Friday, December 30, 2005

We Live in Interesting Times

We fired the raku kiln today.


After a raku session, there is a smokey odor that you carry with you. Its almost a sweet, carmelized smell, which may come from the partial combustion of newspaper.

We rented the use of the raku kiln at The Ceramics Shop, down in Philadelphia. We have to drive across the Betsy Ross Bridge to get there.

Their raku kiln is behind their building, which is an old, four or five story red brick building, with foundations made of cut stones covered in concrete. The kiln sits in a brick courtyard, surrounded by tall buildings, and is accessable by a flight of wood stairs out the back of the building. The courtyard is lower than street level, and also plays host to a rusty swingset, several wooden lawn chairs, and a planter made by cutting up an old automobile tire, and painting it white. The back of the building is panes of glass, held in wooden frames. Most of the windowns have sheets of plastic screwed over them, but some are left uncovered, and, in some places, the wooden frames have rotted, and the panes fall out.

My first task of the day was to sweep up some broken glass, a pane that had fallen out of a window, and broken at the base of the stairs. I borrowed a broom, dustpan, and a cardboard box from Mark, the shop owner.

The kiln sits under a sort of awning, built out of two by fours, with an old camper shell for a roof. The raku kiln is a converted electric kiln, and sits on the same red brick that the courtyard is paved with. The first course of kiln above the kiln floor is made from soft kiln brick, which has been cut to match the octagonal base of the kiln, with a hole cut for the gas burner to fit in. There are two steel cased rings of kiln, the remains of the electric kiln, including the heating elements inside. The lid is fashioned from ceramic fiber, a matted, white material, with a sheet of rusted metal mesh on top, with a hole in the center to act as a vent. Inside the kiln, two kiln shelves are supported by a set of kiln bricks. One of the kiln shelves has cracked into two pieces, and there is a heavy residue of glass in a few spots from the previous firings of the kiln. We remove the kiln shelves, and paint over the glaze spots with fresh kiln wash. We then put the shelves back in the kiln to dry.

Off to the side of the kiln, but still under cover, are there metal trash cans, covered with their lids. One lid is missing the handle. These are the primary reduction chambers. Once fired, the hot pieces of pottery will be transferred from the kiln to the reduction chambers. We have brought sawdust, newspaper, and shredded documents (aka, 'shredded secrets') from our home office to place in the chambers, to ignite when the ware is placed amongst them. A fourth can sits off to the side, and has a large square of plywood on top. Julie and I use it for a table. A large bucket sits to the side, full of cold water.

On the table, I place two shiny new gallon paint cans. When I rakued in California, Jan Babcock developed a technique for reduction using paint cans and corregated cardboard. It works well for smaller pieces and heavy reduction. I have brought them for my rockets. I have two with me. Julie has two dragon pots, and we also have three test pieces.

We turn on the gas, and light the kiln. The kiln is run from a large propane tank, maybe three times as tall as one found on a home grill, but the same diameter. We place a digital pyrometer through a small peep in the wall of the kiln to monitor temperature. We fire the kiln to about two-fify degrees fahrenheit, then kill the gas. This is to dry out the kiln wash on the kiln shelf, and the fiber in the lid of the kiln.

We reopen the kiln, and place in one rocket, one dragon vase, and three test pieces. The kiln had room for more, but we spread things out, and didn't want to be too rushed when the kiln is opened. I relight the kiln to start the firing. Julie and I then start to prepare the 'nests' in the reduction chambers.

I show Julie how to take a double sheet of newspaper, wet them, and drape them around the rim of an open trashcan. This makes a tighter seal when the lid is slapped on. It takes four doubled sheets to go around each rim, and we prepare two of the larger chambers. We take several sheets of newspaper, and rip them the long way to make long strips of paper to place in each chamber, shaking them into the chamber to spread the strips out. Once a pile of strips is in the chamber, they are spread out to make a birdnest shape. Shreaded secrets are sprinkled on top, to aid in quick combustion.

We watch the pyrometer. Whenever it slows to the point where it takes several seconds to increase a degree, we boost the gas pressure a little. Eventually, so much gas is entering the kiln that flames start to lick out of the vent hole, the cracks in the kiln brick, and back through the opening where the burner fits in. There isn't enough oxygen in the kiln to burn all of the gas, so some of it is burning after it leaves the kiln. The interior of the kiln is in a reducing atmosphere. Taking with Mark afterwards, we could have prevented this by moving the lid of the kiln over a little, to allow a larger vent hold to form at the edge of the kiln. The exterior flames would have died out.

