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Date: 18 Aug 2007 00:17:33
From: =?ISO-8859-1?Q?S=F8ren_Jacobsen?=
Subject: thoughts on pressure
I was thinking about pressure...

many machines hav 15 bars of pressure.... is that the industry standard or?

the thing is that grindlevel seems to be the way to control brew speed,
but Id think the pressure would be equally important?




 
Date: 25 Aug 2007 07:05:28
From:
Subject: Re: thoughts on pressure
On 25 A ustos, 13:26, r...@math.hawaii.NOSPAM.edu (D. Ross) wrote:
> yuvali...@gmail.com wrote:
>
>


 
Date: 24 Aug 2007 14:10:03
From:
Subject: Re: thoughts on pressure
On 24 A ustos, 23:37, Danny <da...@nospam.gaggia-espresso.com > wrote:
> yuvali...@gmail.com wrote:
> > It's about pressure, not force. Most old members of this group may not
> > understand what pressure is, but at least the new members shall have a
> > chance to get it right, I mean. Anyhow, some progress seems to be
> > accomplished.
>
> > David
>
> With an attitude like that you are sure to impress, old & new.
>
> Pressure = force
> -----
> area
>
> The unit of pressure is the Pascal - the force of 1 Newton exerted
> over 1 square metre.
>
> pressure is directly proportional to force, and inversely proportional
> to area.
>
> Espresso machines are designed with the (I assume) optimal area, the
> area of a 58mm pf, and the pressure needed to ensure the correct flow
> through the cake was calculated in order to arrive at the force needed
> from a spring in the early days or a pump in later machines. The
> pressure on this area is directly propotional to the force exerted on
> this area, and can be calculated.
>
> --
> Regards, Danny
>
> http://www.gaggia-espresso.com (a purely hobby site)
> (apparently bad grammar but I like it that way...)


No! It's not the area of the P/F and there is not a single relevant
force (force of the spring or else). The calculation of the pressure
in this case is complicate, it involves theoretical models, serious
math., surface area of all coffee partikels etc.. Therefore the
pressure will be not calculated, for the sake of simplicity. It will
be measured, directly or indirectly. Direct measurement: pressure
gauge in circuit. Indirect measurement: measurement of the flow i.E.
mass per unit time. That's what Illy did, he hasn't try to calculate
the performance of coffee machines!

David



  
Date: 24 Aug 2007 22:43:45
From: Danny
Subject: Re: thoughts on pressure
yuvali300@gmail.com wrote:

> No! It's not the area of the P/F and there is not a single relevant
> force (force of the spring or else). The calculation of the pressure
> in this case is complicate, it involves theoretical models, serious
> math., surface area of all coffee partikels etc.. Therefore the
> pressure will be not calculated, for the sake of simplicity. It will
> be measured, directly or indirectly. Direct measurement: pressure
> gauge in circuit. Indirect measurement: measurement of the flow i.E.
> mass per unit time. That's what Illy did, he hasn't try to calculate
> the performance of coffee machines!
>
> David
>

OK, this is probably my last post on this subject.

Illy does coffee. He was great at knowing about coffee. He knew the
best particulate mix (in size) and the chemistry, crushed rather than
sliced etc etc. Illy didn't invent an espresso machine - he invented
a machine that used compressed air (1935), but was never acknowledged
as the creator of the espresso machine, although his interest was in
this area. Bezzera invented a machine that used pressure and brewed
coffee faster, which was good, and sold this to Pavoni. But it used
steam pressure, which burnt the coffee. Gaggia actually did it, in
1938. (Actually he stole/bought/was indebted the patent from the wife
of Cremonesi (sp) after the man had died, so legend has it). Thus was
born the first machine that produced crema and didn't use steam to
create the pressure needed for this, instead using a spring and
piston. Gaggia's design also had other advantages, which mostly got
lost on later pump machines - preinfusion and correct brewing temp
from a single boiler. Illy has always been interested in the coffee -
packaging etc (using inert gas to extend freshness etc).

It doesn't matter how you describe it - the (well designed) espresso
machine produces the water at the right temperature and pressure to
extract coffee. It's up to the barista to ensure that the grind is
correct to achieve the correct extraction time, taking into account
bean freshness, ambient humidity etc etc.

I suspect that we are probably not poles apart in our views, but your
doggedness to split hairs over descriptions and word usage seems that
we will never agree (nor will I understand exactly what it is you are
trying to say).

You may actually possess much knowledge that I don't (I'm not a clever
person), but god help anyone who would learn anything from you - a
teacher you are most certainly not.

I sell coffee. I try to make the best coffee I can for my customers.
I pull shots 5 days a week, and I teach others how to pull good
shots, commercially. I don't split hairs, or use unnecessary jargon.
I just teach the good housemanship of understanding the machine they
have and of being a barista.



--
Regards, Danny

http://www.gaggia-espresso.com (a purely hobby site)
(apparently bad grammar but I like it that way...)



 
Date: 24 Aug 2007 13:19:57
From:
Subject: Re: thoughts on pressure
On 24 A ustos, 20:58, Danny <da...@nospam.gaggia-espresso.com > wrote:
> yuvali...@gmail.com wrote:
> > With coffee or without coffee?
>
> > Without coffee: top of the nonsense! No pressure without coffee.
> > With coffee: slightly nonsense.. The pressure depends on coffee, not
> > on spring-specification.
> > Imaginary third case: with blind filter. Still nonsense: The ending
> > pressure will be higher than the starting pressure.
>
> For goodness sake. It's a spring. Compress it and then release - it
> generates a force. This force can easily be calculated, knowing the
> dimensions and materials used in the spring, and the specifics of the
> piston at it's end. Google this group for discussion in the past,
> but, in essence, the following is what the local university calculated
> with one of the springs (excuse possible loss of formatting):
>
> (=B6 =3D Pi)...
>
> Piston area =3D =B6D2
> -------
> 4
>
> =3D =B6(.047)2 m2
> ------------
> 4
>
> =3D 1.735 x 10 -3 m2
> ------------------
>
> Max spring force =3D 2640 N
> Min spring force =3D 1620 N
>
> Max pressure =3D 2640
> -------
> 1.735 x 106 N/ m2
>
> =3D 1.522 x 106 Pa (N/ m2)
>
> Min pressure =3D 1620
> ------
> 1.735 x 10-3 N/ m2
>
> =3D 0.933 x 106 Pa
>
> 1000 Pa =3D 1 bar
>
> Therefore Max pressure =3D 15.22 bar
> Min pressure =3D 9.33 bar
>
> Now, the spring will generate this force, whatever is beneath it. If
> it is sealed beneath, the spring won't move. If there is coffee and a
> portafilter present, and water in the chamber below the piston, it
> will force the (measured volume) water through the coffee at a rate
> determined by the grind. Get the grind right and your (measured) 2fl
> oz of water will pass through the cake in 25 seconds. With no
> resistance (no pf) the spring will eject the water immediately, at the
> force specified. The force is still there!
>
> Same as a car generates a force when driven forward. Drive forward
> against a bush, the car gets through. Drive forward against a
> concrete wall, the car doesn't get through (assuming same engine speed
> and vehicle stationary against the object).
>
> I'm bored with this - either we don't understand one another or you
> are just being aggressive and/or are obfuscating the issue.
>
> --
> Regards, Danny
>
> http://www.gaggia-espresso.com (a purely hobby site)
> (apparently bad grammar but I like it that way...)

