Jeff Lawrence on tue 31 aug 99
Hello Clayart,
Experience is an awesome thing. Mel-sama and Louis Katz homed in on things
that may well solve my reduction difficulties. Here is the requested data,
followed by further questions stimulated by these informed questions:
1. staggering of shelves - these shelves are staggered well from end to
end, but not from side to side. Three side-by-side pairs of 20X20 shelves
make up the distance from flue to door, with no two shelf pairs lining up
from front to back, though I have all pairs lined up side to side.
2. placement of the probe - the probe is through the door, which is fairly
tight -- two clamps on each side and one on the top in the middle. I can
wave my hand over the top of the door joint without losing any major hand
function, and the side joints show no glow at temperature. I need to pack
the bottoms, again, however -- I think there may be vandal air infiltrating
where the fiber shrank.
Questions:
- Should I stagger the shelves side to side as well? I was afraid for some
inarticulable reason of side-to-side unevenness if I did that.
- I've left an inch at the door side, an inch between pairs and an inch
from the flue wall and the flue-end shelves - is this inadvisable? Might
one try eliminating the possible chimney effect along the flue and door
walls? Seems like this might be leading my instrument astray...
- How about dampering? Assuming my flame is right, I seal the kiln well,
and I stagger like a drunk, how much of the flue cross section should be
blocked off for the right amount of backpressure? Or do you measure
backpressure as a given length of flame from a peep of a particular area?
- How about an ultralight loading? the firing that drove me to publish my
ignorance here was a wimpy load - maybe a dozen pots just to see if I could
get the rascal to reduce right. Will I only get good reduction if I bet
the whole kiln load?
Ready to wager as soon as the obvious problems are eliminated!
Jeff
Jeff Lawrence Sun Dagger Design
jml@sundagger.com Rt. 3 Box 220
www.sundagger.com Espanola, NM 87532
vox 505-753-5913 fax 505-753-8074
Malcolm Cooke on wed 1 sep 99
>----------------------------Original message----------------------------
>Hello Clayart,
>
>Experience is an awesome thing. Mel-sama and Louis Katz homed in on things
>that may well solve my reduction difficulties. Here is the requested data,
>followed by further questions stimulated by these informed questions:
>
>1. staggering of shelves - these shelves are staggered well from end to
>end, but not from side to side. Three side-by-side pairs of 20X20 shelves
>make up the distance from flue to door, with no two shelf pairs lining up
>from front to back, though I have all pairs lined up side to side.
>
>2. placement of the probe - the probe is through the door, which is fairly
>tight -- two clamps on each side and one on the top in the middle. I can
>wave my hand over the top of the door joint without losing any major hand
>function, and the side joints show no glow at temperature. I need to pack
>the bottoms, again, however -- I think there may be vandal air infiltrating
>where the fiber shrank.
>
>Questions:
>- Should I stagger the shelves side to side as well? I was afraid for some
>inarticulable reason of side-to-side unevenness if I did that.
>
>- I've left an inch at the door side, an inch between pairs and an inch
>from the flue wall and the flue-end shelves - is this inadvisable? Might
>one try eliminating the possible chimney effect along the flue and door
>walls? Seems like this might be leading my instrument astray...
>
>- How about dampering? Assuming my flame is right, I seal the kiln well,
>and I stagger like a drunk, how much of the flue cross section should be
>blocked off for the right amount of backpressure? Or do you measure
>backpressure as a given length of flame from a peep of a particular area?
>
>- How about an ultralight loading? the firing that drove me to publish my
>ignorance here was a wimpy load - maybe a dozen pots just to see if I could
>get the rascal to reduce right. Will I only get good reduction if I bet
>the whole kiln load?
>
>Ready to wager as soon as the obvious problems are eliminated!
>
>Jeff
>Jeff Lawrence Sun Dagger Design
>jml@sundagger.com Rt. 3 Box 220
>www.sundagger.com Espanola, NM 87532
>vox 505-753-5913 fax 505-753-8074
Hi Jeff
Sounds like you do not have enough back presure from the flue for a
steady light reduction. In a gas kiln any size proper reduction is
happenning with a light flame at the damper. The burners do not have
to be altered just leave then as for a normal ox firing. If you have
a flueless kiln an flame (generally Blue) and about 20 in high is all
that is needed for strong reduction starting at 950c. The flame when
you pull out the spy hole is not very big or strong either. I fire a
100 cub ft fiber kiln standard shelf setting this way it has air gaps
every where and this has no effect on the firing. Wood firing work
on the same principle the volume of the expanding gas in stoking
causes presure in the kiln which causes the flame to come out
everywhere and since there is not enough ox to fully burn the
expanding gas it reduces the atmosphere. I used to use an oxy probe
and after a few firings seeing what worked have not used it for the
last 10 years.
Regards
Mal Cooke
mcooke@tyndale.apana.org.au
http://www.spirit.net.au/~mcooke
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