rsnidjik Senior Member Joined: 23 Oct 2003 Posts: 66 Location: Dislocated Expertise: I love coffee
Espresso: PID'd Silvia 230v, 110°... Grinder: Baratza Vario Vac Pot: nope Drip: nope Roaster: West Bend Poppery 1500W; am...
Posted Fri Mar 15, 2013, 7:07am Subject: Static electricity and post-roast resting
My grinder's plastic coffee receptacle (where the coffee goes after grinding) has wonderful anti-static qualities. The ground coffee slides out of the container with little or no adherence to the plastic sides of the receptacle, regardless of weather conditions.
This morning, though, I ground my first batch of self-roasted beans (used a West Bend Poppery, stopped 30 seconds after start of 2nd crack). When I tried to pour the ground coffee from the grinder receptacle, about 20 percent of it stuck to the plastic sides.
I had waited two days after roasting.
My question: does the fact that the ground coffee was much more subject to static electricity than usual mean that I didn't wait long enough after roasting, or maybe that I under-roasted?
I have a Baratza Vario. If you've used one of these, you know what I mean about the static-free coffee receptacle. (I don't use the optional single-cup attachment.)
The coffee tastes very good, which is really the only thing I should be concerned about, I suppose. Still, I'm trying to understand this new phenomenon.
Posted Fri Mar 15, 2013, 10:09am Subject: Re: Static electricity and post-roast resting
There's no good answers on WHAT causes static.
Anecdotal observations are that home roasted tend to have more static, but it isn't a hard rule. General thinking is that underroasting will tend to have less static, more static in the City to Full City+, but less static and more oil sticking in the darker roasts.
Some observations are that fresher coffee, or coffee with more bloom is also coffee that tends to have more static when ground, so older coffee may have a lower tendency for static.
Some thinking is that chaff has some to do with it. There's also a hypothesis that moisture content of the roasted coffee (which ranges from 0.25% to 7%) may also be a factor.
Relative humidity, which changes on average during the season, depending on how much heating your home needs or AC it needs in the summer and winter seasons, is also thought to have an effect. Higher relative humidity tends to have less static.
There's some thoughts that the type of burr, coatings, etc. have something to do with static too.
None of these are completely exception-free rules.
I've personally found partial support of these. Most of the time, static is maddeningly unpredictable. I see it come and go on a single batch, as it ages. There's just a general correlation to relative humidity.
The one thing we do know is how to make it go away for good. I've found RDT, the "Ross Droplet Technique", is VERY effective at eliminating static. For me it involves adding 1 drop of water from a pipette per 15g of roasted coffee beans, shaking the beans, then tossing them into my grinder (whatever grinder it is).
Here's the start at the "why" of static (Tutorial on static electricity in grinders), but while it's a great start at potential mechanisms for static, it still doesn't create prediction of when we might or might not see static during grinding.
A broad brush model that might be proposed would (in my mind) look like:
Static Index = f(Humidity)+f(moisture in coffee)+f(coffee age)+f(chaff content)+f(roast level)+f(gas level of the coffee)+....
As to your original question:
rsnidjik Said:
...
My question: does the fact that the ground coffee was much more subject to static electricity than usual mean that I didn't wait long enough after roasting, or maybe that I under-roasted?...
The coffee tastes very good, which is really the only thing I should be concerned about, I suppose. Still, I'm trying to understand this new phenomenon...
Trust your taste buds. In the end, that's what matters.
When easy methods of measuring coffee strength became available, people found that they preferred 15%-17% extraction on a Press Pot. Every time I personally tried to hit the magic 20% extraction, it tasted over-extracted to me. I'm not the only one - but this trusting the taste buds and not the numbers also lead to the current knowledge that immersion methods are different than percolation methods for calculating extraction. What appeared to be underextracted tasted nicely extracted - the numbers weren't wrong, the taste wasn't wrong - the conventional model of the system was wrong.
You liked the taste, it is unlikely that you under-roasted, nor is it likely you didn't wait long enough post roast. OR, you're not that sensitive to changes in these ranges.
Hope that helps. Good luck!
