Do you purge the steam wand before steaming?
Hello all, I have noticed that when steaming with my Rancilio LUCY that the weight of the milk increases by about 25%. If I steam 100g of milk up to 68C and weigh it again its about 125g. Im letting the steam build up for about 2min after pulling the shot. Is this long enough? Is my steam too "wet"? Or is this normal? The same happens for other volumes as well. The texture of the milk seems OK, no big bubbles.
Do you purge the steam wand before steaming?
Yes, its normal - you are adding air to the milk; air has weight (weigh a balloon before and after inflation).
25% increase in weight sounds like a lot. You would be adding a small amount of water, I imagine, as steam condenses in the initially cold milk.
You could try steaming plain water without adding air and see how much the weight increases (ie just keep the steam tip completely submerged). That could give you an idea of any water being added.
25g would be 25ml of weight if all water.Originally Posted by 68627760606F7B7D0E0 link=1242702533/2#2 date=1242703525
Thats about 5 teaspoons isnt it?
I think youre understating it flynn.
Sounds more like a bloody lot to me.
My machines off now but Im willing to sacrifice 100ml of milk tomorrow to see what happens.
P.S. I dont think air weighs very much.
How do I zero my scale in a vacuum so I can weigh the air in my balloon?
Flyn, the balloon weights more after blowing up due to an increase in pressure, Im not sure that the microfoam can hold air at pressure significant enough for it to increase the weight. For all intensive purposes I think that all the weight increase can be attributed to water from the steam.
As TG suggests I will have a go tomorrow and see what results I get.
No it doesnt weigh much - certainly not 25g. But I do remember the science experiment I did at school where we use a beam balance scale to weigh the balloon before inflation. When you inflated it, the scale tipped towards the balloon side proving it was heavier. Conclusion: air has weight.Originally Posted by 516D706B616077626A61050 link=1242702533/3#3 date=1242717318
You dont need a vacuum to conduct the experiment.
I suspect Charlie could be on to the main reason for the weight increase
In all practicality, air has no weight. If it did, we would be weighing the column of air above any object we were weighing as well as the object.
Indeed, air is actually just lots of different molecules floating around and technically these will have weight. Thus, if we squeezed an amount of air into a smaller space, we will increase the density of air (or pressure of air) within that space...making it heavier than air that has not been compressed into a smaller space. At least thats what my brain tries to pass off as logic.
Thats a lot more than I would estimate. Once I get some scales Ill check (or maybe someone else could do it). Remember (admittedly at sea level and 20ºC) air has a density of 1.2kg/m^3.
My suspicion is youre getting a lot of water – are you bleeding the wand dry before you steam? I turn it on until no water comes out, just steam, and the boiler light is on.
You do its just when you zero your scales you are adjusting for it. If I recall my highschool chemistry 1 atmosphere is equivalent to a column of water 10m high.Originally Posted by 46776079787F74796F160 link=1242702533/6#6 date=1242725317
How wide? Makes a bit of a difference to the calculation ;DOriginally Posted by 5A7665637E767B485A78797C726E170 link=1242702533/8#8 date=1242726196
according to wolfram dry air is
28.96g per mole what ever that is
I can guarantee that there would probably not be enough air in your textured milk to account for 1g let alone 25g
There are 44 Moles of air in 1m3.
1m3 weighs 1.28kg
so 1 mole= 29grams
(thx to Wolfram)
This is getting quite OT but: -
a mole is 6.12 times (10 to the power of 26) atoms. the width is the surface area of the item in question (could be 1mm or 100m - in other words the greater the surface of the object the more air is sitting on top of it).
And no the quantity of air in the microfoam would not even register on a set of scales yet alone account for an increase of 25% (this would have to be water).
To derail to almost unheard of levels, Im not sure about your mol figure (but whats three orders of magnitude between chums?).
Hes still right though, I didnt want to be so explicit though. But, I am still just a mathematician, so I dont want to be so exact. Its almost surely ( ;) for those who understand) not air causing your weight increase.
Another thought: When you weigh your milk, do you have the thermometer in? Maybe that would do it, too.
Originally Posted by 1D3223153B36343C14363132570 link=1242702533/1#1 date=1242703470
Yes, I purge the wand several times before steaming. Initially a few spurts of water then only dry steam comes out right at the tip.
