Here, water boils @ 195F. Your recommendations for espresso roasts?

[Trisha]

Given the wealth of experience and expertise within the ranks of the members, I ask for recommendations based, if at all possible, on your experience with espresso when there is no possibility of brew temperatures of even 198F. Roasting to Full City and letting the beans rest for four days makes a wonderful cup, but curiosity has me!

What would be your choice in espresso beans if you were close-in to timberline?

[another_jim]

This is a common misconception. The water brewing the espresso in the puck is under pump pressure and has a boiling point of around 280F. Most of the pressure drop occurs at the bottom of the basket, so there is almost no chance of getting the water boiling inside the PF.

The key problem is the water exiting the PF; it starts out around 15F below the brewing temperature, but climbs during the course of the shot to within 5F to 7F of the brewing temperature. Chances are you can get away with 202F brewing temperature and thus even the lightest roasts; but it could be that 200F is your practical limit, confining you to medium or darker roasts, or very low acid lighter ones.

[HB]

I ask for recommendations based, if at all possible, on your experience with espresso when there is no possibility of brew temperatures of even 198F.

I'm obviously overworked. My first thought when reading your post was, "Hmm-m, why not enclose the grouphead in a pressurized chamber, then you could brew at any temperature!" Then my brain re-engaged and I searched the forums ("denver effect"), finding How does high altitude affect brewing?

The key problem is the water exiting the PF; it starts out around 15F below the brewing temperature, but climbs during the course of the shot to within 5F to 7F of the brewing temperature.

Most vibe pump machines take a few seconds to pressurize while some rotary pumps fill the chamber in less than a second. In Trisha's case, there would be a slight advantage to fast pressurization since the puck would be exposed to less steam. Machines with a slower initial temperature rise might help too. The first shot or two from a lever machine fills both needs (fast pressurization, slow initial temperature rise).

[Trisha]

Thanks, AJ - that's been the way I've brought out the best, to date. The pressurestat was right on the edge of tripping as the thermostat ran up - altitude is a wonderful thing! Dialing the thermostat down a little has greatly reduced the strain on everything with my Elektra MCaL, and the coffee is superb.

The input is greatly appreciated; curiosity remains.

HB, it's been thirty years since I had access to a pressure chamber (NASA DFRC NDT Lab) - they tended to be a little on the bulky side. . . The altitude compensation chart shows lab measurement for boiling water here to be right at 195 F. (air's a bit thin. . .)