ceramic science

You are currently browsing articles tagged ceramic science.

celadon banner_small

According to the internet, where truth reigns ::sarcasm:: the color blue is the favorite child across gender, ethnicity and culture. In one survey conducted in 10 countries over 4 continents, blue came out the overwhelming winner every time (brown, not so much)

I like green. I don’t dislike blue. It’s just that green has so much more to offer…like, yellow (see what I did there?) Compositionally, green is an Everyman; holding it’s own, yet plays well with others. Green has the ability to function in the foreground as well as the background…because, yellow.

My love of green has never been a secret (neither has my annoyance with the overuse of blue) I’ve been known to base a decision solely on the availability of green. And then…and then in the ceramic world there is celadon (ah, yes) A traditional celadon glaze is characterized by a soft gray-green color resulting from firing iron oxide in a reduction atmosphere*.

In my forth semester as an undergraduate in ceramics, our assignment was to design, create and fire dinnerware for eight, including service pieces. The set would require at least 50 some-odd pieces and a lot of prayer to finish with enough surviving work to complete the assignment. My first solo firing of the kiln would be the culmination of this semester’s work – with my entire dinnerware set inside (eek!)

I went about making my dinnerware with an iron rich, toasty clay decorated with a white slipped rim that just cried out for celadon.

Some of you are already ahead of me, here. What was I thinking?

My first solo firing.
The kiln loaded with my entire semester’s work.
I chose a glaze that is dependent on a specific firing atmosphere.

When you don’t know what you don’t know, you occasionally find yourself in a pickle. More often – no…most often, novice potters focus on the making rather than the finishing (there’s your pickle)

I’m a little beyond novice these days. Still love celadons. In fact, I’ve recently committed to develop a family of celadon glazes for my functional work. Firing in oxidation**, celadon really just refers to green(s) since oxidation eliminates the mystery of the iron-in-reduction-resulting-green. My hope in developing related celadons is to approximate the beauty of the subtle surface variation I saw when I opened the door of my first solo firing.

* reduction atmosphere = creating a surplus of carbon in the firing kiln
**oxidation atmosphere = preventing a surplus of carbon in the firing kiln




Tags: , , ,

an anthology

The 2nd Occasional Cup and Mug Sale

BethShook_300

Let me start with a huge thank you to all those who came out to spend a little hard earned cash on a mug and donate a backpack for a junior high!! Also, thank you to all the artists that participated in the sale – couldn’t have done it without you.

Our goal was to collect new backpacks for a local junior high by creating a big tadoo about cups and mugs. Here’s the Cliff Note version of the sale weekend: 32 participating artists, 576 mugs and cups, ¼ of our inventory sold in the first hour of the 10 hour sale, awarded 8 mixed sets of cups and mugs to drawing entrants, and (this is the very best part!) collected 55 new backpacks for one grateful junior high school.

That was fun!

Dear John, you left so soon

On the morning of October 13, 2014 my studio-mate from graduate school passed away. He was 54.

John's studio space, 1989.

John’s studio space, 1989.

John and I shared a divided 500-600 square feet of studio space during grad school. He always had parts and pieces scattered about (drove me crazy). Somewhere in his process all these parts made sense.

I considered him a friend. Graduate school creates a special bond – cemented by stress and lack of sleep. We tried to provide practical support for each other. For instance, John helped document a large site specific piece for me and another grad student. By document, I mean – he ran along the Mill Avenue bridge at the break of dawn for three consecutive days photographing our progress as we worked to draw from the shadows cast on the dry rocky bed of the Salt River. I bought breakfast.

On one particularly cold morning, I rid the studio of the black widow that made her home under the wall heater, next to the switch. (John had grown considerably weary of arachnids after sleeping with a scorpion on more than one occasion) He bought me lunch.

And so it went….

John seemed to lose his way a bit during grad school. But, I’m confident he was drawn back before he left us so soon for home.

A Conductive carbon

I’ve been working on what seems like the longest continual commission ever – that, from this day forward shall be referred to as ‘the dinnerware’. My progress has been stymied by an unruly class schedule, a cup and mug sale, kiln repairs, and a clay problem.