It's about pressure, not force. Most old members of this group may not
understand what pressure is, but at least the new members shall have a
chance to get it right, I mean. Anyhow, some progress seems to be
accomplished.

David



  
Date: 24 Aug 2007 21:37:37
From: Danny
Subject: Re: thoughts on pressure
yuvali300@gmail.com wrote:

> It's about pressure, not force. Most old members of this group may not
> understand what pressure is, but at least the new members shall have a
> chance to get it right, I mean. Anyhow, some progress seems to be
> accomplished.
>
> David
>

With an attitude like that you are sure to impress, old & new.

Pressure = force
-----
area

The unit of pressure is the Pascal - the force of 1 Newton exerted
over 1 square metre.

pressure is directly proportional to force, and inversely proportional
to area.

Espresso machines are designed with the (I assume) optimal area, the
area of a 58mm pf, and the pressure needed to ensure the correct flow
through the cake was calculated in order to arrive at the force needed
from a spring in the early days or a pump in later machines. The
pressure on this area is directly propotional to the force exerted on
this area, and can be calculated.


--
Regards, Danny

http://www.gaggia-espresso.com (a purely hobby site)
(apparently bad grammar but I like it that way...)



   
Date: 24 Aug 2007 16:49:32
From: pltrgyst
Subject: Re: thoughts on pressure
On Fri, 24 Aug 2007 21:37:37 +0100, Danny <danny@nospam.gaggia-espresso.com >
wrote:

>With an attitude like that you are sure to impress, old & new.
>
>Pressure = force
> -----
> area
>
>The unit of pressure is the Pascal - the force of 1 Newton exerted
>over 1 square metre.

I suspect he's rather blaise, not wirth much, and doesn't give a fig.

-- Larry


 
Date: 24 Aug 2007 08:09:39
From:
Subject: Re: thoughts on pressure

>


  
Date: 25 Aug 2007 10:26:54
From: D. Ross
Subject: Re: thoughts on pressure
yuvali300@gmail.com wrote:



 
Date: 24 Aug 2007 08:03:14
From:
Subject: Re: thoughts on pressure
For the
> springs in my lever machines the pressure has been calculated and
> posted in this group in the past, and from memory, the starting
> pressure was around 10 bar and the ending pressure around 7.5 bar.

With coffee or without coffee?

Without coffee: top of the nonsense! No pressure without coffee.
With coffee: slightly nonsense.. The pressure depends on coffee, not
on spring-specification.
Imaginary third case: with blind filter. Still nonsense: The ending
pressure will be higher than the starting pressure.

David







  
Date: 24 Aug 2007 18:58:11
From: Danny
Subject: Re: thoughts on pressure
yuvali300@gmail.com wrote:

> With coffee or without coffee?
>
> Without coffee: top of the nonsense! No pressure without coffee.
> With coffee: slightly nonsense.. The pressure depends on coffee, not
> on spring-specification.
> Imaginary third case: with blind filter. Still nonsense: The ending
> pressure will be higher than the starting pressure.

For goodness sake. It's a spring. Compress it and then release - it
generates a force. This force can easily be calculated, knowing the
dimensions and materials used in the spring, and the specifics of the
piston at it's end. Google this group for discussion in the past,
but, in essence, the following is what the local university calculated
with one of the springs (excuse possible loss of formatting):

(¶ = Pi)...


Piston area = ¶D2
-------
4

= ¶(.047)2 m2
------------
4

= 1.735 x 10 –3 m2
------------------


Max spring force = 2640 N
Min spring force = 1620 N


Max pressure = 2640
-------
1.735 x 106 N/ m2


= 1.522 x 106 Pa (N/ m2)


Min pressure = 1620
------
1.735 x 10-3 N/ m2


= 0.933 x 106 Pa


1000 Pa = 1 bar


Therefore Max pressure = 15.22 bar
Min pressure = 9.33 bar


Now, the spring will generate this force, whatever is beneath it. If
it is sealed beneath, the spring won't move. If there is coffee and a
portafilter present, and water in the chamber below the piston, it
will force the (measured volume) water through the coffee at a rate
determined by the grind. Get the grind right and your (measured) 2fl
oz of water will pass through the cake in 25 seconds. With no
resistance (no pf) the spring will eject the water immediately, at the
force specified. The force is still there!

Same as a car generates a force when driven forward. Drive forward
against a bush, the car gets through. Drive forward against a
concrete wall, the car doesn't get through (assuming same engine speed
and vehicle stationary against the object).

I'm bored with this - either we don't understand one another or you
are just being aggressive and/or are obfuscating the issue.



--
Regards, Danny

http://www.gaggia-espresso.com (a purely hobby site)
(apparently bad grammar but I like it that way...)



   
Date: 24 Aug 2007 13:27:56
From: Robert Harmon
Subject: Re: thoughts on pressure
Great explanation (simply put & easily understood) of the mechanics of
espresso making Danny!

--
Robert Harmon
--
http://www.tinyurl.com/mb4uj - My coffee pages.

http://www.tinyurl.com/2tnv87 - My 'Guidelines For Newbies' page.

http://www.tinyurl.com/2cr3e2 - I have things for sale here.
"Danny" <danny@nospam.gaggia-espresso.com > wrote in message
news:5j8kh7F3qk18jU1@mid.individual.net...
> yuvali300@gmail.com wrote:
>
>> With coffee or without coffee?
>>
>> Without coffee: top of the nonsense! No pressure without coffee.
>> With coffee: slightly nonsense.. The pressure depends on coffee, not
>> on spring-specification.
>> Imaginary third case: with blind filter. Still nonsense: The ending
>> pressure will be higher than the starting pressure.
>
> For goodness sake. It's a spring. Compress it and then release - it
> generates a force. This force can easily be calculated, knowing the
> dimensions and materials used in the spring, and the specifics of the
> piston at it's end. Google this group for discussion in the past, but, in
> essence, the following is what the local university calculated with one of
> the springs (excuse possible loss of formatting):
>
> (¶ = Pi)...
>
>
> Piston area = ¶D2
> -------
> 4
>
> = ¶(.047)2 m2
> ------------
> 4
>
> = 1.735 x 10 –3 m2
> ------------------
>
>
> Max spring force = 2640 N
> Min spring force = 1620 N
>
>
> Max pressure = 2640
> -------
> 1.735 x 106 N/ m2
>
>
> = 1.522 x 106 Pa (N/ m2)
>
>
> Min pressure = 1620
> ------
> 1.735 x 10-3 N/ m2
>
>
> = 0.933 x 106 Pa
>
>
> 1000 Pa = 1 bar
>
>
> Therefore Max pressure = 15.22 bar
> Min pressure = 9.33 bar
>
>
> Now, the spring will generate this force, whatever is beneath it. If it
> is sealed beneath, the spring won't move. If there is coffee and a
> portafilter present, and water in the chamber below the piston, it will
> force the (measured volume) water through the coffee at a rate determined
> by the grind. Get the grind right and your (measured) 2fl oz of water
> will pass through the cake in 25 seconds. With no resistance (no pf) the
> spring will eject the water immediately, at the force specified. The
> force is still there!
>
> Same as a car generates a force when driven forward. Drive forward
> against a bush, the car gets through. Drive forward against a concrete
> wall, the car doesn't get through (assuming same engine speed and vehicle
> stationary against the object).
>
> I'm bored with this - either we don't understand one another or you are
> just being aggressive and/or are obfuscating the issue.
>
>
>
> --
> Regards, Danny
>
> http://www.gaggia-espresso.com (a purely hobby site)
> (apparently bad grammar but I like it that way...)
>




