Styrene-based plastics — GPPS, SAN, and Styrolux SBC

	ABNS	DES	Cleaning	Beer/wort
GPPS rating	B (working dilution) / D (WDC)	B	A	A
SAN rating	A	A	A	A
Styrolux SBC rating	B (working dilution) / D (WDC accumulated)	B	A	A

The Cleaning column aggregates all cleaning product categories used in homebrewing at working concentrations. For a breakdown by cleaner type — alkaline percarbonate, phosphate-based, and oxidising — see the Cleaning compatibility section below. ABNS ratings reflect single-event WDC exposure; see the zone ratings and WDC accumulation discussion for the airlock fill/evaporate/refill scenario.

This page covers three chemically related but practically different styrene-based materials. General-purpose polystyrene (GPPS) is an amorphous, rigid, transparent polymer — inexpensive and widely used. Outside brewing it is found in CD jewel cases, disposable cutlery, yoghurt pots, and cheap transparent packaging. Styrene-acrylonitrile copolymer (SAN) is a copolymer of styrene and acrylonitrile — similarly transparent and rigid, but with substantially better chemical resistance. Outside brewing, SAN is used for transparent kitchenware, measuring jugs, mixing bowls, and refrigerator components where that resistance is needed. Styrolux SBC is a styrene-butadiene block copolymer — transparent and impact-resistant. The polybutadiene mid-block gives it better impact resistance than GPPS through a crack-arrest mechanism, but also introduces a non-polar rubber phase with different chemical vulnerability from pure polystyrene. All three are visually indistinguishable in service. In homebrewing, two Enolandia airlock types have been confirmed as GPPS by Declaration of Conformity: the compact 2-piece airlock (cod. 14037/14038) and the cylindrical fermenter with float (cod. 11965). Two further Enolandia airlock types — the 6-bubble airlock (cod. 13526) and the spiral airlock (cod. 09000) — are confirmed Styrolux SBC. Beyond Enolandia, styrene-based materials appear to be common across airlock manufacturers — an S-shaped airlock sold under The Vintage Shop brand (SKU FE371, MoreBeer) has been confirmed Styrolux SBC by Proposition 65 disclosure, suggesting the pattern extends well beyond a single supplier. Other styrene-based articles may exist in the homebrew market that have not yet been documented in this register. Airlocks are the only confirmed homebrewing articles in this material family identified to date; they are used throughout this page to illustrate the compatibility principles, which apply to any PS, SAN, or SBC article in equivalent use.

Identifying styrene-based plastics

General-purpose polystyrene carries Resin Identification Code 6 — three chasing arrows with the number 6 inside and PS below.

Resin Identification Code 6 — PS (Polypropylene)

The RIC 6 symbol as it appears on PS articles. SAN and Styrolux SBC carry no standard RIC codes of their own and may appear under the same marking, or unlabelled.

RIC symbol: Anton Poliakov, Wikimedia Commons, CC BY-SA 4.0. Modified: fill colour adapted for dark-mode display.

As with all RIC markings, code 6 is voluntary — many PS articles carry it, many do not. SAN has no dedicated RIC code of its own; it falls under the general category 7 ("other") in the RIC system, or it may carry a RIC 6 marking if the manufacturer has used that code loosely for styrene-based materials. Styrolux SBC similarly has no dedicated RIC code — it may appear under RIC 7, or unlabelled. A RIC 6 marking does not confirm GPPS; it identifies a styrene-based polymer, which could be GPPS, SAN, or SBC. A RIC 7 marking on a transparent rigid article in this context should prompt the question of whether the material is SAN or SBC.

Visually, all three styrene-based materials are nearly indistinguishable in practice. GPPS, SAN, and Styrolux SBC are all highly transparent and water-clear. General descriptions of the materials suggest GPPS may show a faint bluish tint in thin sections and SAN a very slight yellowish cast, but these differences are subtle, dependent on section thickness and lighting, and not reliable as a field identification method — direct observation of two Enolandia airlocks (compact 2-piece and spiral) showed neither tint on either article. Styrolux SBC is similarly transparent and water-clear. A product specification or manufacturer confirmation is the only reliable identification route short of destructive testing.

The Enolandia compact airlock is confirmed GPPS — crystal polystyrene — by Declaration of Conformity (DoC, 19 February 2024, signed Recchia Pietro, Legal Representative).¹ This covers cod. 14037 (Compact Mini, up to 30 L) and cod. 14038 (Compact Medium, up to 60 L); the grommet variants (14041, 14042) share the same airlock body. The DoC confirms compliance with EU Regulation 1935/2004, GMP Regulation 2023/2006, and EU Regulation 10/2011. The airlock is sold standalone and as part of beginner kits, including the Mr-Malt 5 L complete fermenting pail, the Georges Beer IPA starter kit, and other Georges Beer kits produced by Enolandia.

Enolandia also produce three other airlock types. The cylindrical fermenter with float (cod. 11965) is also confirmed GPPS (DoC, 7 January 2020). The 6-bubble airlock (cod. 13526) and the spiral airlock (cod. 09000) are both confirmed Styrolux SBC — a styrene-butadiene block copolymer. The styrene matrix gives it similar base chemistry to GPPS; the polybutadiene phase gives it better impact resistance but also different chemical vulnerabilities that are analysed in the compatibility sections below.

