wa2.gif (4241 bytes)

abut9.gif (3095 bytes)

abut12.gif (3207 bytes)
abut10.gif (3636 bytes)

abut11.gif (4039 bytes)


How cork is made
An illustrated guide to the cork production process

Ever since wine bottles were adopted in the 18th century, cork has been the one-size-fits all closure solution. It's only recently that it has faced competition from alternative closures such as screwcaps and plastic corks, which some winemakers have adopted because they've been frustrated with the high incidence of 'cork taint'. This is a musty taint caused by the presence of trichloroanisole in the cork, and affects (depending on who you ask) from 2-5% of all bottles sealed this way.

But cork is fighting back. Producers are changing their production processes, implementing quality control steps and turning to curative strategies to rid cork of contamination. They are also emphasizing cork's green virtues: it is sustainable, has a low carbon footprint, and its economic importance preserves rural communities and the ecosystems of the cork oak forests. 

In this illustrated guide, I'll be taking a look at how this remarkable - albeit somewhat flawed - natural material is transformed into wine bottle corks. The pictures and video were taken during a visit to the largest cork producer (Amorim)'s production facilities in the Alentejo (south of Portugal) and near Porto (in the north)  

A cork forest in Portugal's Alentejo region: the exposed red/brown part of the trunk is where the cork bark has recently been harvested. Cork is grown across the mediterranean, with most of the forests in Portugal, quite a few in Spain, some in France, some in Sardinia and some in North Africa. 

The interface between the cork bark and the harvested portion of a branch. Just after harvest the denuded trunk is a vivid orange colour.

The bark is harvested every nine years. A number is left on each tree indicating the year of harvest. This tree was harvested in 2007; it will next be harvested in 2016.

Cork bark planks after harvesting. These are removed from the forests and stacked up in the open air to season at the cork factories. Recently, the best cork producers have made sure that this seasoning takes place on concrete, not bare earth. For Amorim this means that there's a hard storage area the size of a couple of football pitches.

Close-up of a cork plank

Planks stacked on pallets, ready for processing

The cork planks being boiled. In the old days, this is where a lot of cross contamination occurred, because the same water was used again and again in a boiling pit. Now, the leading cork producers will use a system that cleans the boiling water, removing potential contaminants. It's much more hygeinic. 

Planks after boiling. This softens them, cleans them and gets them ready for further processing.

Planks after boiling, stored on a metal pallet: wooden ones are a bad idea because this can lead to contamination from the chemicals used to treat wood.

Close-up of freshly boiled planks. The lines running through them are called lenticels: these are the gas exchange pores allowing air to get through the bark layer to the tree.

On to part 2, in the factory

Back to top