 
Date: 21 Aug 2007 11:38:22
From: lockjaw
Subject: Re: thoughts on pressure


Notice: harmon hates silvias -- regardless.



 
Date: 21 Aug 2007 11:33:35
From: lockjaw
Subject: Re: thoughts on pressure


Listen to the snobbery from 'ol fox!

as if la cimbali was the "be all and end all"



 
Date: 20 Aug 2007 12:25:13
From: Robert Harmon
Subject: Re: thoughts on pressure
No argument from me regarding that post Ken - far too many folks don't
treat their espresso machines with proper respect. Probably the same
folks that change the oil in their cars every 10,000 or 15,000 miles
or whenever the whim hits them.

In this regard, is there any difference between a $200 Gaggia Espresso
or a $4000 GS3? Or a $16,000 KIA or a $90,000 Mercedes? That has
nothing to do with pressure or it's effect on brewing espresso.

Any machine with an adjustable pressure should be adjusted to 9
atmospheres or as close as is possible. Machines without a pressure
adjustment will not brew as good a shot as one that can be adjusted.
This is based on empirical evidence I've gathered, as well as the
published statements of Ernesto Illy.

I've converted two Gaggia machines without OPV's into machines with
adjustable pressure. To my taste, there is a difference when the
pressure is set to 9 bar dynamically and the grind matched to that
pressure.

I believe this is because when Dr. Illy established the accepted
standard of 1 ml per second, it was based on a machine with an
adjusted dynamic pressure of 9 atmospheres pressing hot water through
certain sized particles. If the machine is pushing 11 bar through the
puck, the particle size will have to be smaller to achieve a 1 ml per
second shot. Wouldn't higher pressure pushing against smaller
particles result in over extracted coffee? Similarly, pressure of 8
bar would require a larger particle size to achieve the target of 1 ml
per second, resulting in under extracted coffee.

Since I don't have the equipment or inclination to duplicate the work
of Illy, I'll settle for my judgment & Ernesto Illy's published work.
Therefore, I say that pressure is just as important as temperature in
determining shot quality.

Robert Harmon
--
http://www.tinyurl.com/mb4uj - My coffee pages.

http://www.tinyurl.com/2tnv87 - My 'Guidelines For Newbies' page.

http://www.tinyurl.com/2cr3e2 - I have things for sale here.



On Aug 19, 4:43 pm, "Ken Fox"
<morceaudemerdeThisMerdeG...@hotmail.com > wrote:
> The fact that you can find 20 year old espresso machines for sale on ebay,
> that might work well with restoration, says nothing about what becomes of
> the typical machine. It is rare to find commercial machines in service in
> actual business locations after they reach a certain age, certainly less
> than 10 years. This is because the cost of the machine is a relatively
> small fraction of the cost of running a cafe or other business that uses
> commercial machines to make coffee drinks, and when you start paying for
> parts and labor to fix them as they age, it often is cheaper just to replace
> them. Some of these used commercial machines do get refurbished, but I have
> been to dealers who take trade ins and seen rows of machines in the back
> that are going out . . . . to the recycler or junkyard. They do not find
> repairing them to be economically reasonable in spite of the fact that
> someone such as yourself might be willing to spend tens or hundreds of hours
> without compensation doing it for yourself, as a hobby.
>
> With home machines there are certainly talented individuals who will keep
> their equipment running for very long periods of time, but a lot of such
> machines get tossed out in the trash or end up in the basement as never to
> be used again "spare machines" after a certain point.
>
> ken
>



 
Date: 19 Aug 2007 14:25:07
From:
Subject: Re: thoughts on pressure
On 19 A ustos, 23:27, Danny <da...@nospam.gaggia-espresso.com > wrote:
> yuvali...@gmail.com wrote:
> > Ristretto or lungo means different pressures..The barista adjusts the
> > pressure by grind (may be a little by tamping too). If the pressure is
> > regulated by an OPV, the ristretto may be extracted at the set OPV-
> > pressure.
>
> I believe you and I will never agree, probably because I don't think
> English is your native tongue (of course, I may be wrong), and your
> use of the word pressure differs from mine. Where I come from, we are
> talking about extraction rate - the pump operates at the same rate,
> and we obtain a shorter or longer shot by adjusting grind fineness
> (adjusting the tamp is cheating, and doesn't result in a true ristretto).
>
> My machines cannot adjust pressure, since they are spring lever
> machines, and will always operate at the tolerence, or design, of the
> spring (which happens to be a reducing pressure (force) since a spring
> doesn't have uniform force along it's length). I have no reason to
> suppose the pump machines I also use behave any differently.
>
> --
> Regards, Danny
>
> http://www.gaggia-espresso.com (a purely hobby site)
> (apparently bad grammar but I like it that way...)

Pressure is force per surface area and refers to the resistance in the
case of coffee extraction. If it's a spring lever machine, let the
filter empty there will be no pressure at all, just water coming out
at zero pressure. Let the coffee in the filter, more or less
resistance will yeald a ristretto or lungo or anything inbetween. The
spring will supply whatever pressure the coffee is asking for, except
it's maximum limit and beyond. That means, the same spring will
operate at different pressures at all times, even when the extraction
rate remains constant! Same is valid for pump machines. Resistance=0
pressure=0. Operational pressure will be made by the coffee puck up to
the limits set by OPV if any.

David



  
Date: 20 Aug 2007 20:21:18
From: Crabman
Subject: Re: thoughts on pressure
yuvali300@gmail.com wrote:

>
> Pressure is force per surface area and refers to the resistance in the
> case of coffee extraction. If it's a spring lever machine, let the
> filter empty there will be no pressure at all, just water coming out
> at zero pressure. Let the coffee in the filter, more or less
> resistance will yeald a ristretto or lungo or anything inbetween. The
> spring will supply whatever pressure the coffee is asking for, except
> it's maximum limit and beyond. That means, the same spring will
> operate at different pressures at all times, even when the extraction
> rate remains constant! Same is valid for pump machines. Resistance=0
> pressure=0. Operational pressure will be made by the coffee puck up to
> the limits set by OPV if any.
>
> David
>

Good description Danny. Resistance=0, pressure=0, flow RATE is NOT 0.

