Carbonation conundrum

[Portreath]

I put together a bit of an ad-hoc brew last month. I guess it could be labelled a brown ale, of sorts.
It fermented out in under a week, so I waked it straight into a pressure barrel with the intention of getting around to priming it after another week. Anyway, I forgot to add the priming sugar, but I noticed the barrel walls were showing sign of pressure build up, so drew off a taster. And I’m pleased to see the beer has good carbonation and tastes pretty dam good too. Happy day, and another good brew for Christmas.
Conversely I made a Guinness clone which is 4 weeks in the bottle, I opened one last night and it pours with a nice head but the head dissipates within seconds. The beer tastes good, but is really quite fizzy, almost as fizzy as a dispensed cider. Does anyone have any ideas why the head dies off so quickly?

 

[JonBrew]

I've experienced head retention issues in recent brews and have gathered the following in terms of possible causes (posted in a previous thread):

• Unhealthy fermentation - apparently stressed yeast can leave behind/create lipids which can cause an issue. The fix is to pitch lots of healthy yeast and control your fermentation temperature etc
• Poor cleaning/sanitation of equipment and bottles
• Linked to the above point - Using something like fairy liquid as a cleaner (as alluded to above in terms of detergents that leave behind oily deposits etc)
• Dirty glassware
• Mash temp issues (albeit I've read that in theory at single infusion at 65-70 degrees for an hour should be all you need with today's highly modified malts)

There will be others.

Your comment about not adding priming sugar, yet the beer still carbonated to a good level in the pressure barrel strikes me as odd. Either it wasn't done fermenting or there could be wild yeast contamination; the latter would certainly play into the fact that your stout seems to be over carbonated. Contamination could also impact head retention.

 

[Portreath]

Thanks for posting some ideas on possible causes. I'm going to remake the clone and make extensive notes at each stage. BTW I used 2 wilko carb drops per 500ml botttle, which I never normally do, but for some odd reason wilko's system went tiddszup and they send me 2 packs with an online order I made!!

Also, I have a porter in a pressure barrel in the garage which is well carbed. I took the flat Guinness in a pint glass and gave it a 1 second squirt of the porter and hey presto a nice big head that stayed almost to the end of the glass.