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Designing a better "non-electric" espresso-maker

For people who want a reasonably portable non-electric espresso-making solution that's also affordable, there are a few alternatives. A few examples:

Pneumatic:

https://www.instructables.com/id/Hand-held-Espresso-maker/

http://www.handpresso.com/

http://mypressi.com/

Brute force:

http://unmodifiedpresso.blogspot.se/



Results are--of course--variable with all of these solutions. From what I've gathered, apart from issues with bad coffee, with grind setting/quality or with tamping, the major issues have to do with temperature and pressure. Then there're the issues of convenience/comfort.

How would you like to address such issues?




Re. temperature, there's the time-honoured method of preheating all the parts by rinsing with just-boiled water. I like the idea in principle but I'd like a way to ensure that the water used for extraction stays in the right temperature range for as long as possible.

Possible solutions:

1. Phase change metals such as the ones used in Joulies: http://www.joulies.com/pages/frontpage (different temperature target of course; not DIY-friendly)

2. A large reservoir of hot water. Make the machine hollow so that it can hold a lot more hot water and ensure that this large volume can stay in contact with the extraction chamber. May make the machine more pleasant to hold and use :) a possibility may be to have a water container encircling the existing water chamber in the Presso. Or just pour a lot of near-boiling water in a tank from which only enough water for one or two shots is released into the extraction chamber. Eg. make the Presso's water-reservoir much larger but design it so that only enough for one or two shots is released when the handles are raised to the appropriate position.

3. Insulation. Design as a thermos in such a way that metal parts won't rapidly transfer heat away from the water.



What're your ideas?