I will try as well, with my next coffee...
I expect volume to be varied depending on the level of my skills, but in all honisty; weight, Na not without adding something...
Thats why you have aero and other chock bars with bubbles / air..... Look bigger and often weigs the same or even less... But the eye plays tricks as one assumes bigger is better...
Opps did I really just type that ;D
Even with DRY steam (unless super heated) the reason you see it is because of teh WEATER condensing in the Air.
Thus on an Em6910 for eg... After purging and if you then run for 60sec (default settings) your expected to get about 20 - 30 ml of water..
The other consideration here, omy, is that you said the milk is fine after texturing.
Why worry about any perception of extra weight? Just enjoy the coffee.
We could speculate all we want about human error, thermodynamics, etc. As I suggested earlier, just steam some cold water to 68o and weigh it before and after steaming. If there is a weight increase, put it down to condensation of the steam.
Exactly.Originally Posted by 7B5445735D50525A72505754310 link=1242702533/1#1 date=1242703470
Molecular structure & heating aside Andrew, I reckon its the water content from the wand accounting for the extra weight.
Also, different milks have different make-ups - what are you using?
Big name milk companies fortify (ie add) their milk with water, so thats also a factor.
There is a solution though matey ... ditch the milk, and enjoy it black! ;D
... the way coffee should be - pure ;)
Its a bugger to measure 100ml when youre used to just pouring to the bottom of the spout in a 300ml jug.
Anyhoo.......weighed 100g....wand purged...milk steamed...new weight = 111g.
hmmm ... so what accounts for the mystery 11gm added?Originally Posted by 526E7368626374616962060 link=1242702533/18#18 date=1242785049
Your rigorous analytical thoughts TG? :D
As surmised before, the only thing it can be is water condensing from the steam.
I can live with 10% but the OPs 25% either means very wet steam or a non-purged wand.
Good one TG.
You dont really have to start with a specific amount providing you weight the jug before and after steaming.
My theory is that it is condensed steam (ie converted to water)
My proposed experiment to investigate this is to steam water (not introducing air as you would to stretech milk).
Do it with jugs of water at various temps - say straight out of the fridge as milk would be, at room temp and warm water. Weigh then steam each jug to 68o and weigh again to determine the % increase in weight.
The hypothesis would be that the coldest jug would show the greatest weight increase as it would cuase the greatest amount of condensation of steam.
As the OP said they are steaming with a rancilio lucy (identical to the silvia just has an integrated rocky). The silvia doesnt have the driest steam so it is definitely possible even with a well purged wand you could see such an increase.
Add: Just checked on my silvia with a 10 second purge after all the water came out of the wand, using water, I got an increase of around around 16%. Considering silvia does take quite a long time to stop spluttering (result of wet steam, too much water in the boiler), if you started steaming too early it is conceivable to get an extra 10mL of water in your milk.
I was just curious as too where it was coming from. I never would have noticed until i put the jug back on the scales once after steaming.Originally Posted by 676D786F6F607472010 link=1242702533/16#16 date=1242771576
It has made for some interesting posting though.
Ill try with water instead of milk and see what happens.
Just got a 12% increase in weight using my LaPavoni Europiccola. This was doing my usual trick of putting the milk into the freezer for 10 mins before steaming to make it extra cold (but not icy).
25% does sound like too much.
Did the experiment this morning and my increase was 13% on 200ml of milk. More than I expected but interesting.
How do you make the stream drier? *Im pretty sure, Ive purge the steam like 10-20 seconds then wait a bit to steam the milk.... the end result is that my latte / cappuccino taste like too much hot water was added, if you know what I mean!!! *:-[Originally Posted by 062A393F222A2714062425202E324B0 link=1242702533/22#22 date=1242788765
Ive managed to get my first rosetta today, but art doesnt matter when the taste isnt perfect...
- Do I need to run the hot water to fill the boiler after purging the initial wet stream? *I feel like it going to run out of steam after purging for so long. Hmm..
Do you drink the coffee as short blacks. It is possibly the coffee which is tasting "watery". But as to getting the driest steam on the silvia, make sure the whole steaming process is done with the heating lamp on and purge the steam wand until you no longer notice any little sneezes stop(fluctuations in how much steam is coming out of the wand - you can hear and see it).
