www.compasscoffeeroasting.com: coffee is culinary

Why do bulk grinders produce a superior grind for non espresso preparation?

Postby cannonfodder on Sat Apr 24, 2010 12:29 am

I have been preparing espresso for quite a few years now but I have always cast an unfavorable eye on other brewing methods. I simply was not getting a cup I liked. Often my brew/press coffee contained off flavors, mostly bitters regardless of how I prepared the coffee. I would change temperatures, doses, steep time and would eventually get something that was OK but still off. So I stuck to espresso.

I always used my espresso grinder to grind my coffee. My thinking was if it is good enough to grind for one of the most unforgiving preparation methods it would surly be good enough for a press pot or drip. Over time experience and the wisdom of others I have realized that is not the case. Espresso grinders produce a range of particle size by design. That range of particulate is critical to proper extraction of espresso. It is theorized that the fines produced by the grinder are one of the keys to the extraction. I would also surmise that this acceptable range is what has been causing my brew issues with other preparation methods.

Assuming that a very uniform grind is needed (or simply the absence of fines) for drip/vac/press preparation, my question comes down to why do some grinders produce this and others do not? I would assume it has to do with the geometry and possibly the size of the burrs, but why? I would think that the espresso grinder, with its three zone burrs and progressively finer teeth would produce a superior grind.

Most bulk grinders use a comparatively rough set of burrs with one or two cutting zones and relatively large teeth. I would think that these large teeth would chunk the beans into rough, ill formed and varying sizes. I may be simply chasing a white rabbit and there is no real answer other than, they just do. I thought I would pose the question anyway since I am looking for a dedicated drip/press/vac grinder. Unfortunately most of the best grinder in this class are big unwieldy bulk grinders like the Grindmaster, Bunn-O-Matic, Mahlkönig. Not holding out much hope for a small, put it in the cabinet when not in use grinder.
Dave Stephens
User avatar
cannonfodder
Team HB
 
Posts: 7878
Joined: May 23, 2005
Location: Downingtown PA

Postby another_jim on Sat Apr 24, 2010 12:44 am

Funny you should mention it. I was forcefully struck by the same difference when visiting Terroir, but couldn't replicate either the level of equipment nor the brewing precision until now

Image

My coffee package for the day, the Bunn LPG. 81 mm burrs, 15 inches high, lid removed and with a single dosing skirt and ground coffee tray. Screening the drip grind (500m average) results in no particles below 200. No grind chamber, so no retained grinds. Basically laid out like a hand grinder with a DC motor instead of crank. All this (and butt ugly too) for only $475 new. Stay tuned on whether it's worth it or not

I'm waiting on some extraction measurement gear that Vince Fedele has kindly lent me for this effort. That way I can make comparisons that all have the identical "golden cup" TDS and solids extraction levels (my previous brewing comparisons were invalid and unposted since I couldn't ensure this). There are two tests: first comparing espresso, bulk and cheap home grinders for brewing, and also comparing fast brewing with finer grinds to slow brewing with coarser grinds.

I'm hoping that will produce some sort of answer.
User avatar
another_jim
Team HB
 
Posts: 9041
Joined: May 05, 2005
Location: Chicago

Postby AndyS on Sat Apr 24, 2010 9:21 am

another_jim wrote:I'm waiting on some extraction measurement gear that Vince Fedele has kindly lent me for this effort. That way I can make comparisons that all have the identical "golden cup" TDS and solids extraction levels


Glad to see you're -- finally -- joining the 21st century. ;-)
-AndyS
VST refractometer/filter basket beta tester, no financial interest in the company
User avatar
AndyS
 
Posts: 1059
Joined: May 05, 2005
Location: NY

Postby earlgrey_44 on Sat Apr 24, 2010 11:34 am

cannonfodder wrote:Most bulk grinders use a comparatively rough set of burrs with one or two cutting zones and relatively large teeth. I would think that these large teeth would chunk the beans into rough, ill formed and varying sizes. I may be simply chasing a white rabbit and there is no real answer other than, they just do. I thought I would pose the question anyway since I am looking for a dedicated drip/press/vac grinder.


This sounds like some great work is in the offing. Cool. :D I've been wondering about how these different grinders work too.

Our friends at Marco have been publishing some data about this for while.

Based on some sketchily described taste tests, they have concluded that a screened grind or the produce of a highly unimodal grinder set around a .8mm median particle size make the "best" press cup. Inclusion of a higher percentage of fines degraded the brew. This seems like a straight-forward conclusion.

There's always been a paucity of info about what different grinders do at drip or press settings. The Marco folks promised a few months ago some comparative data between a cast steel burr grinder (like the kind in Jim's grinder above), a "dragon's tooth" type of burr like the kind in my old commercial Hobart, and a burr set they are developing that looks much like the general design found in the Mazzers and MACAPS and similar grinders of the world. I prodded Paul to post the results recently, and he just did:

http://marco.ie/uberproject/?p=401

The "espresso grinder" design (for lack of a better label) produced the least fines, the "dragons tooth", the next least, and the cast burr the most. Whooo ha.

Kyle at Baratza recently contributed a graph made on the same measuring equipment for the relatively cheap Virtuoso grinder. See it here:

*Which* Baratza grinder for drip/press?

So, there's a cheapish grinder that can produce a unimodal particle curve at a press setting competitive with the best.