We can peek slantwise through the hole in the lid of the kiln to inspect our pieces. At first, everything is fairly dark in the kiln, with a glow coming from the combustion taking place below the kiln selves. As the temperature rises, the interior of the kiln, and the pieces it contain, start to glow orange.

Julie and Steph make a run to Wendy's to get burgers. By the time they return, we have enough time to start eating before the firing is complete.

We have the best visibility on Julie's dragon. We can see reflections in some of the glaze on the vase.

The kiln reaches our target temperature. We had chosen 1828 degrees F, which corresponds to cone O6. Julie puts on one of our gloves, and turns off the gas valve. We wait a few seconds for the flames of combustion to die out.

We use two pairs of long handled tongs to remove the lid of the kiln. Julie has a three foot long pair of simple tongs, with a single pivot. Mine are articulated scissoring tongs, and are a little harder to use. We place the lid on top of a hard lid, the former lid to the electric kiln that had been removed.

The pieces are glowing orange hot; some of the glazes look shiny. There sounds of cracks and pings as they start to cool. We have to reach into the kiln with our tongs to pull the work out, but we encounter problems from the excessive heat. I give Julie the other glove, and she the pulls her dragon vase out. I was going to help spritz water onto the piece to promote cracking, and got off the first shot from my spray bottle, when Julie asks 'How come the glaze has turned green?'

My brain shuts down. Her piece is supposed to be a deep red, but it looks minty green. I'm clueless. She places her piece into its nest, the paper burst into flames, then she puts the lid on, and hands me the gloves. I fish out my rocket, and move it to its can. After fiddling with the lid a bit, I get it sealed. Greasy gray smoke curls around the lid of the paint can.

I give Julie back the gloves, and she places two more test pieces, drafted rocket chucks, into another of the larger reduction chambers, and seals the lid. I move the last test piece, a little vase, into the second paint can, and slap on the lid.

First firing is done.

We allow the kiln to three hundred degreeds before reloading. One more dragon, one rocket, and two test pieces. We fire off the kiln, then wait to inspect the cooling pieces. Julie's dragon vase is mysteriously minty green instead of deep crimson. The other glazes made with Mason Stains have held their color, but not the Deep Crimson. She had used a glaze called alligator matte for the skin of her dragon, and it had lived up to its name, breaking into cells and rectangular shapes. I had moved my rocket so fast to the reduction chamber that I had forgotten to allow it to cool and heat fracture the glaze. My white crackle was a seamless white.

We wondered if we overfired the kiln.

The second firing was taken to 1730 degrees F. We had more strange results. The following two issues need to be resolved before the next firing:

1) We mixed up a base glaze to use with Mason Stains. The base glaze was 80% gerstley borate, and 20% cornwall stone (by weight). I mixed in 25%, by weight, of Deep Crimson Mason stain. We fired twice, once taking the kiln to 1828 degrees F (cone O6), and the second time taking it to 1730 degrees F. In both cases, the glaze came out mint green instead of red (or deep crimson). We had success using Lobster and Tangerine Mason Stains on test pieces, as well as the Florentine Green in the same manner (25% by weight). The one caveat that we have is that
the kiln might have been under heavy reduction for the entire firing cycle for both firings.

2) In the same two firings, we had samples of Seth's Luster that I had had mixed up for us. At the higher temp, Seth's came out almost black, with a really rough surface. At the lower temp, we have two samples, one where Seth's was thick, and the surface is really rough, and the collor looks like bad corrosion, with one or two drops of bright copper color. The other is where it is rough, very matte, and a deep blue color. I seem to recall Seth's needing to 'age' a bit after mixing the dry glaze chemicals with water, but that might be a recollection of Floating Blue.

We have sent an email off to Vicki, my former instructor in Georgia, to ask for her advice.

I've posted pictures of two rockets and two dragons on the flickr pottery photo site. You can access it in the links column on the right side of this page, right above the flikr badge that shows preview of our pictures.

Thursday, December 29, 2005

Tomorrow's Forecast: Smoke and Flames

We called The Ceramics Shop, found out their hours for tomorrow, and chatted with them about the availability of their raku kiln.

We are scheduled for a raku firing tomorrow.

