Chad Nielson on sun 9 oct 05
Hello all
My Question is concerning the dialog on ifb and itc
how does this combination hold up in the wood firing
environment?If the lenght of use simular to gas or is
the products f cumbustion detrimental to the lenght of
time the kiln can be considered functional.To the
point of not being practical or is this the way to go.
Chad B. Nielson
John Baymore on mon 10 oct 05
While there is a lot of slagging from wood ash on the GENERAL kiln
chamber's walls... it is nowhere the same in the GENERAL chamber when
compared to spraying in a liquid water-based soda solution....... and no
where NEAR the deterioration of salt on IFB with or without ITC.
I have used IFB with and without ITC in the linings of many wood kilns.
It certainly will deteriorate faster than it would in a gas kiln when it
is used in the same location........ but is still of a longevity that
makes it easily reasonably practical.
That being said, there are some locations in a wood kiln that straight IFB
for the lining might be a poor choice even with the addition of ITC
coating. A big issue is the mechanical abrasion that happens from
activities like wood banging into the walls as it is chucked into the
fireboxes, wood in the firebox being shoved into the walls by "aggressive
coal raking" , raking tools hitting the walls, and so on. Hardbrick or
hard castable typically fits this abuse better.
In any kiln design you also have to consider WHO is going to be firing it
as you design various areas. There will be a difference in the likelyhood
of the above being big or small issues between a highly experienced
woodfirer..... and a group of workshop participants or students new to the
process.
Also there is the concept of "flame abrasion" to look at. Like water
flowing in a stream bed, the flow of hot gasses (typically laden with all
sorts of "chemistry") can erode refractory surfaces. The faster
the "water" is flowing.... the more the errosion. So "throat" areas where
the gases are aaccelerated in velocity .....particulary when combined with
maximum temperature areas.......... might not be a good place to use IFB
either.
One other consideration in locating IFB in a wood kiln is areas of maximum
slagging. Many areas just downstream of firebox areas take heavy slagging
on the walls. In these places I'd consider hard refractories also over
IFB.
Different kiln designs affect this also. A kiln that burns less wood
thereby gets less ash and volitiles into the chamber. So the experience
of the person only using the Fast Fire kilns is "Hey..... it works fine."
So a "Fast Freddie" fired for 16 hours is a bit of a different beast from
say, an anagama fired for a week and a half, for example. What is OK in
one does not necessaruily work well in the other.....even though they are
both "wood kilns".
Sort of like asking "What tires work good on a car?" Well, a set of stock
Goodyears bought at Sears may work fine on my minivan for driving the kids
to school....... but not so good on the Formula 1 in the Indy 500 .
A lot of design decisions depend on how often you are going to fire the
unit. A big periodic kiln fired twice a year will last longer (years
wise) than a small kiln fired once a week. A huge part of the "life" of a
periodic kiln is the number of firings it has on it. Refractories
don't "like" to be heated and cooled. That is why continious duty ratings
for refractory materials are a bit misleading for craft potters.
But such longevity is not based totally the number of firings... because
the rate of heating and cooling matters on refractory life, as does the
atmosphere. Also the selection of the construction materials used plays a
BIG part. In many ways, it is the "pay now or pay later" bit .
When I build kilns for clients, I typically use a LOT of grades and types
of materials in the same kiln,....... specified for the specific locations
and situations they will encounter. Never is the entire lining layer
Brick X and the backup layer Brick Y.
Hope this helps.
best,
................john
John Baymore
River Bend Pottery
22 Riverbend Way
Wilton, NH 03086 USA
JBaymore@compuserve.com
http://www.JohnBaymore.com
"Please use compuserve address for any direct communications."
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