Robert Harmon and I already had this discussion, and I enjoyed it.

Clay


 
Date: 19 Aug 2007 13:15:44
From:
Subject: Re: thoughts on pressure
On 19 A ustos, 23:05, Danny <da...@nospam.gaggia-espresso.com > wrote:
> yuvali...@gmail.com wrote:
> > Bingo! The "resistance" makes the pressure if the pump is at the other
> > end. Up to 15 bar.
>
> You're missing my point (not that I can be that bothered to labour it,
> since you seem set on being a condescending individual) - of course
> you need a basket with some coffee in it, but after that, there's not
> much you can do to alter the flow. Adjusting the grind will get you a
> ristretto or a lungo, but tamp won't.
>
> --
> Regards, Danny
>
> http://www.gaggia-espresso.com (a purely hobby site)
> (apparently bad grammar but I like it that way...)

Ristretto or lungo means different pressures..The barista adjusts the
pressure by grind (may be a little by tamping too). If the pressure is
regulated by an OPV, the ristretto may be extracted at the set OPV-
pressure.

David



  
Date: 19 Aug 2007 21:27:30
From: Danny
Subject: Re: thoughts on pressure
yuvali300@gmail.com wrote:

> Ristretto or lungo means different pressures..The barista adjusts the
> pressure by grind (may be a little by tamping too). If the pressure is
> regulated by an OPV, the ristretto may be extracted at the set OPV-
> pressure.


I believe you and I will never agree, probably because I don't think
English is your native tongue (of course, I may be wrong), and your
use of the word pressure differs from mine. Where I come from, we are
talking about extraction rate - the pump operates at the same rate,
and we obtain a shorter or longer shot by adjusting grind fineness
(adjusting the tamp is cheating, and doesn't result in a true ristretto).

My machines cannot adjust pressure, since they are spring lever
machines, and will always operate at the tolerence, or design, of the
spring (which happens to be a reducing pressure (force) since a spring
doesn't have uniform force along it's length). I have no reason to
suppose the pump machines I also use behave any differently.


--
Regards, Danny

http://www.gaggia-espresso.com (a purely hobby site)
(apparently bad grammar but I like it that way...)



   
Date: 20 Aug 2007 20:13:47
From: Crabman
Subject: Re: thoughts on pressure
Danny wrote:
> yuvali300@gmail.com wrote:
>
>> Ristretto or lungo means different pressures..The barista adjusts the
>> pressure by grind (may be a little by tamping too). If the pressure is
>> regulated by an OPV, the ristretto may be extracted at the set OPV-
>> pressure.
>
>
> I believe you and I will never agree, probably because I don't think
> English is your native tongue (of course, I may be wrong), and your use
> of the word pressure differs from mine. Where I come from, we are
> talking about extraction rate - the pump operates at the same rate, and
> we obtain a shorter or longer shot by adjusting grind fineness
> (adjusting the tamp is cheating, and doesn't result in a true ristretto).
>
> My machines cannot adjust pressure, since they are spring lever
> machines, and will always operate at the tolerence, or design, of the
> spring (which happens to be a reducing pressure (force) since a spring
> doesn't have uniform force along it's length). I have no reason to
> suppose the pump machines I also use behave any differently.
>
>
Danny your description relates to flow. Pressure doesn't work at a
"rate". Time AND flow are part of the "rate" and pressure is part of
that control function. A pump flows at a certain liters per minute rate
AT a certain pressure.

Let's all agree that the espresso formula takes time, pressure, and
water volume

Your analogy of springs and pressure is also suspect. A spring has a
constant force at at constant compression. "lbs per inch" If you
maintain a 1" compression it will maintain a constant force. Pressure is
a measurement of force and area, hence PSI, or pounds per square inch.

> I have no reason to
> suppose the pump machines I also use behave any differently.


I'm not sure I understand this sentence, because pumps and springs are
not similar in function at all.
Could you clarify for me?

Clay



    
Date: 21 Aug 2007 06:32:47
From: Danny
Subject: Re: thoughts on pressure
Crabman wrote:

> Danny your description relates to flow. Pressure doesn't work at a
> "rate". Time AND flow are part of the "rate" and pressure is part of
> that control function. A pump flows at a certain liters per minute rate
> AT a certain pressure.
>
> Let's all agree that the espresso formula takes time, pressure, and
> water volume
>
> Your analogy of springs and pressure is also suspect. A spring has a
> constant force at at constant compression. "lbs per inch" If you
> maintain a 1" compression it will maintain a constant force. Pressure is
> a measurement of force and area, hence PSI, or pounds per square inch.

A spring in a lever machine isn't at a constant compression, otherwise
it couldn't work. It is moving (decompressing) in order to apply the
force stored when the lever was pulled and the spring compressed. The
release of this force is non linear as the spring decompresses, even
if the spring is partly compressed at it's idle position. For the
springs in my lever machines the pressure has been calculated and
posted in this group in the past, and from memory, the starting
pressure was around 10 bar and the ending pressure around 7.5 bar.

This force exists, whatever the state of the puck, although the puck's
resistance affects what pressure actually exists in the brew chamber.

>
> > I have no reason to
> > suppose the pump machines I also use behave any differently.
>

Springs apply force to water, pumps apply force to water.


--
Regards, Danny

http://www.gaggia-espresso.com (a purely hobby site)
(apparently bad grammar but I like it that way...)



     
Date: 21 Aug 2007 06:48:28
From: Crabman
Subject: Re: thoughts on pressure
Danny wrote:
> Crabman wrote:
>
>> Danny your description relates to flow. Pressure doesn't work at a
>> "rate". Time AND flow are part of the "rate" and pressure is part of
>> that control function. A pump flows at a certain liters per minute
>> rate AT a certain pressure.
>>
>> Let's all agree that the espresso formula takes time, pressure, and
>> water volume
>>
>> Your analogy of springs and pressure is also suspect. A spring has a
>> constant force at at constant compression. "lbs per inch" If you
>> maintain a 1" compression it will maintain a constant force. Pressure
>> is a measurement of force and area, hence PSI, or pounds per square inch.
>
> A spring in a lever machine isn't at a constant compression, otherwise
> it couldn't work. It is moving (decompressing) in order to apply the
> force stored when the lever was pulled and the spring compressed. The
> release of this force is non linear as the spring decompresses, even if
> the spring is partly compressed at it's idle position. For the springs
> in my lever machines the pressure has been calculated and posted in this
> group in the past, and from memory, the starting pressure was around 10
> bar and the ending pressure around 7.5 bar.
>
> This force exists, whatever the state of the puck, although the puck's
> resistance affects what pressure actually exists in the brew chamber.
>

This is what I thought you meant. As the spring extends the force
applied decreases, decreasing the pressure, as well as the flow rate.
Assuming resistance to flow is constant.


