Kathie Johannes on thu 1 jul 04
I have just recently moved to 3 ft elevation from 2000 ft elevation,and
just fired my first load of Raku since the move. All of the colors and
effects are different from the ones I have been getting in the higher
elevation. Can anyone tell me if this could be the reason for all the
strange changes? Same glaze, same temp. Thanks Kathie
Craig Dunn Clark on thu 1 jul 04
Kathie, I had experienced the same occurance in glazes that I used while
living at 8000ft in the middle of Bolivia and the difference at a15ft
elevation in Houston Texas. My supposition is that much of it has to do with
the amount of oxygen that is present in the air. I also think that the
humidity and the water that is used to mix the glazes has something to do
with it as well.
To get a similar type of reduction at sea level there are a few things
which may help. While at sea level there is "need for speed" when getting
the pot from the kiln into the post firing reduction chamber (I use garbage
cans).
The cans must also seal well. If they are old and leaky, or brand new
with a lid that doesn't yet fit tight, there will be some leakage and you
won't get as much reduction. The glazes will reoxidize. This is all
dependant upon what glaze you are using and what you want with the finished
product. You will have to play with it a bit to get things back to where you
want them to be. Kinda like changing dance partners.....there won't be a
graceful glide across the floor until you've practiced together for a bit.
Keep notes about what does or doesn't work if you need to.
You might also try drapping a coupla sheets of damp newspaper across the
top of the can before sealing it with the lid. This will help to prevent
reoxidation as well. A half sheet of crumpled damp paper in the can will
help to produce a positive pressure in the can, due to steam that is
released, will help toward the same end.
A few other things to check are: Are you using the same scale...Are you
using the same ingredients from the same supplier? I previously mentioned
the potential difference in the water could be a big component in your
troubles. Are you firing them in exactly the same way? If you are firing in
a reduction kiln, there is a very good chance that there are substantial
atmospheric differences in the firing between sea level and several thousand
feet. Are you using the same type of burners, kiln, fuel etc.?
Hope this helps
Craig Dunn Clark
619 East 11 1/2 st
Houston, Texas 77008
(713)861-2083
mudman@hal-pc.org
----- Original Message -----
From: "Kathie Johannes"
To:
Sent: Wednesday, June 30, 2004 11:19 PM
Subject: Weather and Raku
> I have just recently moved to 3 ft elevation from 2000 ft elevation,and
> just fired my first load of Raku since the move. All of the colors and
> effects are different from the ones I have been getting in the higher
> elevation. Can anyone tell me if this could be the reason for all the
> strange changes? Same glaze, same temp. Thanks Kathie
>
>
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Jon Whitney on fri 2 jul 04
A good friend of mine likes to raku while it is raining. he says his glaze always comes out better. I am not sure if it is high or low pressue while it is raining, but you may want to try it and see if they look like they used to. jon
-------------- Original message --------------
> I have just recently moved to 3 ft elevation from 2000 ft elevation,and
> just fired my first load of Raku since the move. All of the colors and
> effects are different from the ones I have been getting in the higher
> elevation. Can anyone tell me if this could be the reason for all the
> strange changes? Same glaze, same temp. Thanks Kathie
>
> ______________________________________________________________________________
> Send postings to clayart@lsv.ceramics.org
>
> You may look at the archives for the list or change your subscription
> settings from http://www.ceramics.org/clayart/
>
> Moderator of the list is Mel Jacobson who may be reached at melpots@pclink.com.
Simona Drentea on sat 3 jul 04
I don't really know, but I've often heard that high humidity causes 'better'
colors in raku.
At first glance it would seem that you & your raku are getting a lot more
oxygen at 3 feet elevation, but seems to me that I read that there's the same amt
of oxygen on top of Pikes Peak for example, but that our lungs can only
process about 2/3's of it at altitude. So how would that affect raku? I have no
idea, it's just some food for thought. Maybe one of the scientific minds on
here can shed some light on it.
Simona in Colorado
<< I have just recently moved to 3 ft elevation from 2000 ft elevation,and
just fired my first load of Raku since the move. All of the colors and
effects are different from the ones I have been getting in the higher
elevation. Can anyone tell me if this could be the reason for all the
strange changes? Same glaze, same temp. Thanks Kathie >>
Snail Scott on sun 4 jul 04
At 01:28 AM 7/3/04 EDT, you wrote:
>...I read that there's the same amt
>of oxygen on top of Pikes Peak for example, but that our lungs can only
>process about 2/3's of it at altitude...
I suppose it depends on what you mean by 'same
amount'. The amount of oxygen relative to the other
components of air is about the same, I believe, but
any given volume of air has fewer molecules in it.
Same proportion, lower density. It does truly make a
difference, often a substantial one. Kilns built at
high altitude need more air volume than those at lower
elevations.
Bad weather generally comes along with low atmospheric
pressure, so reduction is generally greater than for
a firing in good weather using the same air-intake
settings. In a kiln with inadequate air supply, low
air pressure can even be sufficient to prevent reaching
its higher temperatures.
There is evidence that moisture increases reduction,
too. As to whether the higher humidity of a rainstorm
is sufficient to make a measurable difference in
reduction (over and above the low-air-pressure
difference), I don't know.
Ths difference for raku would seem to be negligible,
though, since for most folks, it's the post-firing
reduction chamber that accomplishes the only reduction
that matters, and many other variables would have
a greater effect than the air pressure.
-Snail Scott
Edwardsville, Illinois, USA, Earth
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