Last night I was involved in a training session on espresso techniques, and as I was done tamping, I polished the puck by spinning the tamper 360 degrees on the puck. The trainee asked me why I polished and I was dumbstruck for a second not knowing the reason behind polishing. I quickly regained composer and thought back to my reading of the Gimme barista manual where it says that polishing "smooths out any small ridges on the surface of the puck and creates a perfectly flat surface for the water to hit once the pour begins." But it got me thinking, about the Reg-barber C-ripple and its waved design... in the evaluation of it at www.espressorun.blogspot.com they say the results of the ripple " is almost resemblant to that of a flat base." Billy Kangas in another discussion here on bx notices a sweeter extraction, but only in certain situations. Which to me means that with relatively huge ridges in the top of puck the effect is almost negligible. So, does polishing really make a huge difference? Is it important? I am not finding much on polishing the puck in any Internet sources... and as a general disclaimer, I am playing devils advocate a bit here to see what will potentially come up?

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Earlier today I posted the above post about the strange experience I had recently with polishing an espresso puck. It brought up some more in depth questions than I thought I would have.

As of right now, I still have not had any responses to the post and do not really foresee any one responding to it in the future. (although I hope someone does) And in thinking this, I took matters into my own hands and began to ask around for some answers.

Ironically this afternoon, my good friend Josh Longsdorf (currently of Ritual Coffee Roasters) called me and I asked his opinion. He said that polishing the surface of the puck essentially smooths out the surface so as to allow water to more easily permeate the espresso allowing for easier saturation and therefore more consistent extraction.

Right after I got off the phone with Josh, I went up to Roast Coffee Company on the East side of Milwaukee to geek out with Brett Boy Wonder. So, with Josh's recommendation I performed the experiment of dosing and weighing out the espresso as accurately as possible, of the polished and un-polished espresso and measuring the difference in weights of the two before and after extraction. As a second measure of quality we also did a taste test of the espresso shots to see which tasted better, taking notes of all the above.

It really came as a suprise to me that the unpolished pucks managed to consistently gain more weight during extraction, leading me to believe that the pucks become more saturated during the shot extraction. Also, the shots seemed to have a fuller flavor profile with more fruity, high notes coming out. Whereas the polished shots seemed to stay within a more narrow range of saturation and weight during extraction as well as giving us more bitter, dryer finish shots.

What I am taking away from this experiment is that possibly the unpolished puck like the c-ripple tamper, has more of a turbulent surface and therefore more surface area for water to come in contact with initially in the espresso extraction. This would (I am assuming) lead to a little bit longer of an extraction, because of the duration of full contact with water. Also, I think it would lead to a potentially more even extraction. This would be because the water in contact with the top of the puck would pass through much easier, not causing an over-extraction of the top half of the puck.

Although, scientifically I can not really verify this information(I don't have the equipment or the means), I can only assume that by the test's results that we performed tonight, that shots un-polished have a better consistent, fuller flavor. The thought also comes to mind if I were to walk into a specialty coffee shop at random, would I be able to identify a shot polished or un-polished? No, definitely not, but in a side by side comparison the results were pretty clear.

I would really like to see some other peoples results from trying this or to know of other people that polish or do not polish and why? I still have not found much information on polishing online.
Neat little experiment. Will play with this and get back to you with my results as well. I too wonder about this.

That said, I'm so sorry it took so long for me to get back to you. In the future, I'll try to stay by my computer and watch for you to post more on this. Patience, grasshopper...
Thanks for posting Eric, very interesting. And it brings up another question for me, one that's probably old new to you. I'm just getting back into the coffee scene and I remember something about pre-infusing the grounds with a little hot water for a few second and then pulling the shot. Is this a myth debunked long ago or do some Baristas still use this technique, do you know? Thanks. - Cash (_)D

Eric said:
Earlier today I posted the above post about the strange experience I had recently with polishing an espresso puck. It brought up some more in depth questions than I thought I would have.

As of right now, I still have not had any responses to the post and do not really foresee any one responding to it in the future. (although I hope someone does) And in thinking this, I took matters into my own hands and began to ask around for some answers.

Ironically this afternoon, my good friend Josh Longsdorf (currently of Ritual Coffee Roasters) called me and I asked his opinion. He said that polishing the surface of the puck essentially smooths out the surface so as to allow water to more easily permeate the espresso allowing for easier saturation and therefore more consistent extraction.

