What was the portafilter "tap" supposed to accomplish?

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#1: Post by Peppersass »

Probably a stupid question, but I'm going to ask it anyway:

Been traveling lately, and most of the professional baristas in the cafes I visited tapped the portafilter with the tamper between an initial light tamp and the final tamp. I'm sure this isn't news to long-time members of this site. I've seen many web videos of the infamous tap, and have read quite a few posts here about how it's a bad idea because it can dislodge the outer edge of the puck from the basket, which is likely to lead to channeling. Of course, being a good HB soldier, I never do a tap :)

But during my travels, I began to wonder just what the now-discredited tap was supposed to accomplish. What do these baristas think it's doing for them? Assuming they've updosed and done some sort of leveling procedure, I would think it's not to complete the distribution.

So, when misguided coffee shop managers train their baristas to tap the PF before the final tamp, what do they tell them it does?

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#2: Post by gyro »

I was always under the impression it was to dislodge the loose grinds along the top sides of the basket before re-tamping to leave everything neat and tidy.
Peppersass wrote:Of course, being a good HB soldier, I never do a tap

I've seen one OCD barista in a favourite NZ shop of mine go thru about 15 taps/tamp cycles. Amusing to watch, but hardly beneficial I would have thought. The coffee is better from the other guy, who's latte art is also beyond reproach...

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#3: Post by another_jim »

One can alternate taps and thwacks to really overload a basket or to get a very even density throughout the untamped puck. I believe the Aussie WBC champ, Paul Bassett, did this. The easily seen thwack-tap got him the reputation of being the ultimate overdoser; but he combined this with using a plastic knife with a curved edge to swipe beneath the top of the basket. So the intent of the tapping was to get a very predictable and even puck density. The two techniques together probably got him very consistent dosing without the delay of using a scale.

I've also heard that tapping removes air pockets from the puck, and when done prior to tamping improves the shot's flow. People using naked PFs do not confirm this. However, it is conceivable that those untrained in a naked PF could reduce the amount of channeling they get by doing this.

If you weigh and use a naked PF, neither reason for tapping has any point. If you are in a shop and need to work fast, the Bassett combo of thwack-tapping and using a curved swiper makes a lot of sense. However, thwack tapping has pretty much died out and been replaced by thwack and twist, where the portafilter is rotated while thwacking out the grinds. This apparently also evens up the distribution and puck densities.

There is a tendency for people to copy Barista Champions without necessarily knowing why they do what they do, so there's probably a lot of completely unintelligible tapping going on out there. Whatever the cause, puck preparing is a magnet for silly rituals
Jim Schulman

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#4: Post by HB »

gyro wrote:I was always under the impression it was to dislodge the loose grinds along the top sides of the basket before re-tamping to leave everything neat and tidy.
That's the usual response when I've asked. If I point out that they're worrying about less than 0.1 grams of coffee making a mess while potentially breaking the puck/basket adhesion, some sheepishly admit they were taught to do it and never questioned the necessity. The most original explanation? "The loose coffee particles heat more quickly than those adhering firmly to the puck, leading to an ash taste." This gem was offered years ago by a highly-respected cafe owner and trainer during an SCAA certification workshop (paraphrased from memory and name omitted out of courtesy).

Nick offers an interesting historical footnote in Why tap the portafilter?
Nick wrote:We stopped "tapping" in 2006.

Instead, we "thump."

Thump = thumping the portafilter on the counter between tamps, instead of tapping with the tamper.

Our reasoning: if, theoretically, you wanted to hit the portafilter with the tamper, and with as little force as possible, and your goal was to BREAK the tamped puck or break the seal with the side of the basket, you'd strike it... pretty much where baristas do now. A lateral and slightly-downward blow with the tamper-handle on the upper-edge of the portafilter.

