So should you choose agglomerated or natural corks for your stoppers? Assuming that you are not going to use a synthetic option (screw tops or worse still a plastic cork imitation), what are the different characteristics of agglomerated and natural corks?
Within the agglomerated cork bracket, you can opt for micro-agglomerated (with 0.5 to 2.0mm granule size) which have the advantage that they are stronger and harder wearing that standard agglomerated corks and then you can choose between extruded and moulded agglomerated corks. Extruded agglomerated corks are the cheapest cork option and the reason is because they are not very strong, so more likely to break when uncorking a bottle and giving a less reliable seal to the bottle. Moulded corks (which are always micro-agglomerated) are a much higher quality option and are becoming increasingly common in the industry now, because they are much stronger and their reliability/consistency is much better than extruded corks, but they are twice the price of extruded corks.
Increasingly moulded agglomerated corks are taking market share from natural corks and the simple reason is price. Natural corks are extremely complex to produce given the fact that they have to be produced from uneven cork bark and then selected and divided by quality (and then selected and divided again after treatment) and are less easy to sterilize than agglomerated corks. This makes good quality natural corks expensive and there is no point pretending otherwise, but is the extra money worth it?
There are three great advantages to natural cork:
- its natural porosity will allow a wine to age in a bottle that an agglomerated cork would not
- agglomerated corks contain synthetic binding agents, which although food-safe are not ideal to be in contact with the delicate flavours that many drinks have
- natural cork looks beautiful and organic, whereas agglomerated cork is uniform and looks semi-synthetic
So natural cork is the best closure for high quality wines and spirits and confers a feel of quality and a nature to drinks that are bottled with it. You can look at natural cork as steak compared to agglomerated cork as burger meat – they both have their place in the food market, but when choosing between natural and agglomerated you need to decide if you are selling fast food or fine dining…….
The system of classifying natural wine corks into different quality categories is to say the least a complex one. The key thing to understand is that there is no cross industry standard applied to corks coming out of Portugal (where the vast majority of natural wine corks are produced) and more complicated still, broad quality standards vary considerably from country to country. So a natural cork considered generally to be of high standard in a south American country, might be generally considered of indifferent quality in the US market. These differences are largely a result of unscrupulous distributors peddling corks as being of a higher quality than they should be and mixing batches of lower quality corks into higher quality ones in order to fool winemakers. The only real solution to all this nonsense is to try and avoid national distributors and buy direct from an honest supplier in Portugal!
Anyway, here you can see a photo of 4 corks that we selected from 4 different quality samples (from left to right – Second – First – Super – Extra). In terms of the mechanical integrity of the corks, they will all be pretty much the same and in terms of the manufacturing process, they have all been treated in exactly the same way. The real difference is in the appearance of the corks, so the “Extra” quality cork will have only minor imperfections in the surface, whereas the “Second” quality may have some quite large holes.
In very broad terms, you might pay 240 euros per thousand for Extra quality 45x24mm corks, but 120 euros per thousand for Second quality (as a reference point, agglomerated corks you might only pay 30 euros per thousand for). Agglomerated and micro-agglomerated corks have there place for providing a low cost option for wine corks, but they do not confer the badge of quality for wine that natural corks do – here you can see an agglomerated, micro-agglomerated and natural cork side by side.
Because cork is a natural product that can only be harvested from one kind of oak tree, there is a limited supply. It is also quite expensive to harvest from the trees, as the bark has to be removed by hand. This means that cork is not a cheap raw material! It has unique properties and has a certain beauty to it, particularly in its more natural forms, but you have to pay good money for it and there is no point as a producer of cork products pretending otherwise and trying to compete directly with cheaper, lower quality synthetic alternatives.
The relatively high price of cork means that not a single speck of cork is wasted however. So cork that comes off the trees that is not of suitable quality to make natural wine corks is either used to make expanded cork (if it is resinous) or granulated, so everything that comes off the tree can be used. Then the off-cuts that are produced when the natural wine corks producers punch them out is also granulated. The dust that is created when the corks are sanded down to size is collected and used to power the furnaces that heat the water used to treat the cork. Larger waste scraps of cork that are produced are added to granules and compacted to make decorative boards for cork flooring. And now in some countries even used corks are collected to be granulated and used again.