Enolandia describe themselves as a manufacturing company producing most of their catalogue in-house, with broad European distribution. Many homebrew retailers stock Enolandia products without manufacturer attribution — the yellow-capped S-type airlock with a "Made in Italy" embossed stamp is a likely Enolandia article. However, field research has identified at least one other upstream manufacturer: Hambleton Bard (UK), whose Better Brew brand produces a red-capped bubbler airlock sold through the same retail channels. Where an airlock carries no manufacturer identification, both the material and the manufacturer are unknown. Cap colour and chamber geometry are partial differentiators but not confirmed as reliable across all retail sources. The only reliable identification route is manufacturer confirmation.

Where a small, injection-moulded homebrewing article such as an airlock is genuinely water-clear and rigid — not translucent, not milky, not flexible — PS (GPPS, SAN, or Styrolux SBC) is the most plausible material. Other transparent rigid plastics exist but are uncommon at this price point and article type. This does not confirm PS; it makes it the reasonable working assumption in the absence of other information. GPPS is the conservative end of the plausible range for unknown articles — if the material turns out to be SAN, PP, PET, or another common transparent rigid polymer, following the GPPS process guidance remains appropriate and in most cases more cautious than strictly necessary. The two exceptions are PC and PMMA: PC has specific concerns around BPA that warrant knowing the material (see the Polycarbonate page); PMMA (acrylic) is more vulnerable to ethanol than GPPS and the GPPS DES guidance may understate the risk. For confirmed Styrolux SBC articles, the ABNS and DES ratings are similar to GPPS — follow GPPS guidance as a working proxy, but note that the SBC-specific mechanism discussion below applies. For brewers who cold crash routinely or want to eliminate the ABNS fill liquid question entirely, a confirmed-PP airlock — such as the KegLand range — is the simpler choice; PP carries no DDBSA concern at any contact pattern.

Enolandia's product photograph of the compact airlock shows a distinct bluish tinge. If genuine rather than a photography or lighting artefact, this would be a weak signal toward GPPS — but direct observation of two Enolandia airlocks (compact 2-piece and spiral) showed neither tint, so the photograph should not be relied upon for identification.

Field identification — the acetone test. Where grade confirmation from a manufacturer is unavailable, a sacrificed article can be tested with acetone (nail polish remover). A drop of acetone on GPPS causes rapid surface attack: immediate crazing, softening, or dissolution within seconds to a minute. SAN is substantially more resistant — the surface may show minor whitening under prolonged contact but does not dissolve or craze rapidly. Styrolux SBC will likely show a different response from both: the polystyrene phase attacks rapidly like GPPS, but the butadiene phase may produce a whitening or rubbery residue rather than clean dissolution, and the overall response may be slower than pure GPPS due to the crack-arrest mechanism. This distinction has not been directly observed on Enolandia articles; it is a mechanistic prediction. The test is destructive and should only be performed on an article that will not be reused.

SAN also has higher surface hardness than GPPS and slightly different acoustic character when tapped — GPPS gives a higher, sharper ring; SAN is marginally more deadened. These differences are subtle and easily confounded by how the article is held, so they are not reliable as standalone tests. The acetone test is the most accessible field test; visual and acoustic inspection are not definitive.

Primary observation — brief IPA contact. One minute of 70% IPA contact (towel application to the stem) produced no visible or tactile change on either of two Enolandia airlocks tested (compact 2-piece GPPS and spiral SBC) — no hazing, no crazing, no change in surface feel. This is consistent with the B rating for brief DES contact on both GPPS and SBC — see DES compatibility below — and with Enolandia's manufacturer compatibility claim for ethanol. It does not extend to sustained immersion.

Images

Images showing the Enolandia compact airlock, a typical RIC 6 marking on a PS article, and the visual similarity between GPPS, SAN, and Styrolux SBC articles — with guidance on where to look for material information — are planned for this section.

Food grade status

The full food contact compliance framework — what makes an article food grade, GMP requirements, EU simulant testing, DoC structure, repeated-use provisions, and what to do without a DoC — is covered on the Food contact compliance page. This section covers only what is specific to GPPS, SAN, and Styrolux SBC.

What makes a styrene-based article food grade?

For all three materials, the polymer backbone is not the primary food safety concern in finished articles — the distinction between food grade and industrial grade lies in the additive package: processing stabilisers, antioxidants, and mould release agents. In food grade articles, these must be selected from the approved substances list in EU Regulation 10/2011 Annex I and must pass migration testing against each substance's specific migration limit. PS has a long history as a food contact material — yoghurt pots, dairy packaging, and clear food containers are common food-grade GPPS applications, including in acidic environments. This context is relevant: the SML for styrene reflects regulatory caution at elevated exposure levels, not an expectation of harm from normal contact with compliant, undamaged articles.

Each polymer family carries monomer-specific SMLs:

Styrene (GPPS and Styrolux SBC): SML 0.045 mg/kg under EU Regulation 10/2011. Among the stricter limits in the regulation, reflecting styrene's classification as a possible carcinogen (IARC Group 2B) at elevated exposure levels. In a compliant, undamaged food grade article under normal cold aqueous contact, migration is well within this limit. The concern rises if the surface is physically degraded — crazing and cracking increase the surface area available for migration and break the compliance basis for the article.
Acrylonitrile (SAN only): SML not detectable (<0.010 mg/kg) — the strictest category. The acrylonitrile content of SAN is typically 20–30% by mass, but in finished articles the residual monomer is extremely low. SAN articles meeting EU 10/2011 requirements are assessed as safe; the limit reflects regulatory caution about acrylonitrile as a genotoxic carcinogen, not a practical expectation of significant migration from compliant articles.
Butadiene (Styrolux SBC only): SML not detectable (<0.020 mg/kg) — similarly strict, reflecting 1,3-butadiene's classification as a known human carcinogen (IARC Group 1) at occupational exposure levels. In a finished Styrolux SBC article compliant with EU 10/2011, residual monomer is expected to be extremely low. The compliance basis depends on the surface remaining undamaged.

