How can 30 lbs be a universal tamper pressure? - Page 2

#11: Post by **timo888** » December 1st, 2006, 3:34 pm

jmatt wrote:OK - I hear about 30 pounds of pressure when tamping. Some tampers even have a "click" or other pressure mechanism set for 30 pounds.

However, I did some math:

A 49mm tamper covers 2.92 square inches. 30 pounds of pressure equals 10.3 pounds per square inch.
A 53mm tamper covers 3.42 square inches. 30 pounds of pressure equals 8.8 pounds per square inch.
A 58mm tamper covers 4.10 square inches. 30 pounds of pressure equals 7.3 pounds per square inch.

Looked at another way, to get 8.8 pounds of pressure with a 58mm tamper requires 36 pounds of force.
To get only 7.3 pounds of pressure with a 53mm tamper requires only 25 pounds of force.

So what's the rule? 30 pounds with a 58mm tamper, but only 25 with a 53mm? 30 pounds with a 53mm, but 36 pounds with a 58mm?

Or is the pounds of pressure irrelevant (within reason) so long as the tamp is consistent, and pull time is adjusted with grind fineness?

Assuming a cylindrical shape for the basket and a flat tamper, the compression of grains diminshes with distance from tamping surface:

TAMPER

\/
| most compressed grains
|
| middling compressed grains
|
| least compressed grains

Two baskets: one broad and shallow the other tall and narrow. The taller requires greater pressure to reach the same depth and degree of compaction as the broader shallower basket. Thus, although the pressure varies by surface area (force remaining constant) the compaction could average out to be much the same degree, the inequality in pressure notwithstanding.

Which isn't to say I'm wedded to the 30# idea. I sometimes do little more than level. Sometimes tamp ~ 30#.

Regards
Timo

#12: Post by **mrgnomer** » December 1st, 2006, 10:16 pm

another_jim wrote:30 lbs is the number Schomer came up with. Presumably it works better than 15 or 45 pounds in his cafes. Most Italians don't tamp at all, but merely level the puck. Then I've seen people prepare for the Mr Universe contest by tamping.

The expert consensus is that any tamp or none, consistently applied, works. The real trick is to distribute and level the grinds perfectly, paying special attention that there are no gaps around the edge.

I believe David Schomer came up with 30lbs after experimenting with lighter tamp pressures to save his and the elbows of his baristas. The recommended standard at the time was 50lbs+, I think he said, which was blowing the elbows out of baristas packing all day long. He found that 30lbs did just as good of a job and saved a lot of arms.

I think it was here on home barista where a thread was talking about the automatic grinder/tamper LaMarzocco was working on and how they found that a continuous tamp of over 18lbs packed the coffee so tight it choked the machine at any setting. The theory seems to be from what they found is tamping a full basket can't compact the bottom portion much. Lighter or heavier tamp wouldn't make a whole lot of difference then unless you're compacting in layers from the bottom up, I guess. I agree with consistency. Some of my best extractions are with a finer grind and a tamp that my hand feels just lightly compacts the grinds and tamping heavier with the same grind slows the extraction noticably.

#13: Post by **Everman** » December 9th, 2006, 5:12 pm

It all boils down to shot consistency. You can tamp however hard you want as long as you consistently get good results.

February 9th, 2010, 3:13 am

mrgnomer wrote:I believe David Schomer came up with 30lbs after experimenting with lighter tamp pressures to save his and the elbows of his baristas.

Good call Kirk. He actually says just that in his book "Espresso Coffee Professional Espresso Techniques"
Save the elbows!

#15: Post by **hperry** » February 9th, 2010, 4:05 am

mrgnomer wrote:I believe David Schomer came up with 30lbs after experimenting with lighter tamp pressures to save his and the elbows of his baristas. The recommended standard at the time was 50lbs+, I think he said, which was blowing the elbows out of baristas packing all day long. He found that 30lbs did just as good of a job and saved a lot of arms.

Interesting how a procedure used to solve a particular problem becomes a universal "standard" which might not be relevant to much more than the environment in which it was originally applied.

#16: Post by **zin1953** » February 9th, 2010, 10:16 am

As with all "rules" of espresso, there are no rules, only guidelines.

#17: Post by **hperry** » February 9th, 2010, 10:38 am

The point I was making was somewhat different than that. The "rule" applied to a particular environment and got "universalized." Based just on the calculations in this thread it may well not apply to other portafilter sizes. The practice of tamping reflected in this forum differs significantly between successful practitioners of the art. It is a reminder to me that the "truths" that we come to believe in are worth reexamining from time to time.

#18: Post by **Randy G.** » February 9th, 2010, 11:37 am

Talk about keep a thread resurrected!... But anyway..

IMO, and from my experience, if you find that you NEED some specific tamping force, particularly one that is quite low (5 to 10 pounds) or one that is quite high (above 55 pounds) then you probably have other problems for which you may be compensating which might include:

- too much dust in the grind (worn burrs or "economy" grinder)
- a grinder that creates clumping
- poor distribution in the basket prior to tamping
- too coarse or too fine of a grind
- too little or too much coffee in the basket
- too high or low of a brew pressure
- poor fit of tamper in basket
- stale or too fresh coffee

There are plenty of reports of folks using just a "leveling tamp," using not much more than the weight of the tamper, and I know of a pro barista/shop owner/roaster who is also a lead judge for the SCAA barista championships who uses a "handstand tamp," and he looks like an NFL lineman.

A few years ago it was said that the tamp should be between 15 and 45 pounds, and many found that the range yielded about the same results. No coincidence that 30 pounds rests in the middle of that range.

#19: Post by **ljguitar** » February 9th, 2010, 12:47 pm

Randy G wrote:...if you find that you NEED some specific tamping force, particularly one that is quite low (5 to 10 pounds) or one that is quite high (above 55 pounds) then you probably have other problems for which you may be compensating...

Hi Randy...
I think the word problem is overstating the issue...

Not sure low pressure tamps necessarily constitute a problem. People can make the choice of low-tamp-pressure by design. I did for my ritual to be designed that way for the sake of consistency, and that I will be able to teach my wife to pull great shots.

I doubt my tamp is more than 5-10 pounds, and I pull dynamite shots...better than when I was doing 30 pound tamps. More repeatable...so if they are a problem, they are the best one I've had in years!

February 9th, 2010, 1:39 pm

No no, hes saying that if you are FORCED to use a VERY light tamp, or VERY heavy tamp, not CHOOSING to do so, then there is other problems at work, as he listed.

You should be able to use whatever dose you want, at whatever grind you want, and whatever tamp you want, to achieve proper extraction. So, if you must dose this much coffee, at that grind, and tamp SUPER hard every time, something is wrong. However, if you CHOSE to do all those things, because thats how you WANT to, then no, there is no problem.