The rack and cloth press

A forming frame — a bottomless open box the size of the press bed — is set on the base or on the last rack. A cloth is laid in it with its corners hanging over the sides, pomace is filled in and levelled, and the corners are folded back over the top to enclose the parcel completely. The frame lifts away, a rack goes on, and the next layer is built on top of that. A cheese may be four layers or twenty, depending on the press.

Evenness matters more than anything else. A layer thicker at one side tips the whole stack as it compresses, and a tipping cheese blows out sideways: cloths burst, pomace escapes under pressure, and the run is lost. Experienced operators level obsessively and keep the stack plumb by eye as it grows.

The racks are traditionally hardwood slats in a lattice, now more often moulded food-grade polypropylene. Their function is purely to hold an open plane between layers and to distribute load; they do not filter anything.

Force comes from below or above, historically from a screw and now almost always from a hydraulic ram fed by a power pack. The essential technique is patience: pressure is raised in steps, allowed to run until flow slackens, then raised again. Going to full pressure immediately compacts the outer skin of each layer into an impermeable film and traps juice behind it.

A full press cycle takes from thirty minutes to a couple of hours. The cake that comes out — the pomace or pommy — is dry enough to break in slabs and stack, and traditionally goes to stock feed, to the orchard, or now increasingly to anaerobic digestion or pectin recovery.

Yields depend far more on fruit condition, milling and maceration than on the press itself, which is why yield figures quoted for presses in isolation are close to useless. What can be said with confidence is that a well-run rack and cloth press extracts more from coarse traditional pomace than a basket press does, and comparably to a good pneumatic press on the same material.

The cheese is entirely open to air and has a very large exposed surface, so a rack and cloth press oxidises heavily. Juice runs down the outside of the stack and across the bed in a thin film. For a traditional bittersweet cider this contributes to the soft, deep character expected of the style; for a pale aromatic cider it is a problem, and the answer is to sulphite in the receiving vessel and to move juice away from the press quickly rather than to try to stop it happening at the press.

Because the pomace can be macerated before building and because the press handles coarse material, the rack and cloth route allows a maker to reach a high phenolic extraction deliberately. That is a genuine reason to choose it over a pneumatic press for tannic fruit, quite apart from yield.

This is the real cost of a rack and cloth press and the thing most often underestimated. Every cloth, every rack, the frame, the bed and the collection tray carry pomace at the end of every pressing, and pomace left on any of them ferments and then turns acetic within a day in a warm cider house. Cloths are washed hot after every session and dried before storage; racks are scrubbed and rinsed; the bed is washed down.

A press that is not cleaned properly becomes the single largest source of acetic acid bacteria and vinegar flies in a small cider house, and the resulting volatile acidity is blamed on the ferment rather than on the equipment that inoculated it.