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