What's all this mean in terms of comparative cup quality? Inquiring minds want to know...
earlgrey_44
 
Posts: 215
Joined: Oct 29, 2008
Location: NW Chicago

Postby Ben Z. on Sat Apr 24, 2010 11:45 am

earlgrey_44 wrote:There's always been a paucity of info about what different grinders do at drip or press settings. The Marco folks promised a few months ago some comparative data between a cast steel burr grinder (like the kind in Jim's grinder above), a "dragon's tooth" type of burr like the kind in my old commercial Hobart, and a burr set they are developing that looks much like the general design found in the Mazzers and MACAPS and similar grinders of the world.


Is there any data on the roller grinders? This would be one of the easiest type to manufacture.
Ben Z.
 
Posts: 178
Joined: Jul 31, 2007
Location: Richmond, VA

Postby Bluecold on Sat Apr 24, 2010 12:39 pm

earlgrey_44 wrote:http://marco.ie/uberproject/?p=401

The "espresso grinder" design (for lack of a better label) produced the least fines, the "dragons tooth", the next least, and the cast burr the most. Whooo ha.

The 80mm burr you call 'espresso burr' looks like the burr from the Tanzania, which is a bulk grinder.
The bulk grinders seem to have longer 'fine grinding' areas.
http://www.espressoparts.com/espressopa...e_2888.jpg
LMWDP #232
"Though I Fly Through the Valley of Death I Shall Fear No Evil For I am at 80,000 Feet and Climbing."
User avatar
Bluecold
 
Posts: 1207
Joined: Jul 10, 2008
Location: The Netherlands

Postby cannonfodder on Sat Apr 24, 2010 1:38 pm

I was actually thinking the opposite. The fine grind zone on an 'espresso burr' may account for the un-uniform grind for other brewing methods. A thought crossed my mind last night. What if I took something like a Super Jolly, removed the burrs and milled off the entire 'fine' zone of the burr. That would leave the crusher and medium zone burr teeth. Would that then produce a more uniform particle?

I will liken it so something I do have a little more knowledge about. Saw blades. I have a solid dozen blades for my cabinet saw. Each blade having a different tooth count and spacing for different jobs. A large toothed rip blade will hog out large slivers of wood and cut the stock fast. The fact that the teeth are large offset chisels they make large ribbons of sawdust with little 'dust'. With a quality carbide blade, even the fast cutting of the blade will leave a relatively smooth and uniform surface.

Now if I switch to say, an extremely high tooth count finishing cabinet blade where the teeth are a fraction of the size of the rip blade. The teeth are even shaped differently with every other tooth being narrower, much like the middle and fine zone on a set of espresso burrs. The small tooth basically cuts half the width of the other tooth. By doing that, I effectively cut each piece of stock twice with one blade. Each tooth removing just a little bit more than the previous. That arrangement produces copious amounts of powder dust mixed with small flakes but the end cut is so smooth and uniform it barely needs any sanding.

Could it be as simple as, big teeth produce large but uniform pieces provided the in-feed speed remains constant (like a rip blade). An espresso burr set in its attempt to cut a small perfect particles using smaller and smaller teeth is ill suited for large uniform grinding because we are essentially only using the first two zones of the burr set. The fine teeth are simply bouncing the larger particle around. That bouncing producing more fines and irregular sized particles much as my super fine tooth finishing blades produce a super smooth and even cut but at the expense of making powder instead of chips.
Dave Stephens
User avatar
cannonfodder
Team HB
 
Posts: 7878
Joined: May 23, 2005
Location: Downingtown PA
prima-coffee.com: coffee & espresso equipment and accessories
prima-coffee.com: coffee & espresso equipment and accessories

Postby earlgrey_44 on Sat Apr 24, 2010 2:17 pm

Bluecold wrote:The 80mm burr you call 'espresso burr' looks like the burr from the Tanzania, which is a bulk grinder.
The bulk grinders seem to have longer 'fine grinding' areas.


The outer edge, fine-grind stage of a mazzer burr does indeed look different than the same stage of the "tanzania" style burr, even if the first and second stages look similar.

I also thought it interesting that the "tanzania" and the "dragon's tooth" or crushing burr produced so similar a profile, even though they are radically different designs.
earlgrey_44
 
Posts: 215
Joined: Oct 29, 2008
Location: NW Chicago

Postby another_jim on Sat Apr 24, 2010 4:54 pm

Espresso grinders end in either a solid outer/lower ring or one with extremely narrow grooves cut in. Bulk grinders have the same burr configuration but no outer ring. This is true of all the bulk grinders as far as I can tell.

There are interesting design differences: the Bunn and Ditting burrs look similar to the espresso grinder flat burrs, Mahlkoenig has an odd burr for the Kenya, only 64mm, but cut at a much more oblique angle and with no crushing area, like the flat burr part of a hybrid. I don't know what these differences amount to. The Grindmaster burr looks like an abrasion system with pegs, and I can't see this being much use for specialty coffee.
User avatar
another_jim
Team HB
 
Posts: 9041
Joined: May 05, 2005
Location: Chicago

Postby earlgrey_44 on Sat Apr 24, 2010 5:29 pm

another_jim wrote: The Grindmaster burr looks like an abrasion system with pegs,


The Grindmaster looks rather like the one that produced the good profile in the Marco test...no?

Image
earlgrey_44
 
Posts: 215
Joined: Oct 29, 2008
Location: NW Chicago