"Thumping" the portafilter moves the loose grounds to the middle, but the puck is cradled by the basket, with the force-vectors of both moving together. With a "tap," your force-vectors are working against each other.
I use thumping to increase the dose when dosing by volume. If using a scale, I'll skip the thump and deal with redistributing the coffee for an updosed shot using the Stockfleths Move for Dummies.
Dan Kehn

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#5: Post by cannonfodder »

I have been thumping the portafilter for some time now, but only 2 times. It settles the grinds and levels the dose when you are dosing below the rim of the portafilter. I gave up tapping the portafilter between tamps several years ago. The only purpose it serves to to crack the puck and break the side adhesion of the puck to basket. If you like channeled shots, tap away. I thump the portafilter on the tamping stand twice and tamp once.
Dave Stephens

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#6: Post by Peppersass (original poster) »

cannonfodder wrote:I have been thumping the portafilter for some time now, but only 2 times. It settles the grinds and levels the dose when you are dosing below the rim of the portafilter.
I've been doing this, too, and using a finger to fill in gaps and level when the dose is below the rim, and NEWS or a Sockfleth-like move when the dose is above the rim. However, I recently decided to skip this part of the ritual for my 13g-14g SO shots, and just grind, lightly shake if I didn't get even distribution when dosing, tamp and go. I've not seen any difference in the quality of the pour coming out of the naked PF, probably due to the big conical grinder and lowish dose. Haven't tried this yet with an updosed shot.

As it turns out, the taste of the shots was much improved over shots prepared with tap and level. I've read that thumping the portafilter on the counter can cause fines to move to the bottom of the puck, resulting in a bitter shot, and it's tempting to assume that my change in procedure has improved the shots. But I'm virtually certain this has more to do with the fact that the previous batch of coffee was received a week past roast and stored in a non-chest freezer for a couple of months, while the present batch was received one day past roast, frozen immediately, and stored only a couple of weeks. It's an SO from Terroir and my conclusion is that it's best as close to roast as possible and doesn't benefit from rest, especially if frozen. I've also concluded that storage in a non-chest freezer (at least, mine) should not exceed a few weeks at most.

I bring this up because it's very easy to attribute a change in taste to the wrong cause.

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#7: Post by RapidCoffee »

Peppersass wrote:I've read that thumping the portafilter on the counter can cause fines to move to the bottom of the puck, resulting in a bitter shot...
My 2 cents on fines migration during puck prep: unlikely speculation. Fines migration has been suggested as a possible mechanism to explain modulation of flow during extraction. AFAIK there is no compelling evidence to support this, but it's a reasonable hypothesis that could be tested by (tedious) puck slicing and particle sizing.

However, puck prep conditions are completely different from extraction conditions. Fines migration during extraction, if present, would occur in a near-boiling liquid medium under 9 bars of pressure. Fines migration during puck prep suggests that particles redistribute in much the same way on a micro scale in air at room temperature and standard atmospheric pressure. How likely is that? (Lest someone be tempted to offer a poor analogy: coffee particles do not act like a mixture of sand and gravel. They are oily and tend to clump.)

I welcome any experimental evidence supporting fines migration, especially during extraction. But there is a far more likely explanation for bitterness associated with PF tapping: overextraction of certain areas of the puck due to channeling.

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#8: Post by @3aan »

I never Tap and do not use a Tamp or whatsoever, just with the soft patch and twist of my hand and thats it, always the same routine and a great espresso.

I always use my own blend, and do the grinding with a K30 vario, its a very consistent grinder.

I have noticed that with the Tap method, the side seal of the puck could loosen and the puck is almost free-floating inside the PF filter, because the Tap is used after the first initial Tamping, this break the puck loose from the site and you will get a uneven extraction.

For me is the Tap a complete No-No.
LMWDP #377 @3aan

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#9: Post by spiffdude »

Hi Adriaan,

Welcome to Home-Barista. You'll notice that the post you responded to is about a year and a half old. You might want to check dates before "bringing" back a thread from the dead. No biggie, but people may not respond as much given that the topic is a bit old.

That being said, i think the tap fad has indeed died out. I'm not sure any of the experiences guys here do it anymore and the 3rd waves cafes i hang out in here in Montreal don't seem to do it either.
Damn this forum, I've had too m..muh...mah..mmmm..much caffeine!

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#10: Post by @3aan »

I did noticed, but was eager to respond on this topic, so i did. 8)

And renewed the timebase a bit :wink:
LMWDP #377 @3aan