------------------------------------------ ----------------------------------------- Le café doit être noir comme le diable, chaud comme l'enfer, pur comme un ange, et doux comme l'amour.
"There is no right answer with coffee. There is only the elixir in your cup at the moment you partake."
"...I often say that when you can measure what you are speaking about, and express it in numbers, you know something about it; but when you cannot measure it, when you cannot express it in numbers, your knowledge is of a meagre and unsatisfactory kind;..." - Lord Kelvin RECIPES thread => http://www.coffeegeek.com/forums/coffee/machines/585708
Posted Fri Mar 15, 2013, 1:42pm Subject: Re: Static electricity and post-roast resting
I have notice that when I use my drum roaster or get some drum roasted beans I do not get the static. When I get fluid bed roasting beans, I do have a static problem.
oldgearhead Senior Member Joined: 25 Jan 2010 Posts: 353 Location: Go Colts! Expertise: I like coffee
Grinder: Virtuoso by Baratza Drip: Chemex,Dilongi DCM900 Roaster: 1/2K Fluid-bed
Posted Sat Mar 16, 2013, 6:34am Subject: Re: Static electricity and post-roast resting
Humm..some complicated answers to an easily solved problem. I still use my Grandmother's solution: dip two fingers under a running stream of water, shake a few drops onto the beans, shake them up, and drop them into the grinder. I always weigh my beans before grinding so I use the cup they were weighed in to add the drops of water. If that doesn't do it for you, try three fingers..
rsnidjik Senior Member Joined: 23 Oct 2003 Posts: 66 Location: Dislocated Expertise: I love coffee
Espresso: PID'd Silvia 230v, 110°... Grinder: Baratza Vario Vac Pot: nope Drip: nope Roaster: West Bend Poppery 1500W; am...
Posted Sun Mar 17, 2013, 12:14pm Subject: Re: Static electricity and post-roast resting
Thank you *very* much, Netphilosopher, steamer and oldgearhead (your names correspond well with the nature of your replies, by the way!).
I'm glad to hear that my "problem" isn't unusual, nor is it necessarily a problem. And, if it is a problem, it's easily solved.
Interestingly, later grinding sessions from the same batch of beans are producing little or no static. So ... well, I just don't know, but it sounds like if this is my biggest problem, I'm doing pretty well.
Posted Mon Mar 18, 2013, 5:18am Subject: Re: Static electricity and post-roast resting
rsnidjik Said:
Thank you *very* much, Netphilosopher, steamer and oldgearhead (your names correspond well with the nature of your replies, by the way!).
I'm glad to hear that my "problem" isn't unusual, nor is it necessarily a problem. And, if it is a problem, it's easily solved.
Interestingly, later grinding sessions from the same batch of beans are producing little or no static. So ... well, I just don't know, but it sounds like if this is my biggest problem, I'm doing pretty well.
Or do you store at room temperature? That's a potential source for moisture absorption...
------------------------------------------ ----------------------------------------- Le café doit être noir comme le diable, chaud comme l'enfer, pur comme un ange, et doux comme l'amour.
"There is no right answer with coffee. There is only the elixir in your cup at the moment you partake."
"...I often say that when you can measure what you are speaking about, and express it in numbers, you know something about it; but when you cannot measure it, when you cannot express it in numbers, your knowledge is of a meagre and unsatisfactory kind;..." - Lord Kelvin RECIPES thread => http://www.coffeegeek.com/forums/coffee/machines/585708
Not a problem at all. Just one potential contributor to variation in static. If you're getting good coffee at the end, that's really all that matters.
------------------------------------------ ----------------------------------------- Le café doit être noir comme le diable, chaud comme l'enfer, pur comme un ange, et doux comme l'amour.
"There is no right answer with coffee. There is only the elixir in your cup at the moment you partake."
"...I often say that when you can measure what you are speaking about, and express it in numbers, you know something about it; but when you cannot measure it, when you cannot express it in numbers, your knowledge is of a meagre and unsatisfactory kind;..." - Lord Kelvin RECIPES thread => http://www.coffeegeek.com/forums/coffee/machines/585708
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