Be warned. I always wanted to speed up the water-boiling process in the lower pot by adjusting up the alcohol lamp provided with this vac pot. Last night, I filled the lower pot to 5-cup mark, adjusted the wick a little above the 3-mm height to create a more intense flame, but took care NOT to let the flame went far beyond the bottom of the lower pot (spreading out to the side) as noted in the instruction sheet for this vac pot. As the water got to the boiling point, it created very large bubbles that rose very quickly from the bottom and the sides of the pot. As the hot bubbles competed to escape, they pushed the hot water up higher and higher and then, all of a sudden, created a water-fountain / volcano explosive effect, sending a column of boiling-hot water out of the lower pot neck, shooting it more than 2 feet high up in the air and splashing hot water every where around the dining table. The total hot water remains in the lower pot was less than 4 cups.
This happened as a combination result of filling the lower pot to the 5-cup mark and using the higher flame. The lower pots of the Super Technica and regular Technica have the smallest left-over air space in the lower pot after the water was filled to the 5-cup mark, along with the smallest neck opening compared to other Hario’s models, and as such, encourage this mishap to happen under the right conditions.
All other Hario’s 5-cup models have more air space above the 5-cup mark and a bigger neck opening; thus, lower of the chance for problems, but the potential danger is still there. So, don’t let the flame go too high on these, especially with the 3-cup models when filled to the max.