What factors contributes to bubble size

[Hazelwood Brewery]

Some things like champagne have a stream of very tiny bubbles. Some champagnes vary from others.
Some thing like coke have very big bubbles
Some beers have a fine stream of little bubbles, whilst some have bigger ones.

The Hefeweizen I'm drinking at the moment has bubbles that get bigger as they go up the glass.



What factors contribute to bubble size?

From what I’ve read the key factors are pressure (level of carbonation), size of nucleation points, temperature, viscosity, and the make-up of the protein matrix that forms the “skin” around the bubbles. The shape of the glass can also make a difference.

 

[Hazelwood Brewery]

I know this is taking it a bit off topic but why are there so many different shapes?

Some to suit the beer style or accentuate some psychological association, others are just marketing.

A wheat beer glass as an example has a large area above the beer for the fluffy meringue-like head. A rounded glass accentuates fruitiness so if you give people a bitter in a straight glass or a rounded glass they will in general say the beer in the rounded glass is more fruity.

 

[Hazelwood Brewery]

Off topic? On this forum?


There is some "flavour science" (like wine/brandy glasses) in that a big tulip glass will retain gases and thus aroma for when the stick your beak into the glass to take a sip. But mostly I guess it's for style/athletics.

Yeah, beers that are hoppy are best served in glasses that are more narrow at the top so the head is pushed in and the aroma concentrated.

 

[Hazelwood Brewery]

Received wisdom says that nitrogen gives smaller bubbles than CO2 and bottle conditioning gives a smaller bubble than a CO2 tank. Don't know why, nor why bubbles get bigger on the way up the glass.

Nitrogen bubbles are smaller because nitrogen has a smaller molecular weight than CO2. Also air is 78% nitrogen so the differential of the concentration of gasses is low compared to CO2 which makes up just 0.04% in the atmosphere.

Bubbles get bigger on the way up because they pick up more gas as they rise. The bubbles represent low pressure so gas diffuses into the bubbles from around it. The bigger the bubbles the lower the internal pressure so the effect is amplified the bigger the bubble.

 

[Hazelwood Brewery]

How many bubbles do you think are in a typical pint of home brew. And to save a sideways argument on style let’s say it’s a hefe

About 2 million.

 

[Agentgonzo]

@Hazelwood Brewery. Thank you! Simple understandable explanation!

 

[Hazelwood Brewery]

This is easy to see with things like Guinness. Does anyone know why?

I've heard this, but never directly from someone observing it. I believe it's apocryphal. From a chemistry standpoint, it doesn't make sense as it's just CO2 molecules dissolved in beer - it's not like they have a memory of where they came from.

With bottle conditioning and secondary fermentation the CO2 is produced throughout the beer so carbonated the beer more thoroughly than top-pressure forced carbonation.

I did also hear an interesting view that as the beer conditions the heavier (larger) particles the form large neucleation points settle out leaving smaller neucleation points that produce smaller bubbles and a more dense foam.

 

[Donegal john]

About 2 million.

Congratulations. Your going for dinner with chippy. Bring your wallet as your paying. (Chippy seems to want to be the bottom and you have to be the top )

 

[Hazelwood Brewery]

Congratulations. Your going for dinner with chippy. Bring your wallet as your paying. (Chippy seems to want to be the bottom and you have to be the top )

I’m easy

 

[Agentgonzo]

Nitrogen bubbles are smaller because the air is 78% nitrogen so the differential of the concentration of gasses is low compared to CO2 which makes up just 0.04% in the atmosphere

I was thinking about this... and I'm wondering whether that is the reason. The bubble forms at the bottom of the glass where there is just beer and no air. So how does the air composition have any impact on the bubble size that forms and then rises through the beer?

 

[Hazelwood Brewery]

I was thinking about this... and I'm wondering whether that is the reason. The bubble forms at the bottom of the glass where there is just beer and no air. So how does the air composition have any impact on the bubble size that forms and then rises through the beer?

Good question! This is to do with bond strength. CO2 forms a hydrogen bond with the water in the beer. Nitrogen relies on weaker van de walls bond forces. This means Nitrogen is not easy to get into beer (why it needs 5 times the pressure) and also doesn’t come out quickly (why you use a perforated disk in the spout).