A RIC code — whether 6 or 7 — says nothing about food grade status or GMP compliance. The food contact symbol (fork-and-glass), where present, confirms the article is intended for food contact use; it does not on its own confirm migration testing or DoC documentation.

Food contact in practice — all four Enolandia articles

All four Enolandia airlock types covered in this register have Declarations of Conformity confirming compliance with EU 1935/2004, GMP Regulation 2023/2006, and EU 10/2011, for contact with wine, vinegar, and beer.¹ The DoCs were received in May 2026 following direct correspondence with Enolandia. For what a DoC covers and how to assess undocumented equipment, see the Food contact compliance page.

Temperature limits

GPPS has a heat deflection temperature of approximately 70–80 °C for unfilled, unstressed material — but this is the material HDT, not the article limit. GPPS is also notably brittle: thermal shock from rapid temperature changes (such as pouring hot water into a cool airlock) can cause fracture at temperatures well below the HDT. The material is not appropriate for dishwasher use — a point consistent with Enolandia's product guidance and with the known behaviour of GPPS under repeated thermal cycling.

SAN has a slightly higher HDT, typically 85–100 °C, with better thermal shock resistance than GPPS due to the acrylonitrile co-monomer stiffening the chain. SAN is used for transparent kitchenware — measuring jugs, mixing bowls, food storage lids — that is expected to handle warm but not boiling liquids. Like GPPS, it is not suitable for dishwasher use.

Styrolux SBC has a lower HDT than GPPS. The polybutadiene mid-block lowers the effective heat resistance of the material — the rubber phase softens before the styrene phase approaches its HDT. For airlock use at ambient fermentation temperatures (16–22 °C) this is not a concern. For cleaning and sanitisation, the same ambient-temperature-only guidance applies as for GPPS, and if anything with greater caution: do not use hot water, do not use dishwasher. Specific HDT values for the Enolandia airlock grades have not been confirmed.

For all three materials in airlock use, the relevant temperature constraints are:

Hot water sanitisation: Not appropriate. Use ABNS or DES at ambient temperature.
Hot liquid contact: Not appropriate above approximately 40 °C. Airlocks are fitted after the fermenter is sealed and the wort has cooled — not a concern in normal practice, but inspect before reuse if accidentally exposed to hot steam or condensate.
Cleaning temperature: Always at ambient temperature.

Migration at elevated temperature. The monomer SMLs for styrene, acrylonitrile, and butadiene are established for standard test conditions. Elevated temperature accelerates migration significantly. For an undamaged article at ambient fermentation temperature (16–22 °C), migration is expected to be well within limits for all three materials. For a damaged or crazed article, or any exposure above ambient, the compliance basis no longer applies.

Compatibility — ABNS: GPPS B/D, SAN A, Styrolux SBC B/D

GPPS and SAN have fundamentally different ABNS compatibility profiles, and the mechanism explains why. Styrolux SBC shares GPPS's vulnerability through the styrene matrix, but the polybutadiene phase modifies the mechanism in a way that warrants separate treatment.

The mechanism — why GPPS is vulnerable

GPPS is an amorphous polymer with pendant phenyl groups along the chain backbone. DDBSA — the surfactant component of ABNS, present at approximately 300 ppm in working-dilution StellarSan — carries an aromatic benzene ring that interacts with the PS phenyl groups through aromatic pi-pi stacking. This facilitates DDBSA's penetration into the polymer matrix. The surfactant reduces the surface energy of the polymer and lowers the energy required to propagate a crack from an existing surface defect — the mechanism is environmental stress cracking (ESC).

Injection-moulded GPPS articles always carry residual moulding stresses, particularly at the gate, at thin-to-thick transitions, and at geometric stress concentrations — the stem of a compact airlock where it seats in the grommet is a typical example. These stressed zones are where ESC initiates. The crack propagates from the surface inward, visible as crazing: a network of fine surface cracks that scatter light, turning the previously clear material white or hazy.

At working dilution (300 ppm DDBSA), the driving force for DDBSA to penetrate the GPPS surface is reduced but present. Repeated contact produces gradual surface degradation — rated B. Under WDC conditions — DDBSA concentrated in the dry residue at CF≈667, approximately 200,000 ppm in the dry film — the interaction is severe. The concentration driving force for DDBSA to partition into the polymer matrix is much higher, and ESC at stressed geometry proceeds rapidly — rated D.

The ISM chemical compatibility chart rates PS as D for dodecylbenzene sulfonate (DDBSA) — severe effect under sustained contact conditions.² This is consistent with the mechanism.

The mechanism — why SAN is resistant

SAN introduces acrylonitrile co-monomer into the chain, typically at 20–30% by mass. The acrylonitrile groups are polar — they disrupt the regular aromatic structure that makes GPPS vulnerable. Two effects:

Reduced pi-pi stacking: The acrylonitrile groups interrupt the phenyl group spacing along the chain, reducing the regularity of aromatic interactions that facilitate DDBSA penetration.
Polar character: The nitrile group creates dipole interactions that compete with DDBSA's tendency to wet the surface and penetrate the matrix.

