Lee Love on sat 25 nov 00
We've been firing the Noborigama since the 23rd (today is the 25th.)
Interesting thing happened today: there are hot air balloon races and part
of the race's course is over Mashiko. We heard the burners on one so we
ran out to see it. It was traveling very high, but its path was coming
right over the Noborigama, which was at red heat in all chambers. I
thought that the warm air from the big woodfire kiln might cause the balloon
to rise, but I didn't think that through clearly. As it came near, at
first it shot up, I think from the currents of cool air outside of the hot
air. But as it entered the hot air downwind of the kiln, it started to
fall like a rock, the balloon was deflating and I thought there was going to
be a bad accident. The saving grace was that the balloon was high enough
that the guy flying it could reinflate it, by laying on the gas. I was
afraid it was going to deflate enough to be burnt by the flame. But after
a few seconds, the balloon filled and started going up again.
A second balloon came by really low and it was going right over
Hamada's museum. Still, the Noborigama was effecting the temperature of
the air. It was much lower than the other balloon & just missed some
powerlines before it landed near a pottery shop on one of the busy streets
of Mashiko.
I got pictures of the second balloon and will put them up after the
firing. I just came home for a 4 hour break.
--
Lee Love
Mashiko JAPAN Ikiru@kami.com
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John Weber on sat 25 nov 00
As an old Balloon pilot before my passion for pots, I can say that your
experience with the Balloon's is fascinating. The dangers of the Noborigama
is that the pilots would probably have no clue that it was out there
generating that much heat. Hot Air Balloons (which I assume were the type
you experienced as opposed to closed system gas balloons) operate on the
basis of heat displacement. Hot air inside the balloon make it lighter than
air, so the air around it falls below it and thus gives it lift. Like a
bubble in water. The balloon system is really quite sensitive to the heat.
For example, a balloon pilot knows that as they fly over green trees which
are fairly cool when the trees end and an open wheat field that is lighter in
color is ahead they need to add heat to their envelope (the balloon part) in
order to maintain level flight. This seems like only a slight difference in
temperature being generated by radiation from the ground but it dramatically
effects the balloon. So, when these guys hit the heat rising from your
Noborigama it would have "pushed" them up with convection heat for a short
while until the heat in the balloon (envelope) reacted to the heat on the
outside of the balloon and the air around it was no longer heavier than the
air inside the balloon, so it fell light a rock. This would have been the
same effect of a thermal current and the only way out is for the pilot to
burn hard until he heats the balloon up to exceed the outside air and pop out
of the top of the current. Anyway, I will stop rambling about my old hobby.
Back to pots, hope your firing went well.
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