# Steaming milk: Consistently 23g more warm than cold



## Glenn (Jun 14, 2008)

I was curious to work out how much the 'hot air' in my milk weighed, and over the past few weeks I have been weighing my cold milk and then weighing again when steamed.

For the purpose of this experiment I always steamed enough to fill 2 x 5.5oz Tulip Cups

I am getting a consistent 23g of volume/weight from the introduced steam

I'm using TempTags to indicate when to cut the steam and the milk is always at 65c when measured

Has anyone else worked out how much extra volume they are getting in their steamed milk?


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## hotmetal (Oct 31, 2013)

23g? That sounds like a lot of hot air! ?

Sorry I couldn't resist that one!

I must admit I've never actually thought about it before. I'm quite curious now. I always purge the wand before steaming (and obviously you will have done so too) but even so the extra weight is going to be the wet weight of the steam. I am actually surprised that it is as much as that though. I'd try it now but have powered the kit down for the day. Might try this tomorrow.


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## Glenn (Jun 14, 2008)

The steam wand was fully purged of any water before steaming


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## hotmetal (Oct 31, 2013)

Indeed. Goes without saying with your qualifications! The steam itself though, that gets blasted into the milk, would contain water vapour which if allowed to condense weighs 23g. The fact that it consistently weighs the same is evidence that your steaming is also consistent. I'm going to try this and see how much water (vapour) I am adding. I don't (yet) have any temp tags though so am unlikely to achieve your level of repeatability.


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## StuartS (Jan 2, 2015)

Just tested this. Steamed 252g milk and it was 32g heavier afterwards. Steamed to 65 degC.


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## Glenn (Jun 14, 2008)

I have twice steamed 220mls today with 26g net increase both times


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## Drewster (Dec 1, 2013)

Glenn said:


> I was curious to work out how much the 'hot air' in my milk weighed, and over the past few weeks I have been weighing my cold milk and then weighing again when steamed.
> 
> For the purpose of this experiment I always steamed enough to fill 5 x 5.5oz Tulip Cups
> 
> ...


Sorry Glenn - Little confused what do you mean by 23g volume / weight??

I assume you mean weight/mass ie Your scales indicate 23g more after steaming than before.

5 x 5.5oz = 5 x (circa) 150 cc = 750 cc (Meant to put 2 x 5.5 oz cups - Glenn)

So 23g would be circa 3% increase which sounds "OK" ie Steam is "just" water so not a massive increase (for all the added heat).

But I would expect the volume to increase somewhat more through "steaming" - ie I think/would expect the volume increase would be mainly due to incorporated air/bubbles/micro-bubbles and very little to do with "steam"... (as soon as the steam cools it condenses back to water)

ie I would expect the volume increase to be substantially more than 3%


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## Glenn (Jun 14, 2008)

What I mean is the weight increase of the milk - from cold to hot

So, if I steam 220g milk cold (starting about 5c) I get 246g at 65c

The volume increase is noticeable - from 1/2 a jug to at least 3/4 - but that always happens

What I was interested in was the 'weight' of the expansion - which for me is totally consistent time after time

Edited my typo - was meant to be 2 x 5.5 oz...


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## Daren (Jan 16, 2012)

Out of interest Glenn, if you steam into an empty jug how much water from the steam is generated? What is the weight of the water left in jug?


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## Glenn (Jun 14, 2008)

I will weigh this tomorrow when the machine is on again

The steam is pretty dry, and I know how long it takes to reach 65c (that's pretty consistent too) so should be able to work out if it is indeed water volume making up the difference

I would have thought it is only about half of that though (c. 10g water)


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## MWJB (Feb 28, 2012)

Try heating the same weight of milk to 65C, then froth it using a "dry" method (french press, manual milk frother) & compare increase in mass with the steamed & frothed milk.


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## Drewster (Dec 1, 2013)

Glenn said:


> I will weigh this tomorrow when the machine is on again
> 
> The steam is pretty dry, and I know how long it takes to reach 65c (that's pretty consistent too) so should be able to work out if it is indeed water volume making up the difference
> 
> I would have thought it is only about half of that though (c. 10g water)


"dry" steam is still steam* it is still basically water.

When it cools it *will* condense out as water.

The very act of it going into the milk cools it and therefore condenses it.

The mass/weight increase is due to the water condensing into the milk.

(If it isn't the "water" - where do you think the extra mass comes from?)

This is a little like the question the other day about the hole in a burr carrier expanding when heated - it is physics. No mass is created.

*technically steam is "dry" - steam is the totally colourless/invisible gas that comes off of water as it boils.

By definition steam is at the boiling point of water. The stuff we often call steam ie the cloudy "wet" vapour that is clearly visible coming out of kettle spouts and indeed "steam wands" is actually when the steam/vapour starts condensing into tiny droplets - the droplets are so small that they still ramain as a vapour. It is only when it cools sufficiently (and the tiny droplets coalesce) that drips and drops appear.


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## Glenn (Jun 14, 2008)

Totally get that as I passed all my physics exams









Just wondered if anyone else had noticed the same and wondered why


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## Drewster (Dec 1, 2013)

Glenn said:


> Totally get that as I passed all my physics exams
> 
> 
> 
> ...


I am pretty impressed with your consistency anyway!!

(Spotted your correction/typo - i did think 5 cups each time was a LOT of milk!!!)


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