The net result is substantially better resistance to anionic surfactants compared to GPPS. SAN rates A for ABNS at working dilution and under WDC conditions. The ISM chart is consistent with this rating.²

The mechanism — Styrolux SBC: two competing effects

Styrolux SBC is an SBS-type triblock copolymer — rigid polystyrene end-blocks with a soft polybutadiene mid-block. It is a rigid thermoplastic, not an elastomer. The polybutadiene is present as dispersed rubbery microdomains within the polystyrene matrix, not as a continuous rubber phase.

Two competing effects determine its ABNS behaviour:

Effect 1 — shared styrene vulnerability. The polystyrene matrix shares exactly GPPS's pi-pi stacking susceptibility to DDBSA. At working dilution, the same ESC mechanism operates at moulding-stressed zones. This alone would produce the same B/D ratings as GPPS.

Effect 2 — crack arrest. The polybutadiene microdomains act as crack arresters — energy absorbers at crack tips. This is the fundamental reason SBC exists as a material: the rubber domains arrest crack propagation through the brittle polystyrene matrix, producing the toughness advantage over GPPS. This means ESC cracks that run freely through GPPS are slowed at rubber-domain boundaries in SBC. Under a single WDC event, crack propagation is meaningfully slower than in GPPS.

Effect 3 — butadiene phase DDBSA absorption. The polybutadiene domains are non-polar rubber with high free volume — thermodynamically favourable territory for DDBSA's hydrophobic alkyl chain. Under WDC conditions, as DDBSA concentrates in the dry residue, the butadiene domains preferentially absorb the concentrated surfactant. This effect increases with each successive WDC cycle as the non-volatile DDBSA residue accumulates — the butadiene phase becomes progressively DDBSA-saturated, the crack-arrest mechanism is degraded, and WDC-cycle ESC behaviour converges toward GPPS.

The practical upshot:

Single WDC (spray, drain, dry) — B. The crack-arrest mechanism provides meaningful protection over GPPS for a single event. Minor effect, acceptable.
Accumulated WDC cycles (the airlock evaporation scenario — each refill/evaporation cycle adds to the residue layer) — D. As the butadiene domains absorb accumulated DDBSA residue, crack-arrest benefit erodes. Repeated cycles converge to GPPS-level severity. This is the key hazard for airlocks used as intended, where fill levels drop through evaporation and the airlock is periodically topped up without cleaning.
Sustained immersion at working dilution — B. DDBSA at 300 ppm drives surface interaction but the crack-arrest mechanism limits propagation. Less severe than accumulated WDC residue.

The ratings for Styrolux SBC therefore match GPPS: B at working dilution, D under accumulated WDC conditions. The mechanism differs — crack arrest buys some protection in single-event scenarios — but the practical zone ratings are the same. Follow GPPS guidance for SBC articles.

Epistemic honesty — what is known and what is not

No published damage threshold exists for DDBSA on GPPS generally — or on SBC specifically. The ratings on this page are chemistry-based assessments derived from ESC literature, ISM chart data, the SBR/SBS mechanism literature, and the analysis above — not from a measured cycle count at which visible crazing appears. The cycle count before visible damage depends on the stress state of the specific moulding, geometry, residue per cycle, and temperature. What the chemistry establishes is this: the styrene matrix in both GPPS and SBC is vulnerable to DDBSA-driven surface attack; that vulnerability increases with each WDC cycle as DDBSA concentrates in the residue; and the crack-arrest benefit of SBC's butadiene phase erodes with accumulated exposure.

There is one PS/SBC-specific dimension to the epistemic honesty point that does not apply to PP or HDPE: surface damage from DDBSA-driven ESC is not just a structural concern — it is simultaneously a migration compliance failure. PP's propylene SML is 5 mg/kg, and the material migrates negligibly in any case; a mildly crazed PP surface is a hygiene nuisance. For GPPS and Styrolux SBC, the monomer SMLs are styrene (0.045 mg/kg) and butadiene (not detectable) — effectively the strictest tier in EU 10/2011. The DoC compliance basis applies to undamaged surfaces at standard test conditions. The same crazing event that reduces structural integrity also increases the surface area available for monomer migration and removes the compliance basis entirely. No data exists on migration rates from crazed PS or SBC surfaces — the regulatory framework does not test damaged articles. This is not an invitation to quantify the risk; it is the reason why retire-at-first-sign-of-damage is not a conservative precaution but the minimum standard for these materials.

Enolandia's manufacturer claim — that Star San and ethanol work well with their airlocks — is direct primary evidence that should not be dismissed.¹ It is backed by Declarations of Conformity confirming material identity and EU food contact compliance. The claim is probably accurate for the typical use pattern: brief spray-and-drain sanitisation contact. It is less clearly supported for the scenario of filling the airlock with working-dilution ABNS as the fermentation fill liquid for two or more weeks, and less clearly still for the accumulated WDC scenario across multiple brews. Whether Enolandia's claim covers sustained immersion or accumulated WDC exposure is not stated in the correspondence. The distinction matters and is addressed in the practical section below.

DuoTight cross-reference

The contrast between these materials and chemically robust alternatives is illustrated most clearly in the DuoTight case study, which covers the POM-to-POK design revision driven by WDC failure. The mechanism there — DDBSA-driven ESC at stressed geometry — is the same mechanism that operates on GPPS and SBC at thread-seat and stem geometries. PP and HDPE avoid it through backbone chemistry; SAN substantially reduces it through co-monomer disruption; GPPS and SBC do not.

