Earlier today I posted on BaristaExchange.com about a strange experience I had recently with polishing an espresso puck. It brought up some more in depth questions than I thought I would have. My post went as follows: "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?"
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. 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.
Update: 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.
Also 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.
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i think you are on to something. im not coming from the barista side just yet, im still learning that, but your thought process makes sense. when polishing, you are laying and maneuvering all the coffee particles into a certain manner that seems like would compact (at least parts of) the surface even more, which would make water distribution through it, less even, as the pressure on the high spots will be more than the low spots, rather than just the even-ness of the tamp all around.
ReplyDeleteif i think in terms of building a snow fort, or sand castle in which i am using my hand to smooth the surface out, on the high spots, i use much more pressure than the low spots, which may not even get any pressure, depending on how high the highs are and how low the lows are......
Heck yes! Something to experiment with. Good stuff so far.
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