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.
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...
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?
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?