Fine grind / small dose versus coarse grind / big dose: Is there a difference? - Page 3

February 5th, 2007, 12:44 pm

jesawdy wrote:When I dose low (on Silvia at least), it will look pretty good on a bottomless extraction, but the puck will be soupy and some evidence of pockets and/or pin holes. Or are you only pulling singles and find low doses to be simpler?

I always get soupy pucks with low doses, and dimples in the surface about half the time (which I assume is the evidence of pinholes you're talking about). I've never seen any reason to worry about soupy pucks -- it's the beautifully dry ones that usually deliver a horrible taste, since they got wrung out against the shower screen. Dimples are more worrisome. But I neither taste nor see any evidence of channeling -- since the puck is so soupy, I'm assuming its almost impossible for a stable channel to exist in one,

I imagine these dimples are evidence of turbulent vorteces

Can you point me to any information on the other leveling devices you have come across?

Luca wrote me about them. According to him, Paul Bassett's original model was a single swiper with a variable diameter curve, so the amount it scooped below the rim depended on the angle at which it was held. Luca's and a few other cafes use a set of fixed diameter curve swipers. They'll pair them up, one for singles, one for doubles, as the blend and conditions change, so they can use the same grind setting for both baskets. I'm hoping to get some pics for the article.

Dogshot wrote:One interesting thing: to maintain the same extraction ratios, assuming that the PF size represents the diameter of the surface area of the bottom of the basket (a rough guide for double/triple baskets), here is what one should be dosing:

I need to clarify this in a rewrite. I measure the diameter of the hole area and square it. For the baskets I used:

------------------------------
Basket      Diameter* Area**
------------------------------
E61 single  31.0mm     9.6cmsq
E61 12 gr   42.8mm    18.3cmsq
E61 double  43.0mm    18.5cmsq
LM single   31.9mm    10.2cmsq
LM double   44.0mm    19.4cmsq
LM triple   49.8mm    24.8cmsq
Ran double  43.2mm    18.7cmsq
------------------------------

* No data on basket to basket variability
** Simply the diameter squared, not a real area.

For the tasting by yield experiment, I used only the LM triple. I can dose this down to 12 grams without having tamping problems, and up to 19.5 grams without colliding with the shower screen. This gives me a yield range of about 17 to 25 percent, which is pretty flexible. I can easily dose the basket up to 23 grams, but colliding with the shower screen on the Elektra is a taste killer.

#22: Post by **cpl593h** » February 6th, 2007, 2:23 am

Jim, what is the difference between a shot with fine grind small dose, and a shot with coarser grind larger dose, both pulled to the same extraction ratio? Is there a difference? It seems, unless I am mistaken, that your methodology for testing involves constant extraction volume, varying dose to manipulate extraction ratio. Is there anything to suggest that varying shot volume to modify extraction ratio will yield different results than varying dose?

Maybe I should just answer my own question when my espresso beans are of age.

February 6th, 2007, 7:24 am

I can't vary the solubles yield dramatically by changing shot time and volume, while staying within normal shot limits, only by changing dose and grind. A given dose and grind in a given basket pretty much freezes the solubles yield within a 3 percent range. Maybe I misunderstood your point.

#24: Post by **cpl593h** » February 6th, 2007, 11:38 am

Compare two hypothetical shots. Shot A was brewed with a 12g dose pulled to a volume yielding an extraction ratio of 20%. Shot B was brewed with an 18g dose pulled to a volume yielding an extraction ratio of 20%. What's the difference? Going back and rereading the article, considering this question, these stood out:

Changes in shot time and weight also affected the yield, but the effect was surprisingly small.

The major predictor of yield is the weight of the puck divided by the hole area at the bottom of the basket (P/A)... a fat or deep puck extracts less solubles than a thin or shallow puck.

In the same extraction time, a fine grind extracts more completely than a coarse grind.

And suddenly we get a glimmering of sense. Extraction at the bottom is delayed, the thinner the puck, the less the delay, and the more complete the extraction

There's a lot more to the story that I don't know or can't document. Thinner pucks require finer grinds, so the extraction is probably accelerated by that. The fines, and finer particles in general, migrate toward the bottom of the puck, so when the extraction at the bottom gets going, it probably proceeds faster than at the top.

Now I understand better that what governs the results in the cup isn't just the ratio of coffee to water, but it is a more complex arrangement that influences solubles yield.

It makes sense that lighter roasted coffees, which contain less solubles than darker roasted coffees, are better in the cup when extracted in a way that extracts more solubles; previously, we weren't tasting shots that were intolerably acidic because the coffees themselves were 'too bright,' but rather we were tasting shots that were the result of incomplete extractions.

