When I began working in ceramics all those years ago (the 1970’s!) I can recall being disappointed, first in high school and then in college, at the “lack” of color in the available glazes. We all had our boxes of crayons bursting with color, and even the cheapest mass-produced consumer goods were glaring with color. Even today, consumer goods (even foods) are bursting with artificial color. We inhabit mostly a built environment (how often are you out in nature?) where a cacophony of accidental color prevails. For example, I’m thinking of a very tastefully designed lounge, with all the furnishings and carpets and such color coordinated-inhabited by people sporting all kinds of colors, carrying bags and things with even more crashing colors that were most decidedly not a part of the designer’s scheme. I think we learn to ignore all these clashing colors as some kind of self-defense mechanism. ​

I have to admit, it could be age. But it could also be looking at lots of great pottery-Bernard Leach, Shoji Hamada, Michael Cardew, Phil Rogers, Matthew Blakey and plenty of works by unknown potters in museums-I’m coming to appreciate the palette of winter. It’s like a palette cleanser for the eyes. For me, the browns aren’t neutral. Some are russet, some cool, some tawny, and these browns are punctuated (some days) with blue sky, and evergreens wearing their dark green winter coats. And when it snows, the blue sky is replaced by white, silver and a range of greys as varied as the browns they cover, to varying extents depending on how much it snowed. Don’t get me wrong, I still love the deep saturated colors of medieval stained glass, for example, but I’m also appreciating the subtle symphony of colors that winter offers. ​

With wood firing, you can’t control exactly how anything is going to come out, and honestly the serendipity of it is a huge part of the attraction. But sometimes a piece comes out of the wood firing and, well, needs some help. Well, I had some pieces that just needed a little oomph, a little spark, an accent.Two of them had a lovely, ivory colored satiny glaze surface; but they were to subtle, they needed an accent, some pop. On the other end of the spectrum, I had a  piece with a kind of mottled surface, mostly quite dark. Finally, I had a piece that had quite nice “flashing”-effects of the fire on the clay, which highlighted the sculptural form really well-but the surface was quite dull and matte, no shine. ​

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The night was beautiful. It would have been cold being out all night like that, but the kiln generated so much heat that being so close, I didn’t need most of the layers of clothing I had brought. The wind was going in the right direction, I think it actually helped us. Pyrometers that measure the air temperature in the kiln are not terribly accurate at the higher temperatures, but they do let us know if the kiln is getting hotter or cooler, which is critical information for figuring out when to stoke for example. As the kiln heats up, everything wants to expand. I’m glad Dave was there when one of the steel tie rods holding the kiln together popped under the pressure! Wow, that made me jump. He had just replaced the tie rod above the one that broke, and assured me it would be fine. You could see the other tie rods bow with the pressure the kiln was exerting as it expanded, but they held. Even if we hadn’t had the pyrometers, as in olden times, you can really tell when a kiln gets up to those higher temperatures well in excess of two thousand degrees! At 9 something in the morning, Cone 10 had made it’s perfect arc on the top right, and both cone 10 and 11 weirdly were bending together on the bottom left; we got to our goal. ​

A delightful part of my part-time job as Manager of Ceramics at the Northampton Community College (NCC) East 40 is firing the wood kiln there! I had fired that kiln a number of times before, but for this Fall’s firing, I took on more of the work than in previous firings. I made the cone packs, for example, and made more of them than we had ever used in a single firing. Cones are scientifically formulated to bend over at very specific levels of “heatwork.” Heatwork is a matter of both time and temperature. The example I always give is lasagna. The oven may be 400 degrees, but if you only leave the lasagna in for five minutes, it’s not going to be cooked through! On the other hand, even if the oven is only 350 degrees, if you leave it in for 40 minutes it’s probably going to be fully cooked. Cones measure to what degree the ceramic is “cooked,” much like how a meat thermometer measures the temperature of the meat itself, not just the air in the oven. ​

It was the first time I actually got to load a wood kiln, which takes a surprising amount of skill, not to mention hoisting really heavy silicon carbide shelves into place. All the hours I had spent watching others load wood kilns was invaluable. The idea is to understand how the flame moves through the kiln, and much like playing pool where one ball bounces off another, you want to bounce the flame onto all the pots, ideally send the flame everywhere, reaching every pot without restricting the path through the kiln. No pot can touch, or even get too close to touching, yet you have to do a kind of Jenga where you get as much work into the kiln as possible. The way ash moves through and lands on the work is another consideration. Suffice it to say it was an honor, and I was holding my breath that certain decisions I had made would work out! For example, Kelly Allen noted that no one had ever put the center shelves as far to the front as I had. Yikes! I was hoping for better flow through the kiln, more ash, but what if it just meant that the work closer to the front door didn’t get hot enough? Gulp. ​

