Flow rate too high

Question

Dear Dr. Brew,

My BUNN coffeepot recently began overflowing the filter (BUNN Filters) whenever I brew coffee. It is a 10 cup pot (NHB). I have had the pot for about two years and while this has happened occasionally it is now happening with every time I brew coffee.

I have cleaned the pot, delimed, etc. and nothing seems to make a difference. I do grind my own coffee beans, although I am using the same medium setting I have always used. It seems as though the pot is pumping water into the filter faster than it can drain into the pot--which doesn't make sense to me. The hole in the filter container is not plugged, although it probably does get plugged somewhat once the coffee grounds overflow and or the filter collapses.

I hope you can help!

Mary

Answer

Mary,

When a sympton comes on suddenly, there is likely a simple fix. From your description it sounds like the sprayhead is no longer attached to the outlet tube from the tank. This will allow an increase in flow rate into the filter and cause your issue. You can order a new sprayhead using this form at BUNN.com.

Happy Brewing,
Dr. Brew

No time like time OFF

Question

Dear Dr. Brew,

In a setting in which users can be forgetful (I’ll give them the benefit of the doubt), coffee pots with very little remaining coffee are often put replaced onto a powered warming plate. The result is wasted, burned coffee.

While we wish that everyone would be both considerate and thoughtful, that is not always the case. Although many home machines feature time-off features, this may not always be practical in an office setting. Therefore, I wish to propose the following suggestion for a commercial coffeemaker: incorporate some sort of photo or light sensor to monitor remaining coffee in the pot. When a particular level is reached, the burner will shut off. This would reduce burnt coffee and pots, and, fire hazards. Alternatively, a weight scale could be built into the plate, but this seems more complicated.

Regards,
Carl Brody
Seattle

Answer

Dear Carl,

Turning off the warmer (s) at the end of the day or when the server is empty should be an easy task. There are models available with time deactivated warmers. The times can normally be set in 1 hour intervals up to 4 hours. The timer is reset with each additional brew so the warmers are active during normal operating hours. Using weight scales is not reliable due to irregular tare weight of servers. Light sensors work as long as the servers are clear and clean.

Here's a brewer with an automatic warmer shut-off feature.

Happy Brewing,
Dr. Brew

Solving funnel overflow

Question

Dear Dr. Brew,

My office has a Model VP17-2 (SST) BUNN coffee maker that we have had for several years. Recently, we have been getting a lot of coffee grounds in the coffee when it brews. Someone suggested we get a permanent filter for this machine, as the filters we use may be too small. Is this available for this machine (or) do you have another possible solution?
Thank you.
Cindy

Answer

Dear Cindy,

When changes in brewing are sudden, there are usually simple answers.

The first thing would be to examine the brewer. Remove the brew funnel and check the spray head to make sure it is still there. The spray head controls the flow rate and pattern of delivery of the brew water.

The next step would be to confirm the correct size (4.25" base with 2.75" sidewall) paper filter is being used. You mentioned the use of permanent filters as a choice in brewing your coffee. In my experience, the coffee produced when permanent filters are used is more like the brew from press pots or French press. Your finished brew will have an increase in oils and sediments that are normally removed with paper. Some coffee drinkers prefer this taste profile. The biggest change will be the cleaning of the permanent filter after each brew: if this task is not done, the coffee oils will build up on the filter and alter your cup profile.

One source for permanent coffee filters

Happy Brewing,
Dr. Brew

Recipe for Iced Coffee

Question

Hi,
Please publish a good recipe for ICED coffee.
Thanks,
Gary
Gary I. Cohen
EB COFFEE
P.O. Box 3431
Cherry Hill, NJ 08034-0332

Answer

Iced coffee recipes can vary widely. A recipe may include all tap water for dilution or ice as part of the recipe to lower temperature of the finished product more quickly. A recipe is based by a very strong coffee in soluble percentage (1.5 -2.0%) , although low in extraction percentage (17-20%). The amount of dilution determines a finished strength that please your taste buds.