After a quick trip to Home Despot for buckets, empty paint cans, and sawdust, I started mixing our raku glazes:
  • A two gallon bucket of Seth's Luster.
  • A two gallon bucket of white crackle
  • Four 160 gram batches of Louden's base, with 25% of the following mason stains: Deep Crimson, Tangerine, Florentine (green), and Lobster
  • The Beads test glaze
  • Laguna Clay Raku Glaze Black Laquer
  • Laguna Clay Raku Glaze Dark Red
  • Laguna Clay Raku 'Mystery Glaze' (suspect that it is glaze called Lithium Slip)
  • Discovered a fourth, smaller bag of Laguna raku glaze - Awabi Shell

Needless to say, we had a lot to choose from when we started glazing. I did two rockets, and Julie did two dragons, and four test pieces to see what the glazes will do.

I'll keep everyone posted on the results.

New Pictures Up

Uploaded some more pictures, most of them Julie's dragon work, but a couple of other pieces.

Quieter than Quiet Time

Its raining. Stephanie says that, at school, everything seems quieter when its raining, including Quiet Time.

Yesterday morning I trimmed the last raku vase, and Stephanie joined me in the studio for a throwing lesson. She had thrown with success before, using a tabletop potter's wheel that Julie had found on eBay (with a wonky pedal that essentially had two speeds, off and full throttle.) For her first time with a real wheel, she did okay.

For her first two cylinders, you can see progress being made. She then asked to 'play' with a piece of clay on the wheel. After the first minute or so, I had to force my self to stop watching; she was playing, not seriously trying, and everything that she did was wrong for throwing a piece. A few times (like when she grabbed the clay with both hands so tightly that it sheared off the wheel) I intervened to get her over a frustrating moment, and explain why what she was doing was not going to be productive. We chatted about the history of potter's wheels, which go back something like four thousand years. I imagine that there have always been times over that history when a student starts playing around, and the master needs to look away. I also imagine that new techniques are developed by someone 'playing around', and not following cannon clay techniques.

We closed out the session with covering the wheel head with slip from the splash pan, and then drawing patterns as the wheel turns. Mainly single and double spirals, but also concentric circles, too.

The mess in the studio was horrific, especially when I missed that one half of the splash pan was up to the connecting tabs with slippy water. It spilled over the wheel and floor when I pulled it apart to clean it.

Julie unloaded the bisque kiln yesterday. It was loaded about a quarter of the way with ware.

Today I must mix glazes.

Tuesday, December 27, 2005


Trimmed two of the pots, the 266 piece, and one of the raku vases.

When I pulled the 266 piece out of the damp box, the rim was uneven, like it had slumped a bit. I ended up having to trim the rim down a bit, so that the step for the rim was no longer usable (I trimmed it away). So the piece is now a vase. I'll try again tomorrow.

The last vase sits on the wheel head, wrapped in plastic. Steph came down to chat for a bit, then I cleaned up, changed into my jammies, and we played a drawing game (Oodles of Doodles) that she got for the holidays, before she went to bed.

Mousewash: Makes Your Mice Squeeky Clean

Cleaning up the studio for a bit, today. We were running into an organization issue, where the place we kept drying ware was invaded by bisqued pieces, and there was nowhere to put glazed pieces. I worked at consolidating some of the 'marginally pottery-related' stuff to fewer shelves, including the use of the top of the damp box. We now have four cleared shelves, one for bisque, one for glazed, one for drying pieces (before they go to the garage shelves), and a spare shelf for whatever overflows.

I ran across a canopic jar that I made back in Atlanta, after I totalled my Honda CRX as part of a five-six car pile-up on the 75 on a rainy evening. I slid into a Mercedes, and then was hit by a pickup at 55 mph. My car was barely drivable, with the hood and rear quarter buckled, but no broken glass, so I limped it back home. I called the insurance company, and they wanted me to bring it in to an inspector the next day. I spent about two hours cleaning the inside and outside of the car, including using Armor-All on every interior surface and the tires. The car looked like new, if you ignored the crushed up bits. The one comment that I got from the insurance company was that it was obvious that I really took care of my car.

The canopic jar is thrown with 266, and has a craving of Anubis driving my CRX off to the underworld. There is a mystical eye on the front left fender of the car, and the color had changed from red to green. Wound around the mouth of the jar is a snake. I had planned to glaze the piece in a white crackle, then heavily reduce the pot out of the raku kiln to get the glaze to turn transparent.

Julie has a bisque kiln going in the garage, preparing for our raku firing this week.

I plan to return to the studio, and throw some more. Julie wants a big planter for one of our indoor plants, a Dracaena Marginata that sits in our family room. The planter will measure about twelve inches wide by ten high, and have a saucer to catch any extra water, and will be throw with Cassius. Julie will add twining dragons to the piece when it is trimmed.