>>
>>
>
> Springs apply force to water, pumps apply force to water.
>
>
Mechanical pumps apply and maintain constant flow and pressure at a
constant resistance, springs in your example do not.

I just want to clarify that rate always has multiple components.

Ie:liters per min. = flow rate OR lbs per in=spring rate

Clay




   
Date: 19 Aug 2007 15:37:45
From: Robert Harmon
Subject: Re: thoughts on pressure
Howdy Danny!
Whether it's a light tamp as I use or the full handstand tamp favored by
others, the tamp should remain constant from shot to shot. The group
pressure, regulated or not will always be the same. The grind is adjustable,
and I recommend the following to get the best results.

* Adjust the grind until it's so fine that the filter is choked.
* Making small adjustments, gradually grind coarser until you achieve a 30ml
pour in 25 - 30 seconds.
* Make adjustments to the grind for each batch of coffee used.

It can be summed up as treating group pressure & tamp as constants, while
the grind is tailored to the coffee used.
--
Robert Harmon
--
http://www.tinyurl.com/mb4uj - My coffee pages.

http://www.tinyurl.com/2tnv87 - My 'Guidelines For Newbies' page.

http://www.tinyurl.com/2cr3e2 - I have things for sale here.
"Danny" <danny@nospam.gaggia-espresso.com > wrote in message
news:5irnd7F3qc3o8U1@mid.individual.net...
>
> I believe you and I will never agree, probably because I don't think
> English is your native tongue (of course, I may be wrong), and your use of
> the word pressure differs from mine. Where I come from, we are talking
> about extraction rate - the pump operates at the same rate, and we obtain
> a shorter or longer shot by adjusting grind fineness (adjusting the tamp
> is cheating, and doesn't result in a true ristretto).
>
> My machines cannot adjust pressure, since they are spring lever machines,
> and will always operate at the tolerence, or design, of the spring (which
> happens to be a reducing pressure (force) since a spring doesn't have
> uniform force along it's length). I have no reason to suppose the pump
> machines I also use behave any differently.
>
>
> --
> Regards, Danny
>
> http://www.gaggia-espresso.com (a purely hobby site)
> (apparently bad grammar but I like it that way...)
>




    
Date: 19 Aug 2007 21:48:52
From: Danny
Subject: Re: thoughts on pressure
Robert Harmon wrote:
> Howdy Danny!
> Whether it's a light tamp as I use or the full handstand tamp favored by
> others, the tamp should remain constant from shot to shot. The group
> pressure, regulated or not will always be the same. The grind is adjustable,
> and I recommend the following to get the best results.
>
> * Adjust the grind until it's so fine that the filter is choked.
> * Making small adjustments, gradually grind coarser until you achieve a 30ml
> pour in 25 - 30 seconds.
> * Make adjustments to the grind for each batch of coffee used.
>
> It can be summed up as treating group pressure & tamp as constants, while
> the grind is tailored to the coffee used.

Blimey Robert, I do know how to pull a shot :), but that's not what is
under discussion in this thread. Research my posts and you will find
that I *always* advocate removing all variables until grind is the
only one left. I adjust the grind many times a day in the trailer.

--
Regards, Danny

http://www.gaggia-espresso.com (a purely hobby site)
(apparently bad grammar but I like it that way...)



 
Date: 19 Aug 2007 12:59:09
From:
Subject: Re: thoughts on pressure
Of
> course there has to be resistance, in the form of a basket with coffee
> in it.

Bingo! The "resistance" makes the pressure if the pump is at the other
end. Up to 15 bar.

David





  
Date: 24 Aug 2007 14:39:38
From:
Subject: Re: thoughts on pressure
On 24 A ustos, 23:49, pltrgyst <pltrg...@spamlessxhost.org > wrote:
> On Fri, 24 Aug 2007 21:37:37 +0100, Danny <da...@nospam.gaggia-espresso.com>
> wrote:
>
> >With an attitude like that you are sure to impress, old & new.
>
> >Pressure = force
> > -----
> > area
>
> >The unit of pressure is the Pascal - the force of 1 Newton exerted
> >over 1 square metre.
>
> I suspect he's rather blaise, not wirth much, and doesn't give a fig.
>
> -- Larry

Fan of RoddICk?



  
Date: 19 Aug 2007 21:05:02
From: Danny
Subject: Re: thoughts on pressure
yuvali300@gmail.com wrote:

> Bingo! The "resistance" makes the pressure if the pump is at the other
> end. Up to 15 bar.
>

You're missing my point (not that I can be that bothered to labour it,
since you seem set on being a condescending individual) - of course
you need a basket with some coffee in it, but after that, there's not
much you can do to alter the flow. Adjusting the grind will get you a
ristretto or a lungo, but tamp won't.


--
Regards, Danny

http://www.gaggia-espresso.com (a purely hobby site)
(apparently bad grammar but I like it that way...)



 
Date: 19 Aug 2007 12:45:13
From:
Subject: Re: thoughts on pressure


> Pressure coming out of a standard ULKA vibrating pump is not going to be a
> major issue in espresso machines using it, whether or not you modify it with
> an OPV or other device. Sure, regulating it may improve the espresso a bit
> but in that class of machine the benefit is not going to be remarkable.
> 15bar of pressure, at MAXIMUM, does not translate to 15 bar of continuous
> pressure in a vibe pump; the average is much less than that.

It's an issue for producing ristretti at a pressure of 9 bar or so,
difficult without OPV.

David





 
Date: 19 Aug 2007 12:38:37
From:
Subject: Re: thoughts on pressure
On 19 A ustos, 19:08, Danny <da...@nospam.gaggia-espresso.com > wrote:
> yuvali...@gmail.com wrote:
> > The barista should take care of the pressure with proper grinding,
> > filling, tamping etc.
>
> What the barista does or doesn't do won't affect the machine's output
> pressure. He can impede the flow but he can't subjectively change the
> pressure, other by adding a gicluer or other device in the water path.
> In any event, tamping etc doesn't actually have much effect on the
> output (see the tamp debate page on my site, below).
>
> --
> Regards, Danny
>
> http://www.gaggia-espresso.com (a purely hobby site)
> (apparently bad grammar but I like it that way...)

Rated pressure of vibe pumps is 15 bar. Output pressure fully depends
of coffee puck i.E. barista. There is no such thing as "average
pressure", not in coffee lingo.

David




  
Date: 19 Aug 2007 20:52:44
From: Danny
Subject: Re: thoughts on pressure
yuvali300@gmail.com wrote:

> Rated pressure of vibe pumps is 15 bar. Output pressure fully depends
> of coffee puck i.E. barista. There is no such thing as "average
> pressure", not in coffee lingo.
>

So you didn't bother reading my site? Tamp has very little effect on
pour rate, or pressure. Try it. Handstand tamp with correct grind =
25 second pour. Zero tamp = 25 second pour, or thereabouts. Of
course there has to be resistance, in the form of a basket with coffee
in it.

