Mitchell Sewall on sat 18 mar 06
----- Original Message -----
From: "Mitchell Sewall"
To:
Cc: "L-Soft list server at clayart (1.8d)"
Sent: Saturday, March 18, 2006 5:49 PM
Subject: Venting an electric kiln
> This might be a real dumb question, but here goes; why would one vent an
> electric kiln? 1. the kiln is sealed. 2. I'm not about to fire anything
> noxious such as lead. 3. I've worked in studios with unvented electric
> kilns and the question never came up.
> I recently bought a secondhand, but unused Skutt1227. It has the vent and
> all the accoutrements with it. I'm debating whether to bother setting up
> the vent system.
> I would appreciate some thoughts on this.
> Mitch
mtigges@NOSPAM.SHAW.CA on sat 18 mar 06
On Sat, Mar 18, 2006 at 05:51:01PM -0500, Mitchell Sewall wrote:
> ----- Original Message -----
> From: "Mitchell Sewall"
> To:
> Cc: "L-Soft list server at clayart (1.8d)"
> Sent: Saturday, March 18, 2006 5:49 PM
> Subject: Venting an electric kiln
>
>
> >This might be a real dumb question, but here goes; why would one vent an
> >electric kiln? 1. the kiln is sealed. 2. I'm not about to fire anything
> >noxious such as lead. 3. I've worked in studios with unvented electric
> >kilns and the question never came up.
> >I recently bought a secondhand, but unused Skutt1227. It has the vent and
> >all the accoutrements with it. I'm debating whether to bother setting up
> >the vent system.
> >I would appreciate some thoughts on this.
> >Mitch
I'm confused about these headers, there are better people to answer
this question than me, but somehow I'm involved in a conversation I'm
unaware of.
Mitchell, first, most electric kilns are not sealed. It's true that
some close more tightly than others, but I would guess that all studio
kilns do exhaust fumes. (If they didn't I would expect them to
explode due to the expansion of the air in them.) The nature of these
fumes is dependent mainly on your clay body and your glazes ... but
also possibly the history of your kiln.
There is little doubt that the exhaust is corrosive. Look at the
stand that your kiln sits on. There are always flakes of black metal
underneath kilns. I use cinder blocks for this reason. In fact the
corrosive nature of these vapours are exactly correspondent with the
corrosive environment in the kiln which is partially responsible for
having to periodically replace elements.
There is no doubt that some of the consituent chemicals in the exhaust
are hazardous to health. There is a well known case of a now deceased
(I believe) potter who suffered grave ill affects which were at least
partially attributed to his use of manganese dioxide, and it is
believed that his breathing the vapours coming off the kiln
accelerated his illness. Venting a kiln is a wise thing to do if you
are going to be in the same room.
There are other reasons though. It has been said on this list by more
experienced people than I that if you close up your kiln you will have
a neutral atmosphere in contrast to a oxidative atmosphere. Meaning
that venting the kiln will ensure that you really do have the
atmosphere that the glazes were designed for.
Still more ... direct venting allow you to ensure that you have a more
even temperature throughout the kiln. When I added a vent to my kiln
I noticed that I no longer had to worry about the fact that I reached
cone 6 at the top while the bottom was cone 5.
If it were me I would use the vent system without question.
Regards,
Mark.
Vince Pitelka on sat 18 mar 06
Mitchell Sewall wrote:
This might be a real dumb question, but here goes; why would one vent an
electric kiln? 1. the kiln is sealed. 2. I'm not about to fire anything
noxious such as lead. 3. I've worked in studios with unvented electric
kilns and the question never came up.
I recently bought a secondhand, but unused Skutt1227. It has the vent and
all the accoutrements with it. I'm debating whether to bother setting up
the vent system.
Mitchell -
You are misunderstanding several things about the firing process. Lead is
by no means the only thing that gives off toxic fumes during firing. But
first, there is no such thing as a sealed kiln unless you are talking about
some sort of exotic laboratory furnace that is actually hermetically sealed.
Electric toploader pottery kilns are not sealed at all, not in any way, no
matter how tightly the parts seem to fit together. Even the slightest
positive pressure inside developing from materials outgassing from the clay
will escape to the outside. It has no place else to go. Whenever
bisque-firing, you have sulfur dioxide escaping from the kiln - that's the
rotten-egg smell you detect during a bisque firing. In mild quantities it
is a serious irritant to throat and lungs, and in sufficient quantities is
severely toxic. If you do not exhaust it to the outside, it will also cause
metals in the vicinity of the kiln to corrode. If you fire claybodies or
glazes containing manganese, you will be producing fumes that are extremely
toxic. One of Americas most beloved potters, David Shaner, died several
years ago from conditions brought about by or aggrivated by manganese fumes
from his kiln.
Unless this kiln is in an outside open shed, then it is not a question of
deciding whether or not to install a kiln vent. You need to install one.
- Vince
Vince Pitelka
Appalachian Center for Craft, Tennessee Technological University
Smithville TN 37166, 615/597-6801 x111
vpitelka@dtccom.net, wpitelka@tntech.edu
http://iweb.tntech.edu/wpitelka/
http://www.tntech.edu/craftcenter/
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