Some of you may have heard me rant and rave about my wood fired Mr. T mug, or prostitute cup, or my little evening beer cup. All three of these were the work of Mr. Kyle Houser - aka Homefry. A potter up north whose work, Gina says, I have a pottery crush on. At the very least, he may be one of my brothers mysteriously seperated fom the family. Check out his two shops if you haven’t already.
Mr. Homefry has been awfully generous with his advice. I, being new to reduction/gas/soda/atmospheric firing and all, had a few questions in my head as to “what is happening” in there at 2300 degrees. Sure, I’ve got the basics, I’m book learned and what not. But there is a real difference in understanding of the combustable happenings inside a kiln when you’ve only fired a dozen times compared with someone who has fired hundred of times. So given the chance, I asked a few questions I had been percolating on, and he responded with some great insight for this fledgling newbie. Here’s how the discussion went:
Keith said:
I think I’m looking for a little affirmation on my theories on my firings. So… I never fired a soda kiln before my little baby in the back. It’s funny, I learn so much with every firing, I’ve had 9 so far. My first load I thought I wasn’t getting reduction. Turns out I think I was getting good reduction. Cause now I’ve switched to Emily Murphy’s soda mixture which I dump in the firebox and I’ve gotten a nice variation in tones (greys and warm reds), which I really dig. What I didn’t realize is that soda turns shinos and other glazes grey, and I think all the soda I was spraying was muting the warm tones I was looking for in those first few firings. So now I think I am creating too much of a reduction atsmosphere because I was over compensating for something that was really the problem.
That leads me to qwestion numero uno: Is there such thing as too much reduction?
I use all porcelain, no stoneware, so I shouldn’t have any issues with black cores. But the last load, I was really dissapointed in my flashing slipped pieces (Orange Bauer, Tile 6 slip, and a Shino Slip), although the shinos looked hot! My theory is that the soda is attaching to the glazes more readily (the shinos and oribes hog it) and not leaving any soda flying free around the kiln for the slipped pieces. The pieces on the top shelf were flashed & glazed pretty well, but other shelves only got it on the edges and had a bunch of plain boring white showing.
Here’s my plan for the next two firings, let me know if this may make sense.
I’m gonna fire two different loads. One will have shinos and oribe glaze using the Emily recipe for soda. I’ll do my normal heavy reduction at 1500 for carbon trapping (which has been coming out very well).
The other will be flashing slips and some glazed pieces on the bottom and insides. I’ll use both emily recipe and some spraying of soda. I won’t do a body reduction on this load but still keep a reduction going into higher temps - in hopes my colors on those other glazes will come out a little brighter since the underlying porcelain isn’t grey.
Whatcha think? I think I was trying to do too much with one firing schedule, and I am better off splitting it up.
My real question is how do you get nice soda build up on plates? I saw some plates of yours and a few on emily’s site and it looks like they are fired stacked (I see wadding marks). Anytime I’ve done this, most the plate is white, let alone flashed or has any soda on it. My draw rings (porcelain) are telling me that soda is building up - a lot, but none of it gets on the plates or anything remotely shaded. Do I have bad circulation in the kiln? Should I pack looser (I come from an electric school of thought that a tightly packed kiln is better - maybe not so with soda). Will splitting the firings help?
Now I have seen I have written too much, and I’ve probably cashed in my alotted homefry time for the year. One last question, now that I see what I’ve written. Would you be comfortable with me posting this and then your responses on my blog?
Much appreciated!
