Skip to content
CiderHQ
Search

Equipment

Corks, agrafes and muselets

How is a sparkling cider corked, and what is the wire cage for?

In short

A sparkling cork starts as a cylinder much wider than the bottle neck. A corking machine squeezes it in jaws and pushes it in; inside the neck it tries to expand back, and the part above the neck does expand, which is why a used sparkling cork is mushroom-shaped.

An agrafe is a sprung metal clip used to hold a cork in during secondary fermentation in the traditional method. A muselet is the wire cage fitted over the finished cork.

Neither the clip nor the cage does the sealing. The cork seals; the metalwork stops the pressure pushing it out.

How a sparkling cork is built

Most sparkling closures are composite. The body is agglomerated cork — granules bonded together — and one or two discs of natural cork are glued to the end that will face the cider, because natural cork is what gives the elastic recovery and the sealing behaviour that granulate alone does not. The number of discs is a quality distinction visible on the underside of any used cork.

Compression is severe. The cork is squeezed to well under the neck diameter, held for a moment and pushed, and it begins recovering immediately. That recovery is what makes the seal, and it is also why a sparkling cork cannot be pushed back into the bottle by hand once removed: it has expanded and it does not go back.

Corks for sparkling use are sold with a defined moisture content and are used as supplied. Boiling or soaking them, which is sometimes recommended for still-wine corks, ruins the compression behaviour and is not appropriate here.

Agrafe, muselet and the traditional method

In the traditional method the cider ferments a second time inside the bottle. Historically that bottle was closed with a cork held by an agrafe — a sprung steel clip that hooks under the bottle ring and clamps over the cork — and a few producers still use them because the cork forms a better seal against the neck than a crown cap and because the aged character is held to differ. The great majority now condition under a crown cap with a plastic cup insert, the bidule, which catches the sediment for disgorging.

When the bottle is disgorged and topped up, the finished cork goes in and is immediately covered by a muselet: a wire cage with a cap plate, twisted tight under the ring. Six half-turns of the wire loop is the conventional number and is a genuinely useful thing to know, because it is how a hand-caged bottle is made consistent.

The cage is not decorative. Pressure inside a sparkling bottle acts on the base of the cork, and a cork that is not restrained will work its way out over time, particularly if the bottle warms. Bottles are never stored or transported with the cage removed.

Corking machines

A sparkling corker has jaws — usually four, sometimes an iris of many segments — that close on the cork and a plunger that drives it down into the neck. Bench and floor models are hand-operated; commercial ones are pneumatic and often combined with a caging head in one machine.

The jaws must match the cork and the plunger must be aligned with the bottle. A misaligned plunger drives a cork in crooked, which seals badly and stresses the neck. The machine also needs the bottle supported from below, because the driving force is considerable.

A still-wine corker is not the same machine and will not fit a sparkling cork. The compression required is far greater, and attempting it damages the cork, the machine or both.

Cork as a source of taint

Cork can carry haloanisole taint, the compound family responsible for the musty, damp-cardboard character usually called cork taint. It arises from microbial methylation of halophenols, which can come from the cork itself, from chlorinated cleaning agents used anywhere in the supply chain, or from the storage environment. It is not confined to natural cork and it is not confined to bottles.

The practical consequences for a cider maker are two. Buy closures from a supplier who can say what their taint control is, and never use chlorine-based cleaning products anywhere near corks, packaging materials or the store where they are kept. Chlorophenols formed by chlorine cleaners reacting with phenolic material are a documented route to taint in a cellar, and the cider maker controls that end of it entirely.

Opening a caged bottle

A sparkling cork is a projectile held in by a wire. It is released by holding the cork firmly, keeping a thumb over it from the moment the cage is loosened, pointing the bottle away from people and from anything breakable, and turning the bottle rather than the cork so the cork eases out under control. Eye injuries from released corks are well documented. A bottle that has been shaken or warmed is chilled and left to stand before opening.

Also answered on this page

Questions this page covers, so you can tell at a glance whether it is the one you want.

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.

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.

Where to go next