With my class schedule under control and the sale a thing of the past, I’ve only got the kiln and clay issues to solve. (which are really linked…I think)

It seems in my attempt to squeeze the last red cent from my turnip, I inadvertently doubled my trouble.

The setting:
I’d been keeping an eye on a sagging element near the bottom of the kiln. If I could just get one more firing in….(that went all wrong) After a slower that normal bisque firing, I checked the elements before reloading and noticed the sagging element touching itself on the return. All the current was running through about six inches of the element (yeah, yeah…replace the element and get on with it)

The conflict:
A month or so later, I’m unloading a glaze and notice micro-bloats* on the work – actually, only the mugs. (geeze, just in time for a mug sale. perfect.) After considerable research and a few impromptu interviews, I’ve come up with a theory. A theory that may well violate one or more laws of thermodynamics, but….

Lichtbogen_3000_Volt

The foil:
My fuzzy science suggests a few things (and some stuff I actually know…like, actually)

  • • the clay I’m using has been known by ceramic artists to bloat. The manufacturer disagrees, but suggests firing the bisque to cone 04 as a means to remove all organics. (not sure what’s in this clay that survives 1860°F…but, okay)
  • • during at least one bisque firing, the second to the bottom element shorted itself; creating a smaller circuit with half the resistance.
  • • the mugs were loaded on the bottom.
  • the shorted element would create uneven heat in the kiln – a cooler bottom.
  • (here’s the fuzzy part) the shorted element would create a voltaic arc, releasing a conductive carbon into the kiln’s atmosphere; meaning there was some localized reduction going on.

The moral:
A penny saved isn’t worth the price of that turnip.

*bloat: the permanent swelling of a ceramic article during firing caused by the evolution of gases. (sounds a bit like too many chimichangas, eh)

 



Tags: , , , , , , ,

trial by fire

I should have been a painter. I can paint, you know. The bonus, there’s no need to set the thing on fire to see if it will survive. I miss painting…or maybe it is that I just miss the intoxicating aroma of linseed oil with a touch of turpentine.

I’d like to blame that —————————->green pin holed
on the person who fired the kiln! If the work doesn’t end up as expected, it’s certainly the fault of the person firing. After all, that’s the only part of the process in which you have little control. Not your fault!!

Though it is true that a poorly managed firing can destroy a lot of work, it’s also true that it does so without respect to any work. Usually you’ll lose much of the load. In this situation, I have only three pieces behaving badly in the entire load; which reasons that the problem wasn’t the firing. I’m off the hook! (said the person that fired the kiln)

I can assume raw materials aren’t the cause of the glaze issue because, again there isn’t general misbehavior with the same glaze on other pieces. Only these three – two green and one brown. So then, I can’t point to the person making the glazes. (um…me again)

In the spirit of full disclosure, the green and brown are the same base glaze. The green has been known to fuss on occasion. But, the brown has always been (until now) my stoic, reliable friend.

brown pin hole

That leaves the process of getting the glaze on the surface. Glaze application issues aren’t generalized throughout an entire kiln load except when a person hasn’t been taught appropriate application. In which case, every piece loaded in the kiln is a test with the hope for a happy accident. Only the pieces you screw up will be screwed up. The rest will be wonderfully predictable. (you have to work very hard to get to predictable)

functional work

There are several variables to consider and not all are worth considering. This kiln load was glazed over the course of a couple weeks; in between preparing for an exhibition. There were a few wet, rainy days, so additional moisture (or slow evaporation) could have played into the application process. There was also a goodly amount of saw dust about the studio. (I do attempt to keep the place tidy. But, for cryin’ out loud, I’m only one person) Free organics on the raw glaze surface might provide an easy scapegoat. Eh…I’m pretty sure that burned off early. I always rinse the bisque before glazing, so I don’t believe there was anything trapped between the bisque and the glaze. I can reasonably tell that the pin holing occurred earlier in the firing process…OK. Maybe. Perhaps, unintended organics contributed to this problem.

shardsI might continue to speculate. But, in the end, I only have three pin holed plates from an entire kiln load for the shard pile. (I take full responsibility for the shard pile)

 

**just updated the Clay Drawings tab with work from exhibition at Central Arizona College.

Tags: , , ,

In the studio sit a row of glaze test tiles like proud third graders waiting to present their painted Styrofoam solar systems to class. Full of can’t-sit-still-in-your-seat potential!

tile_banner

These tests are mostly blues. Beautiful blues. Those who run in ceramic circles understand that blue just isn’t that difficult to create. And yet…I have an inordinate number of blue tests. It’s not so much the color as it is the behavior of the glaze I’m interested in. The tests are part of an attempt to finesse an existing glaze. My original blue has an occasional cosmetic glitch. No big deal. That is, until it cosmetically glitches all over a commission piece. (frustrating!)

tile_blues

At times the continual testing seems like an exercise in futility. So many of the results should be tossed directly into the trash from the still warm kiln.

