[Stoves] Rolling Boil

[Crispin Pemberton-Pigott]

Dear David

>I [think] the SA method leaves to much to 
>the tester to decide.

Actually if you try it, the different in time between (say) 100 C and a
rolling boil is very short for a lot of stoves.  It is longer if the lid is
off, of course.  If the pot is going to have a rolling boil it has to be
seen, which is an issue in my view because the lid should be glass or off
which will give a different time-to-boil.  It so happens that the ethanol
stove protocol calls for a 225mm diameter pot to have only 1 litre of water
in it which is very little.  There is no mention of a lid so I think I will
suggest adding that.  Ethanol stoves are famous for being low powered and
they should definitely be used with the lid on.

The idea is that the test should prove that the stove supplies a minimum
quantum of heat.  Stoves that are not powerful enough to 'cook' will not be
allowed.  The power required is quite small but still, it assumes that
watchmen's stoves as seen in Senegal are not needed. They are tiny charcoal
JIKO's about 4 inches in diameter.  The SANS Ethanol stove standard does not
foresee this, nor for the hyper-efficient stoves of the future.

>In this case, I believe the WBT protocols are more precise.

I think the idea of using the local boiling point is OK  Asking someone when
a pot is boiling they will probably look and say it is when there is the
rolling circulation the SANS talks about.

>It seems from your post that you too agree that this method gives  
>better and more comparable data.

I want to be sure that we agree on several conceptual things.  I have been
involved in writing a few stove testing protocols and you would be surprised
at how different they are from the ones we use.  There is no general
agreement within this group on testing, but we are more in agreement than
the ones used by governments.  The process for writing them is more
consultative and people have to pitch up concrete wording, not
philosophising which is of course disciplining!

I favour the temperature measuring method for the reason that people in
remote places can check the data and make new calculations based on the raw
data to test other ideas.

For your region, I ask that you ensure that your test data is corrected for
the need to measure a temperature rise in the pot that is the same as
whatever protocol you are rating the stove with (from another place).  By
this I mean that you need to either start with colder water, or make
mathematical adjustments for the lower boiling temperature at altitude.  The
correction method should be shown so it can be checked and used by others.

If you use 75 or 80 degrees of water temperature rise (I favour 80) for the
boiling portion of the test, it doesn't matter much what the boiling point
is, and you will be able to make legitimate comparisons across the globe if
you are using the same protocol.

Best regards
Crispin

"It was Winston Churchill who first wrote, "We make a living by what we get,
but we make a life by what we give" "
http://www.uwalumni.com/home/onwisconsin/archives/fall2007/siftingmakealife.
aspx

As Harold Blake Walker wrote, "We make a living by what we get, but we make
a life by what we give."
http://www.profam.org/docs/jah/thc_jah_submission.htm

See?  There isn't even agreement on that!