Red fermentation asks more of a tank than any other job in the cellar. The cap has to be worked, several times a day, for weeks. Temperature has to move through a planned curve. Pomace has to come out at the end, and something has to happen to the vessel for the rest of the year.
Format is usually argued as open-top versus closed. That framing is too coarse to decide anything. These four questions decide it.
1. How is the cap worked?
The single most consequential question, because it determines what the team physically does every day of vintage.
Punch-down wants an open surface and a working platform above it. Reach matters more than anything else: a tank that is too wide, or whose opening is too small, turns a routine operation into an awkward one performed forty times a vintage.
Pump-over works through a closed tank perfectly well, and for larger volumes it is usually the only practical option. It is gentler and more repeatable, at the cost of a pump in the circuit.
If the programme is built around punch-down and on a winemaker being able to see and reach the cap, the argument for open-top is not aesthetic. A square open-top format such as the Diamond Square OT Fermenter gives that access while keeping the tank rectilinear against a wall; the OT Conical Fermenter does the same on a conical base.
If pump-over is the method, a closed tank such as the Enclosed Fermenter removes the exposure question entirely and does other jobs the rest of the year.
2. How does the pomace come out?
Skins and seeds have to leave the tank, and this is the job cellar teams rate as the worst of vintage.
A flat bottom means someone gets inside with a shovel through a manway. It is slow, it is hot, it is a confined space, and it happens once per ferment per tank. Multiply by the number of red ferments and it is a meaningful share of the vintage labour budget.
A conical bottom lets gravity do it. Pomace migrates to the discharge and the tank substantially unloads itself — the Enclosed Conical Fermenter empties a five-tonne ferment in around five minutes.
The trade is floor. A cone needs support height, which raises the tank and costs headroom that a flat or sloped base does not.
Two useful tests: how many red ferments does this tank do per year, and does the cellar have the height. Where both answers are large, the cone pays for itself in the first vintage.
3. What does the tank do for the other eleven months?
Fermentation occupies a few weeks. The tank is an asset for fifty-two.
This is where open-top formats have historically been weak. An open tank cannot hold wine safely for months, so a cellar built around open-top fermenters needs a second set of vessels for storage — capital that sits idle during vintage while the fermenters sit idle for the rest of the year.
Two answers exist. A closed fermenter is a fermenter in autumn and a storage or aging tank afterwards; the Enclosed Fermenter is specified around exactly that multi-role life.
Or the tank’s boundary changes with the season. The Everseal™ System closes an open-top format with a verified seal — sixty days of maintenance-free seal pressure — so the same vessel that was worked open in March holds wine protected in June. The Diamond Square VC Fermenter and the Variable Capacity Tank are the formats built around that.
If a cellar is capacity-constrained — and most are — this question is worth more than the first two. A tank that does two jobs is not a compromise; it is the reason the cellar fits in the building.
4. Who sees this room?
Not a vanity question. It changes the specification.
A cellar that visitors walk through has to be presentable on an ordinary Tuesday in February, not only when it has been prepared. Open tanks holding wine are not presentable at arbitrary moments; sealed tanks are. Tank geometry also decides whether a row reads as an ordered room or as utility equipment that happened to be installed in a line.
Square formats align flat against a wall and against each other, which is why the Square Tank Series exists — the same fermentation work, in a shape that makes a room out of a tank farm. If the cellar is part of the visitor experience, this belongs in the specification rather than in the fit-out budget.
Putting it together
The four answers usually converge quickly.
| If the deciding factor is | The format that answers it |
|---|---|
| Punch-down access, tight floor | Square open-top |
| Punch-down access, conical emptying | Open-top conical |
| Pump-over, multi-role vessel | Closed fermenter |
| Emptying speed above all | Enclosed conical |
| Open access and year-round holding | Everseal™-sealed VC format |
Where two factors pull in different directions, the honest answer is usually that the cellar needs both formats in some ratio — and working out that ratio is a planning problem, not a product comparison. That is the subject of planning equipment as a cellar system.
The full set of red fermentation formats is at red fermentation tanks.