Interesting topic. You've piqued my curiosity.
I thought my steamer was putting out too much wet steam so did a test to check it. My machine is a basic Sunbeam EM2300 so it's probably to be expected, but still I was shocked at how much water it was adding:
I put the milk pitcher on a scale and zeroed it, then added 100g milk. I then steamed the milk (yes I purged the steam wand) and weighed it again. The result: 137g!!
That's more like dilution than stretching.
It would be interesting to see what results other people are getting. Please post your machine and result here.
I couldn't find this being discussed previously so feel free to post a link her if it has.
Interesting topic. You've piqued my curiosity.
Even dry steam is water. How long did you steam for?
Have never thought about weighing my milk before and after. I might give it go...
360g -> 395g here
(Saeco Via Venezia = small single boiler)
Wega mini nova
215gm > 241gm
Full cream woolies brand milk
Not sure of temp, assume 3.5C > 65C (judging from my standard end point)
1.15 bar boiler pressure (steaming commenced whilst heating up from about 0.9 bar)
Last edited by noidle22; 8th June 2015 at 08:32 PM.
Interesting. Would be worthwhile to note the % increase. Will try with my machine later and post results.
Would be more meaningful with some additional data - duration, temperature (milk before and after), boiler pressure or temperature, milk fat content...
Yes. And if everyone steams the same amount of milk, same end temp (start temp ex fridge should be comparable) it would be easier to compare the results.
I think that is less important, as it is easy to normalise for differences in milk quantity (given the other information).
Browns Heart plus (Low fat milk +), box says 1.5g per 100ml total fat
Using an Alex Leva, well warmed up.
three hole steam tip.
123 degrees setpoint
well purged before starting.
250g Milk, Cold from the Fridge ~3 degrees
stretched for 38 seconds.
Drinking temp (not scalded, but could be hotter), I don't have a thermometer.
276.5 grams result, more than enough foam for 2 caps.
Looks like the trend so far has been ~10% increase in mass, whereas DanielC had a 37% increase. I'll have to give this a go in the morning and see if I can add some significance to the trend.
Well I gave this a try this morning, and the results were surprising!
Rancilio Silvia v2
200g A2 full cream milk
3.5°C to ~65°C
30 seconds steam time
End mass = 336g
So a 68% increase! Not great I think. I'll repeat this with half the milk and see if there is a difference.
One more for the data bank..
85 gms ( piccolo) , A2 lite milk, 4-65 deg in 5 secs
10gms , (12% ) weight gain using purged dry steam
1.1 bar pressure , Isomac Millenium .
I'm not sure what relevance mass has with milk texturing. Isn't it the volume of textured milk that is important, not the mass?
I agree, if it pours well and tastes good... I guess it could be worth looking at if you feel your coffee should be creamier - or just start with richer milk :-)
I did some searching on this topic but didn't find too much about it other than this article How to Froth Milk with the Finest
Anyway, it's shown me I need to be a lot more careful with my steam heating, priming and purging.Prepare Your Steam
With this step, you want to ensure that your espresso machine will dispense not only ample steam to froth your milk, but also the right kind of steam. You mean steam isn't steam? Yes and no; there is dry steam and wet steam. Wet steam adds unwanted water to your milk, making it harder to froth and less sweet. To get the dry steam, you need to bleed out the water from the pipe that runs between the boiler and the valve that controls the flow of steam. When you turn on your espresso machine's steam mode (for machines that do not have always-on steam), wait about 5 seconds and then open the steam valve briefly into an empty container until water turns to steam. Wait about 20 seconds, and do it again. You now have dry steam. To keep the steam coming throughout the process, you need to begin frothing your milk before the heat turns off. If your machine is a heat exchanger or other kind with always available steam, this will not be a concern for you.
10%-15% seems like the average watering-down from the results people have posted here so it seems like that is the best that can be expected.
If you know the mass of the milk, and the before and after temperature, you can calculate (approximately) how much heat was transferred to the milk. If you know the mass and temperature (or pressure) of the steam (i.e. water) which is added, you can estimate how wet the steam was. It will be a coarse estimate.
In my opinion, volume is a lot less useful than mass in most of these types of calculations.
Edit: That, and the density of the milk changes as you stretch it.
My quick and dirty back of the envelope (really, Google spreadsheet on my phone) indicates that just condensing 10g of saturated steam at 1bara will release enough heat to raise the temperature of 100g of milk from 5°C to 65°C. If you consider the other factors, you would actually need less.
Last edited by MrJack; 9th June 2015 at 01:05 PM.
texture - is the milk of the right consistency for (to your preference)
volume - is there enough to make the number of milk-based coffees you need?
temperature - is the milk hot enough (to your preferences - use a thermometer or by feel)
Sorry, I don't get it. I don't know how the the knowledge that my milk's mass has increased by 10-15% because water has been added will help in making my coffee. It would be more important to know that if I start with a certain quantity of milk, I will end up with a certain increased quantity after stretching which usually ends being enough, not enough or too much. You usually work this out by trial and error as it depends on the quality of the machine and the skill of the user.
