That made my day

shadowfax wrote:Oh no!

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Touché!

malachi wrote:for 99% of buyers - none of these machines will be the gating item
thus the choice is largely an emotional, personal and somewhat irrational one

wrapping this reality in technical detail doesn't change the fundamental truth

Cracks me up to see you keep quoting this, but at the same time, it's such the truth!

First: I can see the point about the post above.

Second: This is simply for a little bit of a science lesson given the words thrown around about the armchair assertions concerning boiler thickness a while back... this is not an armchair assertion at all but a very common fact not just in the theoretical engineering world but also in the practical manufacturing world. For a bit of reading check out a few wiki pages

Specific Heat (concerning boiler thickness, this is actually a large factor in heat transfer equations, hence why boiler thickness has a lot to do with stability... thicker boiler = more stability = less ability to change temperature quickly... read especially the section on Heat Capacity)
http://en.wikipedia.org/wiki/Specific_heat

Heat Transfer (basic info for those wondering about this whole subject)
http://en.wikipedia.org/wiki/Heat_transfer

Convection (this is how much of the heat is carried away in an uninsulated boiler, although it really is a combination of convection and conduction... insulation works by preventing natural convection and is also very non-conductive thus preventing any significant conduction from the boiler to the insulation material)
http://en.wikipedia.org/wiki/Convection

A very common lab assignment during a Thermo and/or Heat Transfer classes is measuring specific heat of certain materials... I have done them, and it is quite accurate (especially for a lab experiment), and actually it is done with water tanks [sometimes] so the espresso machine connection is a good one (though pragmatic espresso quality effect is most likely negligible). B/c specific heat is a constant for the material, the less metal, the less capacity it has to store heat (its Heat Capacity) therefore it has less heat to impart to the water as one attempts to reduce the temperature of the water or less energy demand to reach an increased temperature if one is attempting to increase the temperature of the water.

And how does the coffee taste?

It's not PURELY about coffee taste. While taste is a HUGE factor there are others to consider. You own a cafe and you have these choices. You get 60 cups an hour traffic.

Machine A: Dual Boiler, PID, Capacity 100 cups an hour. Coffee 9.0
Machine B: Single Boiler, PID, Capacity 20 cups an hour. Coffee 9.3

I know, I know buy a triple group machine B , but you get the idea.

There aren't too many cafe's with knowledgeable (or patient) enough baristas out there that could withstand what it takes to flush an HX for the proper temp given a long line of customers. That, and the fact that the length of flush depends on what else the machine has been doing prior, and it's stated recovery time - PID or not.

I think what Chris was getting at is the taste of the coffee given those parameters of brew boiler thickness, convection, specific heat, et al is the coffee will taste the same, given proper preparation.

It was just an example , apparently I'm not so good at those. What I was trying to say is let's say the coffee does taste the same you still want to consider + and - of thinner/thicker boiler. If your going to insulate than clearly you don't care about the temp. change so thicker boiler is probably better due to durability.

This is starting to become a boiler/science battle and not a "Double boiler espresso machine recommendation" so maybe I should start a new thread If anyone would like to split it off that's cool too.

what i was pointing out was actually that the espresso machine is a means to an end - not an end in and of itself.