-Keith
Homefry replied:
ok,so sit back and get comfy…First question…man, do you get free gas? I ask because I do know the expense of firing a gas kiln these days…some friends of mine who live in more rural areas here in Pa do get free gas…so as a real cheapo I wonder do you really need to split the firings…
my experience has been that all kilns seem to have their own firing rhythms and that goes for direction inside the chamber too. The Bourry box kiln that Nancy and I fire is similar to what you explain when talking about where the soda seems to hit…the top gets the load of ash and soda, that seems to carry over the inside of the arch to the oppisite wall of the bag wall …the top and a few shelves down really benefit. The pieces immediately in front of the bag wall get nailed with stuff and that is true for that whole side…but it is the pieces lower and more in the middle that only get slightly touched by the soda and fly ash.
ok, first thing, soda is very directional and doesnt consitantly vaporize like salt would inside your chamber…instead it will travel more in a line with the flow of flame,etc. So a looser packed kiln or a kiln that is strategically loaded might increase the benefits of the use of soda. We use a soda mixture and introduce through the firebox as well as a port that is next to the bag wall…directly over where the flame comes into the chamber. That is also another possible solution…have a port in your chamber where you can introduce soda mix to those hard to reach places. Like many wood kilns have side stokes in the chamber to directly introduce wood right next to the wares…I have even seen people put a little container of salt/soda into the chamber…like in the lower middle. This in theory might mean that the soda will vaporize in the nether reaches of your kiln…I dont know…and yes, too much soda/salt turns the work grey and muddies the color…some people dont seem to mind. I guess it is about what you want out of the work…juicy color…orange peeling texture.
In our last firing we fired about 5 different clay bodies…Nancy and I both love stoneware…we do alot of rough altering of the work and stoneware seems to be much more loving when this is happening. But we are soon to be trying out the new Jack Troy Porcelain that our local clay co. is now making…the Jack Troy stonware was so creamy and nice…it exhibited many qualities of porcelain… and seems to blush well on its own due to the helmer content. A looser more course clay body will hold onto the soda and ash and really show the build up well…a tighter body will repel it more and you may be seeing runs more or just real juicy glazes. This can be witnessed by looking at my last kiln load. I used a course clay body for a bunch of the cups I put in the last firing and they caught the atmospheric stuff flying around on the surface great… and the more smooth,tight,stonware body gave me the warm tones and very bright and juicy glazes without the soda/ash build ups…I like both, and now know pretty conclusivly what types of clays will give what types of results in the wood kiln.
so, plates…I think that goes back to soda being directional…and trust me, its hard to get a good blushing on the surface of flat stuff sometimes. I think the soda just rushes over without really smaking into the surface area. I do stack my plates…we use a special wadding mix that includes red art clay. This is helpful…check my set of plates out on the etsy…leaves nice red marks most of the time and helps the glaze around it blush some. My plate surface is a white ostreich shino…it will blush nice in good reduction…and we reduced more than usual this last time. Heavy body reduction and continued lighter reduction in the higher temps. But it is tough to always get that on a plate surface…maybe creative wadding could help…wads higher on one end so the plate sits at a diagonal. who knows?
…and that leaves me with your main question…is there a thing as too much reduction…I do not know, but I will say for me …Yes. I have seen other people whose wood fired pieces look like the kiln was in reduction the whole time and I do not like it. The body is dark and the glazes all went crazy and there are weird colors more associated with a reduction gas atmosphere. I believe there has to be a balance. In my wood fired work I want warm juicy colors…I want my greens and blues to come out green and blue and not reduce to a red or purple. I use a helmers flashing slip that is very reliable when applied thin and just a few shinos that I know are what I am looking for. To some extent I want a little control over the look. Nancy and I control how the kiln is fired no matter who else hangs out and helps…so as to not always have the kiln in a state of heavy reduction. I have learned alot from her about really watching,listening, and trying to get what you want from a kiln that seems to have so many variables…holy smokes…im going to stop here…hope that has helped or at least shed a little light on stuff…and as far as splitting the firing, I do not think that the glazes take the soda away from the flashing slips…so unless you are getting free gas…I wouldnt split the firings…try placing the slipped pieces against the walls or near bricks in the kiln…that might work some…did I say Im stopping…NOW im done.
dude, that was a big one.
K
