Craig Clark on fri 12 aug 05
Hank Murrow wrote:
>
> Dear Craig;
>
> ...there is a special reason for using stainless for fiber
> kiln construction instead of mild steel or its equivalents. Ceramic
> fiber is porous to water vapor, so the combined waters from the
> fuel(whether propane or natural gas) and the atmosphere will condense
> on the inside surface of the shell, leading to corrosion and eventual
> failure of those surfaces. The first lifting fiber kiln I designed was
> made of zinc-clad mild steel, and inspection after 40 or 50 fires
> showed much corrosion on these inside surfaces. It was a puzzler until
> we found out why and that led to the decision to use stainless steel,
> in our case.......... 304L alloy.
Hank, as much as I would love to use stailness as a shell for the
workshop kilns I just don't think it is doable. I will however use it
for a shell on my 40 cubic foot behomoth when I reline it sometime after
the new year. Did you use steel sheet or did you use a "hardware cloth"
type of material when you discovered the corrosion which led to your use
of stainless? Forty or Fifty firings just ain't enough life for a kiln
in my book. I had noticed a similar problem with kiln that we had built
out of 11 gauge mild steel in school (basic box....2 inch
lining.....bendle burners) but had figured, apparantly incorrectly, that
the corrosion was from the caustic atmosphere in SouthEast Texas. The
kilns still worked after several years but the jacket was slowly but
surely giving up the ghost and it had a heavy angle iron frame to keep
the pieces together.
If I use a nice heavy hardware cloth as I plan do you think that
there will be as severe a corrosion problem with the open mesh? If I
treat it with a compound such as OSPHO or other type of primer or paint
do think that may mitigate the problem? What if I treat the fiber with
ITC? This is the first time I've really addressed the particular issue.
Thankyou for any and all help
Craig Dunn Clark
619 East 11 1/2 st
Houston, Texas 77008
(713)861-2083
mudman@hal-pc.org
Craig Clark on fri 12 aug 05
Here's the link to Ward Burner
Supply...http://www.wardburner.com/raku_kilns.cfm His kiln certainly
isn't the cheapest around but it is demonstrably one of the best. He is
forthcoming with information and one of the best in his field, INHO. I
especially like the stainless steel shell (can't afford one though...LOL).
If you are thinking about building one yourself there are a wide
variety or plans and sources of info. I remember the article in PMI that
Marcia Selsor mentioned but can't emember what issue it was in. Just
check the back issues. I believe you can do it on the web. There is a
very good article in the January/February 2000 issue of CLay Times,
Volume 6, No. 1, written by Charlie and Linda Riggs. It is excellent.
There is a complete material list as well as step by step instructions.
You might also take a look at "Alternative Kilns and Firing
Techniques," by James C. Watkins and Paul Andrew Wandless. It full of
specific info on a variety of raku firing procedures as well as other
"primitive" firing techniques. You can pick up a copy of it from Amazon
for less than twenty dollars. There are several well designed and easily
built plans for kiln construction in the book. One thing that is
incorporated into their kiln that I had not seen used on raku kilns
before is an array of soft brick slices around the interior perimeter of
the kiln. These act as flame spreaders. A good idea indeed. I've seen
them used frequently in larger kilns but never in a raku kiln before.
"Raku, A Practical Approach," by Steve Branfman, is one of the
pre-emminent sources of info on raku and raku kiln building. While you
are at it, if you are so inclined and interested in learning more about
basic kiln contruction consult a copy of The Kiln Book.
There are many other sources of information than the ones that I
have listed. Just do a search of trade publications and periodicals and
you will find an incredible range of thoughts, designs and ideas around
raku and raku kiln building. I read an article in what I think was
Ceramics Monthly, from the 1970's, that was about a raku firing party
out on the beach somewhere in California. There was a picture of one of
the participants who had converted her old Volkswagon Beetle into a raku
kiln. Keep in mind that raku can be, comparitively speaking, free and
loose. The kilns can indeed reflect this.
Hope this helps
Craig Dunn Clark
619 East 11 1/2 st
Houston, Texas 77008
(713)861-2083
mudman@hal-pc.org
Hank Murrow on fri 12 aug 05
On Aug 12, 2005, at 7:44 AM, Craig Clark wrote:
> Here's the link to Ward Burner
> Supply...http://www.wardburner.com/raku_kilns.cfm His kiln certainly
> isn't the cheapest around but it is demonstrably one of the best. He is
> forthcoming with information and one of the best in his field, INHO. I
> especially like the stainless steel shell (can't afford one
> though...LOL).
Dear Craig;
I sympathize with your reluctance to shell out for a stainless steel
shell. However, there is a special reason for using stainless for fiber
kiln construction instead of mild steel or its equivalents. Ceramic
fiber is porous to water vapor, so the combined waters from the
fuel(whether propane or natural gas) and the atmosphere will condense
on the inside surface of the shell, leading to corrosion and eventual
failure of those surfaces. The first lifting fiber kiln I designed was
made of zinc-clad mild steel, and inspection after 40 or 50 fires
showed much corrosion on these inside surfaces. It was a puzzler until
we found out why and that led to the decision to use stainless steel,
in our case.......... 304L alloy. Of course, one may simply say to
oneself, "Hey, I will only need 40 or 50 fires in this thing anyway,
so.........".
Since I was selling these kilns to folks as a lifetime investment, I
bit the bullet and made them from stainless.....and only sold around
twenty of them at commensurate prices. I am very happy making pots and
firing them in my kiln........so I am happy to let others fight the
marketing battles.
Cheers, Hank in Eugene, doing one more firing before heading off to
present in Kelowna BC.
> www.murrow.biz/hank
Hank Murrow on sat 13 aug 05
On Aug 12, 2005, at 7:09 PM, Craig Clark wrote:
> I will however use it
> for a shell on my 40 cubic foot behomoth when I reline it sometime
> after
> the new year. Did you use steel sheet or did you use a "hardware cloth"
> type of material when you discovered the corrosion which led to your
> use
> of stainless?
Dear Craig;
The open 'mesh' stainless will solve the corrosion problem at the
expense of creating a more serious condition. Since the fiber is porous
to gases under pressure, every time you are in reduction the hot gases
will be fighting their way toward the steel, which can warp it at high
temperature, thereby losing its structural integrity for supporting the
fiber. I testified in a liability hearing concerning just such a case,
where the worker walking by the new kiln carrying a load of pots was
blasted in the face with hot gases leaking from the kiln. He sued the
pottery, who sued the kiln company, who sued the fiber manufacturer.
The kiln company was held liable in the end, because it was their lack
of recognition of the problem which led to the incident. Not the fault
of fiber, which just needed a different design to perform well. The
longest-lived(so far) of my kiln design is the one at Shadbolt Center
in Burnaby BC, which has gone over 1000 fires with no damage to the
shell. In fact, I am going up there in September to install a new
lining of much better fiber than was available in 1984. "Your mileage
may vary".................
Cheers, Hank
www.murrow.biz/hank
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