 

[Agentgonzo]

Good question! This is to do with bond strength. CO2 forms a hydrogen bond with the water in the beer. Nitrogen relies on weaker van de walls bond forces. This means Nitrogen is not easy to get into beer (why it needs 5 times the pressure) and also doesn’t come out quickly (why you use a perforated disk in the spout).

That makes more sense!

 

[Agentgonzo]

How many bubbles do you think are in a typical pint of home brew. And to save a sideways argument on style let’s say it’s a hefe

I remember someone on a tour of a champagne house saying each bottle contained a quarter of a billion bubbles. I presume they got an intern to count them all.

 

[Sadfield]

Why isn't there two bubble sizes in beer 'carbonated' with mixed gas?

 

[Hazelwood Brewery]

Why isn't there two bubble sizes in beer 'carbonated' with mixed gas?

Pressure is one of the factors for bubble size (lower pressure = smaller bubbles) so the CO2 bubbles are likely to be smaller in a low carbonated stout.

The concentration of gasses also affects bubble size (more dissolved gas = bigger bubbles) because the rising bubble comes into contact with more gas, feeding the bubble. In a stout carbonated with mixed gas there is a relatively low concentration of gasses.

The CO2 bubbles have a lot more energy than the nitrogen bubbles so will reach the surface and escape while the nitrogen bubbles lazily find their way up. This is the long settling time.

If you overcarbonate your beer with mixed gas you will see far more large CO2 bubbles in the head - higher pressure, more dissolved gas.

 

[foxy]

Pressure is one of the factors for bubble size (lower pressure = smaller bubbles) so the CO2 bubbles are likely to be smaller in a low carbonated stout.

Precisely, I remember having my first Pepsi as a little tacker, couldn't drink it. I remember my first soda water at about 15 years of age, couldn't drink it. I have read that humans are the only species to drink carbonated beverages. The shock of drinking British bitters through the hand pump warm and virtually no carbonation, but also magnificent.
It is a fact the higher the ABV the lower the life of the foam. The lower the ABV the longer the foam will last.
I have mentioned this before in posts, the first impression of a beer is with our eyes.
High ABV Porter, a nice head but dissipates quickly, leaving little cling on the glass.
My preference is on the British beer side of low carbonation.

Lower ABV ordinary bitter, nice fluffy head, though breaks down as it travels down the glass it does cling nicely.

 

[Sadfield]

CO2 bubbles have a lot more energy than the nitrogen bubbles so will reach the surface and escape while the nitrogen bubbles lazily find their way up. This is the long settling time.

Do the two gasses keep to their own bubbles as they join to form bigger bubbles?

Why use co2 at all if the goal is smaller, longer lasting nitrogen bubbles?

 

[Hazelwood Brewery]

Do the two gasses keep to their own bubbles as they join to form bigger bubbles?

Why use co2 at all if the goal is smaller, longer lasting nitrogen bubbles?

I’m not sure if the two gasses are exclusive but they are different so any mixing would be quite small I imagine but I am making an educated guess here. CO2 is polar (electrical charges) so “sticks” like a magnet. Nitrogen is non-polar so just hangs about in the spaces between other molecules.

It’s easier and faster to carbonate with CO2 so I guess that makes it cheaper and the production process more straightforward? You can use Nitrogen though and I have heard of people using nitrogen in other beers. One important point though is that nitrogen strips out hoppy aromas and flavour though I’m not sure if the mechanics behind this…something else to research!

 

[Sadfield]

Is it not a case that nitrogen is insoluble, so there's an initial rush of nitrogen leaving the beer that causes a creamy head. The latter, smaller bubbles are actually the co2 coming out of solution?

100% nitro beers don't exist, because all you get is a creamy head οn a flat beer. Nitro was invented so Guinness could dispense very low carbonated beer from keg, which requires pressure.

 

[Hazelwood Brewery]

It requires a far higher pressure to get nitrogen into the beer but you can and I have.

It’s CO2 that rushes out, it’s very keen to get out into the world. For nitrogen the atmosphere is already over populated and so is far more relaxed about the whole thing. I’m always happy to be proved wrong though because I will have learnt something - any references?

Re: your second point - what forms the creamy head?