As I was battling my chronic channeling/early blonding and bitter/sour (tannic?) problems again this morning, the technique described in this thread came to mind. I gave it a try, and while it didn't fix my problems, I did notice a subtle difference visually. The slick stainless bottom of a tamper isn't really that grippy though, so it probably won't do much to fix a fundamentally flawed distribution from the grinder. For that, there's WDT, nutation, etc.

None of those have gotten me where I'd like to be though, and I probably need to solicit some semi-professional training. Starting with a mound of coffee in the basket, simply leveling with the weight of the tamper as many have recently suggested results in serious donut extractions. Tightening the grind enough to eliminate that results in a nearly choked extraction. WDT doesn't seem to help much. I've had the most luck with nutation, but even that isn't immune to channeling.

However, while also thinking about this simple twisting technique and the latest cutting edge consensus that tamping really isn't that important, I started to wonder about alternative tamper surfaces. My uneducated theory is that denser areas of the puck compress less and act as a load-bearing pillar that "protects" the less dense areas during tamping, which then open up as fissures during extraction. I'm imagining a tamper with ~.5-1mm grooves cut into its bottom surface, spiraling outward from the center (not unlike the cutting pattern of flat burrs). This surface would be set gently on the mound and spun with nothing more than its own weight. This surface would exert more force on higher/denser spots, and grounds there would be forced into the grooves. Through backpressure in the grooves, these grounds would be deposited into lower/less dense areas, where less pressure exists against the surface. After a few revolutions, the force applied from each point on the bed of coffee to the tamper will reach equilibrium, and the migration of grounds would stop. The tamper will have settled as these pillars of grounds are torn down and relocated, hopefully resulting in optimal (and perfectly repeatable) distribution. The grooves would still be filled with a negligible amount of wasted coffee, but would create a flat surface and effectively polish the puck.

Unfortunately, this is a theory from someone with no background in materials/fluids/mechanics/etc, and also from someone with zero metal-working equipment or spare tampers to test this hypothesis. I guess that doesn't mean it's not an idea worth entertaining. Thoughts?

Edit: this is unrelated to VST baskets. Too far off topic for this thread?


Split from New dose/distribute/tamp technique for VST? by moderator

mitch236 wrote:the grinder and initial distribution are very important, I don't think anyone is discounting tamping

Some members in recent threads (i.e. this) have advised against any tamping whatsoever, and instead recommend a simple levelling then lock & load. Granted, this is not universally accepted. Duly noted.

Thanks for the "ripple" tamper heads up. I wasn't aware that existed. However, there's a fundamental difference between that and what I was trying to describe. That ripple pattern looks merely cosmetic to me. Grounds might collect here and possibly be relocated. However, considering a particle's location in polar coordinates (radius, theta), spinning the tamper will change theta, but radius will remain constant. In other words, particles from the tall center of the mound will never migrate to the edges, which is necessary for even distribution.

The key to the pattern I was describing is that the grooves originate at the center and spiral outward. Particles that collect in these grooves (primarily from the center, given an undisturbed mound) would be forced towards the edge of the basket until they found a point of lower resistance. As the tamper is spun, this process would continue until a completely even distribution of coffee is achieved (a socialist utopia of ground coffee, really). The tamper might even provide sufficient tactile feedback to the user to indicate when the process is complete.

RapidCoffee wrote:Dose matters. Do you weigh your dose? You may be dosing more than you realize.

Fresh Redbird, to the hundredth of a gram. I was pleasantly surprised by the accuracy/consistency a $30 scale.

tcaton wrote:Yes, definitely OT. We forgive you, but don't let it happen again.

I was deliberating on whether to start a new thread. While this idea is unrelated to VST baskets, it is closely related to the technique described here. I figured the moderator gods can always fork() a new thread.

Man, been a long time since I even thought about fluid-dynamics in problem-solving terms, let alone turned the crank, furthermore we don't have any real good distribution models; but never let ignorance stand in the way, what? What?

Fines particle size and shape is sufficiently complicated, irregular, and in the muddled middle to not act like a fluid or a bunch of tiny ball bearings; but not act like a bunch of cinder blocks either. The effect that size and shape have on distribution is one of the least recognized aspects of everyday physics in this and every other espresso forum.

When you use a tamper and press down a relatively symmetric distribution (with perhaps more in the middle than the circumference -- but the circumference more or less equalized, (my semi-informed guess is that) you're probably doing more to equalize distribution than just lock distribution in. But you are by no means doing everything.

And when the distribution is lopsided around the circumference, oy.

Not to name names, but don't confuse what water coming through a showerhead at 9 bars will do to a puck with what 130psi (or for that matter 15psi) of tamper pressure will do. They are not the same.

Other than from a purely results oriented standpoint (e.g., "works good" or "doesn't work so good") the no-tamper technique doesn't seem to have received much sophisticated analysis. Give it a try. See what you think. Then, if called upon to explain it, at least come up with something entertaining.

The idea of texturing the puck's surface is interesting. You can test a variety of options, the ridged Barber, dragging a fork across a polished surface, across an unpolished surface, polishing, not polishing, all sorts of things. Anything which you think works for you, is a good thing. Don't count on it working for every basket and/or every coffee.

I'm not sure what the anti-ridged Barber argument is other than "doesn't work." The pro-argument and rationale is increased surface area.

What you can count on is that if you write about it enough someone will come along later and do a statistical analysis on an invalidly small and insufficiently anonymous population. It's how we roll.

BDL