COFFEE , BREW WATER, DILUTION WATER, ICE, FINISHED VOLUME
(OZ) (OZ) (OZ), (Lbs) (GAL) approximate
24 240 128 8.34 3.5

16 160 85.25 5.55 2.3

8 80 42.62 2.78 1.2

Just a note: not all coffees have a desirable flavor when cooled. Try your favorite coffee at room temperature.

Happy Brewing,
Dr. Brew

Energy to save

Question

Dear Dr. Brew,
Are there any numbers or research available regarding the
energy savings using the Thermal Pot brewers (example: Axiom Thermal Pot
Brewers) verses the normal glass carafe brewers with double warmers that may run
continually due to constant use?
Thanks,
Jim McLean
Pinete'
850-499-3284

Answer

Dear Jim,

Warmers are generally in a range from 90 to 130 watts in output to maintain temperature in the server. As an example: a 100 watt warmer, ON for a 10 hour shift would consume 1Kilo Watt Hour. The energy savings between a unit with warmers and units with thermal carafes would be the warmers and the time of usage.

Happy Brewing,
Dr. Brew

The softener side of life

Question

From Chris in Michigan

Dr. Brew,
I own a restaurant in Traverse City, Michigan, and use city water (which tastes very good). Yesterday I was given a sales pitch for a water softening system, and one of the points they made was about coffee. The salesperson said that if I brew coffee with soft water I can use less coffee, and it will stay fresher longer. When I asked my coffee roaster about it, he said both points were wrong, and that over- softened water can lead to brewing problems with the grounds. What is the truth and what is the fiction here?

Chris Girrbach

Answer

Chris,

Quality water is a key ingredient, from your pizza dough to every beverage you serve. The quick test of your water supply is as simple as clarity, odor & taste.

If you see impurities, smell odors or the taste is offensive, don't use it for consumption. I suggest contacting your local municipality and asking for the water report for your city. They can answer many of your questions. A drip brewed cup of coffee is between 98.5 & 99% water and 1% coffee flavoring can not hide the chlorine that is placed in our water to make it potable and safe to drink. A basic water filter for sediment reduction and activated charcoal (taste & odor) will take care of most concerns. Generally, a softener system may be recommended when the mineral content is above 7 grains (1 grain = 17.1 mg/L) hardness. The most common minerals, calcium & magnesium (lime scale) can cause scaling issues within your equipment. Brewing standards of the Specialty Coffee Association of America (SCAA) recommend water in the range of 3 -6 grains (50 to 100 mg/L) for brewing coffee with the drip method.

The process of removing minerals (generally calcium & magnesium) alters the composition of dissolved solids in your city tap water by ion exchange. Tap water is passed through a resin bed charged with salt (sodium). As the calcium and magnesium ions are attracted to the resin, sodium ions are released. This alteration of the water aids in equipment maintenance by reducing scale, although it can have a detrimental impact on the coffee brewing process. The sodium ions combine with the carbonate and bicarbonate ions in the water and create a coating effect on the ground coffee particles and on the filtering media. This can result in an overflow of the filter media within the funnel. Softened water also inhibits the extraction phase of the coffee brewing process by extending brew contact time as the filter media seals over.

Should your primary brewing system be espresso, then you may want to consider a softener for that supply line. You want as little mineral content as possible for the steam tank and pressurized brew system. Do not install on your ice, soda fountain or drip coffee brewer. A previous blog post, "Soft Response", may provide additional information for you.

Happy Brewing,
Dr. Brew

Pulse brewing's role in coffee brewing

Question (Part 2)

From Roastmaster Tom

.... (in the last post, Roastmaster Tom asked about pre-infusion)

For the pulse brewing parameters, what specifically are we looking for? Should both the "wetting" stage and the "dry" stage be the same length of time? How long should that be? Should they differ in time and if so why? Does the roast level or caf/decaf affect those parameters? Does the size of the batch affect those parameters? As you can see I have a number of questions with what appears to be very little info available. Can you please help me understand how best to use these functions on your equipment?

Thank you.

Tom Walsh

roaster/owner
Cambria Coffee Roasting Co.

