UPDATE: now with readers’ photos of Party Seven!

Beer has been a vital part of society for almost all of civilised history. 4000 years ago the Sumerians were brewing in honour of their gods; in medieval Europe beer represented something clean to drink when the purity of water was questionable; nowadays it’s used more as a social lubricant. And which discipline of natural philosophyhttp://static.guim.co.uk/Guardian/business/gallery/2008/mar/18/inflation.spending.history/xpartyseven-990.jpg is responsible for this nectar of culture, health and prosperity?

Well of course I wouldn’t be writing about it if it weren’t chemistry. But therein lies the problem – who these days cracks open a can and thinks to themselves “thank goodness for the clever research chemist who invented a vinyl co-polymer/C-enamel coating for tin cans”? But chemists are the ones behind all these advances in canning technologies and the art of zymurgy (“chemistry of brewing and distilling”, dontcha know).

As we put out the call for surviving cans of “Party Seven”, a septa-pintal vessel taken to parties in the 60s and 70s containing (allegedly) decidedly ungourmet beer, I thought I’d look into the chemistry of beer cans – and would you believe it, the beer can’s 75th birthday is later this month. See the bottom of the post for more details on our Party Seven quest.

On 24 January 1935 a revolutionary product from a relatively small brewery hit the shelves in Richmond, Virginia. Krueger Finest Beer came from the Gottfried Krueger Brewing Company in Newark, New Jersey, and was the first beer to be sold in cans. Far enough away from their home turf that rejection of the cans wouldn’t hit their profits, Richmond became the birthplace of a new beer storage phenomenon, as while the other breweries watched from a distance the public literally lapped up the new canned beer.

Canning had of course been around for a while before 1935, but two major problems had hampered progress of canned beer: pressure and corrosion. The welded seams which held cans shut couldn’t stand the pressure required for beer at the time (80lbs/sq in), but more troubling was the drink’s tendency to react with the tinplate of cans at the time.

The pressure problem was solved with better welding techniques, but it took until 1933 for American Can to come up with a process to protect cans from their contents. Vinylite, the polymer also used to make vinyl records, was applied to the inside of the cans and protected them from corrosion. Another year’s research led them to a “dual coat process” involving enamel and Vinylite, which they called “Keglined”, and this was the coating used in Krueger’s groundbreaking first cans of beer.

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Krueger's first canned beers: Finest Beer and Cream Ale

So that’s the cans themselves, but what about the beer inside them? Brewing itself is perhaps the earliest successful example of biotechnology, but the bit of chemistry/physics I’d like to focus on is the problem of giving beer a creamy head as it’s poured out of the can. Enter the widget.

After mediocre success with a syringe-kinda-thing known as an initiator, Guinness (of Guinness fame) were keen to bring that draught smoothness to cans. Two revered names in brewing, Tony Carey and Sammy Hildebrand, are on the patent that suggested a “sudden gas discharge from an internal compartment” to inject a bit of life into the beer as it was opened.

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The widget in a Guinness can

This was initially from a compartment attached to the can itself, but was a bit tough to manufacture so this was left alone for a while. A few years later the widget, a hollow plastic sphere about an inch across with a little hole in it, was developed.

Guinness hasn’t as much CO2 dissolved in it as some beers, so when it’s poured from the can (as opposed to from a tap) it seems a bit lifeless. The widget is filled with nitrogen and held in the can while it’s filled with beer, and as the can is sealed off they add a shot of liquid nitrogen. As this evaporates it pressurises the can and further pressurises the nitrogen in the widget.

When the can is opened, the pressure drops and the nitrogen shoots out of the hole in the widget, agitating the beer and bringing the carbon dioxide out of solution – giving you a nice creamy beer. Magic, maybe. Chemistry? Definitely.

There’s two of the many ways that chemistry has improved our enjoyment of the good stuff since the 30s. If you’d like to know or share any more info about the science of beer, let me know in the comments!

And now to the nub of the matter: Party Seven. If you have a can of Party Seven, reasonably well-preserved, please do send us a photo – or if you don’t mind relinquishing it, arrange to send it to us! Contact Brian on emsleyb AT rsc DOT org with your photos or submissions.

We may, of course, take it unto ourselves to put the preservative chemistry to the test with the RSC press office’s vast array of “complex scientific experiments”, developed in the pub. It seems to me that there’s only one way to prove this 75-year-old technology…

Your Party Seven photos

Andy Barkley sent in this photo of his thirsty friends holding with pride a Party Seven. “Sorry, can’t supply a real can, but here’s a photo from a trip to the Isle of Man.  I went there in 1974 with the pictured guys.  We were 6th formers doing our A levels in a very troubled Northern Ireland,” Andy told us.

Students holding can of Watney's Party Seven

Andy's friends clearly pleased with their beerhemoth

Neil from Shrewsbury sent this in – it’s a commemorative can from the 1980s in very good nick. See Neil’s comment for more info.

"Party Seven" commemorative can from 1980s

A "Party Seven" commemorative can from the 1980s