Monday, December 26, 2005

Boxing Day

Returned to the studio this afternoon.

The two raku test pieces were bone dry; it appears that when we open the vents to keep the studio warm in the winter, then the damp box doesn't work as effectively. The dryness of the pieces isn't really a concern with these, since I didn't really need to trim them. We plan to glaze the test pieces, along with all of the throwing chucks from my rockets, to use as raku test pieces.

I threw two raku vases. On the first, I got things a little too thin about two inches from the lip of the piece. I collared the piece in at the top, and was starting to finish the lip of the piece, when the weakness of the wall caused the piece to start to collapse. I saved the piece by trimming everything above the weakness off with my needle tool, so the piece flares out instead of closing in, and looks like a vase for a dozen roses. Since the raku piece is never vitrified, it can't hold water, so the vase can only be used for dried flowers.

When I throw a cylinder, the mouth tends to flare out. After I raise the walls, I end up going back to collar the piece back in. I tend to pull the clay with my inside fingers above my outside fingers. Picture looking down on a piece on the wheel, the pot looking like a circle. I'm pulling from the foot to the rim of the piece at about the four o'clock position. The second joint of my left pointer is wrapped over the top of my thumb, and the length of the second joint is in contact with the piece on the inside of the pot. The fingers of my right hand are held the same way, but on the outside of the piece, but held a little lower. I can feel my opposing hands through the wet clay. As the wheel turns, I'm compressing the clay between the second joints of my pointer fingers, and drawing my hands evenly up. This is raising a wave of clay from the base of the piece into the walls.

What I remembered on my second vase was that, as I raised the walls of the piece, I could change the position of my opposing hands so that the inside fingers were below the outside fingers. What this does is reverses the flare at the lip of the piece as I finish each pull, so that the walls of the pot curve inwards at the rim.

I switched from raku clay to 266, and threw another piece. It is a lidded vase, with the opening for the lid only four inches across. It took me three tries to create the step inside the throat that the lid rests on, using three different techniques. I finally suceeded when I used the right angle in one of my ribs to push outward from the inside of the rim. I measured the opening with a 'lid master', which is like a double ended pair of calipers, one for measuring the inside of a piece, the other for outside. I then threw a domed lid. I asked Julie if she would put one of her dragons on the piece. My plan is to glaze the piece in Floating Blue, with the dragon left unglazed. The finished piece will be a rich blue, with everything unglazed being like a bittersweet chocolate.

A mug was the last piece I threw, since I had a little piece of clay left over from making the lid. I put some lines around the rim for decoration, and will pull a handle for it tomorrow.

Friday, December 23, 2005

The Need for Test Pieces

When going through the studio, I found three paper bags that must be fifteen or so years old. I had bought them years ago, when I still lived in Glendale, California, and threw at the Youth House. They are three dry ruku glazes from Laguna Clay Company.

One is called dark red, the second is black lacquer, and the third lost its label sometime in the five or so moves since the glazes were acquired. It might be a glaze called awabi shell, or it might be lithium slip.

We have seven raku glazes. Four of them we have no idea what they will look like, and the fifth one is a base to add mason stains to, so it can be one of four different colors (basically, shades of green or red).

I went returned to the studio this afternoon, and threw again.

Two tallish, quasi-vase like shapes. I put slow spirals into the pieces, so I can see what different thicknesses of glazes accomplish.

The plan is to trim them tomorrow, and then let them dry until early next week. We will do a bisque firing early next week, and then take a collection of glazed pieces down to The Clay Studio for our first raku firing.

Julie has been saving the bits from our shredder for use in the reduction chambers. Our shredder puts out diamond shapes shards of paper.

Wednesday, December 21, 2005

Turkish Delight

Steph started reading "The Lion, the Witch, and the Wardrobe" a little over a month ago.

I awaited the question, the same question that I asked my Mom when the book was read to us in grade school:

"What's Turkish delight?"

My vision as a child was that it was a candy, shaped like slices of turkey breast. There was a frosting glaze over it, and maybe some designs drawn with dark icing.

She got to the part of the book where the Queen gives Edmund Turkish delight, and asked the question.

We ended up doing a google search together, to find pictures.

Think blocks of gelatin, flavored with fruit juice and zest, dusted with powdered sugar.

It can also be dipped in chocolate.

Nuts are optional.

Earlier this week, I dug through our cookbooks, and found two recipes in my copy of "The Joy of Cooking". We tried earlier in the week, but didn't cook the sugar long enough, and we didn't use enough unflavored gelatin, so it never firmed up enough. Stephanie chose to dye it blue, so we have something like a lemon-lime jelly.

