bottle — sustained storage is not WDC cycling

A common practice in cask dispense (and in some homebrew contexts) is keeping ABNS working-dilution solution in a spray bottle for sanitising the tap exterior and spile before reinserting. This bottle may sit for days or weeks between uses.

ABNS in a closed spray bottle does not undergo a wet-dry cycle — there is no evaporation from a sealed bottle. The WDC mechanism requires air exposure and evaporation; a sealed bottle simply stores the working-dilution solution, which remains at its initial DDBSA concentration indefinitely (subject to the pH stability of the product, which is adequate over weeks).

Sustained ABNS storage in a spray bottle is appropriate. The spray bottle seal material (EPDM for the Biltema pH 7–14 bottle; confirmed for ABNS use) is the relevant material check — not the WDC model.

What cask dispense is — and isn't​

Cask components​

Cask vessel — stainless steel​

Shive and keystone​

Spiles​

Tap — Pint365 (material specification open item)​

Sustained wet storage — the key distinction from keg​

Cleaning sequence​

The cask ABNS spray bottle — sustained storage is not WDC cycling​