The door for the kiln gets built for every firing! First, the bricks. I actually really enjoyed custom fitting the last brick at the top of the arch, you can see it’s a lighter color than the bricks next to it. In previous firings we had done two bricks that stick out beyond the others, so you could remove them and see the cone packs strategically placed in the kiln for that purpose. For this firing, in addition to the two “peep” bricks, a third one with a hole in the middle was set up as a “blow hole.” Long story short, when flame is no longer coming out of the blowhole, you know it’s time to stoke. After the bricks were in place, Gabby Gentile (professor at NCC) and I “mudded” the door, which is pretty much like it sounds, although we used wet reclaim clay, not the kind of mud you have in a garden. Nothing like hands wet with “mud” in the winter. Then, for extra help so not so much heat escapes from the “door,” a special high-temperature cloth that looks like cotton but is not flammable, supported with a wire mesh was placed over the door. The pots were all loaded, the kiln was ready; but we had to leave it like that for weeks waiting for the burn ban to be lifted. ​

I harvested more than on June 19, but I used about the same amount of water when I processed it. This led to a super-concentrated batch, which of course led to new discoveries. More on that later in the post.

I decided after adding the wood ash (to bring the PH up to 10) but before pouring it back and forth between the buckets (to oxygenate) to dye a bamboo rayon scarf. As is usual with both woad and indigo, when the vat is reduced (low oxygen) it’s a deep green, and so is the fabric when you first pull it out. But then when exposed to air (oxygen) it turns a true blue. In the case of fresh woad leaves like I was using, there is a significant amount of fugitive yellow in the leaves; and when I dyed the scarf, I had done nothing to get rid of that yellow. In any case-the scarf ended up a really lovely blue; so lovely it’s tempting to just keep it as is. But of course I’m curious about what if…I’ll get to that later. But now onto getting rid of the fugitive yellow. ​

After dyeing the scarf, I did the pouring back and forth to oxygenate the infusion of woad leaves (I had already taken the leaves out, it’s like making tea.) Woad and indigo are actually pigments, that is, a solid; dye penetrates fiber, indigo and woad coat the fiber. When I used a higher water-to-woad ratio to make the “tea,” (see my last post) the heavier, solid pigment sank to the bottom, and the yellow liquid could be scooped or siphoned off the top. But this batch was SO PIGMENT HEAVY that the pigment didn’t settle at all-even after sitting overnight! ​

I just went ahead and tried to strain it; normally, again, the yellow goes through the cloth and the blue pigment gets trapped on top of the filter cloth. But the  “waste” water after I strained the liquid (first photo at the top of this post) was not yellow-it was  really  dark. Obviously there was a lot of pigment left, so I strained the “waste” water a second time. Sure enough, this second straining captured plenty more pigment on top of the cloth. Doing a more concentrated batch seems to be a great way to avoid lifting larger, heavier buckets! However, it means that the pigment won’t settle, and has to be strained at least twice. 

The weird thing was just how easy it seemed. I would compare it to making dinner; it took effort, yes, but it wasn’t like it sucked up the whole day, just one smallish part of a normal day. (If you want to see the whole process, reference this blog post.not-what-youre-supposed-to-harvest-in-october.html) I used less than 500 grams (about a pound) of fresh woad leaves. The first step is like making tea; you don’t boil the leaves, you pour the water onto the leaves and let them steep. You’re supposed to weight the leaves down, so they are surrounded by water during the steeping; I’ve used bricks inside of tupperware and all kinds of crazy things to try to do this, but last night’s innovation was I just stuck my tea kettle (with water in it for weight) on top and it was so easy! The kettle of course has a handle, so it was easy to lift the kettle and stir occasionally. O.K., not exactly earth-shattering but when you do something enough times, all these little discoveries and refinements help to streamline the process, and make it easier. ​

As promised, some results from the test kiln firing. After making the part 1 post, I realized that it was just too technical for a blog post. I reached a kind of crossroads where I realized I needed to create a section of the website for technical information. If you want something more in depth than this post, go to my new Ceramics-Technical page, and the pages that branch off of it.
The little test kiln did reach cone 10 (approx. 2,381 F) but not without a battle of many hours in the sweltering heat.  Luckily, it was worth it. The firing gave us really critical information; how will the new clay body behave at high-fire temperature in reduction (oxygen starved)  kiln atmosphere, which is how we fire the wood kiln? And, how will the 25 glaze recipe variations with the East 40 clay look and behave on the new clay body? Overall, the results were a smashing success. Both clay body, glazes, and the way the glazes look on the clay body passed with flying colors. Again, I'm not going to go into all the technical results here, but I do want to show you some of the highlights of what came out of the little kiln. 

