What happens if you overfill a bottle and don't leave a gap?

[fego]

There was some chat on another thread about the effects of overfilling or not leaving an air gap in bottles when filling and what might happen as a result. (Here's the link to the discussion viewtopic.php?f=38&t=78017). I happened to be bottling up a pale ale when i saw this thread so took the opportunity to try a little test to see for myself what the difference might be. I deliberately filled one bottle completely to the rim to later compare side by side to a 'normal' one. Both contained the same beer and other than the fill level, they were re-fermented and conditioned in exactly the same way. They were then tested side by side in the same glasses both cleaned and dried in the same way to give the most comparative view I could provide.

This is what I found...

These are the two bottles side by side after taking from the cellar...



and another view...



The bottles were a bit cold so look a tad cloudy through the condensation. Nothing looks any different at this stage so I poured them out. On opening, the normal one hissed as expected whereas the full one hissed a lot less. I poured the normal one first followed immediately by the full one and this is what they looked like side by side (the full one on the right)



Here's another view...



As you may be able to see from the pictures, what immediately strikes is the difference in head, but you may have also noticed the difference in colour too. The head with the normal one was fluffy and light and creamy and exactly as you hope and pray for. However, the other one was disappointing and quickly fizzed away to nothing as we probably all expected it would.

After a minute or so...



The colour difference was really surprising though and was enough to give the impression of them being two entirely different beers. In fact, I had a few friends round and asked them to do a taste test to see which one they preferred and they were all easily convinced they were trying two different beers, all preferring the one on the left (the one with the gap). So did I.

I poured some of the beers into two other glasses to eliminate the chance of the difference being down to the glasses I used and as you can see, the effect was the same...



I then started drinking them both...



Again, the head of the normal one stayed with me all the way whereas the full one was flat and lifeless. The normal one had head left over at the end whereas the other one didn't have anything.



and all done...



There wasn't even a trace of any lacing throughout the full one's life...



So, there you have it. I've no idea what the science behind this is, but I do now know what I thought I always knew anyway - not to overfill my bottles. You might think you'll get more in your glass, but it will at best be more of what you don't want - flattish, unconditioned slop.

[jaroporter]

very interesting results bud! i bottle very rarely but i'd now like to try this. theoretically it seems like there would be a difference, but it's interesting to see such a practical contrast!

[MarkA]

Nice experiment fego, cheers!

[Rusticus]

Thanks for conducting the interesting experiment, I always leave a good space but have wondered whether it's the right thing to do. I know now.
Russell.

[AdrianTrace]

Great experiment, and a great looking beer. Do you know yet how it compares to a "normal" filled bottle, halfway up the neck?

I'm wondering if there is a point where it starts to drop off, as I tend to fill my bottles quite full (I won't in future)

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[BarnsleyBrewer]

Interesting experiment, thx for posting....
I never overfill bottles but I will definitely try a little less to see if it improves head retention..

BB

[46philh]

Interesting experiment, thx for posting....
I never overfill bottles..
BB

Neither do I, but that's more down to coming from Yorkshire...

[BeerBloke]

Great post. On the flip side don't underfill a bottle or you'll get the opposite effect to overfilling.

If you're unsure how much to fill a bottle there wil usually be a number around the bottom of the bottle. That's the distance in mm from the top of the bottle to 500ml (or whatever size the bottle is) Beer bottles are designed to allow the 'ideal' headspace to that point. Plus it gives Trading Standards a measure point.

[WalesAles]

Fego,
Excellent post!
I didn`t think my original post would cause so much interest.
What really pissed me off with the overfull bottles was at the point of pouring, you hold the tilted glass in one hand,
bring the bottle to the glass, tilt bottle and gently pour, but before I got the bottle to the glass, it was pouring out all over
the bloody place before I got it to the glass!
Bloody Hell Mun!

WA

[tourer]

Good post Fego, I discovered something similar filling the last bottle it came to about 3/4 full, i thought dont waste it but the taste was not good and flat. So underfill or overfill is not good.

[Chug]

Thanks for sacrificing your good beer for a nice experiment

[BarnsleyBrewer]

Bottled a crate last brew day using your results and the result was interesting. I left a good space of around 2.5" from the cap compared to my usual 1" and the bottled beer is loads better regarding head retention and lightly carbonated..
Thx for taking the time to compare.

BB

[f00b4r]

I wonder what the effect would be with counter pressure filled bottles and if it would be time sensitive.
Great thread btw and good to see people getting results from it.

[WalesAles]

Bottled a crate last brew day using your results and the result was interesting. I left a good space of around 2.5" from the cap compared to my usual 1" and the bottled beer is loads better regarding head retention and lightly carbonated..
Thx for taking the time to compare.

BB

BB,
2.5" from the cap! Wow, that is about a mouthful of Beer. (And You a Yorkshire Man)!
Good things coming from this thread.

WA

[BarnsleyBrewer]

Bottled a crate last brew day using your results and the result was interesting. I left a good space of around 2.5" from the cap compared to my usual 1" and the bottled beer is loads better regarding head retention and lightly carbonated..
Thx for taking the time to compare.

BB

BB,
2.5" from the cap! Wow, that is about a mouthful of Beer. (And You a Yorkshire Man)!
Good things coming from this thread.

WA

Yeah, but worth it for a northern top.....

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