Right after I got off the phone with Josh, I went up to Roast Coffee Company on the East side of Milwaukee to geek out with Brett Boy Wonder. So, with Josh's recommendation I performed the experiment of dosing and weighing out the espresso as accurately as possible, of the polished and un-polished espresso and measuring the difference in weights of the two before and after extraction. As a second measure of quality we also did a taste test of the espresso shots to see which tasted better, taking notes of all the above.

It really came as a suprise to me that the unpolished pucks managed to consistently gain more weight during extraction, leading me to believe that the pucks become more saturated during the shot extraction. Also, the shots seemed to have a fuller flavor profile with more fruity, high notes coming out. Whereas the polished shots seemed to stay within a more narrow range of saturation and weight during extraction as well as giving us more bitter, dryer finish shots.

What I am taking away from this experiment is that possibly the unpolished puck like the c-ripple tamper, has more of a turbulent surface and therefore more surface area for water to come in contact with initially in the espresso extraction. This would (I am assuming) lead to a little bit longer of an extraction, because of the duration of full contact with water. Also, I think it would lead to a potentially more even extraction. This would be because the water in contact with the top of the puck would pass through much easier, not causing an over-extraction of the top half of the puck.

Although, scientifically I can not really verify this information(I don't have the equipment or the means), I can only assume that by the test's results that we performed tonight, that shots un-polished have a better consistent, fuller flavor. The thought also comes to mind if I were to walk into a specialty coffee shop at random, would I be able to identify a shot polished or un-polished? No, definitely not, but in a side by side comparison the results were pretty clear.

I would really like to see some other peoples results from trying this or to know of other people that polish or do not polish and why? I still have not found much information on polishing online.
Preinfusion is alive and well.
Brady said:
That said, I'm so sorry it took so long for me to get back to you. In the future, I'll try to stay by my computer and watch for you to post more on this. Patience, grasshopper...

ARGGG, it took 5 hours for a response!!! The pain and horror!!! Haha. I was not really up-set, just trying to instigate a conversation of sorts....

A second note to what I had previously posted we were measuring the difference of weight of the puck before and after shot extraction with an average of quarter to slightly over half a gram more weight in the unpolished puck... Which got me thinking what the normal weight tolerance difference +/- is on average of baristas are??? Should the weight gain of an unpolished puck in the proportions of half a gram make a huge difference? My thoughts would lead me to think that like everything else in the coffee industry the small things tend to make a huge difference.

And as a response to Cash, I know there are some other forums on BX that talk heavily about it but the consensus that I know about at most shops leads them to do "soft pre-infusion" where line pressure is introduced to the espresso at the beginning of extraction until the first drip is seen. This gives the espresso time to expand and give uniform density to the puck, ideally minimizing fissures and channeling in espresso. Whereas a "hard pre-infusion" is full tank pressure for a period of time and is thought to do more damage than good, meaning you might as well just pull a shot without turnin on and off your pump.
I figured that was a little tongue in cheek, hence the response in kind :)

You know, I'm getting ready to run a "tamp force" experiment this week with a friend (in response to another discussion on here), and am glad you mentioned the "weight gain" thing. I'll add that to the matrix, but perhaps not in the way you might think...

I wonder if the difference you saw in spent puck weight really means that it retained more water. Might the difference instead be attributed to a difference in extraction efficiency? Did they both gain the same amount of water weight but the polished puck had a larger amount of solids extracted, thus resulting in a lighter spent puck? This would explain the bitter, drier finish on the polished shots... were they perhaps over-extracted?

Repeat the experiment, bake your pucks, and weigh them dry. While you're at it, buy Extract Mojo and take readings of your finished espresso. Wait!? I'm lost now... is this bX or Coffeed?
Brady said:
I figured that was a little tongue in cheek, hence the response in kind :)

You know, I'm getting ready to run a "tamp force" experiment this week with a friend (in response to another discussion on here), and am glad you mentioned the "weight gain" thing. I'll add that to the matrix, but perhaps not in the way you might think...

I wonder if the difference you saw in spent puck weight really means that it retained more water. Might the difference instead be attributed to a difference in extraction efficiency? Did they both gain the same amount of water weight but the polished puck had a larger amount of solids extracted, thus resulting in a lighter spent puck? This would explain the bitter, drier finish on the polished shots... were they perhaps over-extracted?