ABNS — zone ratings for GPPS and SBC airlock geometry

The zone model produces different ratings for different parts of an airlock, because the ABNS contact pattern varies by geometry. Full operational detail — installation workflow, fill liquid choice, sanitisation method, washing practicality, and the grommet/stem interface — is on the Airlock equipment page. The material ratings are summarised here.

In normal use, an airlock installed with ABNS sanitiser goes through a WDC event on its outer body and stem at every installation: sanitiser is applied, drains partially, and dries in place. This is not a worst-case scenario — it is the normal outcome. The stem then sits in compressed contact with the grommet under load for the duration of fermentation, with dried DDBSA residue trapped at the contact zone. The fill liquid trough is the one zone where the brewer has control: ABNS fill liquid means sustained surfactant contact; water means no chemical concern at that zone.

The airlock evaporation scenario — where the fill liquid level drops through evaporation during a long fermentation and is periodically topped up — is equivalent to accumulated WDC cycling at the liquid trap zone. Each evaporation cycle leaves a concentrated DDBSA residue layer on the trap walls above the fill level; the next top-up dissolves some residue but the non-volatile fraction accumulates. For both GPPS and SBC, this is the highest-risk scenario for the liquid trap zone.

For SAN, all zones rate A. For GPPS and Styrolux SBC, zone ratings are identical.

Zone	ABNS — GPPS / Styrolux SBC	ABNS — SAN
Outer body (WDC at every installation)	D	A
Inner surfaces above fill line (WDC at installation; accumulates on top-up)	D	A
Liquid trap — ABNS fill liquid (Zone B)	B	A
Liquid trap — water fill liquid	A	A
Stem at grommet seat (Zone C)	D	A

D ratings here are structural. DDBSA-driven ESC causes crazing, embrittlement, and eventual loss of seal integrity — visible on inspection. The airlock is not in direct contact with the beer under normal conditions, so structural degradation of the airlock body does not directly create a product-contact migration event. The exception is suck-back.

Suck-back during cold crash transfers fill liquid into the fermenter. If the fill liquid is water, the material concern is negligible — styrene migration into a small volume of water at ambient temperature is well within the SML, and the suck-back volume diluted into the batch makes it immaterial. If the fill liquid is ABNS, the concern is taste (DDBSA at approximately 0.15 mg/kg in a 5 L batch), not toxicology. This is the primary reason water is the correct fill liquid choice — consequences of suck-back are minor. For operational detail on cold crash and suck-back volumes by airlock type, see the Airlock equipment page.

WDC accumulation charts

Per-material accumulation charts — mapping WDC exposure against damage thresholds by zone — are planned for this register. The airlock evaporation/top-up scenario will be modelled as accumulated WDC cycles.

Compatibility — DES: GPPS B, SAN A, Styrolux SBC B

GPPS, SAN, and SBC behave differently with ethanol. Critically, DES has a fundamentally different WDC accumulation profile from ABNS: ethanol is fully volatile and leaves no non-volatile residue. Unlike DDBSA, which concentrates in the dry film after each WDC event, ethanol evaporates completely. Each DES contact event is therefore independent — there is no residue accumulation across cycles. The concern with DES is purely the duration of liquid contact, not cycle accumulation.

For GPPS, ethanol at 70–80% in sustained contact causes swelling of the PS matrix. Ethanol is a small molecule that can penetrate between the amorphous chains, causing them to swell and separate. Repeated swelling-and-drying cycles fatigue the surface polymer, leading to microcrack formation over time. The ISM chart rates PS as D for ethanol at standard engineering concentrations under sustained contact.² The typical DES use pattern in homebrewing is spray-and-evaporate, not sustained immersion, and because ethanol is fully volatile there is no residue accumulation. Brief spray-and-evaporate contact is rated B — consistent with Enolandia's observed compatibility and with the IPA contact observation.

For SAN, ethanol resistance is significantly better. The acrylonitrile co-monomer disrupts the regular chain packing that allows ethanol to penetrate GPPS, and SAN's higher polarity reduces swelling by organic solvents. SAN rates A for DES at all homebrew contact patterns.

For Styrolux SBC, the polystyrene matrix is vulnerable to ethanol exactly as GPPS. The polybutadiene mid-block introduces an additional concern: butadiene-based rubbers rate C to D for high-concentration ethanol in elastomer compatibility data — the non-polar rubber phase swells under sustained ethanol contact. For brief spray-and-evaporate DES contact this additional vulnerability is not significant, because contact duration is short and ethanol evaporates completely — rated B, same as GPPS. For sustained DES contact (ethanol as a fill liquid), the butadiene phase swelling adds to the PS matrix swelling — the concern is equal to or greater than GPPS. Do not use DES as a fill liquid for SBC airlocks — this applies equally to GPPS, but is stated with the same force for SBC.

Because ethanol leaves no residue, the fill/evaporate/refill airlock scenario does not accumulate DES exposure across cycles the way ABNS does — but sustained immersion during a long fill period remains the concern for both materials.

DES fill liquid for all materials: Use water. Not ethanol. Water entering the fermenter on suck-back has fewer consequences than any chemical fill — the primary suck-back risk is biological (airlock contaminants, insects) rather than chemical, and that risk is managed by keeping the airlock clean and covered, not by the fill liquid choice. For a full discussion of suck-back risk and cold crash, see the Airlock equipment page.

