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Thread: Trouble shooting help? Shiny bubbles in caps

  1. #1
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    Trouble shooting help? Shiny bubbles in caps

    Gene Cafe Coffee Roaster $850 - Free Beans Free Freight
    Hey all, just a little bit of trouble shooting help.
    Recently all of the caps I make seem to get big shiny bubbles all over the top after about a minute.




    Ugly! Any ideas about where this comes from? I dont think its the milk, I havent changed my style lately.

    Possible problems:
    Fast Extraction? (except it looks fine, tastes pretty good and is about the right time/volume.
    Roast? Un-modded Popper. Roast time was about 9 minutes.
    Beans? Ethiopian Harrar 5 days post roast.


  2. #2
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    Re: Trouble shooting help? Shiny bubbles in caps

    Id be suprised if it was the coffee.

    I know you said that you havent changed your style lately, what about the milk youre using? Could make a difference. Or even the difference in the same brand of milk between seasons?

    Try just pouring some steamed milk into a cup and letting that sit for a minute or so and see if you get the same thing.

  3. #3
    Mal Dimal's Avatar
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    Re: Trouble shooting help? Shiny bubbles in caps

    Hmmm,

    Interesting Icarus.... Seems that it is only present in the patches with crema, the white parts of the Rosetta seem to be bubble free. Might be related to the coffee itself Id say. Have you roasted this particular bean before? Maybe it needs even further degassing than usual for some odd reason. I guess you could just see how it behaves over the next few days and see if it diminishes at all. Sorry Im not much help mate....

    Mal.

  4. #4
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    Re: Trouble shooting help? Shiny bubbles in caps

    hi
    it is probably the milk
    some of the milk laely has been separating early, with the heated milk having a fatty taste / aroma( like the smell from a roast lamb)

    findin that it makes the crema bubble or gets tiger stripes

    if this is the case, lower your milk temp and see if it improves

    graham

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    Re: Trouble shooting help? Shiny bubbles in caps

    Thats so weird.... and kinda gross.

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    Senior Member redzone121's Avatar
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    Re: Trouble shooting help? Shiny bubbles in caps

    Thanks Graham, I have had this on a minor scale from time to time and wondered what the heck was going on.

    Chris

    Yes that too Dan !

  7. #7
    Sleep is overrated Thundergod's Avatar
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    Re: Trouble shooting help? Shiny bubbles in caps

    I sometimes get a little bit of it too.
    Not lately that I recall.
    The bubbles always looked a bit oily to me.
    What about yours Icarus?

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    Re: Trouble shooting help? Shiny bubbles in caps

    could well be time to call in Lt Horatio Caine to solve this ;)

    Darren

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    Re: Trouble shooting help? Shiny bubbles in caps

    Quote Originally Posted by g00se link=1219814351/0#1 date=1219816194
    Try just pouring some steamed milk into a cup and letting that sit for a minute or so and see if you get the same thing.
    Done. Didnt do it. Went kinda matt, but it was sitting there for about 6 minutes. No big bubbles.

    The bubbles always looked a bit oily to me.
    What about yours Icarus?
    Yeah. Kinda. More like soap bubbles.

    OK, thats it. Scientific method. Now Im interested!

    Solve Problem: What causes bubbles in my coffee.

    Hypothesis:
    1. Milk
    *a) Quality of the milk has changed
    *b) Milk too hot.
    *c) Steaming style is incorrect.

    2. Espresso
    *a) Fast Extraction (Sweet Marias lists this as a possible)

    3. Beans
    *a) Not rested enough.
    *b) Maybe this type just does this

    4. Roast
    *a) Too light
    *b) Too fast

    Experiments:

    1. Try skim milk/different brand/ soy.
    2. Try cooler milk
    3. Froth some milk in those little glass frothy things.
    4. Try longer extraction
    5. Try again in a few days
    6. Roast (same profile?) some more and try again.
    7. Roast to a different profile (longer).
    8. Try different beans.

    Im gunna get this sucka...

    EDIT:
    Tried Devondale Skim (instead of Kiewa Full). Same result.


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    Re: Trouble shooting help? Shiny bubbles in caps

    A you using a naked portafilter by any chance?