The key to the industry is natural wine corks however, because these are the most valuable part of the industry (a single ‘flor’ quality wine cork can cost over one euro!). The value that comes from these wine corks, means that the rest of the cork used for agglomeration, flooring, moulding etc can be sold at a lower price. The natural wine cork sector is competing with synthetic corks and screw-tops as well as being undermined by the growing popularity of micro-agglomerated and technical wine corks; without the relatively high value sales that come from natural wine corks however, there will not be sufficient value left in the industry to pay for the expensive harvesting of cork. So it is vitally important that natural wine corks get all the support possible, because the entire cork industry depends on them. Natural cork is a wonderful product and in a world where “natural” is increasingly prized over “synthetic”, we have to hope that wine producers and drinkers will continue to value the amazing properties and beauty of natural cork and not always look for cheaper alternatives, because an entire industry depends on it.
Or put another way – this is why you should use natural cork!
Here is our price list for expanded cork boards (also known as black cork). The prices are per m2 and some minimum order quantities apply according to thickness. Our products will be delivered direct from the factory in Portugal to your address – we have extremely competitive shipping costs to the UK, northern Europe and beyond, so please ask us for a quote.
Please note that prices do not include VAT and the exchange rate for £ may vary.
Natural wine corks are still used to seal the vast majority of the world’s best wines, because all the other solutions (either synthetic or other cork options, such as micro-agglomerated, normal agglomerated or 1+1 technical corks) do not offer the unique properties that natural cork offers as well as the cosmetic appeal. We are not going to look at which is the best cork option for wine bottles here, or how natural wine corks are made. Rather we are just going to look at classification.
Natural wine corks are generally classified as Flor, Extra, Super, First, First/Second, Second and Third. The main differences between the different options are cosmetic, but sorting them out into the different categories is a major headache for cork producers. There are 6 stages of quality selection:
1. It starts with the selection of the cork as it comes off the trees; high quality cork bark will be thick and will be relatively smooth throughout its thickness, so the cork producers make their first selection when they buy the cork from the cork forest owners.
2. The large planks of cork are cut to smaller sizes by men with very sharp knives – as they cut they also separate the best looking pieces of cork with greater thickness and smoothness from the less good parts.
3. After being boiled (cooked) to make the cork more pliable (and to disinfect it), the boards are cut into strips, which then have the corks punched out of them, like a hole punch going through paper. For premium cork production, this is still done by hand, with experienced workers taking the strips of cork in their hand and choosing the best place from the strip to punch the corks from (so they will look for the smoothest sections). In the photo below you can see the effect (here the corks have been replaced into the holes they came from).
4. These corks are now trimmed to size and washed to make them completely sterile, after which they are machine sorted. This is done by passing the corks one by one through a laser, which analyzes their surface and separates the smoothest corks from those with more imperfections. The lower quality corks are then taken out of the selection process (they can be used to make colmated corks, for 3rd quality corks or regranulated).
5. The corks that pass the machine test are then put on a conveyor belt, which also slowly rotates the cork as they pass along. Sitting next to the conveyor belt will be several women (in the cork industry it is still always women!) who will inspect every single cork and reclassify any that they see the laser has classified incorrectly.
6. Finally the samples of corks from every production batch are taken for lab analysis to make sure nothing has been missed and their humidity level, shearing strength, dimensional recovery and sterility will be checked.
Different producers may have slightly different selection processes and of course some are more rigorous than others. There is a real problem with classification however in that there is no universal system of distinguishing one quality grade from another. So for example one cork producer’s “Extra” might be another’s “Super”. And to complicate things even more there are major divergences between countries as to what is generally considered a certain grade of cork. So a certain cork producer will know that when he sells his first grade corks in to country A he should classify them as Super, but when selling to country B he should classify them as First/Second. It makes it extremely difficult for wine bottlers to compare pricing from one cork supplier to another and the only way to do it is to compare samples and hopefully to build up a relationship of trust with their supplier.
The final complication is that it is unfortunately common for cork distributors in their various countries to reclassify and mix up corks that they receive from their supplier in Portugal (Portugal supplies the vast majority of the world’s natural wine corks). So the will mix a batch of Second quality corks in with some Firsts and call them all first for example (Second quality corks would typically be around 30% cheaper than First quality, so it makes a big difference.