**There are some clay folk who refuse to contribute a test to the shard pile; squirreling away years of tiles in an old, bulging cardboard box, never to be seen again. Never. Ever. (that…right there…an episode of Hoarders)

Not completely exclusive, my row of tests include several varied greens. I’m always interested in another wonderful green. (not obsessed. not.)

tile_greens

Each of these tests fail in one way or another for it’s intended purpose. Hopeful efforts crushed by disillusionment. (sigh) Still, I try to live with them for awhile. (they will eventually make their way to the trash)

If the tests are close to my target, I will spend some soul searching with my chemistry in an effort to tweak the glaze into submission. However, I refuse to work glaze improprieties like the never ending task of Sisyphus. I will adjust it a time or two and move on.

tile_burnt

If my results stray far from the goal, I often find myself considering how I might encourage such bad behavior for the purpose of clay drawings. Encouragement generally comes in the form of unconventional – sometimes abusive – application methods. These are the glazes I enjoy the most. Rebellion: the most exciting part of the glaze process!

Full of can’t-sit-still-in-my-seat potential!


Tags: , , , ,

a bird in the hand…

On Sunday I started the first glaze firing since early summer; ending my firing hiatus through some of the hottest months

In the spirit of full disclosure, I wasn’t really firing the kiln so much as candling. In ceramics, candling refers to slowly heating up the kiln and ware inside the kiln in order to dry the work (if firing a bisque) and/or heat up the inside of the kiln. The term candling seems more appropriate to a gas kiln – you know, where there is an actual flame and all.

I refer to candling in the electric kiln as creating ‘thermal momentum’. That is, the process of building heat (and drying out work in a bisque) with the purpose of firing evenly and more rapidly the following day.

So then, on Sunday I was creating thermal momentum.

While I was loading the kiln on Saturday, I noticed the top element looked like it might be close to burning out. There was a small corrosive ulcer on the upper portion of the element. I couldn’t quite tell how far the decay had progressed. A little festering wound.

For a split second I considered replacing the element.

Installing a new element would involve unloading the kiln, dismantling the upper ring of the kiln to access the switch box, removing and then replacing the element, reassembling the kiln, reloading…. The day lost and back to where I started.

Yeah, that thought faded fast. However, as soon as I closed the kiln lid, a slew of proverbial warnings came to mind.

He who hesitates is lost.¹
A small leak will sink a great ship.²
Curses, like chickens, come home to roost.³ (I’m not entirely sure I know what that means)
An apple a day keeps the doctor away.² (this one doesn’t really apply)

The issue here is that the glazes for my utilitarian ware don’t allow for any wiggle room in the firing. There are no mulligans here. If the element burns out, the kiln won’t make it to temperature (about 2290° F). Then, I will be forced to re-fire the load to vitrify the glaze and clay – making the pieces functional.

The last (only) time I re-fired a load with these unforgiving glazes, I found the color to be off, the yellow glaze became too fluid (spoiling the drawn surfaces) and, my clear glaze blistered. Lost the entire load.

Perhaps I should have paid heed to those warnings and eaten an apple to boot!

Today (Monday) I am firing*. While I’m writing (9:30am), the kiln is at about 75% power. The affected element is still glowing (this is good). Praying my decision to wait on repairs wasn’t foolish. I have a deadline and past experience tells me this isn’t a simple replace/reload/re-fire fix. If things go awry, I will need to re-make the work. Too much pressure!

*The kiln reached temperature at 4:06pm  🙂

1) Joseph Addison
2) Benjamin Franklin
3) Florence Scovel Shinn


Tags: , , ,

« Older entries