I didn't say "average pressure" in my post, so what is this "coffee
lingo" that I may not be privvy to?


--
Regards, Danny

http://www.gaggia-espresso.com (a purely hobby site)
(apparently bad grammar but I like it that way...)



 
Date: 19 Aug 2007 09:23:44
From: Flasherly
Subject: Re: thoughts on pressure
On Aug 17, 6:17 pm, S=F8ren Jacobsen <kurgan@spammergoaway_kurgan.dk >
wrote:
> I was thinking about pressure...
>
> many machines hav 15 bars of pressure.... is that the industry standard o=
r?
>
> the thing is that grindlevel seems to be the way to control brew speed,
> but Id think the pressure would be equally important?

Everybody pretty much dials in their grinder (step or stepless
settings) for their machines, not their machines for their grinder
(discounting PID-ers at an individual premium above the norm). The
bean grind fineness and condition and subsequent timed resistance
across evenness account flow, however tamped, as consistency lending
to replication an end and maxim for a derived result most agreeable to
the consensus (a taster's select choice).



 
Date: 19 Aug 2007 08:17:39
From: Travesso
Subject: Re: thoughts on pressure
On Aug 19, 12:19 am, "Ken Fox"
<morceaudemerdeThisMerdeG...@hotmail.com > wrote:
> "Dee Dee" <deedo...@shentel.net> wrote in message
>
> news:fa8fds$t37$1@registered.motzarella.org...
>
>
>
>
>
>
>
> > "D. Ross" <r...@math.hawaii.NOSPAM.edu> wrote in message
> >news:46c6ca2d.47756640@localhost...
> >>


  
Date: 19 Aug 2007 10:15:22
From: Ken Fox
Subject: Re: thoughts on pressure
"Travesso" <cpasoren@hotmail.com > wrote in message
news:1187536659.599667.101130@k79g2000hse.googlegroups.com...
> >
> I thought the silvia had a vibrating pump?
>
> You must have good temperature, grinder, and pressure. Saying that
> one is better than the other is like picking your favorite child--
> can't be done.
>

I explicitly stated that the Silvia has a vibe pump; reread my post.

Pressure coming out of a standard ULKA vibrating pump is not going to be a
major issue in espresso machines using it, whether or not you modify it with
an OPV or other device. Sure, regulating it may improve the espresso a bit
but in that class of machine the benefit is not going to be remarkable.
15bar of pressure, at MAXIMUM, does not translate to 15 bar of continuous
pressure in a vibe pump; the average is much less than that.

Temperature control and consistency are more of an issue, but given an
acceptable quality machine, there are many, machine-specific ways of dealing
with this which require a little bit of experience on the part of the user.

ken




  
Date: 19 Aug 2007 15:27:26
From: Ian Smith
Subject: Re: thoughts on pressure
On Sun, 19 Aug 2007 08:17:39 -0700, Travesso <cpasoren@hotmail.com > wrote:
>
> You must have good temperature, grinder, and pressure. Saying that
> one is better than the other is like picking your favorite child--
> can't be done.

Not so.

Good grinder and poor temperature and pressure gives much better
espresso than a poor grinder and precise temperature and pressure. If
you have a cheap thermoblock and no grinder, for eample, teh best
upgrade for coffee taste is a good grinder.

regards, Ian SMith
--


 
Date: 19 Aug 2007 06:44:59
From:
Subject: Re: thoughts on pressure

> But since you ask a question - of course pressure is important, but we
> assume the machine takes care of that, by means of it's pump, lever or
> other method of generating 9 bar (there's not a lot of user input that
> can change that).

The barista should take care of the pressure with proper grinding,
filling, tamping etc.

David







  
Date: 19 Aug 2007 17:08:32
From: Danny
Subject: Re: thoughts on pressure
yuvali300@gmail.com wrote:

> The barista should take care of the pressure with proper grinding,
> filling, tamping etc.
>

What the barista does or doesn't do won't affect the machine's output
pressure. He can impede the flow but he can't subjectively change the
pressure, other by adding a gicluer or other device in the water path.
In any event, tamping etc doesn't actually have much effect on the
output (see the tamp debate page on my site, below).


--
Regards, Danny

http://www.gaggia-espresso.com (a purely hobby site)
(apparently bad grammar but I like it that way...)



 
Date: 19 Aug 2007 06:40:52
From:
Subject: Re: thoughts on pressure


> Don't use this sort of information as a basis for buying an espresso
> machine. It is useless advertising nonsense.
>
> Cheaper espresso machines, which would include certainly anything below
> $1000, will have vibratory pumps, usually one made by ULKA. Although they
> produce a PEAK pressure of around 15bar, this is not the average pressure,
> which is lower. Some knowledgable people think it is of little value to
> regulate a vibratory pump to deliver less than 15bar, and others believe it
> is worthwhile.
>
> In any event, the only sort of machine which would be sold with this sort of
> advertising, e.g. "our pump produces 15bar," are cheap machines that may or
> may not be adequate to your needs, but decisions about which one to buy
> should not be based on this little piece of more or less useless
> information.
>
> There are few machines cheaper than a Rancilio Silvia that will last for
> more than a few years. Although limited in many ways, and not something
> that I would personally want to own, the Silvia has the advantage that one
> can own it for a year or so then sell it used on ebay for not a whole lot
> less than what you paid for it. Anything much cheaper than this is likely
> to be worth very little in the resale market.
>
> And do not forget, the grinder is at least as important as the espresso
> machine, and you absolutely cannot make good espresso without a decent
> grinder. At entry level, grinders cost around $150 and more, and at the low
> end they won't last long and will not be very adjustable. Very good
> grinders start around $500.
>
> ken

Nobody should be ashamed of selling coffee machines pointing to their
15 bar pumps. First, it's the industry standard for pump machines,
second, other machines have no pumps at all, so it's right to
advertise with the presence of a pump. BTW most Silvia sellers refer
to the POWERFUL (sic) 15 BAR pump of the machine:

http://www.espressozone.com/8836.html
http://www.jlhufford.com/detail.asp?product_id=ra1002

and others in a more tricky form pointing to a "41 Watt" pump.

