Follow up:
Yesterday, 25. july, I was supposed to demonstrate prototype one for my parents. They are old outdoor enthusiasts who have tried several commercially available alcohol stoves before. The first thing I noted was that the simmering ring was destoyed in my back pack after slipping off the rest of the stove - You have to be careful of where you keep the stove and especially the ring. I got some old denaturated ethanol alcohol (rødsprit) that was stored in their basement as fuel. I filled the fuel cup to the rim with alcohol. This is supposed to be sufficient to boil two cups of water. The stove was supposed to burn clean after what I felt was like an eternity of priming, but stopped burning after that. My theory is that the alcohol did not sink into the fuel cup. Now this is strange: After removing the coin, filling to the rim, reinserting the coin and priming for a very long time the flames where all red and yellow. This is strange compared to the nice tests with the blue flame just a few days ago. I am not sure what caused this, but I have a suspicion that some of the alcohol has turned to acid when stored for a long time. My mother claims that the bottle has always been properly closed before storage. It was a huge embarrassment for me anyway :(
