Hi there.
So I got to be familiar with this "dance" - two variables that play an important rule in the overall outcome of the golden extract (19g, 24sec, ~30g extract).
My question is - how do you know how much pressure to apply when tamping?
If there is one variable that, in my opinion, is the most inconsistent, is the pressure applied.
Yes, I know there are products in the market for the suggested pressure, but they are overpriced.
Anyone out there with a creative idea?

Push the same amount every time. The espro tamper doesn't seem over priced if you are really concerned.

I'm surprised to learn that. Knowing how extraction works, I would believe is is a variable (density of "packed" particles). But... I might be wrong.

Try it. Little or no difference.

On the other hand, I do see day to day changes in flow rate that I don't know where it comes from. Grind, dose, pressure and temperature are supposedly well controlled.

I am suspicious that pulsed tamping or nutating have an effect.

I think a firm, hard tamp may affect the evenness of the initial diffusion of water across the puck prior to pressurization. Once the chamber has fully pressurized, the tamp isn't relevant. Not surprising once you think about the pressure difference: A 30 pound tamp spread over approximately 4 square inches of the puck (less than 8 PSI) versus more than 130 PSI from the pump. I agree that consistency is important, however learning how do tamp consistently is the easiest barista skills to master.

I agree with the first two sentences and the last, but I don't agree with the third sentence. Many posts here claim that tamping pressure has no real effect because it's a small fraction of the water/pump pressure. But the effect of a solid metal surface on top of a bunch of loose grounds is entirely different from the complex and multi-directional effect of pressure from a column of water that has already penetrated the compacted puck.

I'm not saying that this means tamping pressure is important, just that the comparison makes no sense and shouldn't be offered as a reason why tamping pressure isn't a critical variable.

FWIW, I do believe tamping pressure can have an effect, very likely for the reason Dan cites in the beginning: it affects the penetration rate of the water prior to pressurization. If I tamp with very little pressure (say 5 lb), I'll get a gusher. This is probably due to gaps between the edge of the puck and the basket that don't get filled in because I'm not pushing hard enough. If I tamp really hard, I can extend the shot time a few seconds (less than five.) I'll do this sometimes after grinding multiple shots in advance and finding that the first shot has run a little too fast (if I have enough coffee, I'll bump the dose instead.)

Basket prep before tamp is more critical than tamping pressure.
A machine that gives you a longish preinfusion or easy ramp to full pressure will be more forgiving of tamp.

What problem are you trying to solve? Sprites? Flow? Inconsistency? How else have you solved it? What are the other variables in the equation - grinder, grind, dose, distribution, blend?

another_jim wrote:It's easy to confirm the irrelevance of the tamp. Dose two identical baskets with the same amount/same grind of coffee; then distribute both baskets properly, using WDT, Stockfleth's or nutation. On one basket, place the tamper on it and rotate it to smooth the surface, without adding any weight. On the second, put the basket on the floor and step on the tamper, tamping at over 100 pounds. Now see if there's a difference.

I'd love to see video of that