Compatibility — cleaning: GPPS A, SAN A, Styrolux SBC A

For GPPS and SAN, the primary cleaning contact scenario is the routine post-brew clean — a brief soak in alkaline percarbonate cleaner, rinse, inspect. Both rate A for all standard homebrew cleaning categories at working concentrations and ambient temperature. The mechanical constraint applies to any PS, SAN, or SBC article: abrasive cleaning creates stress concentration points where ESC initiates in the styrene matrix. For airlock-specific cleaning practice — when a water rinse is sufficient versus when a cleaner is needed, and how geometry affects cleanability — see the Airlock equipment page.

For Styrolux SBC, alkaline percarbonate, phosphate-based, and oxidising cleaners at working concentrations and ambient temperature present no specific concern. The polystyrene matrix is resistant to these formulations. The polybutadiene phase contains unsaturated carbon-carbon bonds that are susceptible to oxidative attack — but at the concentrations and contact durations of standard homebrew cleaning, this is not a concern. Extended hot soaks in oxidising cleaners would be a different scenario and are out of scope regardless of material. Rating: A.

KegLand StellarClean and Five Star PBW

KegLand markets StellarClean as Powerful Brewery Wash (PBW); Five Star makes a separate product, Powdered Brewery Wash. Both use the abbreviation — both rate A for all three materials here and the guidance below applies equally to either product.

Alkaline percarbonate cleaners (Five Star PBW, StellarClean, ChemClean, ChemiPro Wash, Enzybrew 10): Sodium percarbonate at pH 11–12, releasing hydrogen peroxide and sodium carbonate in solution. All three materials are not susceptible to alkaline hydrolysis or oxidation from these formulations at working concentrations and ambient temperature. A brief soak to loosen soils, followed by a gentle rinse, is appropriate. Do not soak at elevated temperature. Enolandia explicitly state PBW and StellarClean are suitable for their airlocks.¹ Rating: A.

Phosphate-based alkaline cleaners (Grainfather High Performance Cleaner): Sodium tripolyphosphate (STPP) with trace metasilicate. All three materials are resistant at homebrewing concentrations. Rating: A.

Oxidising cleaners (ChemiPro OXI, StellarOxy): Purely oxidative action at working concentrations and ambient temperature. No concern for brief contact with any of the three materials. Rating: A.

Caustic cleaners (NaOH-based): Out of scope for this guide — see the Cleaning page. NaOH at high concentration and elevated temperature can attack PS, but this is not a homebrewing cleaning scenario.

Compatibility — beer/wort: GPPS A, SAN A, Styrolux SBC A

For all standard beer and wort contact scenarios in homebrewing, all three materials rate A. Beer and wort are aqueous systems at moderate pH — they do not present the surfactant or organic solvent challenges that make GPPS and SBC vulnerable to ABNS or DES. The DoC for the Enolandia SBC airlocks explicitly confirms food contact compliance with wine, vinegar, and beer.¹

Standard wort (pH 5.0–5.4, ambient): Weak organic acid environment. All three materials are resistant. For an airlock in normal use, wort does not contact the airlock body — the fill liquid separates wort from the airlock. Suck-back of fill liquid into the fermenter is addressed in the ABNS section above.

Standard beer (4–8% ABV, pH 4.0–4.4): No concern for any of the three materials. Ethanol at 4–8% is many times below the concentrations that drive swelling in GPPS or SBC.

High-ABV beer (above 8%): Still far below the concentrations that concern PS or SBC. No concern.

Sour beer (pH 3.2–3.5, lactic and acetic acid dominant): All three materials are resistant to dilute organic acids at homebrewing concentrations. No concern.

Hot wort: Airlocks are not present during hot wort handling. Not relevant.

Styrene-based plastics in homebrewing — the practical picture

Styrene-based materials appear in homebrewing primarily as airlocks. The confirmed articles in this register are the Enolandia compact airlock (cod. 14037/14038, GPPS), the Enolandia cylindrical fermenter with float (cod. 11965, GPPS), the Enolandia 6-bubble airlock (cod. 13526, Styrolux SBC), and the Enolandia spiral airlock (cod. 09000, Styrolux SBC). Beyond these confirmed articles, most cheap transparent rigid airlocks in the homebrew market are plausibly styrene-based — PS (GPPS, SAN, or SBC) is the dominant material at this price point and article type. Without manufacturer confirmation, grade is unknown; treat as GPPS, which is the most conservative assumption. The compact airlock is the most widely encountered in the Swedish market — sold standalone at Mr-Malt and included in beginner kits such as the Mr-Malt 5 L complete fermenting pail and Georges Beer kits. Its compact form factor suits fermenters where space above the lid is limited, and its two-piece design is quieter than bubble-trap airlocks. These are genuine advantages.

The practical process guidance is the same for GPPS and SBC, because the ratings are the same. Use it as follows.

What these airlocks are good for

Brief ABNS spray-and-drain sanitisation — consistent with Enolandia's compatibility claim and with the mechanism analysis. Drain thoroughly before adding fill liquid.
Water as the fermentation fill liquid — the correct choice regardless of material grade.
Routine inspection for crazing or whitening before each use.
Replacement at the first sign of surface degradation.
Beer and wort contact at ambient fermentation temperatures — no concern.

What these airlocks are not good for

ABNS as fill liquid. Do not fill the liquid trap with working-dilution ABNS for the duration of fermentation. Sustained surfactant contact is rated B — and the airlock evaporation/top-up scenario accumulates WDC exposure to D levels over time. Despite this being the instruction in at least one beginner kit sold with this airlock, it is not appropriate for GPPS or SBC.
Ethanol as fill liquid. Do not fill the liquid trap with undiluted DES. The sustained contact scenario is not appropriate for either GPPS or SBC. Use water.
Hot water sanitisation or dishwasher use. Not appropriate for any of these materials. Use ABNS or DES at ambient temperature.
Abrasive cleaning. Never use brushes or abrasive pads. Scratches create stress concentration points and trap biofilm.