Who would be getting out a calculator and applying some sort of equation?
That wouldn't be significant. Here's what I think is happening:
Steam is simply water in a gas form - above 100C. As soon as it drops below 100C it reverts back to liquid water.
The steam in your boiler is running at around 125C.
Pretty much the instant the steam hits the cold milk in the jug, it starts condensing back to water. This added water increases the overall mass of the jug contents.
Regardless, this is quite a fascinating thread!
Last edited by herzog; 9th June 2015 at 05:49 PM.
I always wondered how much water was being added to the textured milk!...
Clearly DanielC's larger mass increase is because of the cooler (or 'wetter') steam. The significance I see is that milk textured with dryer steam will be richer. It doesn't necessarily make it easier/better... as I recall some people like to add a dash of water to the milk before texturing.
So if you had a birthday balloon filled with steam and squeezed the steam into your milk it would only add 1 to 2ml of water.
I noticed though that there was a spitting of water spray coming out of my steam want because it does not heat the water enough or it is condensing in the pipe.
Steam is a clear gas so you should see very little of anything at the point that it comes out of the steam wand. By purging some wet steam, re-priming (by switching on the water pump for a few seconds), letting it reheat and then purging again the steam is almost clear and I can get much better results frothing the milk.
Given that others are reporting about a 10% increase in the milk weight, that's around 10 mL of water being added when steaming 100mls.
Using your formula that's 16Litres of steam in gas form. So if you're steaming for 30 seconds, that's about half a litre of steam coming out of the jets every second.
Another interesting experiment would be to pour 100 mL of iced water into a nice big clear glass. (like a whisky glass). Mark the level of the water with a whiteboard marker, then steam it.
After steaming it, leave it to settle and see what level the liquid is at in the glass compared to the initial mark.
Coffee snobs meets Mythbusters!
Don't mean to flog a dead horse, but because we're getting all sciency... The air in an inflated balloon should have the same boyancy as the air around it. The only increase in apparent mass would be from 1) very minor compression of the air; 2) the CO2 in your breath; and most likely 3) the water in your breath. While 1 litre of air might have a mass of 1.2 g, a litre of helium still weighs ~200 mg yet it makes a balloon float.An inflated balloon weighs more than a non-inflated one.
Last edited by burr; 10th June 2015 at 12:28 AM.
Thought I'd do a similar experiment today:
mi = 272g (of milk)
mf = 289g (milk + water)
dm = 17g (added steam)
Ti = 9.5°C
Tf = 43.5°C
dT = 34°C
That's 6.25g / 100g of milk for 34°C temperature rise.
Prorated to the 60°C temperature rise I used yesterday:
6.25g × (60°C/34°C) = 11g per 100g milk for 60°C
Not far off my 10g estimate.
To give something easily scalable, thats 0.0018g of steam per gram of milk per °C - for my machine (Bezzera BZ99).
In reality it may not scale so linearly (for example, some of the energy is used to heat the jug, and your hand), but its a reasonable approximation.
Ok this morning I poured the milk, weighed it, steamed it .... Then poured it into the cup!! D'oh!
Just did another one.
Alex Duetto II
1.4 bar boiler pressure
Start temp fridge
Start mass 191.4
End temp 65
End mass 215.3
12.5% increase in mass
So between 0.0020g & 0.00225g / g milk / °C (assuming your milk was initially 1°C - 9.5°C).
Last edited by MrJack; 12th June 2015 at 09:38 PM.
Woolworths lite milk
Start temp: Around 3C
Start weight: 200gm
End temp: Don't know, around 65C perhaps?
End weight: 224gm
I have been targeting a 10% but usually end up with 11% or 12% added weight. In my case, the duration of the process is the key to getting less water added to my microfoam. Longer purge and faster steaming time. No longer chilling the Espro Toroid 12oz. pitcher probably helped too.
Since I posted this thread I've replaced my machine and my results are far more in line with others here:
Machine: Sunbeam EM7000 double boiler.
Cold milk weight: 85g.
Steamed milk weight: 95g.
I would suspect (although it depends on how stable the thermoblock temperature is):
- Increase temperature
> dryer / hotter steam
> shorter steaming time (i.e. milk heats faster)
> less water added (per °C rise in temp)
- Increase pump rate
> wetter / cooler steam
> steaming time may be shorter or stay the same (don't think it would increase, but needs more thought)
> more water added (per °C rise in temp).
When I make coffee for the two of us I weigh the milk mainly to minimise wastage, knowing the right amount for our standard morning drinks. Doing this with an ECM Mechanika for the first time, I found on filling the cups that I had lesser volume in mine, yet the milk foam was excellent, nothing unusual.