Answer

(I addressed Tom's questions about pre-infusion in my last post. Now, for his questions on pulse brew...)

Pulse brew is a tool that allows the user to manage water delivery time. This tool is valuable for increasing the water contact time for smaller volume brews on multi-batch equipment.

Let's say you want to brew one-half gallon of coffee and you have a 4-minute water cycle for a one-gallon brew. The half-gallon would be dispensed in 2 minutes, with approximately half of the bed depth. The resulting brew would likely be weak and under extracted compared to the one-gallon brew.

Using pulse brew, you can increase the water contact time with the grounds. A pulse brew routine might consist of an initial ON time followed by a series of OFF and ON times. Similar to the pre-infusion setup, the initial ON time needs to be sufficient to saturate the grounds and get the bed in float. The Off time can be as little as 5 seconds, followed by ON times as little as 5 seconds. As an example: a pulse brew routine of 25 ON - 05 OFF - 5 ON would result in adding over 1 minute to the original 2 minute dispense time.

If you want to read more about the roles of pulse brewing and pre-infusion, check out this article from Tea and Coffee Asia written by yours truly.

Pulse Brew and Pre-Infusion -- New Tools for Filter Drip Brewing

Happy Brewing,
Dr. Brew

Pre-infusion and the brewing process

Question

From Roastmaster Tom

Dear Dr. Brew,
I am in the retail coffee industry. I have owned your CDBC brewing systems as well as the ICB system that I have in my shop currently. I have searched for information regarding pre-infusion and pulse brewing parameters without much success: (SCAA.org, Ted Lingle's book on coffee brewing, all over the Internet, etc).

I assume that pre-infusion is to prepare the grounds for extraction. How long should the grounds be wet before brewing takes place? How wet should the grounds be (ie, should I see drips of coffee coming from the brew basket, a stream, or no evidence of water at this point? How long should the grounds remain wet before brewing takes place? ...

(more of Tom's letter in the next post)

Thank you
Tom Walsh
roaster/owner
Cambria Coffee Roasting Co.

Answer (Part I...Preinfusion)

Dear Tom,

Here's how pre-infusion fits into the brewing process.
Pre-infusion, or pre-wet as some refer to it, saturates the coffee grounds and begins the brewing process. This allows the ground particles to absorb water and swell in size and release carbon dioxide, opening the paths for the remaining water to more easily penetrate and extract the coffee (soluble material). I have found this brew method to be effective with extremely fresh coffee that still contains most of the Carbon Dioxide in the bean from roasting. This also helps with decaffeinated coffee that does not expand as far as its regular counterpart during the wetting proces

To explain pre-infusion, I often use the analogy of a pre-soak cycle in laundry. The purpose is the same -- to expand the material from which we want to extract the soluble. Pre-infusion as a cycle consists of an initial ON time, a pause, and the remainder of the brew cycle. Of course, there are variations depending upon manufacturer. The initial ON period should provide enough volume to saturate the ground coffee.

Ground coffee absorbs approximately two times its weight in volume -- for example, a brew formula of 8 ounces of ground coffee to 128 ounces of water. The initial ON time needs to be sufficient to deliver 16 ounces of water at a minimum to saturate the ground coffee. I prefer to deliver between 15 - 20% of the brew volume for the Initial ON time. This seems to get the grinds saturated and in float.

The pause or OFF time can be for as few as 5 seconds or as long as 4 minutes. I personally do not allow the OFF time duration to allow flow to stop from the funnel outlet. This has something to do with grind size; I have found the finer the grind, the shorter the OFF time. With some fine-ground coffees, if the wet bed of grounds is allowed to collapse, the particles stick together and the water flow for much of the remainder of the cycle flows around the coffee rather than through it.

To convert initial ON time to volume for your brewer follow this example:
Determine spray head flow rate in ounces per minute. 32 opm/60 sec = .53 opsec 15% of 128 ounces = 19.2/ .53 ops = 36 seconds of initial ON time

To find the right preinfusion -- experiment, experiment!

Happy Brewing,
Dr. Brew

(in the next post I will answer Tom's questions about pulse brew)