Below you can see a photo showing 4 different qualities of natural wine corks (Second, First, Super and Extra):
The differences are mainly cosmetic as the way they have all been made and processed is exactly the same. Unfortunately the only way you can make sure that you will get what you pay for is to work with a trustworthy supplier and to buy corks direct from Portugal, so that you do not buy reclassified corks from local distributors.
Our local cooperage has 350 used brandy oak casks (500 litres) available for sale. Price is €180 per cask ex works.
All broken staves will be repaired by the cooperage. Please contact us at email@example.com if you are interested.
We are able to supply a broad range of casks new and used (particularly from the port wine trade), so if you are interested, you should contact us at CorkLink. We have also been doing some work sourcing leather products from Portugal for some of our clients recently and it has been fascinating to get involved with this industry.
It is great to see people from outside the cork industry talk about the benefits to the planet of using cork rather than synthetic alternatives – this is true for cork closures for wine bottles and of course for its other uses such as insulation or flooring. Elizabeth Royte has recently written a fantastic article for onearth magazine , in which she talks about a visit to Portugal’s cork forests and how the cork industry is winning a battle to demonstrate the environmental benefits of using cork. In the article she talks about the low carbon footprint of cork closures relative to aluminium or plastic, the success that the cork industry has had in all but eliminating cork taint (technically known as TCA) from cork closures and how important it is to preserve the unique ecosystem that the cork forests nourish and protect.
So a great article and something for environmentally aware consumers to think about when they want to choose between buying wine with a synthetic closure or with natural cork!
On top of a haystack, five kilometers from Evora, the Ecorkhotel has been built, with the principal external walls clad in expanded cork. It is a four-star hotel, located in Évora an area rich in cork forests, where the ferocious summer heat can make building insulation a very important factor. The hotel as used the concept of Eco Tourism as a main selling point, using solar and geothermal energy as the principal sources of power, building using locally sourced clay and recycling water. And of course the expanded cork used for insulation is 100% natural, using the resin contained within the cork to bond the cork granules together.
Cork and expanded cork in particular has seen rapid growth in sales in the construction sector over the last 10 years in part because of growing knowledge about its green credentials and unique insulation characteristics, but also because the cork sector has seen numerous innovations to make the appearance of cork building products more attractive to bring out the natural beauty of cork (so for example in cork flooring panels and wall coverings).
If you would like more information about the range of cork materials for the construction sector we have available, please contact us.
We have been selling a lot of tapered or conical corks recently in both agglomerated and natural cork. Generally we do not work from stock and for orders of the larger conical corks we can make up orders of just 1000. There is a sizing system for conical corks which is detailed below. Generally we can produce an order in less than two weeks and we can make sizes outside of those detailed below.
|Size No.||Top mm||Bottom mm.||Length mm||Size No.||Top mm||Bottom mm.||Length mm|
Five to ten years ago there were various people declaring that the cork industry would be largely consigned to history as screw caps take over from cork stoppers for wine bottles, but in fact over recent years corks have been increasing their share of the market rather than losing it. The truth is that the major players in the cork industry had become complacent and the threat of screw caps and even plastic stoppers precipitated a spate of innovation which has left the cork industry in a much stronger position.
Going into a cork factory now you see a lot of changes from what they would have looked like ten years ago – one of the big changes is that you see serious looking people with clipboards and white coats walking round; these are the lab staff who control quality and who have been largely responsible for virtually eliminating TCAs (the chemicals from corks that can taint wine) from cork production, by introducing new treatments and dramatically improving quality control.
The other major difference in cork production is that technical corks have become a major part of the wine stopper market. Technical corks in their most common form (known as 1+1 corks) consist of an agglomerated cork body with a natural cork disc on each end. So the wine only comes in contact with natural cork (rather than agglomerated cork and the synthetic adhesives that this contains) and the user sees natural cork whilst the cork is still in the bottle, making the appearance much more attractive.
The technical corks are much lower cost than natural wine corks (for example, depending on quality they may cost say 60 euros per thousand rather than 120 euros per thousand for natural wine corks), but they have many of the benefits of natural wine corks. So although they may be a little more expensive than screw caps they are a compelling alternative, because not only do they lend the wine the quality feel that natural corks give, with the vastly improved quality control that corks come with nowadays, they also give the winemaker total security that their wine will be safe inside the bottle.