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    Re: Trouble shooting help? Shiny bubbles in caps

    Quote Originally Posted by YeeZa link=1219814351/0#9 date=1219825613
    A you using a naked portafilter by any chance?
    No. Standard two spout. Would a naked do it?

  12. #12
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    Re: Trouble shooting help? Shiny bubbles in caps

    Naked sometimes makes it cremafest with heaps of micro bubbles, thought that may be the case hmmm..... back to the drawing board.

  13. #13
    Senior Member GregJW's Avatar
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    Re: Trouble shooting help? Shiny bubbles in caps

    Hmm... Havent had this at home, but seen it at a cafe where they use local milk that has nothing added to it and is relatively unprocessed. Same thing - bubbles appearing on the surface after about a minute or so.

    At the time I thought it could have been the milk fats separating and rising to the top in the appearance of oily bubbles. (But Ive also been using the milk and not had that problem. Possibly only separating after being heated beyond a certain temperature?)

    :-?

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    Re: Trouble shooting help? Shiny bubbles in caps

    Hmmm, I dont reckon its the quality of milk that youre using, or stretching technique - as Mal observed theres no evident bubbles on your rosetta.

    Ive a couple of thoughts as to possible reasons ...

    1) To re-iterate the wise sage Mals thoughts, let your beans de-gas a bit longer - from my home-roasting experiences, it seems that some SOs need longer resting to minimise the bubbly crema to achieve optimal extraction;

    2) Could possibly be an air pocket or slight blockage in your Gaggias line, which means water flow via the hose/boiler to group has bubbles in it before & while extracting ... is it spurting a bit coming out of the group? Not enough optimal water flow will produce bubbles, because the pump pressure is there, but not the water content/mass means just aeration - & consequently bubbles. Do you have the Gaggia properly plumbed in, or just add water? If plumbed, does the water travel to the boiler via a filter?;

    Anyways, happy investigating - hope you resolve it.

    Tony


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    Re: Trouble shooting help? Shiny bubbles in caps

    it is a milk fat / coffee crema problem
    it is happening consistently with our house blend, using woolworths light milk, but not with dairy farmers light milk

    we heat to 60*c approx, find by lowering milk temp that it improves but doesnt go away

    graham

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    Re: Trouble shooting help? Shiny bubbles in caps

    Quote Originally Posted by fix link=1219814351/0#14 date=1219905735
    it is a milk fat / coffee crema problem
    it is happening consistently with our house blend, using woolworths light milk, but not with dairy farmers light milk

    we heat to 60*c approx, find by lowering milk temp that it improves but doesnt go away

    graham
    Hey Graham,
    Thanks! Im pretty sure thats exactly right. A few more experiments should prove it in my case. Ive noticed our butter seems to be significantly lower quality lately too, especially when melted.
    Dan

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    Re: Trouble shooting help? Shiny bubbles in caps

    Hey mate let me know how you go finding the problem I have recently noticed the exact same thing! Shiny soapy bubbles on the surface about half a minute after pouring the milk.

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    Re: Trouble shooting help? Shiny bubbles in caps

    Quote Originally Posted by Huhness link=1219814351/0#16 date=1220149234
    Hey mate let me know how you go finding the problem I have recently noticed the exact same thing! Shiny soapy bubbles on the surface about half a minute after pouring the milk.
    Where are you? Im pretty sure its the milk. Im onto a different roast now, Brazil yellow bourbon, and it still happens. Do you home roast? What milk do you use? It was really bad with local milk, (Kiewa), but not so bad with Safeway milk from around Sydney.

    Great. Now Im a milk snob too.

  19. #19
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    Re: Trouble shooting help? Shiny bubbles in caps

    Ive always been a milk snob but Im trying different brands now.

    Ive had this when a blend hasnt degassed much...usually 2-3 days rather than a week. Ive noticed that if coffee is really fresh this sometimes happens - Ive seen it at Mecca in the city a few times and like me, they like it really fresh.

    Probably the milk this time though....I just got through 6 litres of Pura and its been pretty crummy. Think Ill go back to Dairy Farmers again.