Sanitisation process

Spray or dip the airlock with ABNS or DES for the manufacturer's recommended contact time, then drain thoroughly — shake gently to clear the liquid trap as fully as possible. Brief ethanol contact (DES spray, allow to evaporate) is also effective and leaves no residue. Either approach is consistent with Enolandia's compatibility claim and with the mechanism analysis above.

Fill liquid: cooled boiled water or bottled water. Once sanitised and drained, fill the liquid trap with water. Some brewers prefer dilute ABNS or ethanol as fill liquid on the basis that it maintains a sanitising barrier against airborne contaminants during fermentation — this is a reasonable position, though how long dilute ABNS remains effective when exposed to air is debated. For styrene-based airlocks specifically, the compatibility argument favours water: ABNS fill liquid means sustained surfactant contact with the trap walls, and ethanol fill means sustained solvent contact — neither is appropriate for extended periods with GPPS, SAN, or SBC. The fill liquid discussion, including the sanitising-barrier debate, is covered in full on the Airlock equipment page.

Migration

For undamaged GPPS and SBC airlocks at ambient fermentation temperatures, styrene migration into the water fill liquid is expected to be well within the 0.045 mg/kg SML. For SBC, the butadiene SML (not detectable) additionally applies — the DoC confirms EU 10/2011 compliance for undamaged articles at normal contact conditions. The concern arises if the surface is crazed or damaged, if the fill liquid is ABNS (which drives surface interaction), or if the airlock is exposed to elevated temperatures.

The airlock is not in direct contact with the beer under normal conditions. Suck-back during cold crash is the exception — for quantified risk see the ABNS zone ratings above and the Airlock equipment page. The short version: styrene exposure from a suck-back event is negligible due to volume geometry; ABNS fill liquid suck-back is a taste concern, not a toxicology concern. Use water fill liquid.

Cost and service life

These airlocks are inexpensive. Treat them as consumables. Inspect before each use; replace at the first sign of crazing, whitening, or loss of clarity. A crazed airlock — where the migration compliance basis no longer applies and where biofilm can colonise the microcracks — should not be reused. The cost of a replacement airlock is not the cost of a batch.

Assessing and retiring equipment

These are the most chemically sensitive small components in a typical homebrew setup. The damage signals to watch for:

Crazing or surface whitening. The primary visual signal for DDBSA-driven ESC or solvent-induced surface fatigue. Crazing appears as a fine network of cracks — visible under a torch held at a low angle. Whitening or haziness where the material was previously water-clear indicates the same process. Crazing is irreversible. Retire immediately — not because the risk is known to be severe, but because the compliance basis no longer applies to a crazed surface and the surface texture cannot be reliably sanitised.

Loss of transparency. A clear airlock that has become hazy or opaque without visible crazing suggests solvent-induced surface swelling or thermal damage. Retire it.

Discolouration. Yellowing or browning of previously clear material indicates chemical degradation, UV exposure, or thermal exposure. Retire it.

Mechanical scratches. Clean with a soft cloth or brief soak only — never a brush or abrasive pad. Scratches create stress concentration points and trap biofilm that sanitiser cannot reliably reach.

Persistent staining or odour. If a thorough alkaline percarbonate soak and rinse does not restore the article to a clean, odour-free state, the surface is too damaged for reliable sanitation.

The principle is the same as for every other article in this register: compliance testing is conducted on undamaged, GMP-manufactured equipment. Once visible damage is present, the compliance data does not apply — not because the risk is known to be elevated, but because it is unknown. The monomer SMLs for styrene and butadiene have no headroom to accommodate a damaged-surface migration increase.

The compliance data no longer applies to a damaged surface — not because the risk is known to be elevated, but because it is unknown.

Summary by article type — scenarios

Scenario	GPPS	SAN	Styrolux SBC	Conditions
Beer / wort contact (fermentation, 0–22 °C)	A	A	A	No restriction
ABNS — single spray-and-drain WDC	B	A	B	Ambient temperature; drain thoroughly
ABNS — accumulated WDC (outer body, stem, evaporation/top-up)	D	A	D	Normal installation outcome; use water fill liquid
ABNS — liquid trap, water fill liquid	A	A	A	No restriction
ABNS — liquid trap, ABNS fill liquid (Zone B)	B	A	B	Sustained surfactant contact; water preferred
DES — single spray-and-evaporate	B	A	B	Fully volatile; no residue accumulation
DES — sustained fill liquid	Not appropriate	A	Not appropriate	Ethanol swelling; use water
Cleaning — all standard homebrew cleaners	A	A	A	Ambient temperature; soft cloth or brief soak only; no abrasives
Hot liquid contact / dishwasher	Not appropriate	Not appropriate	Not appropriate	All three materials; thermal stress and HDT concern

Rating key: A = unrestricted within stated conditions · B = suitable with precautions; monitor over service life · D = severe effect; avoid · Not appropriate = outside safe use conditions