Understood but I wanted it easier for the OP to compare my result.Originally Posted by 23293C2B2B243036450 link=1242702533/21#21 date=1242786729
Nah.. just Latte/Cappucinno depending on how much froth I can get on the day giggled like a schoolgirl..... ;D, I dont know why my milk based coffee taste so watery after adding the milk.... I purge for pretty long, upto 20 secs or so.. but even then... if I use an empty jug.... there will be water from the steam. >:(Originally Posted by 05293A3C21292417052726232D31480 link=1242702533/27#27 date=1242818159
You cant. Steam = water. The extra weight is just the condensed steam.Originally Posted by 3E2A2C2C363A3D2A38383E3E5F0 link=1242702533/26#26 date=1242813967
Where do you think the steam goes when steaming milk? Right, into the milk. Not surprised about 10-25% at all, if you steam for a minute, thats a lot of steam.
Put a cold lid on a pan of boiling water for a minute and notice how much water condenses on it. Its not different when steaming milk.
At 1 bar / 100kPa / 1 atmosphere, a liter of steam is 1.6g (see http://www.simetric.co.uk/si_steam.htm). So 25 gram amounts to about 15 liters of steam.
Now, in order to convert water to steam at 100 degrees you need 2200 J/g (I think). So for 25 grams thats about 55kJ. To get that in 60 seconds, you need about 1kW (1W = 1 J/s). Which sounds more or less in-line with an average heater.
So RJ please explain why I only got 11 grams not 25.
Im certainly a simpleton -- I cant believe I didnt think about the steam condensing...this is why I stick with numbers (numbers represented by letters). Anyway, for your difference Thunder:
- milk / pitcher temperature / size
- frothing time
Are all variables I can imagine would change the amount of condensation.
If you can tell me:Originally Posted by 6458455E545542575F54300 link=1242702533/31#31 date=1242900509
The wattage of your heater
The time it took to steam
The amount of milk you started with
Ill give it a try... :)
...... *::) ::) ::)Originally Posted by 66616166707E757A140 link=1242702533/33#33 date=1242902141
I theory, you can do the math yourself btw. The key value is 2200KJ / kg water. You can roughly translate that to about 0.5g /second for every kW.Originally Posted by 72757572646A616E000 link=1242702533/33#33 date=1242902141
Thats assuming no steam escapes obviously.
the time it took... corrected.Originally Posted by 776365657F73746371717777160 link=1242702533/34#34 date=1242903086
.................. :o :o :o I’m still pretty new in this world of coffee, but I think you have no idea what youre talking about....... Theory is as good as is on paper.... **(Does all machines pumps out the same type of steam? *Why purge before steaming?) :-XOriginally Posted by 787F7F786E606B640A0 link=1242702533/35#35 date=1242903621
I tried steaming with just water, 200ml (or grams) of cold water heated up to 68c and ended up with 240g or about 20%. So this seems about normal then.
Realized last night two flaws in my assumptions:
1. The heater element isnt switched on all the time
2. The water in the boiler is superheated/under pressure, and will therefore keep on producing steam whilst the heater is turned off.
2 ensures 1 has minimal effect, so my calculation should roughly be compensated for the time the heater is turned off. Might be better to express the amount of condensed water in the start and end temperatures of the milk and the amount of milk. That would be independent of wattage and time (assuming no heat loss).
If anyones still interested... just did the math:
Specific Heat of water/milk 4.2 J/gK
Start temp 4 C
End temp 65 C
Volume 200 g (=ml)
Heat required 51240 J
Steam enthalpy 2200 J/g
Steam required 23.3 g
Steam required 12% (of milk weight)
What I did above is calculate how much heat is required to bring 200ml milk from 4 degrees to 65 degrees.
I then calculated how much steam you need to condense to get this amount of heat.
Then I expressed the amount of steam as a percentage of the amount of milk.
Conclusion is that the weight of the milk is expected to increase by 12% if it is heated from 4 to 65 degrees using steam.
RJ there is some discussion on different machines having "wetter" steam than others care to comment?
See...and I didnt have to answer your questions.Originally Posted by 4E49494E58565D523C0 link=1242702533/40#40 date=1242953797
The OP used 100g of milk but seeing as you arrived at 12% and I got 11% thats close enough for me.
Im guessing that my Expobar has drier steam than the LUCY and/or more steam on hand.