  20. #20
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    Re: Trouble shooting help? Shiny bubbles in caps

    Quote Originally Posted by Icarus link=1219814351/0#17 date=1220151691
    Quote Originally Posted by Huhness link=1219814351/0#16 date=1220149234
    Hey mate let me know how you go finding the problem I have recently noticed the exact same thing! Shiny soapy bubbles on the surface about half a minute after pouring the milk.
    Where are you? Im pretty sure its the milk. Im onto a different roast now, Brazil yellow bourbon, and it still happens. Do you home roast? What milk do you use? It was really bad with local milk, (Kiewa), but not so bad with Safeway milk from around Sydney.

    Great. Now Im a milk snob too.
    I dont think it is the milk because like you said if you leave it after steaming no soapy bubbles but pour it and then there is bubbles! My shots dont look bubbly though? :-/

    Yea i home roast and havent noticed this happen with my market bought stash.. Maybe it does require more degassing? :( but i want it now!

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    Re: Trouble shooting help? Shiny bubbles in caps

    made hot chocolate and coffee from the same mug of steamed milk.. Hot chocolate no bubbles but shiny bubbles in the coffee! Did this x2 with 1 week old roasted coffee and 3 day old... Coffee still tastes good though

  22. #22
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    Re: Trouble shooting help? Shiny bubbles in caps

    Mine seems to have gone away. New coffee perhaps. This lot is roasted with a heat gun, not a popper. Maybe its that. (Maybe not. I gave up being scientific a while ago.)

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    Re: Trouble shooting help? Shiny bubbles in caps

    Sorry to resurrect an old thread but this is happening to me atm. Im using Beanbay bought Ethiopian Gambella, and initially I thought it might have been from too fresh coffee - but its 11 days post roast! I wouldnt have thought it needs to degass any longer than that!
    Anyone know what causes this?

  24. #24
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    Re: Trouble shooting help? Shiny bubbles in caps

    Quote Originally Posted by 7E75797167647671756778716D140 link=1219814351/22#22 date=1338273273
    Anyone know what causes this?
    Acidity- often in lighter roasts

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    Reviving this old thread...It's the only one with the same problem I have that I could find.

    I have the same problem. Discussion and images can be seen here:
    https://www.home-barista.com/tips/be...es-t54342.html


    I wonder if anyone found the root cause for it.

  26. #26
    Senior Member Koffee_Kosmo's Avatar
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    It’s my belief

    This is a combination of three things
    1) Oil from the beans
    2) Fat from the milk
    3) Airated crema and or introduced steamed air ( The coffee extraction under pressure produces airated crema )

    The explanation
    Introduced air that the milk steaming produces combines with the airated crema making larger bubbles
    Heat from steaming also seperates the small amounts of bean oils and milk fats and this rises to the surface forming a membrane
    The bubbles rise to the top as milk is poured and trapped under the surface
    While on top the bubbles can’t pop because the surface tension of the oily cap is to great

    The reason you see the bubbles only on the brown crema is because this area has greater surface tension than the white milk only section

    Its simple physics but if there is a better explanation I’m happy to be corrected

    KK

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    Thanks KK!

    I tend to agree. I am sure it's interaction between the specific beans and the milk. With other beans and same milk it does not happen so I put the blame on the beans.

    These beans were bought very fresh and I kept them in vacuum sealed box. I suspected that they might have been too fresh and still emitted CO2 but even when I tested them again after a few days not sealed and it was not as bad as I seen before but they still had some reaction. They might be a bit too acidic. It is strange as they should not be sold like this.

    It's also interesting that this happened to me twice with similar origin (Guatemala) from different roasters.
    I will try to get some more soon to test again and I'll send my feedback. If it happens again, this time I will take it back to the shop so they can also test.

  28. #28
    Senior Member Lyrebird's Avatar
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    Quote Originally Posted by Koffee_Kosmo View Post
    the bubbles canít pop because the surface tension of the oily cap is to (sic) great


    KK
    Lipids and fatty acids have lower surface tension than aqueous fluids, lipids generally around 30 mN/m compared to aqueous solutions around 70.

    This is why presence of fats at the surface destroys beer foam for instance.



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