KegLand have recently released an interesting video on YouTube claiming that the silicone O-rings they have been including with their corny kegs as the seal for the main keg opening have been tested and believed to allow significant amounts of oxygen to leech through them and into the keg.
The video itself is well worth a watch, as Kee from KegLand interviews Bruce Gunn, the owner of GunnLab Plastics Testing Pty Ltd and discusses the testing they performed and associated results. KegLand commissioned GunnLabs to perform a controlled test of their silicone keg O-rings to measure oxygen ingress from outside of the keg lid to the inside of the keg, and discovered that the silicone that these are made of allowed worryingly high amounts of oxygen to permeate through them.
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| Image from the GunnLab report showing the test being performed |
As you can see from the image above, for the test they cut the top of a keg and welded it to a flat metal sheet underneath. A full size keg couldn't be used as the volume/capacity inside it would be too large for the testing machine to accurately measure.
The report has been published on the KegLand website, and shows (among other things) that the silicone O-rings (white in colour) allow transmission of 11.3cm³ ox oxygen per day through them.
As you would expect, KegLand have developed another O-ring which is yellow in colour and constructed of different materials to address this issue and are referred to as "Low2" seals . In it's testing it allowed 0.41cm³ of oxygen per day to permeate through. A fairly significant difference by any measure when compared to the results of the white silicone O-rings.
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| The new re-designed keg O-rings are yellow in colour Image Copyright of KegLand |
While the numbers for the white O-rings seem quite high, it's worth noting that this is based on a test where the seal is exposed to 100% oxygen for the duration of the test, so under regular atmospheric conditions the actual number would be around 21% of this (which is the percentage of oxygen in normal air). We should also point out that the report mentions they didn't check if any oxygen ingress occurred through the pressure relief valve (PRV) or ball lock posts on the lid itself, but given the significant difference in readings by changing only these seals over, it's reasonable to assume any oxygen ingress through the other openings in the keg lid would be negligible.
So why is this important? Well, for finished beer (ie. beer that has completed it's fermentation) - oxygen is public enemy number one, with even the smallest amounts of oxygen causing an effect called oxidation which leads to discolouration, off flavours and essentially ruins the beer. Brewers go to great lengths to avoid their finished beer coming into contact with oxygen, by using processes such as pressure transfers to essentially eliminate O² contact and ingress. Having oxygen leak through the O-rings potentially brings all this hardwork undone - a chain is only as strong as its weakest link and all that.
Admirably, KegLand are admitting that the silicone O-rings they've been selling are problematic and are offering an "amnesty" where they are including some of their new yellow O-rings to customers when placing an order on their website by including a special promo code. You can of course just buy them separate if you wish - they're currently selling for $4 each on the KegLand website.
Some common myths and misconceptions were also addressed in the YouTube video - like the theory that because kegs are typically presurrised with carbon dioxide gas (CO²) this will provide protection against oxygen ingress, however this is not true. Although the keg is kept under pressure, materials like silicone will still allow air and oxygen to travel through them - regardless of the pressure on either side. This isn't indicative of a leak in the seal, but rather the gas permeating through the seal itself.
So is it time to hit the panic button and cease all brewing and kegging operations until you've replaced your seals? We don't think so - we're actually mildly skeptical of the severity of this problem. We're certainly not debating the accuracy of the test results, but perhaps there's a bit more to it. You can see from the photo in the GunnLab report (also included at the top of this page) that only the top section of a corny keg lid was used and welded to a sheet of steel providing a relatively small keg 'body' where the oxygen levels were measured from. In a full size corny keg, however, if oxygen leaks through the lid seal at the top, does it mix evenly with the carbon dioxide gas and come into contact with the beer? Or does the heavier CO² gas form a 'blanket' over the surface of the beer, with the lighter oxygen molecules floating above it at the top of the keg and therefore not coming into contact with the beer itself?
We're not sciency enough to know the answers to all of this, but what we do know is that we've had beers stored for months in kegs using the silicone O-rings for months without any oxidation issues. Of course we've experienced some oxidized batches in the past but put it down to other poor practices/mistakes rather than an issue with the keg seal allowing oxygen ingress, and no doubt there are hundreds of other brewers who have had similar experiences. The type of beer you're storing can also determine it's susceptibility to oxidation with more hop forward styles being more severely affected.
Will we be replacing the seals in our kegs anyway? Absolutely - with KegLand offering the O-rings for free with orders that are placed that include a special promo code, it certainly makes sense to take advantage of this. And if you miss out on the free offer, at only $4 each for a new seal it's undoubtedly a worthwhile and relatively cheap investment to help reduce the chances of any kegged beers suffering the effects of oxidation.
And while KegLand didn't mention any other particular brands of keg manufacturers, it's probably reasonable to assume that other brands are susceptible to the same problem, so regardless of what keg you're using it's probably worthwhile changing your seals over.
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