<p>The bubbles are the result of "degassing" — carbon dioxide escaping from the coffee. Degassing will be especially dramatic in the first 24 hours after roasting, during which 40% of the CO2 leaves the bean. See this blog post: <a href="http://fellowproducts.com/understanding-degassing-is-fresh-best/" rel="nofollow">Understanding Degassing</a>.</p>

CC BY-SA 3.0
2016-07-30T16:44:37.563Z
After waiting a week to brew I do not see these large bubbles anymore. This does seem to indicate degassing is to blame.
Nick
CC BY-SA 3.0
2016-07-25T23:21:30.800Z
2016-07-25T23:21:30.800Z
Tyler Tate
<p>I've seen these bubbles when pressing coffee that I've home roasted in two different presses with two different water sources. I've seen it with coffee from multiple roasts now. The beans are the same in all cases (Rwandan single origin). I am grinding with a burr grinder. Do these large bubbles in the bloom indicate anything about the bean or the roast?</p>

<p><img src="https://i.sstatic.net/kXwml.jpg" alt="enter image description here"></p>

CC BY-SA 3.0
2016-07-18T11:50:36.163Z
The bubbles almost look like they have a sheen of dish detergent (rinse well!). Otherwise, I suspect it's a product of the particular processing process used in your beans; can you share anything else you know about the beans? Specifically, how long ago they were roasted, and whether wet, dry, or semi-washed process? Might be caused by mucilage if it's dry processed...? I think I have noticed this before but haven't pinpointed a source.
hoc_age
CC BY-SA 3.0
2016-07-18T12:14:04.993Z
[This is the coffee](https://www.sweetmarias.com/product/rwanda-kivu-kanzu-4945), the description says wet washed and sun dried. This roast was done yesterday - 18hrs ago or so. I am generally consuming 24-48hrs after roasting. The sheen is what bugs me too. I have not used any detergent in a long time - I water rinse my presses. Maybe it is time to wash out all of the oils? I am not brewing with filtered water so I suppose it could be water supply related, but I work in a different city than I live in so I am seeing this with water from two different municipal supplies.
Nick
CC BY-SA 3.0
2016-07-18T13:40:35.310Z
You're roasting this yourself, then... to what roast level -- Full City-ish? Might be worth allowing the beans to rest longer (48+ hours after roast perhaps) to see the difference in bloom from the same roast batch. Does the coffee taste good? If so, is there a problem? :) Do you have another specific concern (e.g., damaged coffee, etc.) or merely asking if there is a potential problem (both okay for sure :))?
hoc_age
CC BY-SA 3.0
2016-07-21T04:59:34.747Z
You mention different presses. Would they have different press nets? I'd expect "larger" bubbles with a coarser net.
Eric Platon
CC BY-SA 3.0
2016-07-21T10:06:57.123Z
@hoc_age I am roasting to full city. I am trying to improve the coffee. It isn't bad but it isn't optimized. So I am trying to be observant of every detail about the brewing to see what insight it can give me. My French press grind level and cupping grind level are the same so I imagine these bubbles would be present if I cupped as well.
Nick
CC BY-SA 3.0
2016-07-21T10:08:53.083Z
@EricPlaton the bubbles are present before the press has been pressed - those bubbles are in the bloom. So nothing has been strained. I do not stir. I put the grounds in the press and try to pour the water slow and even wetting all of the grounds as the bloom floats up.
Nick
CC BY-SA 3.0
2016-07-21T21:17:28.743Z
By chance, is this CO2? It may be carbon dioxide produced during roasting and released by grinding just before preparing the French press. 18 hours is not quite enough for degassing IMHO. 3-4 days seems more appropriate. Could you please try after a few days with the same batch of roasted beans and observe again?
MTSan
CC BY-SA 3.0
2016-07-21T22:58:25.970Z
@MTSan I am working on finding that out. I roasted double (2 1/4lb roasts done the same way) what I normally do on Tuesday and drank it Wednesday and Today. I'll keep brewing it for the next 3 days and see if there is a change.
Nick
<french-press><cup>
What do these large bubbles in my French press indicate?
Nick
# What do these large bubbles in my French press indicate?

(Asked by: username_0 on 2016-07-18)

I've seen these bubbles when pressing coffee that I've home roasted in two different presses with two different water sources. I've seen it with coffee from multiple roasts now. The beans are the same in all cases (Rwandan single origin). I am grinding with a burr grinder. Do these large bubbles in the bloom indicate anything about the bean or the roast?

![enter image description here](https://i.sstatic.net/kXwml.jpg)

**Tags:** french-press, cup

> **Comments:**
> **username_1**: The bubbles almost look like they have a sheen of dish detergent (rinse well!). Otherwise, I suspect it's a product of the particular processing process used in your beans; can you share anything else you know about the beans? Specifically, how long ago they were roasted, and whether wet, dry, or semi-washed process? Might be caused by mucilage if it's dry processed...? I think I have noticed this before but haven't pinpointed a source.  
> **username_0**: [This is the coffee](https://www.sweetmarias.com/product/rwanda-kivu-kanzu-4945), the description says wet washed and sun dried. This roast was done yesterday - 18hrs ago or so. I am generally consuming 24-48hrs after roasting. The sheen is what bugs me too. I have not used any detergent in a long time - I water rinse my presses. Maybe it is time to wash out all of the oils? I am not brewing with filtered water so I suppose it could be water supply related, but I work in a different city than I live in so I am seeing this with water from two different municipal supplies.  
> **username_1**: You're roasting this yourself, then... to what roast level -- Full City-ish? Might be worth allowing the beans to rest longer (48+ hours after roast perhaps) to see the difference in bloom from the same roast batch. Does the coffee taste good? If so, is there a problem? :) Do you have another specific concern (e.g., damaged coffee, etc.) or merely asking if there is a potential problem (both okay for sure :))?  
> **username_2**: You mention different presses. Would they have different press nets? I'd expect "larger" bubbles with a coarser net.  
> **username_0**: @username_1 I am roasting to full city. I am trying to improve the coffee. It isn't bad but it isn't optimized. So I am trying to be observant of every detail about the brewing to see what insight it can give me. My French press grind level and cupping grind level are the same so I imagine these bubbles would be present if I cupped as well.  
> **username_0**: @EricPlaton the bubbles are present before the press has been pressed - those bubbles are in the bloom. So nothing has been strained. I do not stir. I put the grounds in the press and try to pour the water slow and even wetting all of the grounds as the bloom floats up.  
> **username_3**: By chance, is this CO2? It may be carbon dioxide produced during roasting and released by grinding just before preparing the French press. 18 hours is not quite enough for degassing IMHO. 3-4 days seems more appropriate. Could you please try after a few days with the same batch of roasted beans and observe again?  
> **username_0**: @username_3 I am working on finding that out. I roasted double (2 1/4lb roasts done the same way) what I normally do on Tuesday and drank it Wednesday and Today. I'll keep brewing it for the next 3 days and see if there is a change.  

---

## 1 answers

### Answer by username_4 on 2016-07-25. Score: 3 | Accepted answer

The bubbles are the result of "degassing" — carbon dioxide escaping from the coffee. Degassing will be especially dramatic in the first 24 hours after roasting, during which 40% of the CO2 leaves the bean. See this blog post: [Understanding Degassing](http://fellowproducts.com/understanding-degassing-is-fresh-best/).

> **Comments:**
> **username_0**: After waiting a week to brew I do not see these large bubbles anymore. This does seem to indicate degassing is to blame.  

---

