The Downside to an Updraft and the Upside to a Downdraft

We fired the kiln from the last post, and it did pretty good. But the whole firing I was thinking that if it was a downdraft it would be way more efficient. As it was firing I kept imaging that the flame/heat was just going up the sides and out the top, never reaching the middle (which is where the pottery is). It did manage to reach a bisque temperature in only a few hours, but the firing was very uneven. A downdraft kiln will cause the firing to be much more even, and as I said before, more efficient. A downdraft kiln works by having the flue and the burners at the bottom of the kiln. The idea being that as the heat rises it will hit the top of the kiln and be forced back down to where the flue is. This causes the heat to work double, because it is touching the work twice instead of once like in an updraft kiln. So I decided to rebuild the kiln again and try to make a downdraft kiln. Simon Leach had done this to one of his electric kilns, and it seems to be working great (although his kiln is much larger than mine, but I’m told size doesn’t matter). The only thing holding me back was not having the materials to make the chimney that would be required. Lucky I have a good friend named Zack who just happened to have two spare kilns that he didn’t mind parting with. So now I had three kilns to play with. One of them was pretty beat up so I decided to cannibalize that one to make the other two kilns into downdraft kilns.



I started out by replacing the lid that I had cut a hole into for the updraft kiln, with the lid that had already fallen off the other good kiln. I then took the lid off of the bad kiln and put it on the other good kiln. I know that sounds kind of convoluted but it’s what had to be done. But then I had two kilns that where in good working condition.








I then started taking apart the kiln I was going to use for parts, this part went pretty quick.



After that I started work on where the chimney would go on the inside of the kilns. I did this by removing the part of the wall where the elements went; it was fairly easy with a hammer and a metal scraper. It did make a bit of a mess, and I would highly recommend wearing a mask or some kind of mask to help protect you from the dust.







I then had to decide on how I was going to build the rest of the chimney. I knew I was going to use the soft brick that I got from the bad kiln, but I didn’t know how I was going to put them in the kiln. My plan was to make these interlocking pieces that would go up the side of the kiln, and then put the larger bricks right up against them.



So I set out to make a bunch of these little interlocking pieces, and to cut the larger bricks down to a size that would work with those little pieces. Around this same time I was also thinking of how they would stay in place once they were all ready. I was going to use some of this old kiln wash that I was hopeful would act like glue. I was sadly mistaken; it didn’t work in the slightest. So I had to rethink the whole idea, and I was only going to be able to use the materials at hand. I don’t like the idea of buying materials just to see if something will work, if I could possibly use something I already have. That’s when I looked at the mess I had made while sawing through all those soft bricks.



It had made a lot of dust, and I thought if I could mix that with some slip (liquid clay) it would make a great mortar for the chimney. So I set out to make a lot more dust by grinding up the little pieces of soft brick that were sitting around. I used our blender to accomplish this task, because grinding them by hand would have taken forever (don’t tell Keturah, she doesn’t know and probably wouldn’t appreciate the time saving route I took). Just after I finished grinding all of the brick I thought I would need Keturah came home, and I showed her what my idea was for the chimney. She thought it was a lot more work than I had to do, and she suggested that I just cut the soft bricks edges at an angle so that the edges would be flush against the part of the kiln that I didn’t cut off. Of course she was right, and it would have saved me a lot of time if I would have thought of it myself. So I decided to make one kiln the way I thought of (mostly because I already had all the parts cut and ready for one of the kilns), and one the way Keturah thought of. Here are the two kiln chimneys. The first one is the one that I thought of and the next is done the way Keturah suggested. In the second one you can see the (barely) the hole at the bottom of the chimney to let the heat escape.





By this time I was feeling pretty good about myself, and decided I was done. As I was walking back to the house I thought to myself “Now how will the heat get out of the kiln…”, and then I realized that I forgot to cut the hole in the lid to complete the chimney. So I head back to the studio to cut some holes in the lids of the two kilns. The green stuff you see around the hole is chromium oxide, which I use in addition to a coil of clay to help me know where to cut the hole. I put the coil of clay around the top of the chimney, and then painted the chromium onto it and while it was still wet I closed the lid. This left a green mark showing me where the hole needed to be cut.





After this I was done, and I went inside to eat lunch and write this blog. Although as I’m writing I have realized that I forgot to cut the burner port out on the new kiln…

I know this has been a long post but if you could hold on for one more paragraph I would appreciate it. My friend Andy is participating in a fund raiser for Leukemia and Lymphoma Society. He and a number of other artists each made a limited edition print that are being auctioned off on EBay. So if you get a chance please go and check them out and if you can make a bid, it’s for a good cause. Here is a link to Andy's print, and a link to the prints by the other artists.

