If you don’t want brick, then I’d build something like the kiln that Peter Ilsley described at the workshop in Palm Springs. Basically, it’s a square box made of wide mesh steel screen and kiln fiber. At this point, you’ll at least have more of a cross draft kiln to work with.
Holly McKeen built one like this, so you could talk more about this with her.

I personally hate dealing with kiln fiber, so I would suggest that you at least consider the magnesium silicate fiber (Isofrax, Unifrax). It is supposed to be a More lung safe (”low lung biopersistence”) alternative to the nastier ceramic fiber that’s more readily available.

After saying all that, a trash can lined with the same fiber above would be by far the most portable. So, if you want to practice the updraft approach, give it a go!

Let me know how things turn out…

~jesse.

I looked at your site. I really like the kiln you created and have access
to a great deal on a used kiln.

It looks like you are using gas, could you use propane in this design?
Would you be willing to share info on how you created this. I would like to
try to implement your design or something like it so I do not have to deal
with a fiber kiln. I hate working with fiber. Plus, I have no idea how to
create a kiln! But, I totally understand if you do not want to share the
info. Would love one of the Geil kilns, but way out of my price range.

I will start experimenting with the recipes. Thank you for the starting
point. My glazes either had too much copper or not enough. This should
help.

After thinking through this and realizing how little I know about building kilns, I have asked a person in Chicago to help me. I really need to assemble something portable so I will not be able create something like your kiln.

If you had to pick would you use a old electric kiln (use it upright) 28 X 21.5. and convert it to use propane or would you build a fiber kiln. I am concerned that the electric kiln will not cool during reduction just like my problem with the Alpine kiln.

I can purchase the electric for about $200!

Thank you for the help,

Anne

Looking forward to seeing some copper reds one day! It is a fun journey,
keeps me challenged.

If your kiln is large and heavy with insulation, it will cause problems. Along those same lines, a kiln that will reduce down nicely from higher temps, may not do so well from a temperature 700-800 degrees cooler.
I remember Diane Creber telling me last year about how much of a chore it was trying to reduce down from 1500F in her larger gas kiln. It may be that even if you shut off the fuel completely at that temp, your pyrometer would drop slowly –so by adding fuel, well…
But hey –I’m not saying it’s impossible!

When I speak of timing how long it takes for the smoke from a scrap of oily rag to travel from the burner to the end of the stack, most people just return a blank stare.
But the rate at which your fuel is traveling through the kiln matters significantly, and the rate achieved at 1500-1100F will be different from that at ^9/10.
It’s not that I can say: ok, it takes x# of seconds for the atmosphere to move through my kiln and I get great reduction, thus giving you the info that you need to do the same. My kiln is built different, having twice the proportional distance for the flame to travel when compared to other downdraft designs. This same design might not work well if it were larger –but kilns built, tested, and modified for specific applications will obviously hold a much greater chance at succeeding.

So, in terms of choosing/building a kiln for post-fire reduction, I would suggest some sort of lightly insulated, small chambered downdraft… Back pressure can be achieved in most any type of kiln by using a damper, but there’s more than just back pressure at work. Terry and I were just talking a few weeks ago about the benefits of the fuel/flame traveling a greater distance before reaching the oxy-probe/sensor (and more importantly, the glazed work).

I know this reply may seem frustrating –and my first several firings were exactly that!
If I were you, I wouldn’t waste any more good work. Throw some basic cylinders about 8-10″ tall, glaze and fire them in with your crystalline firings. Use a glaze with 1-2% CuCO3, and practice post-firing with these. They’ll tell you what kind of reduction your getting, or if you’re getting any at all.
Especially if you’ve got a larger kiln, the glazes will be more honest than a statically positioned oxygen sensor. Do keep notes of your sensor’s readings however, as the numbers will make sense later.

1. After two firings, I can not figure out how to reduce my Alpine kiln temperature while reducing at the same time. Finally gave up after firing to 1500 and dropping only to 1380. I turned the kiln off and blocked all sources of oxygen. At the end, before I shut down the kiln, I had the blower off, all primary air ports blocked, gas at 0.2, and damper at 3/4″. How in the world do you drop temp and reduce at the same time!! Is it possible in a gas kiln?

2. I used an oxygen sensor that Terry designed using an auto sensor. It worked great, but the only time I saw a reduction range on the voltmeter was when I had a small red flame with a little smoke. Does this make sense? I am use to a strong orange flame when reducing in my cone 9 firings.

3. Had 10 pots in this firing. The attached picture is the best I received. Most of the pots were gun metal (they had over 4% red copper oxide alone or silica carbide or ilmenite in with the copper). I torched all these to get some great raku-like crystals, but really not what I was going for.

4. I think my gas kiln is far too large to ruin so many pots at one time! Probably move onto a garbage can or fiber kiln of some kind. Any thoughts on which design you would try first?

The experimenting continues and I am having a great time. I think I would be pulling my hair out if my livelihood depended on these crystalline glazes. So much to learn, so little time! Thanks ahead for your help.

______________________________________________________

Jesse Hull says:

Thank you David,

Your own “smoked” work (as Phil calls it) looks really nice… that recent piece on Phil’s site is a pretty brilliant red.

I have tried using wood in post-firings… but I was usually only able to get the heaviest levels of reduction with it. The more subtle iridescent colors I aim for, as with the redn’d rainbow glaze are lost, replaced with an overall blood red.
This past summer (after returning from South Korea) I did some complete ^9 wood firings in the kiln pictured on this page. The first attempt was surprisingly good… the second not so much. Because I don’t actually have a firebox to work with, the entire firing was a constant process of adding wood with little down time, and I ended up having to rebuild my chimney (stack) after the 2nd run.
I do understand that what you’re speaking of in terms of using wood is different, but I thought the above might be interesting to you nonetheless.

As you mentioned, getting the back pressure is key …just running excessive amounts of fuel/combustibles through a kiln won’t do much, even if you’ve got flame and smoke pouring out of the exhaust. Then there’s the thought that if you’re actually producing smoke, then your reduction effects suffer.
You mentioned a kiln sitter… I also fire to a cone, although of the upright self-supporting variety, using a 2″ spy hole that I cut into the front door.

I actually did a full slide presentation at Krystallos 2007 on the creating (and later amendments) of my post-fire kiln, also covering how I fire and even adjust the kiln for barometric pressure, etc prior to each attempt.
Time is short -but at some point, I do plan on putting all of the images and info from that presentation up on the site here.

~jesse.