🍷 Agglomerated cork

An agglomerated cork is a stopper pressed from ground cork granules. The granules are by-products left over when natural corks are bored out of the bark. A binder approved for food contact holds them together.

Making one is simple in outline. The granules are milled to the size wanted. The stopper is then either moulded one at a time or squeezed out as a long rod and cut to length. Grade depends on granule size and final density, and the surface is treated to fine-tune how it behaves.

Its best quality is sameness. Every stopper in a batch is alike, which natural corks are not. There is a limit, though. APCOR says the seal is reliable for 12 to 24 months at most. That is why agglomerates go into simple wines that sell quickly and are drunk young.

On oxygen the comparison favours agglomerates. The AWRI says technical and agglomerated corks vary less than natural ones and let through little to moderate oxygen. In a 2017 OENO One trial, two technical stoppers passed about 0.005 mg of oxygen a day. A Saranex-lined screw cap passed the same. Synthetic stoppers let in 0.0143 and 0.047.

The name covers several types. A technical cork has an agglomerate body with discs of natural cork on its ends, and a Sparkling wine cork is built the same way. A plain agglomerate has no discs at all. For the family, see Cork (stopper) and Natural cork, and for the plastic alternative, Synthetic cork.