A Kiln is Born (well reborn really)

So today I started work on converting my electric kiln into a gas kiln. It went pretty well if I do say so myself. I haven’t had a chance to fire it yet but I’m very optimistic about it reaching at least a bisque temperature (which is about 1850F/1010C or 1283.15 Kelvin). I started this project by cutting a way a circle of the thin metal that surrounds the kiln near the bottom. I was hoping to be near the floor of the kiln without cutting into the actual bottom. I was not successful in avoiding the floor, but I realized this before I cut into the floor. So I had to move my hole up about two inches which was fine, although now it looks a little goofy. I used a hammer and chisel to cut through the metal and the soft brick, I was originally going to use a drill but I didn’t have one big enough and the smaller one I did have was having trouble getting through the metal. Here is a picture of the resulting hole for the burner.



After running amuck on the burner port I moved onto the flue. Which in this case is a hole roughly the same size as the burner port. This hole was also created using the hammer and chisel method, although it turned out better because I didn’t have to worry about cutting into anything that I wasn’t supposed to. I beveled the edges (inside and out) to give the flue a more finished look, I didn’t want it looking unfinished you know.



I will be using a kiln shelf to open and close the flue to help regulate the temperature inside the kiln. Also this will help when I attempt my first high fire reduction, which I have never done with an updraft kiln (which is what this type of kiln is now, basically the heat/exhaust goes from the bottom through the kiln and out the top).



Here is a picture of the kiln with the lid up, so you can see both the flue (at the top) and the burner port (at the bottom).



I have two venturi burners that I acquired through my journeys as a graduate student. I plan on using one of them for this kiln, I believe it is small enough that one will be enough, but if I need it I have the other one waiting in the bullpen. I did need to find some pieces so that I could connect the burner to a propane tank (I’m using a small tank similar to the one used for barbeques).



This is the first piece it’s a 90 degree 3/8 flared nipple, I wanted a straight one but lowes didn’t have any and that’s where I work so I didn’t go anywhere else.



The next piece I needed was the regulator that attaches to a barbeque propane tank.



This was attached to the burner via the nipple, and here is the finished burner all assembled and working. I fired it up just to make sure it works, and managed to burn some of the hair off of my forearm in the process.



I’m hoping that it rains here for the next few days because I know we need the rain. But at the same time I’m hoping it doesn’t because I would really like to see if this setup works. I was going to fire it today but I might as well have it filled and ready for a bisque load when I do, so I don’t waste the fuel. I wish I would have had the fore thought to make some cone packs before today, but I didn’t so now they are drying out so they don’t explode in the kiln. The cone packs are used to determine the temperature in the kiln. Each cone is design to melt at a specific temperature. I use four of them so that I have an idea of how much longer the kiln will need before it’s finished.

How Does Our Garden Grow…

Our garden is growing nicely these days. Some of our plants are starting to flower, which is very exciting. Although some of our other plants are not doing so well. Take our corn for instance; our tallest one is only about 2 feet tall while the rest of them are struggling to reach a pathetic 6 inches. This doesn’t stop them from trying to grow full sized ears of corn (ears that are getting to be bigger than the plants), some of them are even trying to grow multiple ears. They are all (all but one) looking pretty sad, here is a picture of the one that is the most respectable out of the lot.



Here is a picture of the first flowers to pop up on our many tomato plants.



This is the first of our pepper plants to flower; I believe this one is the bell peppers.



This is the first sunflower flower to open up. These guys are looking pretty sad as well, although I still hold our hope for them unlike the corn.



And finally here is one of our lettuces; these guys are getting quite large. I’m actually surprised at how well they are doing. It looks like these will be the first things we will eat out of our garden.

A Dirty Wheel is a Happy Wheel

At least that’s what I always thought; although it might not be that healthy (all that dust isn’t good for the lungs you know). Anyway, work is being produced!! And here are some photos of said work, check it out…





These first two pictures are of some orchid planters that I threw for Keturah to carve into. As you can see there are quite a few of them, and she’s a bit over whelmed.



Here are the four that she has already carved into, and they look great I think.



This is a photo of some cups (obviously) that I made just the other day. I have always been bad at handles but I think these ones came out okay.



This last photo is of some butter dishes and some Japanese style tea bowls (these are my favorite type of cup to make, mostly because there are no handles). Anyway, that is the work so far, it’s taking quite a while for me to get back in the habit of working in the studio, but I’m gaining momentum. Next big project for me is to convert my electric kiln to a propane kiln, it should be fun!

Oh, here are some stamps I was making the other day with some old wire tool handles and my dremel tool.