We tried again last night, and got it right this time. We put a little rose food coloring in, so its like blocks of pink lemonade.

Steph is happy. Because we made the recipe twice, she did almost everything herself the second time around (cutting and juicing the fruit, grating the lemon zest, and all of the measuring. I supervised the cooking of the sugar, since sugar syrup is scary stuff when its still hot).

My hope is that this can turn into a yearly treat that she can make for the holidays.

Tuesday, December 20, 2005

Choosing Glazes

Julie and I are going down to The Ceramics Shop to pick up raku glazes today.

We are having Megan mix up four glazes for us.

The first glaze is Seth's Luster. It is a matte raku glaze that contains bone ash, so that the surface is rough instead of smooth. The glaze goes copper under heavy reduction, but flames licking onto the piece give light and dark blue, yellows, pinks, and purples (almost the same color spectrum that anodized titanium provides, except that the high voltage 'bug green' and low voltage 'gold-brown' don't appear.)

The second glaze is a clear crackle glaze. In order to get it to be stark white, we will put a white underglaze under it. I was looking for an opaque white crackle, but couldn't track one down that wouldn't go transparent under heavy reduction (you can then see the color in the clay body, so the white crackle goes grey, or tan). I'll probably contact Vicki, my ceramics instructor down at Spruill House, to see if she has a glaze formula that she recommends.

The third glaze is a small batch of a beading glaze that contains a high percentage of magnesium carbonate. It is the one that I found on Dewitt Gimblet's list. Since I have seen this glaze recipe in several places on the net, but have never seen anyone discuss the glaze results, let alone post pictures, I will be interested to see what the results are.

The final glaze is Louden's Base, which will be colored using Mason Stains. Mason stains are colorants that can take the high temperature of ceramics. The linked picture uses 20% #6033, 'Sunset' added to the base. We are planning buying several stains, and adding them to the dry glaze mix as needed. I just want to make sure that we use enough colorant to really pop.

Wednesday, December 14, 2005

Glaze Search

I was searching for raku glaze recipes last night.

Julie and I want to use Seth's Luster (got it), a white crackle (will probably use the one I have from Spruill Center), but are open to whatever we run across.

Back in Atlanta, there was a gallery (The Gifted Hand?) that had works by a potter who had broken vases into pieces, glazed and fired each piece, and then glued the pieces back together for the finished vase, creating a patchwork quilt effect.

Very cool.

One of the shards caught my eye (and has stayed with me for the last twelve years), where the glaze had crawled on the surface of the shard, forming little beads on an unglazed surface. Betwixt the beads of glaze, were little dotted lines that were pinpoints of glaze, that bounded the region of clay surface that the beads pulled back from in the firing. The glaze was a glossy black, the unglazed surface was matte black, and the overall effect was of cells with a black nucleus and cell walls.

Resetting the Wayback to last night, I encountered a website where the author talked glazes, sold compendiums of glaze recipes, and provided an answer column for raku potters. Someone inquired about a similar glaze to the one I recall, and the potter provided not one, but two glazes, each with its own name.

Needless to say, I was excited. I decided to copy down both recipes, thinking that I'd study the glaze chemistry, and figure out how they work.

In about thiry seconds, I realized that both recipes had the exact same ingredient lists, but in different order. Okay.

Then I looked at the ratios of chemicals in each recipe, and pairs of chemicals lined up in both recipes with the same ratio (but not the same number).

It turns out that both of the recipes are for the exact same glaze composition, but for different amounts of glaze.

Question: How does someone think that they have two recipes, when they really only have one? Answer: When they didn't originate either one.

I poked around a bit longer on the net, and discovered another website, which contained a list of raku glaze recipes compiled by Dewitt Gimblet in 1998. A comparison of the Gimblet list and the one sold by the other website popped up too many matches in glaze names and compositions to be a coincidence. The Gimblet list contained only one recipe for a beading raku glaze, but seems to be the main source.

I would feel better if the same attributions that the Gimblet list provides for the original source of each recipe had been carried forward into the list available for purchase on-line.

Wednesday, December 07, 2005

Returned to the Studio

Went back into the studio yesterday afternoon.

Everything in the damp box had to be wetted down.

I trimmed Steph's rocket, and started to carve on the body. There is a little bit more work that I need to do on it before I can attach the engine bells and fins.

I threw a small vase, and another small rocket. The small rocket is proportioned skinnier than the others that I have thrown.