David






  
Date: 19 Aug 2007 08:32:07
From: Ken Fox
Subject: Re: thoughts on pressure
no wonder very little useful content is ever posted on a.c. anymore. All
the thoughtful discussions have gone elsewhere.

ken

<yuvali300@gmail.com > wrote in message
news:1187530852.514865.96850@d55g2000hsg.googlegroups.com...
>
>
> Nobody should be ashamed of selling coffee machines pointing to their
> 15 bar pumps. First, it's the industry standard for pump machines,
> second, other machines have no pumps at all, so it's right to
> advertise with the presence of a pump. BTW most Silvia sellers refer
> to the POWERFUL (sic) 15 BAR pump of the machine:
>
> http://www.espressozone.com/8836.html
> http://www.jlhufford.com/detail.asp?product_id=ra1002
>
> and others in a more tricky form pointing to a "41 Watt" pump.
>
> David
>
>
>
>




   
Date: 21 Aug 2007 08:45:08
From: D. Ross
Subject: Re: thoughts on pressure
"Ken Fox" <morceaudemerdeThisMerdeGoes@hotmail.com > wrote:



   
Date: 19 Aug 2007 12:20:40
From: Moka Java
Subject: Re: thoughts on pressure


Ken Fox wrote:
> no wonder very little useful content is ever posted on a.c. anymore. All
> the thoughtful discussions have gone elsewhere.
>
> ken
>

apparently.

Did you get any of the Biloya from the Green Coffee Coop? Possibly the
best coffee I've ever had. I've roasted it to several different levels.
Taken into the 2nd crack it makes a wonderful SO espresso.

R "time for another shot at 8.3 bar" TF


    
Date: 19 Aug 2007 11:21:01
From: Ken Fox
Subject: Re: thoughts on pressure
"Moka Java" <rtwatches@fishyahoo.com > wrote in message
news:5ir8voF3qujvnU1@mid.individual.net...
>
>
> Ken Fox wrote:
>> no wonder very little useful content is ever posted on a.c. anymore. All
>> the thoughtful discussions have gone elsewhere.
>>
>> ken
>>
>
> apparently.
>
> Did you get any of the Biloya from the Green Coffee Coop? Possibly the
> best coffee I've ever had. I've roasted it to several different levels.
> Taken into the 2nd crack it makes a wonderful SO espresso.
>
> R "time for another shot at 8.3 bar" TF

Yeah, I did. It is a lovely coffee.

ken
p.s. try roasting it to just BEFORE second crack.




 
Date: 18 Aug 2007 21:53:39
From: Moka Java
Subject: Re: thoughts on pressure
Søren Jacobsen wrote:
> I was thinking about pressure...
>
> many machines hav 15 bars of pressure.... is that the industry standard or?
>
> the thing is that grindlevel seems to be the way to control brew speed,
> but Id think the pressure would be equally important?

The pumps put out 15 bar but it's regulated down from there. Lower
priced machines are regulated by the over pressure valve. Better
machines have an adjustable pressure regulator of some sort, either in
the OPV or at the pump.

R "8.3 bar is the sweet spot" TF


 
Date: 19 Aug 2007 00:57:07
From: lockjaw
Subject: Re: thoughts on pressure
On Aug 18, 2:55 pm, Danny <da...@nospam.gaggia-espresso.com > wrote:
> lockjaw wrote:
> > S:
>
> > the 15 bar thing is just B.S. marketing hype. the "15 bar" (and
> > I've even seen "17" is possibly the MAX the pump could generate -- all
> > or virtually all regulate it far lower than that -- to say 9 or 10
> > bar.
>
> > And yes, pressure is important!
>
> > but not nearly important as proper, stable repeatable TEMPERATURES.
>
> Not so. Just trying to sell another PID? Most machines take care of
> pressure just fine. Grind is the important variable. If you want to
> change the temp for a particular blend, then fine, but for day to day
> use, you don't need .1 degree stability (which most couldn't detect
> anyway).
>
> --
> Regards, Danny
>
> http://www.gaggia-espresso.com (a purely hobby site)
> (apparently bad grammar but I like it that way...)

NO, idiot.
another red herring vomited up by you.

are you saying I'm wrong about pressure.

and we were talking about the machine here not the grind



  
Date: 19 Aug 2007 09:59:30
From: Danny
Subject: Re: thoughts on pressure
lockjaw wrote:

> NO, idiot.
> another red herring vomited up by you.
>
> are you saying I'm wrong about pressure.
>
> and we were talking about the machine here not the grind
>

No point in attempting useful conversation with replies like that.

But since you ask a question - of course pressure is important, but we
assume the machine takes care of that, by means of it's pump, lever or
other method of generating 9 bar (there's not a lot of user input that
can change that).

And of course temperature is important, and sometimes needs to be
modified by temp surfing or other means when switching between steam
and brew on single boiler machines (unless like mine). User input
obviously does have an impact here.


--
Regards, Danny

http://www.gaggia-espresso.com (a purely hobby site)
(apparently bad grammar but I like it that way...)



 
Date: 18 Aug 2007 09:56:13
From:
Subject: Re: thoughts on pressure
On 18 A ustos, 01:17, S=F8ren Jacobsen <kurgan@spammergoaway_kurgan.dk >
wrote:
> I was thinking about pressure...
>
> many machines hav 15 bars of pressure.... is that the industry standard o=
r?
>
> the thing is that grindlevel seems to be the way to control brew speed,
> but Id think the pressure would be equally important?

Pumping pressure is proportional to flowrate, for coffee or elswhere.
Espresso flowrate is 2 oz per 25 second, the required pressure is 9
bar. Such a vibration pump must be rated at 15 bar by 0-flow. The
industry standard is 15 bar. Similar rating will be observed in case
of rotational pumps for coffee, multiplied by the number of outlets in
case of professional equipment.

David



 
Date: 18 Aug 2007 10:30:24
From: D. Ross
Subject: Re: thoughts on pressure


  
Date: 19 Aug 2007 00:03:07
From: Dee Dee
Subject: Re: thoughts on pressure

"D. Ross" <ross@math.hawaii.NOSPAM.edu > wrote in message
news:46c6ca2d.47756640@localhost...
>


   
Date: 18 Aug 2007 22:19:06
From: Ken Fox
Subject: Re: thoughts on pressure
"Dee Dee" <deedovey@shentel.net > wrote in message
news:fa8fds$t37$1@registered.motzarella.org...
>
> "D. Ross" <ross@math.hawaii.NOSPAM.edu> wrote in message
> news:46c6ca2d.47756640@localhost...
>>


    
Date: 19 Aug 2007 12:36:04
From: Robert Harmon
Subject: Re: thoughts on pressure
Howdy Ken!
Although I seldom disagree with you, this is one of those times. There are
*many* fine machines priced less than $1000 that will last for many decades,
providing quality espresso the entire time. Gaggia Coffee machine from the
80's are in daily use by many knowledgeable coffee people, and I had a 60's
La Pavoni that until recently was as ready to make quality espresso as
anything you can buy today. Resale value on eBay merely reflects the hype
received by Rancilio's Silvia, not necessarily the superior quality of the
machine. In fact that's what makes the Gaggia so desirable as an entry level
machine - low cost for a quality machine leaves more of the noob's budget
for a quality grinder.
--
Robert Harmon
--
http://www.tinyurl.com/mb4uj - My coffee pages.

http://www.tinyurl.com/2tnv87 - My 'Guidelines For Newbies' page.

http://www.tinyurl.com/2cr3e2 - I have things for sale here.
"Ken Fox" <morceaudemerdeThisMerdeGoes@hotmail.com > wrote in message
news:5ipulcF3r3rg8U1@mid.individual.net...
>
> There are few machines cheaper than a Rancilio Silvia that will last for
> more than a few years. Although limited in many ways, and not something
> that I would personally want to own, the Silvia has the advantage that one
> can own it for a year or so then sell it used on ebay for not a whole lot
> less than what you paid for it. Anything much cheaper than this is likely
> to be worth very little in the resale market.