In the test bars above, you can see the color of the clay with no glaze for yourself. In addition to the tile in the test kiln firing, the dark one at the bottom of the photo, Gabbry Gentile was kind enough to fire the one on top in the electric kiln up at the ceramics studio in Penn Hall on the main campus. I formulated this clay body for high temperature firings like we do in the wood kiln at the East 40; the real shocker, was that this clay body works at the medium range temperature used in the studio on campus! I won't go into the technical details here, but suffice it to say I was honestly shocked at how well this clay performed in an electric kiln at mid-range temperature! 

Ash glazes are supposed to show dramatic drips; the trick is, you don't want them to run off the pot. This test tile was photographed on its back because of sun glare, but it was standing up on vertical when fired in the kiln. The pleasant surprise was that all the variations of the ash glaze stayed up on the tile, none of them ran off the tile at the bottom which is a big problem with a lot of ash glazes. Many ash glazes can only be used at the top of the pot, they are so runny. This was the runniest variation, and even it didn't run off the tile. Long story short, we already have usable glazes based on the East 40 clay and wood ash, and they work great on the new clay body!

Above is the simplest glaze recipe I tested-and my favorite result! The drips are less dramatic without the eggshell. It's such stable glaze that I can see using it on an entire pot, not just at the top for a drippy effect. The color comes primarily from whatever is in the East 40 clay, educated guess, a lot of iron. 
Getting back to the vase at the top of this post, the dark part at the top is the same as the tile above, except there is an addition of copper oxide. The pot was first dipped in a glaze we had on hand from previous wood kiln firings, we wanted to see how it worked on the new clay body. The red you see, especially on the view to the right is actually from the copper-rich glaze I was testing at the top! All in all, we got lots of very helpful information from the test kiln firing. In all honesty, I didn't expect this much success in a first time at full-temperature firing!
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Adding Wood Ash to East 40 Clay
This test uses only two ingredients. Going left to right, I added increments of more wood ash to the East 40 clay. A few notes about this; for the ceramic artists out there, this was cone 6 oxidation. It's obvious that the 5 parts clay to one part ash is not nearly enough ash. (The ash is used as a flux, that is, to help melt the clay into a glaze.) I made impressions into each square with a finger, making a kind of "lake" within each square, and also applied the glaze unevenly to see how various thicknesses of the glaze would work. I'm working with such tiny amounts here that of course more testing is needed to nail down percentages, but it's pretty clear that the wood ash I was using, which was from the wood kiln at the East 40, needs to be over half the mix to melt the clay. I'm currently working on glazes for cone 10, so at that hotter temperature obviously everything will melt more than at this cone 6 (lower temperature) test. 

Adding a colorant
I wish I had done the line blend of just the clay and wood ash first! Here there isn't enough wood ash in the mix to start, and as you add a colorant like copper carbonate, that tends to retard melting and make matters worse. Note that even .3 grams is way too much colorant for a first step! Instead of green, which we would expect from copper carbonate, we're almost at black. That's why I start with simple line blends-I'm not using much in materials to get this kind of information that points me in the directions I should go. 

Above, I used 4 g of East 40 clay to 2 parts of a commercially produced flux, the same percentage of clay to wood ash from the last test. The commercial flux has a stronger action but even so, it's under-melted.  I'm using a commercial mason stain for the colorant. The main problem is that the clay when properly melted into a glaze is so inherently dark, it's hard to notice much color difference from the base glaze at left with no colorant. 

In the basic mix at left before I started adding rutile, it's melting ok but not great. Rutile can add color, texture and odd what I'll just call variations to the look of a glaze. Like the cobalt carbonate, it also makes the glaze more matte, or under-melted, under vitrified in ceramic terminology. Matte glazes are a thing, we don't always want super glossy glazes, but they can be more prone to leaching and other defects/weaknesses. I do want to do more tests with rutile going forward, just that every time I add an increment of rutile I know I need to add an increment of flux (melter) at the same time. 
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​The way-back story
I first used this clay when I was working on my master’s thesis, using a simple mix of half East 40 clay and half of a commercially available clay to make loom weights. (See crossing in my portfolio section) In my summer of 2022 Residency at the East 40, I used the clay, raw and roasted in a bonfire, as pigments for paints that I made and used in the “Imaginary Landscape” series of paintings that were featured in my Fall 2022 solo exhibition. During the residency, Walter Heath saw me grinding up rocks for pigments, and immediately had visions of using them to develop glazes. That summer I wasn’t ready to go there-but in 2023 I began preliminary testing, not just for the East 40 clay, but from local rocks I had picked up and processed. In this post I’m only showing the initial line blends I did with the East 40 clay, omitting all the rock glaze tests and tests on clay I dug out of my front yard-it’s a long enough post as is!