I recall that the Silvia was adding at least 10% water to the milk, probably more, even though I cleared the steam wand before starting and let it reheat half way through. This was something I noticed more or less by accident, after putting the jug back on the scales which were not yet off.
I am presuming the ECM has a higher steam temperature so is not generating as much water content while foaming the milk. I shall have to weigh it before and after next time to get a measure. Has anyone else checked this on their machine?
I have not seen water content discussed in other reading, hence mentioning it now.
I noticed the same when I moved from Isomac Zaffiro to ECM Technika. I wasn't weighing but noticed a definite change in volume of steamed milk. The steam from the ECM seems much drier than what was produced from the Zaffiro.
Beensean your on the right path towards excellent specialty espresso!
weighing your beverage components is an easy way to help you decipher the
different tastes your taste buds are experiencing!
I.e. 10g dose > 25g shot out> blended with 150g milk = what my other half luvs
however yours may be more a 20g dose>37g shot out with 210g milk etc.
You get the drift ?
RE your question ...Its not errant water upweighing your stretched milk ...
its the added air = greater volume by mass
I found on average a constant +10% give or take.
More info please? I am yet to fully work it out...Maybe more scientific minds here
can kick the milk pitcher ... further !!
And Good Morning to you Yelta.
I'd luv to if I had a high level scientific mind....where's Dr. Karl when you need him !!
Simply my drive to produce better coffee led me to - all the things here we know already.
Consistently good espresso needs a consistent input from the Barista.
Anyway one of my locals who makes a cracking good shot used 10oz cups
I used 8 at home.
So chasing their flavour as a basic guide led me to comparing not only Inputs at the Machine side
but also what goes in the cup.
Simply as said above if I used a different recipe as a flat white I started considering how much milk was required to be blended
in a 20g dose to achieve the taste I had on my palate memory.
Anyway whilst measuring the final cup I found a variance in the numbers.
Long story short every time I way the milk pitcher (tared for milk qty ) pre and post stretching I
see an increase of approx. 10% ...flat white stretch.
I put it down to the same weight variance experienced at the roasting stage where the beans will weigh post roast
between 12-16% less.
Anyway over to you Yelta and the combined intellect of CS'ers ...
@espressoadventurer: It is not the air, as confirmed in the other thread when it is mentioned that air weighs 1.3g/litre. Also, I suggest that uncompressed air is "weightless" on a set of scales, whether mixed into something else or not. Imagine weighing a jar twice, with its airtight lid on and off. Then smash and grind the jar into glass powder (eliminating air) and weigh it again. It (with lid) should be the same each time. Air at atmospheric pressure is neutral to measured weight at a given altitude. I think.
The scales measure the mass of the object minus the mass of the displaced air*. If the entrapped air has the same density as the displaced air it will cancel.
FWIW the above means that the entrapped air in a milkydrink will slightly reduce the weight as measured by the scales as it is is both warm and saturated with moisture, both of which will serve to reduce its density WRT the air it displaced**.
*For our purposes the air density correction is assumed to be too small to matter but there are situations where it is important: weighing a pycnometer for instance.
** Yes, moist air is lighter than dry air. Counterintuitive but provable.
Last edited by Lyrebird; 1st August 2018 at 08:07 PM.
I'm guessing that the Doppler Effect could make the milk appear to change colour (and sound different) if we approached the pitcher at sufficient velocity.
I don't know that it would: milk is actually yellow, it appears white for the same reason that the sky appears blue (Rayleigh scattering).
Rayleigh scattering increases strongly with frequency so I don't see how doppler shift would affect the perceived colour much: if we are approaching the milk that will shift the yellow base colour towards green but then the Rayleigh scattering will shift upwards as well, I think the two effects would partially cancel.
(Insert smiley thing here)
Last edited by Lyrebird; 1st August 2018 at 09:07 PM.
Just a note to thank Beensean
Re: Post 'Milk & Water" for raising the subject (once more)
And more so to regular contributors here -
Yelta & Noonar for highlighting the reality of what is going on with the re-weighting of milk post stretching,
by linking the prev post of 2015. Which I missed somehow, or don't recall.
Maybe that was around the time I had a serious get off on my Enduro Bike up around the Border Ranges NP and headbutted a tree!
But seriously tho great discussion & good info that clears up my misguided thoughts !!
Good stuff and just why so many of us that make this site the marvellous thing it is....
And we dips our lid to you Andy !
Last edited by Barry O'Speedwagon; 2nd August 2018 at 08:08 PM.
You may rest assured that at no stage did I believe that your post was a serious analysis of a real world situation.
My reply, however, is to be taken absolutely at face value and I would be highly offended if you were to roll your eyes and say to yourself "what the eff is this guy talking about".