jcjm on thu 2 mar 00
Joyce A. mentioned something about pit fires being more effective than
sawdust firings. I assume that means greater contrasts, deeper smoke
effects etc. Is this because of a more contained space and atmosphere? Is
there a big difference in temperature? Pit firers? Sawdusters? Can anyone
speak of their experience with both?
Thank you
j-m
Scott North on fri 3 mar 00
Hey j-m,
I have never done a sawdust firing in a barrel, but have done
several pit firings in the ground. I would guess that the pit firings have
the potential to reach much higher temperatures due to the greater exposure
to oxygen. The greater temperatures volatize the copper and other
materials more readily. The air movement caused by the temperature
differences within and around the pit move this volatized material. If
your hot pot is in the path of this material, then it gets flashed with
some color. For my last pit firing, I built an air induction vent into the
bottom of the pit with curved clay roof tiles. After firing for about 1
1/2 hours with redwood branches, the pit got so hot that some of the ash
melted into a glaze, and some of the copper carbonate melted onto the pots
and was reduced to metallic copper. Also lots of red and orange color in
dancing flame patterns. Less black, as all of the combustibles at the
bottom of the pit were thoroughly burned due to the vent system. The
dynamics of fire is a wonderful thing.
I use copper carbonate, ammonium ferrous sulfate, rock salt ( like
you use for making ice cream), and seaweed, in addition to wood and
leaves. This is a great way to get rid of dead Christmans trees.
Hope I answered at least one question. Scott
Scott C. North
Geology Department
Humboldt State University
Arcata, CA 95521
phone: (707) 826-3210
FAX: (707) 826-5241
Marcia Selsor on fri 3 mar 00
It gets hotter.
Marcia in Montana
jcjm wrote:
>
> ----------------------------Original message----------------------------
> Joyce A. mentioned something about pit fires being more effective than
> sawdust firings. I assume that means greater contrasts, deeper smoke
> effects etc. Is this because of a more contained space and atmosphere? Is
> there a big difference in temperature? Pit firers? Sawdusters? Can anyone
> speak of their experience with both?
> Thank you
> j-m
--
Marcia Selsor
selsor@imt.net
http://www.imt.net/~mjbmls
http://www.imt.net/~mjbmls/spain99.html
http://www.silverhawk.com/ex99/selsor/welcome.html
Martha Griffith on sat 4 mar 00
My experience with sawdust and pit firing is that you get different effects
from each. My Saw dust firing results in mostly black and gray with muted
coloration from the copper and salt, if used. More vibrant colors are
possible with pit firing because of the higher temperature. This can be
achieved by layering paper, wood and sawdust on the bottom then stacking the
ware on that along with more sawdust, paper, & wood. Top with more
combustibles and get a good fire going. Keep it at "bonfire" intensity until
all material is burning and colored flame gives evidence of the fire having
reached the bottom. We use kindling size wood for quick heat and some larger
wood for longevity. Then cover and let smoulder and burn. A mixture of
copper sulfate, soda, and salt is sprinkled throughout the layering which
will fume the pieces. Some I wrap in newspaper containing the salt, soda,
copper mixture and sometimes some sawdust. Experiment!
Martha
Clayhannie@aol.com
Richard Ramirez on sat 4 mar 00
My experience in sawdust and pit-firing, Richard Ramirez,"The Clay stalker".
My observation on both has been that pitfiring can a bit hotter then
sawdust. Taking a bit more to get it going in the beginning, keeping in mine
the size of the pit, depth and type of material using to burn and smolder,
and also active color agents for adding color. Most of the pitfiring that
I've attended and witness used bisque pots and are under and over
considerable amounts of material to be burn, not to mention the ingredients
we use to add color and "flashing." We usually add rather large burnable
material on top, and it quickly burns hot, starting the next material burning
downward until over a length of time, it reaches the pots with their color
agents smoldering in hot coals until it's all burned out and cool again. Keep
in mind that in a pit there is much insulated and reflective soil around the
pit which helps to heat and keep the heat localized.
Now as for saw dust firing. I use burnish, bone-dry pots, fine, clean
sawdust on ground level or small trash can, with plenty of drilled holes for
ventilation. Light with newspaper and watch for good smoldering embers. As
long as I see no flame, I'm sure my pots will come a shinny carbon black,
when all the sawdust burns away. Too hot and my pots break or have pits blown
away from the surface. Really enjoy the fragileness of those black shinny
pots. Anyone else do them that way? Thanks Ram.
Antoinette Badenhorst on mon 6 mar 00
There is a definite difference in different firing methods. The denser your
fire (not too dense that it dies before firing) the more heat. If it fires
over a longer period heat get a chance to build up.
I do not know if there is a real difference between pit -- and sawdust
firing. The difference come in how you control the fire. I have good
experience of firing in a pit in the ground (allows less air flow) and a pile
of bricks, loosely or closely packed together.
The less oxygen available for the combustibles to burn will force the fire to
take oxygen from the pots and that causes blacks and gray. If you make an
experiment and put copper sulfate on a clay shard and heat it with b blue
flame you will get a color change to reds and greens. If you take this same
shard and put it in a reduced atmosphere you will get the same colors, but
much more intense and permanent. This experiment proves to me that color
comes from a control between oxidation and reduction.
Sawdust was always part of my materials when I fire. If I loosen it up with
coarser combustibles, I get different colors, but since it may fire a little
quicker, I believe that the fire is cooler. I fire overnight though and the
ashes is still a little hot the following day at noon. I get wonderful colors
with no secret materials and chemicals.
I believe the hand that touches a pit is like a cooks hand that touches his
favorite recipe. It is not what you do, but the way you do it.
Antoinette. (who just experienced Vince`s way with bon fire)
| |
|
