Equipment
Stainless steel tanks
What should I know about stainless steel fermentation tanks?
In short
A stainless tank is a welded vessel, usually cylindrical, in an austenitic stainless grade chosen for corrosion resistance in acidic, chloride-containing conditions. It contributes nothing to the cider and lets no oxygen in.
That neutrality is the point. Everything that happens in a stainless tank is something the maker chose: oxygen, temperature, lees contact and time are all controlled rather than inherited from the vessel.
The main variables in choosing one are grade and surface finish, whether it is jacketed for temperature control, whether it is closed or has a floating lid, and how well it can actually be cleaned.
Grades, finish and why they matter
The common grades in beverage work are the 304 and 316 families, with 316 containing molybdenum for better resistance to chlorides and to acid. Cider is acidic and cleaning regimes may involve chlorides, so 316 is specified for the most exposed parts even where 304 is used for the shell. What is not acceptable is mild steel, galvanised steel or aluminium in contact with juice or cider; all react, and the result is metal pickup, haze and a metallic taint.
Surface finish matters more than most buyers expect. Stainless resists corrosion because of a passive chromium oxide layer, and that layer forms and re-forms on a clean surface. A rough, scratched or contaminated surface holds soil, harbours organisms in a biofilm and is the place pitting corrosion starts. Interior welds are ground and polished for the same reason, and a tank with rough internal welds is a tank that will be hard to keep clean for its whole life.
Steel wool, wire brushes and carbon-steel tools should never touch a stainless tank: embedded iron particles rust and initiate pitting. Stainless is cleaned with plastic or stainless tools and with chemistry, not with abrasives.
Closed tanks, floating lids and headspace
A closed tank has a fixed head, a manway, a valve for CO₂ or an airlock arrangement, and usually a spray ball for cleaning. It is filled to a defined level with a headspace that can be flushed with carbon dioxide or nitrogen, so oxygen contact after fermentation is under complete control.
A variable-capacity or floating-lid tank has an open top with a lid that sits on the liquid surface, sealed against the wall by an inflatable gasket or a channel filled with water or a food-grade liquid. The lid is lowered as volume falls, so a partly emptied tank need never carry a headspace at all. This is a genuinely useful design for small producers whose batch sizes do not match their tank sizes, and it is the practical answer to the ullage problem that ruins so much cider.
The seal on a floating lid is a maintenance item. A dried, cracked inflatable gasket, or a water channel that has evaporated, leaves the surface open to air and to vinegar flies while looking as though it is sealed. This is a common and quiet cause of surface film and rising volatile acidity.
Jackets and temperature control
A jacketed tank has a dimpled or channelled cooling surface welded to the outside of the shell, through which glycol or chilled water circulates, and an insulating layer over it. This is the standard means of holding a fermentation at a chosen temperature, and at commercial scale it is close to essential: a large ferment generates enough heat to run itself far above ambient without it.
Jacket placement determines what can actually be controlled. A single jacket low on the tank cools the bulk; a second jacket high up allows a temperature gradient to be managed and helps during cold stabilisation. Temperature is read by a probe in a thermowell in the liquid, not by a strip on the outside of an insulated tank.
Fittings are where tanks go wrong
- Valves: butterfly valves with a removable seat can be stripped and cleaned; ball valves with an internal cavity are notoriously hard to clean and are a standard source of contamination.
- Sample taps, sight glasses and level tubes are dead legs that CIP flow does not reach; they are cleaned by hand and by disassembly.
- Gaskets are consumables. A perished or swollen gasket harbours organisms and can taint the product; food-grade elastomers appropriate to the temperature and chemistry are specified.
- Threaded fittings in the product path should be replaced with hygienic clamp or dairy fittings wherever possible, because threads cannot be cleaned in place.
- Spray balls have a coverage pattern and a required flow and pressure; a spray ball fed by too small a pump wets the tank without cleaning it.
Also answered on this page
Questions this page covers, so you can tell at a glance whether it is the one you want.
- What grade of stainless steel for cider?
- What is a variable capacity tank?
- Do I need a jacketed tank?
Related
What people ask next
Questions readers ask about the things this page mentions. Each one goes to the section that answers it rather than to a page written to receive the question.
- What temperature should cider ferment at — Most cider is fermented cool, commonly between about 12 and 18 °C. Cooler ferments keep more fruit aroma and run slower; above the low twenties the cider tends towards hot, solvent-like higher alcohols.
- What vessel should i ferment cider in, and does the shape matter — The material question comes down to three properties: how much oxygen crosses the wall, whether the vessel adds or absorbs flavour, and whether the surface can genuinely be cleaned and sanitised.
- How do i sterilise cider bottles — Wash them clean first, then sanitise with a no-rinse sanitiser or a sulphite solution, and fill while still wet with it. Bottles that look clean but have dried deposits inside are the usual source of bottle spoilage.
- What should i ferment cider in — Anything inert, cleanable and closable: glass demijohns, food-grade plastic, stainless steel, or a wooden cask if you can keep it sound. Vessel shape and material change how much oxygen the cider sees and how fast it clears.
- Does cider need oxygen to ferment — Yeast needs a little oxygen early on to build the sterols it uses to stay healthy, but the ferment itself is anaerobic. After the first days oxygen is a liability, because it feeds acetic acid bacteria and oxidises the cider.
- How is cider matured
Sources
What this page rests on. Where a source is marked as registered rather than read, CiderHQ is recording that the body is authoritative on the subject without claiming to have worked through the document itself. See our evidence policy for what each state means.
Cider and perry production technical training material
Peter Mitchell / Cider and Perry Academy · reference work · registered as competent for this subject
Searched again on 2026-08-25 and it remains the one printed source here that a bibliographic check cannot fix, because it is not a published work with an edition. It is course material issued to participants of a training programme, so there is no catalogue record to verify, no ISBN, and no lawful public copy. Its state stays `registered` for that reason rather than through inattention.
Hochschule Geisenheim University — beverage technology
Hochschule Geisenheim · university · retrieved 2026-08-24
German beverage-technology research covering apple wine and fruit juice processing, including the enzymology of clarification.
The Science of Cidermaking and associated technical writing
Andrew Lea · reference work · passage verified 2026-08-24
Written by a food chemist who worked at Long Ashton on apple phenolics. Unusual among specialist cider writing in that it is primary-research-adjacent: the author is describing work he did, and cites the literature. This is why it is registered at tier 1 for chemistry while a general cider book is not.
Where to go next
- Cider making equipment — The rest of the equipment material, grouped by what each piece is for.
- How cider is made — The methods this equipment exists to carry out.
- Troubleshooting — The faults that are traced back to equipment and to cleaning.