Bottles and bottling

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

Gravity bottling is the lowest-barrier packaging method — no CO₂ infrastructure, no kegging equipment, no counter-pressure filling. It is also the method where oxygen management is most difficult, because every step from fermenter to capped bottle introduces an opportunity for oxygen pickup. This page covers the materials (PET, glass, crown caps) and the practices that minimise that exposure without requiring equipment beyond what most beginning brewers already have.

PET bottles

Food-grade PET bottles — the carbonated soft drink bottle — are the most practical vessel for homebrewing bottle conditioning. They are reusable, recyclable, inexpensive, and they have a property that makes them superior to glass for one purpose: you can squeeze them.

Food contact status: food-grade PET is A-rated for ABNS, DES, and alkaline cleaners within the temperature constraint (40°C maximum). Regulation (EU) No. 10/2011 covers PET as an authorised substance for food contact packaging.

Oxygen transmission: plain PET transmits approximately 0.04–0.08 mL O₂ per day per 500 mL bottle at standard conditions. Over a 4-week conditioning period, this represents 1.1–2.2 mL total oxygen ingress — meaningful for hop-forward styles, but generally within the tolerance of robust beer styles conditioned and consumed within a few weeks of packaging.

Service life: PET bottles are reusable but not indefinitely. Scratches and micro-crazing develop on the interior surface with repeated use, increasing particulate release and creating harbour for biofilm. Visual inspection: reject bottles with visible interior scratching, cloudiness in the wall that was not present when new, or any deformation of the bottle geometry. Recarbonated soft drink bottles are ideal — clean, food-grade, correct pressure rating.

Squeeze-before-capping

The single most effective oxygen-reduction technique available for PET bottle conditioning, requiring no equipment:

With the bottle filled to the correct level (2–3 cm headspace), squeeze the bottle walls inward before applying the cap — until beer rises to just below the cap. The headspace gas (air) is displaced by the rising beer. Cap immediately while the bottle is still squeezed.

The calculation: a 500 mL bottle with 2 cm headspace has approximately 7–8 mL of headspace gas containing 1.5–1.7 mL of oxygen. After squeezing to approximately 70% headspace reduction: 0.3–0.5 mL O₂ remaining — a reduction of approximately 60–70% from the unsqueezed baseline. Across a 10-bottle, 5 L batch, total oxygen exposure falls from approximately 15–17 mL to 3–5 mL. This is a meaningful reduction achievable in seconds with no equipment.

Why it works and where it has limits: squeezing displaces headspace gas but does not purge the bottle with CO₂. Dissolved oxygen in the beer is not addressed. For hop-sensitive styles or extended storage, counter-pressure filling or CO₂-purge kegging remains superior. For beers consumed within a few weeks of conditioning, squeeze-before-capping is a practical and effective intervention.

Microplastics and PET bottles

The concern that PET bottles add meaningfully to the microplastic content of beer is not supported by the available evidence. ANSES 2025 data shows that glass-bottled commercially produced beer contains more microplastic particles per litre than PET-bottled beer in some measurements — the dominant sources of microplastics in beer are environmental and process-related, not packaging-derived. See Microplastics for the full analysis.

The relevant practical guidance remains: do not use abrasive cleaning tools on PET bottles (scratching increases particle release), and replace visibly damaged bottles.

Glass bottles

Glass bottles are preferred for extended conditioning — months rather than weeks — and for oxygen-sensitive styles where wall oxygen transmission from PET is a meaningful concern. Glass is impermeable to oxygen; the only oxygen ingress pathway in a glass bottle is through the crown cap seal.

Food contact status: glass is A-rated for all brewing chemicals and for food contact.

Practical disadvantages: weight, breakage risk, and the requirement for a bottle capper. Glass bottles are harder to inspect for internal cleanliness than PET (you cannot squeeze the walls to check the seal), and the narrow neck makes cleaning more demanding than a PET bottle that can be shaken with cleaning solution.

Sanitisation: ABNS fill-and-drain or DES spray-and-drain. The bottle interior is a Zone A surface — smooth, open, complete drainage. No special technique needed beyond ensuring full contact and adequate drain time.

Crown caps and liners

Standard crown caps

A standard crown cap consists of a steel shell and a liner. The liner is the food-contact component; it deforms under capping pressure to create the gas seal against the bottle rim. The liner material is typically PVC, LDPE, or oxygen-scavenging compound.