     
Date: 19 Aug 2007 11:53:10
From: Ken Fox
Subject: Re: thoughts on pressure
Robert,

Perhaps you should reread my post; I said nothing about needing to spend
$1000 to have a machine that will last for decades, rather that "few"
machines less expensive than a Silvia (currently overpriced at $595 list)
will last this long. As a matter of genuine fact, very few espresso
machines at any price level will still be in operation after even a decade,
although there are many exceptions.

ken

"Robert Harmon" <Texas_Coffee@earthlink.net > wrote in message
news:13cgvru8pfe0q4a@corp.supernews.com...
> Howdy Ken!
> Although I seldom disagree with you, this is one of those times. There are
> *many* fine machines priced less than $1000 that will last for many
> decades, providing quality espresso the entire time. Gaggia Coffee machine
> from the 80's are in daily use by many knowledgeable coffee people, and I
> had a 60's La Pavoni that until recently was as ready to make quality
> espresso as anything you can buy today. Resale value on eBay merely
> reflects the hype received by Rancilio's Silvia, not necessarily the
> superior quality of the machine. In fact that's what makes the Gaggia so
> desirable as an entry level machine - low cost for a quality machine
> leaves more of the noob's budget for a quality grinder.
> --
> Robert Harmon
> --
> http://www.tinyurl.com/mb4uj - My coffee pages.
>
> http://www.tinyurl.com/2tnv87 - My 'Guidelines For Newbies' page.
>
> http://www.tinyurl.com/2cr3e2 - I have things for sale here.
> "Ken Fox" <morceaudemerdeThisMerdeGoes@hotmail.com> wrote in message
> news:5ipulcF3r3rg8U1@mid.individual.net...
>>
>> There are few machines cheaper than a Rancilio Silvia that will last for
>> more than a few years. Although limited in many ways, and not something
>> that I would personally want to own, the Silvia has the advantage that
>> one can own it for a year or so then sell it used on ebay for not a whole
>> lot less than what you paid for it. Anything much cheaper than this is
>> likely to be worth very little in the resale market.
>
>




      
Date:
From:
Subject:


 
Date: 17 Aug 2007 23:37:31
From: lockjaw
Subject: Re: thoughts on pressure
S:

the 15 bar thing is just B.S. marketing hype. the "15 bar" (and
I've even seen "17" is possibly the MAX the pump could generate -- all
or virtually all regulate it far lower than that -- to say 9 or 10
bar.

And yes, pressure is important!

but not nearly important as proper, stable repeatable TEMPERATURES.

DAVE

www.hitechespresso.com



  
Date: 18 Aug 2007 19:55:41
From: Danny
Subject: Re: thoughts on pressure
lockjaw wrote:
> S:
>
> the 15 bar thing is just B.S. marketing hype. the "15 bar" (and
> I've even seen "17" is possibly the MAX the pump could generate -- all
> or virtually all regulate it far lower than that -- to say 9 or 10
> bar.
>
> And yes, pressure is important!
>
> but not nearly important as proper, stable repeatable TEMPERATURES.
>

Not so. Just trying to sell another PID? Most machines take care of
pressure just fine. Grind is the important variable. If you want to
change the temp for a particular blend, then fine, but for day to day
use, you don't need .1 degree stability (which most couldn't detect
anyway).


--
Regards, Danny

http://www.gaggia-espresso.com (a purely hobby site)
(apparently bad grammar but I like it that way...)



   
Date: 24 Aug 2007 14:57:01
From:
Subject: Re: thoughts on pressure
On 25 A ustos, 00:43, Danny <da...@nospam.gaggia-espresso.com > wrote:
> yuvali...@gmail.com wrote:
> > No! It's not the area of the P/F and there is not a single relevant
> > force (force of the spring or else). The calculation of the pressure
> > in this case is complicate, it involves theoretical models, serious
> > math., surface area of all coffee partikels etc.. Therefore the
> > pressure will be not calculated, for the sake of simplicity. It will
> > be measured, directly or indirectly. Direct measurement: pressure
> > gauge in circuit. Indirect measurement: measurement of the flow i.E.
> > mass per unit time. That's what Illy did, he hasn't try to calculate
> > the performance of coffee machines!
>
> > David
>
> OK, this is probably my last post on this subject.
>
> Illy does coffee. He was great at knowing about coffee. He knew the
> best particulate mix (in size) and the chemistry, crushed rather than
> sliced etc etc. Illy didn't invent an espresso machine - he invented
> a machine that used compressed air (1935), but was never acknowledged
> as the creator of the espresso machine, although his interest was in
> this area. Bezzera invented a machine that used pressure and brewed
> coffee faster, which was good, and sold this to Pavoni. But it used
> steam pressure, which burnt the coffee. Gaggia actually did it, in
> 1938. (Actually he stole/bought/was indebted the patent from the wife
> of Cremonesi (sp) after the man had died, so legend has it). Thus was
> born the first machine that produced crema and didn't use steam to
> create the pressure needed for this, instead using a spring and
> piston. Gaggia's design also had other advantages, which mostly got
> lost on later pump machines - preinfusion and correct brewing temp
> from a single boiler. Illy has always been interested in the coffee -
> packaging etc (using inert gas to extend freshness etc).
>
> It doesn't matter how you describe it - the (well designed) espresso
> machine produces the water at the right temperature and pressure to
> extract coffee. It's up to the barista to ensure that the grind is
> correct to achieve the correct extraction time, taking into account
> bean freshness, ambient humidity etc etc.
>
> I suspect that we are probably not poles apart in our views, but your
> doggedness to split hairs over descriptions and word usage seems that
> we will never agree (nor will I understand exactly what it is you are
> trying to say).
>
> You may actually possess much knowledge that I don't (I'm not a clever
> person), but god help anyone who would learn anything from you - a
> teacher you are most certainly not.
>
> I sell coffee. I try to make the best coffee I can for my customers.
> I pull shots 5 days a week, and I teach others how to pull good
> shots, commercially. I don't split hairs, or use unnecessary jargon.
> I just teach the good housemanship of understanding the machine they
> have and of being a barista.
>
> --
> Regards, Danny
>
> http://www.gaggia-espresso.com (a purely hobby site)
> (apparently bad grammar but I like it that way...)

OK Danny, I noticed your patience with me, I tried to be flexible with
you. Your knowledge of coffee is out of my topics, it seems to be
superior with respect to me. I guess you may owe more respect to these
uncomfortable technical things. Actually you need not. It's just the
love for coffee.

Thanks

David