Summary by article type

Article	Food grade	Temp limits	ABNS	DES	Cleaning
Enolandia compact airlock — GPPS confirmed (cod. 14037/14038, with and without grommet 14041/14042)	DoC confirmed: EU 1935/2004, GMP 2023/2006, EU 10/2011. Signed 19/02/2024.¹	No hot liquid contact. Not dishwasher safe. Ambient use only.	Single WDC: B. Accumulated WDC / outer body / stem: D. Use water fill liquid.	Single spray-and-evaporate: B. Sustained fill: not appropriate. Use water.	A — soft cloth or brief soak only.
Enolandia cylindrical fermenter with float — GPPS confirmed (cod. 11965)	DoC confirmed: EU 1935/2004, GMP 2023/2006, EU 10/2011. Signed 07/01/2020.¹	No hot liquid contact. Not dishwasher safe. Ambient use only.	Apply GPPS ratings as above.	Apply GPPS ratings as above.	A — soft cloth or brief soak only.
Enolandia 6-bubble airlock — Styrolux SBC confirmed (cod. 13526) and spiral airlock — Styrolux SBC confirmed (cod. 09000)	DoC confirmed: EU 1935/2004, GMP 2023/2006, EU 10/2011. Signed 09/12/2021 (13526).¹	No hot liquid contact. Not dishwasher safe. Ambient use only. Lower HDT than GPPS — same cautions apply with greater emphasis.	Single WDC: B. Accumulated WDC / outer body / stem: D. Same ratings as GPPS; crack-arrest benefit erodes with accumulated WDC cycles. Use water fill liquid.	Single spray-and-evaporate: B. Sustained fill: not appropriate — butadiene phase adds to PS matrix ethanol vulnerability. Use water.	A — soft cloth or brief soak only.
The Vintage Shop S-shaped airlock — Styrolux SBC confirmed (SKU FE371, sold via MoreBeer)	No DoC. Material confirmed by California Proposition 65 disclosure naming Styrolux as the listed substance.³ No EU food contact documentation identified.	No hot liquid contact. Not dishwasher safe. Ambient use only.	Apply SBC ratings above.	Apply SBC ratings above.	A — soft cloth or brief soak only.
Generic unlabelled airlocks (bubbler / S-type / 3-piece)	Unknown — material and manufacturer unconfirmed. May be Enolandia (SBC) or Hambleton Bard / Better Brew (material unknown) or other. Do not assume GPPS without confirmation.	Unknown.	If confirmed GPPS or SBC: apply ratings above.	If confirmed GPPS or SBC: apply ratings above.	A if any styrene-based material confirmed.

Enolandia, direct email correspondence with the author. Two exchanges: (1) 8 July 2025, Andrea Giannetto, Marketing & Sales — confirmed material as "usually polystyrene" without specifying grade; (2) 20 May 2026, Andrea Giannetto — confirmed compact airlock (14037/14038) as Crystal polystyrene GPPS; 6-bubble (13526) and spiral (09000) airlocks as Styrolux SBC; provided Declarations of Conformity for all four articles. DoC for compact airlock (14037/14038) dated 19/02/2024, signed Recchia Pietro, Legal Representative. DoC for cylindrical fermenter (11965) dated 07/01/2020. DoC for 6-bubble airlock (13526) dated 09/12/2021. All DoCs confirm compliance with EU Regulation 1935/2004, GMP Regulation 2023/2006, and EU Regulation 10/2011, for contact with wine/vinegar/beer. The airlock body carries a "patented" marking; patent IT201900002259A1 identifies the compact airlock geometry. Enolandia product page — compact airlock (accessed May 2026). ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶ ↩⁷ ↩⁸
ISM Industrial, Chemical Compatibility Chart — Polystyrene (September 2021). ISM's scale: A = Excellent, B = Good/minor effect, F = Fair, D = Severe effect. Rates PS as D for dodecylbenzene sulfonate (DDBSA) and D for ethanol at standard engineering concentrations and sustained contact conditions. These ratings reflect bulk chemical exposure — the distinction between brief spray contact and sustained immersion is not made in the chart. Covers general PS; SAN rates significantly better across most categories. Accessed May 2026. ↩ ↩² ↩³
The Vintage Shop S-shaped airlock (SKU FE371) — MoreBeer product page carries a California Proposition 65 warning reading: "WARNING: This product can expose you to chemicals including Styrolux, which is/are known to the State of California to cause cancer." The named substance "Styrolux" is the BASF trade name for styrene-butadiene block copolymer (SBC), confirming the material as Styrolux SBC. No DoC or EU food contact documentation has been identified for this article. "The Vintage Shop" appears on the product page as a brand attribution; manufacturer identity has not been independently confirmed. Accessed May 2026. ↩

Identifying styrene-based plastics​

Food grade status​

What makes a styrene-based article food grade?​

Food contact in practice — all four Enolandia articles​

Temperature limits​

Compatibility — ABNS: GPPS B/D, SAN A, Styrolux SBC B/D​

The mechanism — why GPPS is vulnerable​

The mechanism — why SAN is resistant​

The mechanism — Styrolux SBC: two competing effects​

Epistemic honesty — what is known and what is not​

DuoTight cross-reference​

ABNS — zone ratings for GPPS and SBC airlock geometry​

Compatibility — DES: GPPS B, SAN A, Styrolux SBC B​

Compatibility — cleaning: GPPS A, SAN A, Styrolux SBC A​

Compatibility — beer/wort: GPPS A, SAN A, Styrolux SBC A​

Styrene-based plastics in homebrewing — the practical picture​

What these airlocks are good for​

What these airlocks are not good for​

Sanitisation process​

Migration​

Cost and service life​

Assessing and retiring equipment​

Summary by article type — scenarios​

Summary by article type​

Footnotes​