Standard crown caps can be sanitised with ABNS or DES before use without concern — the steel and liner materials are compatible with brief sanitiser contact.

Oxygen-scavenging liners (Amorim Oxyguard and equivalents)

Oxygen-scavenging crown cap liners contain a reactive compound that absorbs oxygen from the headspace gas after capping. The scavenging reaction is activated by moisture — contact with water or sanitiser consumes some of the scavenging capacity irreversibly before the cap has done its job.

Do not sanitise oxygen-scavenging crown caps with liquid sanitiser before use. Wetting the cap deactivates a portion of the scavenging capacity, reducing the benefit you paid for. The steel shell is sterile from manufacture; the liner does not need sanitisation for beer contact in normal bottle conditioning.

If you want to sanitise the caps: use a brief DES spray on the steel exterior only, allowing it to evaporate completely before capping, which minimises liner contact. Or accept that the cap shell is clean from the sealed packaging and proceed without sanitising.

See also: Crown cap liners for the ABNS deactivation mechanism.

The bottling wand

A bottling wand (gravity fill tube with a spring-loaded tip) fills the bottle from the bottom, minimising turbulence and splash. Turbulence at the fill surface introduces oxygen; bottom-fill substantially reduces this compared to top-fill from a loose hose.

Material: the wand body is typically PVC, PP, or LDPE; the spring tip is stainless. All are appropriate for beer contact. The junctions between the wand body and silicone hose are the points of interest — ensure these are cleanable and inspect them for residue build-up.

Sanitisation: DES spray-and-drain, or ABNS dip before use. The wand bore is a narrow-geometry surface; visual inspection of the bore is not reliable. PBW soak after every use clears proteinaceous residue that would otherwise build up at the tip junction.

Silicone transfer hose: sanitise by boiling (25–35 minutes; silicone is rated for it), ABNS flow-through (30 seconds contact in the bore, then drain and use immediately), or DES flush (spray through the bore, drain, proceed). See sanitising.

Carbonation drops

Carbonation drops (dextrose tablets) provide consistent priming sugar dosing without the measuring and mixing of a liquid priming solution. Each drop contains a calibrated mass of fermentable sugar sized for a 500 mL or 750 mL bottle.

Practice: drop directly into the dry bottle before filling. This avoids the oxygen-pickup associated with preparing a priming solution in a separate vessel and adding it before filling — the CO₂ produced by the sugar during conditioning helps purge residual headspace oxygen as conditioning proceeds.

The limitation: carbonation drops provide one drop = one bottle dosing. For exact carbonation level control (specific volumes of CO₂ by target style), liquid priming sugar with measured dosing is more precise. For consistent domestic use, drops are adequate.

Integrated bottling sequence — minimal oxygen pickup

Clean and sanitise the fermenter tap (ABNS, no-rinse) and the bottling wand and hose (ABNS dip or DES flush).
Prepare bottles: rinse clean bottles with fresh water. Sanitise with ABNS fill-and-drain or DES spray-and-drain. Stand upright.
Drop carbonation drop into each dry bottle.
Fill from the bottom using the wand — wand tip seats on the bottle base; fill at low flow rate; remove wand as beer rises to neck, leaving 2–3 cm headspace.
Squeeze (PET only) before capping.
Cap immediately. For oxygen-scavenging caps: apply dry, do not pre-wet.
Label with batch number and date. Store at conditioning temperature (typically 18–20°C) for 2–3 weeks.
Transfer to fridge to clarify and slow conditioning. Test a bottle at 2 weeks; adjust conditioning time based on carbonation level.

Honest limitation: headspace oxygen pickup is unavoidable in gravity bottling. The measures above reduce it substantially compared to uncontrolled filling, but counter-pressure filling (which fills the bottle pre-purged with CO₂) and kegging (which eliminates the bottle-filling step entirely) provide superior oxygen control for oxygen-sensitive styles. Gravity bottling is appropriate for robust styles, high-ABV beers, and beers consumed within a few weeks of conditioning.

PET bottles​

Squeeze-before-capping​

Microplastics and PET bottles​

Glass bottles​

Crown caps and liners​

Standard crown caps​

Oxygen-scavenging liners (Amorim Oxyguard and equivalents)​

The bottling wand​

Carbonation drops​

Integrated bottling sequence — minimal oxygen pickup​