IAGary Senior Member Joined: 9 Jun 2012 Posts: 5 Location: IA Expertise: Just starting
Posted Sat Jun 9, 2012, 5:08pm Subject: How Much Coffee?
Hi, I just purchased a brand new Bunn Commercial Brewer and I can't get my coffee to taste right. I know I'm doing something wrong. How much coffee should I be using to brew a 64 ounce pot? Any help would be greatly appreciated. Thanks!
Posted Sat Jun 9, 2012, 5:57pm Subject: Re: How Much Coffee?
Welcome to Coffeegeek, IAGary!.
Lets start with a few details. What kind of grinder are your using? (or are you using pre-ground beans). By chance, do you use a scale to weigh the amount of beans?
64oz? are those all for you or for an office/ restaurant?
IAGary Senior Member Joined: 9 Jun 2012 Posts: 5 Location: IA Expertise: Just starting
Posted Sat Jun 9, 2012, 7:37pm Subject: Re: How Much Coffee?
Hi, Thanks for the welcome and your reply. :) I'm using a Bunn LPG Grinder. Yes, I do have a scale that I weigh the coffee grounds. The 64 oz is for my wife & I, but I also fill the airpot and take it into work with me.
Posted Mon Jun 11, 2012, 4:57am Subject: Re: How Much Coffee?
Just checking - you are PRODUCING 64 oz or that's the amount of water you're putting in the displacement reservoir?
Based on a couple of quick checks on the large Bunn machines around here (before they replaced them with machines that have pre-stale "freshly brewed" coffee <eyes rolling back in my head>, absorption for the Bunn seems to be right around 1.7-1.8 g/g.
Let's assume you are attempting to PRODUCE a total of 64 oz of hot coffee. 64oz is ~ 1.89 liters, at ~140°F will be about 1855g.
Simple check for how much coffee depends on your preferred strength. Let's also assume you want your strength to be normal North American coffee, around 1.25%:
1855g * .0125 = 23.19g of TDS.
Let's also assume you want to extract ~20% or so. 23.19/0.20 = 115.9g of coffee.
If your Bunn is typical, you need to add enough water to PRODUCE 1855g of coffee:
1855 = (Brew Water) - (Absorption * Coffee)
Brew Water = 1855 + (1.7 * 115.9g) = 2052g of brew water.
This is also the same thing as calling it a brew ratio of 17.7 (Water to Coffee) or 5.65% (Coffee to Water). These would all be by mass - not volume - so weigh out 2052g of brew water and use 115.9g of coffee and go from there.
If you find out that your brew water tank itself is only 64oz, then adjust the coffee accordingly and prepare to yield less coffee.
64oz of COLD water is 1890g of brew water, same ratio = 108.7g of coffee, and you'll get:
1890 - (1.7 * 108.7) = 1705g of hot coffee produced.
If you measure the strength, it will be right around 1.25%.
The Bunn should work fine, it's an awesome brewer - IF you have the grind level correct. Take a look at Bunn's site, I think they have some guidelines for brewing (or I'm just remembering a conversation I had with one of their experts... if so, then I apologize). At the end of brewing, the grounds should be nicely flat, with no signs of pooling. The grounds should not have "crawled" up the sides of the filter, and there shouldn't be any signs of the filter being overtopped.
The Bunn is a nice machine - but you MUST MUST MUST make sure that the heater tank is completely up to temperature before brewing. It's not like an auto-drip (which heats small chunks of water at a time). The spray head must not have any lime/calcium deposits on it. The machine that used to be here took around 30 minutes to get the tank up to temperature, and had significant lime deposits in it. People would make pot after pot in it, and the temperature of the brew water would hover around 170°F because nobody would leave it reheat long enough - so the best pot was the first one in the morning. If the lime deposits got too bad, the brew valve would get clogged and extend the brew cycle time.
I'm surprised that many people don't understand that the Bunn has basically a pot's worth of water pre-heated in a tank, just like a mini-hot water heater in your house. When you add water in the reservoir, it displaces the hot water in the tank, providing fairly constant, optimum temperature brew water throughout the percolation cycle until the very end (which is fine, you're near the end of the extraction by then anyway, if the temp drops a bit it helps prevent nasty overextraction). All you need to do is set up the brew ratio and find the grind that allows proper percolation.
------------------------------------------ ----------------------------------------- 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
IAGary Senior Member Joined: 9 Jun 2012 Posts: 5 Location: IA Expertise: Just starting
Posted Mon Jun 11, 2012, 7:29am Subject: Re: How Much Coffee?
Hi Netphilosopher,
Thanks so much for your response, sounds like you are very smart when it comes to coffee and way over my head. LoL! Anyway, I did 3 1/2 ounces of coffee and it's tasting pretty good. However, my grounds are creeping up on the sides of the filter a ways, but not going over the top. According to what you're saying, this should not be happening. What do I need to do to correct this? Thanks!
Posted Mon Jun 11, 2012, 10:27am Subject: Re: How Much Coffee?
IAGary Said:
Hi Netphilosopher,
Thanks so much for your response, sounds like you are very smart when it comes to coffee and way over my head. LoL! Anyway, I did 3 1/2 ounces of coffee and it's tasting pretty good. ...
then try a pot using 4 oz of coffee. Based on what you've posted, I bet you will like this best.
IAGary Said:
...However, my grounds are creeping up on the sides of the filter a ways, but not going over the top. According to what you're saying, this should not be happening. What do I need to do to correct this? Thanks!
------------------------------------------ ----------------------------------------- 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
randytsuch Senior Member Joined: 11 Jun 2009 Posts: 578 Location: LA, Ca Expertise: I like coffee
Espresso: Expobar Office with... Grinder: Baratza Vario Roaster: Customized Alpenrost,...
Posted Mon Jun 11, 2012, 10:46am Subject: Re: How Much Coffee?
Since no one asked yet, are you using freshly roasted coffee?
You should use coffee that was roasted 2 weeks ago or less, but with drip you can probably go a little older than that. After that, the coffee is stale. You should also grind right before brewing.
The beans you buy should have a roasted on date, and not an expiration date.
I used less coffee per cup before I found this place, and learned about using fresh coffee.
One warning about fresh coffee, it will bloom more, and may make your creeping problem worse.
Posted Mon Jun 11, 2012, 11:21am Subject: Re: How Much Coffee?
Simply put, if you're thinking in oz, and you're looking for ballpark amounts:
Divide the oz of coffee (beverage) by 16 and you'll get the oz of coffee (dry grounds) to use to make it.
64 oz ÷ 16 = 4 oz of coffee.
------------------------------------------ ----------------------------------------- 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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