#25: Post by **LeoZ** » February 6th, 2007, 1:30 pm

Dogshot wrote:A few days ago I received an order of 2 new (to me) blends from a local roaster. One of those roasts was quite light, and when I brewed it up at my usual 17gms, it had a tinny taste that I associate with a puckering brightness that I cannot tame. After dinner, I brewed it at 15gms and a full turn tighter on the M4. Both shots were 2oz, 30 second extractions brewed at the same (higher than usual) temp, but the 15gm (lower dose, tighter grind) shot was distinctly tamer, and revealed some of the pleasant notes that had been subdued by the puckering brightness.

Mark

i did the same this morning after reading jims other post/paper on this subject. youd assume that with more head clearance the water would sit on top of the puck and water things down, but it doesnt happen. much less bitterness with the fine grind/smaller dose method.

#26: Post by **LeoZ** » February 6th, 2007, 1:37 pm

Dogshot wrote:Very interesting study Jim, and congratulations on producing something that I'm sure will be referred to in future as often as your water FAQ. I look forward to getting the chance to send you a few comments, if you don't mind.

One interesting thing: to maintain the same extraction ratios, assuming that the PF size represents the diameter of the surface area of the bottom of the basket (a rough guide for double/triple baskets), here is what one should be dosing:

58mm PF - assume 15gm dose.

53mm PF - same extraction requires 12gm dose (perhaps this is why La Spaz has such a thick dispersion screen, with the option to get an even thicker one).

45mm PF - same extraction requires 8.7gm dose. I am very interested to hear if any Ponte Vecchio owners are dosing down as low as 10gm in their double basket.

...or have I misunderstood the concept of P/A ratio and extraction?

Jeff - Although I am a devout Eurocurve tamp user, my limited experience shows that when I dose below 16gm, the flat tamper gives better results (less pinholing).

Mark

how can smaller baskets warrant the same final shot volume? if a 58mm basket @15grams provides a 1.5oz/45ml ristretto, how can a 53ml basket, with 3 grams less beans (whats that, 1 bean!?) provide the same outcome?

are smaller baskets designed to produce lower volume shots? personally, i would have assumed smaller diameter baskets would be deeper to compensate, but have never compared to know.

February 6th, 2007, 7:06 pm

Again -- the yield is fixed by the height of the puck: the ground coffee's weight divided by the area of the holes at the bottom of the basket.

Again -- the yield is fixed by the height of the puck: the ground coffee's weight divided by the area of the holes at the bottom of the basket.

Again -- the yield is fixed by the height of the puck: the ground coffee's weight divided by the area of the holes at the bottom of the basket.
..

You can't get high yield from 17 or 20 gram doses unless you find yourself a 65mm group. The LM triple has the largest hole area I've seen so far, and over about 15 grams yields go below 20%.

In any case, here's the main practical point. If the shot is too sharp or sour, dose less; if it's too bland, dose more. That's it.

You can adjust the grind to get whatever shot volume, time or concentration you want just as easily with any dose you use.

Again -- the yield is fixed by the height of the puck: the ground coffee's weight divided by the area of the holes at the bottom of the basket.

#28: Post by **LeoZ** » February 6th, 2007, 8:21 pm

another_jim wrote: In any case, here's the main practical point. If the shot is too sharp or sour, dose less; if it's too bland, dose more. That's it.

this is genius. i never thought of using less coffee. it almost seems counter intuitive. absolutely genius.

oh, and ill keep this in just because. :p

another_jim wrote: Again -- the yield is fixed by the height of the puck: the ground coffee's weight divided by the area of the holes at the bottom of the basket.

#29: Post by **LeoZ** » February 8th, 2007, 2:50 pm

heres a thought.

its counter intuitive thinking at first to use less espresso to remove bitterness. one would assume (at least i did) that less espresso would force more water to gather on the puck (sort of how a drip coffee maker works), and catch more bitters.

HOWEVER, if you think about the design of a lever machine, its a straight water column right above the grouphead, right? im not sure, ive never used one, but it looks that way to me. the reason, i think, that lever machines create 'better' espresso, or smoother as some say, is because of this. you are allowing a column of water to provide a stable and direct means of pressure over the puck.

now, correlating this to smaller dosing, the larger gap may actually create a water column, albeit small, over the top of the puck. this column allows for a steady pressure to be applied through the puck, as the water is acting like a buffer between the grouphead and the grinds.

make sense? maybe this was trivial to some, but made sense to me!

#30: Post by **malachi** » December 6th, 2008, 1:47 pm

Huge difference.
Sadly... the differences are different not only from coffee to coffee but also brew temp to brew temp.
The combinations of course increase.

Fine grind / small dose versus coarse grind / big dose: Is there a difference? - Page 3

Fine grind/small dose versus coarse grind/large dose: Is there a difference?