Bottle froths up after 1st sip - Why

I have always bottled into 750ml bottles and then drank from the glass but in my last few brews have been bottling a few six packs of 330ml bottles to drink staight from the bottle. Why is it that more often than not after i or someone else has had their fist sip the bottle froths up and there is a bit of beer spillage.

These bottles are not gushers and start frothing as soon as i open. its after the frirst sip. WHY???

If i serve the beers into a glass they pour perfectly, have a normal amount of head. I am sure they are not infected nor overcarbed. nor do i have a rough drinking style and slam my beer down after the first sip.

I either use carbonation drops or sometimes normal cane sugar to carb.
Can any one shed any light on why this happens or what is going on with the frothing after first sip.

Cheers

This might sound funny, but it could be due to poor drinking technique. If I take a swig quickly and the set a bottle down that happens to me once in awhile, too, even with commercial brews... pour in a glass and the problem disappears. Or drink more gently!

I'd imagine that it comes from the agitation of the liquid. Before you tilt the glass, everything is in happy equilibrium. Once you rock it, you excite some of the carbon dioxide molecules and that sets off a chain reaction. Think of it sort of like when you take a REALLY cold water bottle out of the fridge - if conditions are just right and you tap it or shake it, it goes from being perfectly clear water to a icy slush almost immediately as you disrupt the happy equilibrium inside by imparting some force.

The bottles may be slightly over-carbed, possibly due to a difference in the ratio of headspace to bottle volume compared to your 750ml bottles. Perhaps bottle slightly less beer in your 330's to account for this.
-Kevin

Additionally when you drink directly from the bottle you stir up the sediment which will provide nuculation sites for the CO2 to bubble up and as a result you get foam.

+1 to post above.

Why not use a beer glass? Many advantages. The beer smells and tastes better. You can see it. You can decant the beer off the yeast and have no sediment. You can control the head via pouring technique. You avoid adding any germs to the bottle, so 3-4 rinses will allow the bottle to be stored (and then sanitized B4 refill).

BadNewsBrewery said:

I'd imagine that it comes from the agitation of the liquid...
The bottles may be slightly over-carbed, possibly due to a difference in the ratio of headspace to bottle volume compared to your 750ml bottles. Perhaps bottle slightly less beer in your 330's to account for this.
-Kevin

Click to expand...

be careful, under-filling bottles will lead to over-carbonation. this is well documented in brewing literature and happened to me on an early batch years ago: a half-filled bomber foamed for minutes after opening. it has to do with the amount of gas in the headspace vs. liquid in the bottle as well as surface area atop the beer. under-filling bottles will over-carb the beer.

the comments above were probably closer to the mark by suggesting it was the agitation of the liquid leading to the foaming.

cheers.