Party Pig cask/gravity results

A while ago I posted here discussing the use of a party pig as a cask by leaving out the pricey pressure pouch and instead letting it carb naturally and pouring with the benefit of gravity. I finally got around to filling it with the mild from my bar exam partigyle. I was out to find the answers to two main questions. First, the party pig is made of thin plastic and without the pressure pouch maintaining pressure so there was a possibility the beer would not build enough pressure to force CO2 back into solution and the beer would be a little too flat, even for a gravity pour. Second, would the beer keep drinkable for more than a few days with all that air coming in as delicious beer pours out? I found my answers.

I filled the party pig and without really thinking about it I put the restrictor plate behind the nozzle. The restrictor plate, as the name suggests, is designed to limit the flow of fully pressurized beer so you don't end up with glass after glass of foam. With a pressure pouch it works great but as the pressure starts to diminish in the pig the pour turns more into a gravity pour but the restrictor plate causes the beer to pour out very, very slow. I should have left it out since I didn't have the pressure pouch trying to shove beer out. So in a second pass at using the party pig as a cask/gravity vessel I would leave the restrictor plate out and see if it improves flow without allowing more oxygen to flow in and spoil the beer quicker.

I filled the party pig four days after fermentation began. Brewing a 4% beer with S-04 meant fermentation was complete within a day or so. The beer was still full of diacetyl but I expected the yeast in suspension would slurp it all up before consumption. I then let it mature for a couple weeks before tapping it. When I filled it the walls of the pig were very flexible. A few days later there was a little more pressure but not nearly as much as the pig would have with the pressure pouch. I tapped it, drank a few pints, and then put it in the fridge. It stayed in the fridge for about a week and a half before I drained off some more pints. Then repeated each weekend until it was empty.

The first few pours were very nicely carbonated with a very cask-like appearance and mouthfeel. Soft carbonation and nice foamy head. The flavor of the mild is delicious and far exceeds expectations. After about six or seven pints over three days the pressure started to balance out in the party pig and the beer started to pour at a creep. There's about a gallon left. The character changed from a foamy beer similar to a cask engine pulled beer to more of a still gravity pour. It's not a bad beer by the time it reaches gravity-like mouthfeel but I really wish I had left out the restrictor plate because it takes a while to pour a pint.

On day five I took a small sample to see how the beer was doing. Surprisingly, it seemed to have carbonated up a little because the pour came out slightly foamy. It wasn't the big beer engine-like foam of the first few pours but not the still pour I was expecting. Not sure where the added pressure came from since the pig has stayed at the same temperature in the fridge the whole time.

Another sample on day seven came out foamy for a couple ounces while the rest poured very slowly. Despite the slow pour there was still a small amount of carbonation. Minor signs of oxidation are setting in but it's actually not too bad in the beer since it gives it some added fruity character that works ok with the English ale yeast. It's not the brilliant cask-like first few pints but I've had worse beers in my life. There's maybe a little under a gallon left. I expect to knock out the rest of the beer within a couple weeks so I will see how much the beer changes over three weeks.  

Tasted on day thirteen and unfortunately the beer is showing signs it's on it's way out. It's still drinkable but it's definitely showing signs of oxidation well past its prime. The fruity flavors are starting to fade out to hints of cardboard-like stale flavors. I plan on finishing it off this weekend (around day fifteen or sixteen) which is probably the limits on this beer. I used a pint to make some spent grain bread so that left about half a gallon to polish off.

Finished the cask on day seventeen. The mild was still drinkable but definitely showed some signs of oxidation. It was completely flat by the last couple pours.

Overall I think it held up fairly well for beer sitting on that much oxygen but I probably wouldn't have felt comfortable giving it to guests as something I was proud of after a week or so when it started to oxidize. Overall the experience was about what I expected but I'd rather not want to drink flat, slightly oxidized beer so I think the party pig makes more sense in this cask format as something drank at one time (you know, at a party). I have some ideas about ways to prolong the life and prolong the carbonation but I'll wait to discuss them until I have a chance to think through it some more.