Repeat the experiment, bake your pucks, and weigh them dry. While you're at it, buy Extract Mojo and take readings of your finished espresso. Wait!? I'm lost now... is this bX or Coffeed?

This morning I traveled back up to Roast Coffee Co to talk with Brett again and he noticed more and more differences in shot extraction between polished and un-polished. He was telling me that the un-polished pucks seemed to pull in the same time, but on the naked portafilter, the extraction began sooner. We performed the experiment again with the same result of last night, where the unpolished puck became more saturated, taking on more water weight. The taste is by far also better, with the unpolished puck. The only difference we did in our test today was that we measured the final shot weight unlike last night where we just didn't for some reason... this was really startling with the shot weight of the polished puck being 5.4 grams lighter... Does this mean that more water was allowed to pass through in the unpolished puck? Dose this mean more solids were extracted in the unpolished puck giving it a heavier weight?

Also, we noticed while on the polished tamp that the extraction on the naked portafilter tended to spiral. Where as the unpolished tended to extract straight and fast with no visual channeling.

Another note is that I have not tried this on a machine with pre-infusion and its effects? Any possiblity of someone giving this a shot? and results.
On your polished tamps, are you putting downward pressure on the puck while you polish it? The polish I was taught, is too let go of all pressure then spin the tamp freely. Also, a 5.4 gram difference in the puck weight is huge, how many times did that happen? Have you tested your dosing weights by popping baskets out after you tamp them, and then weighing them, just to make sure you're being consistent with your pre-extracted weight?
Are you pulling 1.5oz doubles across the board, or is there a volume difference in your shots? Certainly you've thought to keep this constant, but just thought I'd verify. 5 grams is a huge difference.
Kevin Ayers said:
On your polished tamps, are you putting downward pressure on the puck while you polish it? The polish I was taught, is too let go of all pressure then spin the tamp freely. Also, a 5.4 gram difference in the puck weight is huge, how many times did that happen? Have you tested your dosing weights by popping baskets out after you tamp them, and then weighing them, just to make sure you're being consistent with your pre-extracted weight?

I think I worded this funny, we weighed the actual espresso shot and the unpolished shot was 5.4grams heavier... So as a response Brady, I dont think that your question"Did they both gain the same amount of water weight but the polished puck had a larger amount of solids extracted, thus resulting in a lighter spent puck?" would be right since we are finding that a larger volume/weight in the unpolished shot...
Working on a GB5 we pulled a lot of shots. Three of us did color, mouth feel, taste, and aroma comparisons.
Spouted portafilter results: 20g for every shot 4 shots polished 4 unpolished.
The average weight difference between the shots for each was 5g more unpolished with a visibly larger volume in cup. The end puck weight was always 38g.

Naked portafilter results: 20g pulled two of each shot
the average weight difference between the shots was 7g more unpolished with larger volume in cup. End puck weight was always 38g.

Naked portafilter results: 22g pulled two of each shot
the average weight difference between the shots was 4g more unpolished with larger volume in cup. End puck weight was always 38g.

Every shot unpolished resulted in less body, an obvious over-extraction, nearly all of them were completely intolerable.

The Naked shot polished at 22g was slightly under-extracted but was tolerable while the non-polished was slightly over-extracted.

Every shot unpolished seemed to exhibit visual characteristics of channeling.

We took video of the shots but a wine maker friend is going to let me barrow his refractometer to measure dissolved solubles so I'm waiting till then to rerun the trials and post video. My conclusion to date is that at least on the GB5 shots that are polished result in more balanced, more aromatic, and more drinkable shots. I vote for polish.
I was intrigued by your post and decided to pull a shot without polishing. My wife and I have learned together and both have always polished it off before installing the pf in the head. This morning I heard her coming down the steps so I decided to make her a cappuccino without telling her that I had changed procedures. When I handed her the drink she took a sip and said, "Something is different," this is really an outstanding cap. She said it several times while drinking and I made myself one. The machine that I have has a paddle for preinfusion and I used a 15 second preinfusion just as I had done with hers. There appeared to be more depth in the flavor with the Black Cat espresso we used. I think this is the first time we had tasted all the nuances of Black Cat and the only change we made was not polishing. When you stated that polishing made it more difficult for the water to saturate the grounds it made sense to me and at this point I think it does. I am going to continue "not polishing" and see if I notice the change.

Good topic...thank you!

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