Mar 21 2011

Ups and downs of firing

Just catching up here. Didn’t I just finish talking about things that can go wrong just as one’s getting ready for a show…? Perhaps I jinxed myself.

From 2 weeks ago:

Woke up this morning ..well I didn’t actually wake up, I was still up.. I wasn’t feeling too good about how the day ahead was shaping up to be. Thanks to the mega storm system blowing in from the west yesterday (tornadoes actually touched down not 15 miles north of us), the kiln didn’t get lit until mid afternoon, much later than I had planned or anticipated.

Propane tank freezing upThis firing cycle, the multimeter I’ve been using as a pyrometer for the last 9 years finally decided to bite the dust just as the kiln temp hit around 1200 degrees Celcius and it started to stall. Great. Felt like I was firing blind. Not only that but I was running out of propane..just 7% left in the tank and it was starting to freeze up. (You can see the 1/4 to 1/2 inch thick layer of ice toward the bottom of the tank in this picture). Its at times like this I get envious of people who fire electric…

Bleary eyed, I dragged the hose around and started a water trickle on the tank to hopefully gain back some of the gas pressure I was starting to lose. Took a breather, made coffee, headed for the phone, sat down and waited for the Amerigas office to open.

Amerigas manThank goodness.. By some miracle, the gas company informed me that they could come out and bring me more propane that morning. Not too happy that the same amount of propane was going to cost $70 more than it was last year, but under the circumstances, now was not the time to quibble. I was just happy to know I’d be able to finish this firing.

Went back out to check on the kiln and cone 8 was starting to bend on both top and bottom. Phew! An hour later, I hear a familiar beeping sound of the propane truck coming down the drive. Total relief.

Porcelain Curio case with dogwood relief design in celadonYou just never know for sure what you are going to get until you unbrick that kiln door. Despite my misgivings and struggle to keep the kiln lit, the firing turned out better than I had anticipated and I actually did get some decent reduction. Here is one of the porcelain pieces you saw in my last post, now glazed in celadon and fired. I love the way this kind of glaze feels and pools, giving a carved design more depth.

Ah yes.. my pyrometer. As an aside, picked up this new multimeter at Lowe’s for $21. It measures both in both Celcius and Fahrenheit and is a good alternative to more expensive pyrometers, like Fluke, out on the market. Thermocouples are available at most pottery suppliers, but I managed to find a group lot on eBay at a really good price a few years ago. I like this one better than my last, actually, as the screen is bigger and easier to read. pyrometer2.


Oct 16 2009

Blog Action Day 2009: Climate change

Blog Action Day is an annual event held every October 15 that unites the world’s bloggers in posting about the same issue on the same day with the aim of sparking discussion around an issue of global importance.

I remember as a child going to Man and His World (the site for Expo ’67, the 1967 International and Universal Exposition) in Montreal, and visiting all the international pavillions. I remember in particular the American Pavillion and always seemed to gravitate to it whenever we visited.  It was a huge, clear panelled geodesic dome structure that really stood out among the rest of the buildings.  It being so long ago,   I admit, memories are a little vague, but I have fleeting images of the experience such as the sun blaring through the glass.. vegetation lining paths on the ground level.. futuristic bits of art and culture.. stairs going up to a different level where screening rooms with films about acid rain, air & water pollution, the depletion of the ozone layer, etc. , etc, were shown.

Biosphere Montreal Expo 67I know I was young, but it obviously left an impression on me, because I still remember it.  The warning was clear that we should be very conscientious of how we live, how we treat the environment, and take care of the world around us, or the fragile natural world as we know it will be lost for future generations.

Despite what certain special interest groups tell us and want us what to believe, I think its naive to think that the climate change is not real and that we can keep on the way we have been.   Human activities might not be the only reason why global warming is occurring, but it is occurring nonetheless. The exponential growth of human populations and industrialization has had a huge impact on the ecosystem and has undoubtedly helped to expedite climate change.  We’ve known about it for a long time but denying a problem does not make it go away.   On that note…

Over the last few days, I’ve tried to think of how life at our studio might relate to the global warming. Thinking back, most of the changes we have implemented in the past few years were for economic reasons, but they have spinoff benefits that are releva for the  environment as well.  In the past 9 or so years, the cost of propane (we glaze fire in a gas kiln) has more than doubled and the cost of raw materials and shipping has gone up by at least 1/3.  Working smarter and more efficiently , obviously, has become all that more of a priority.

THE KILN

Nitride Bonded ShelvesWhen I think of climate change and how it relates to pottery, what first comes to mind is my kiln which uses propane.  A fuel burning anything is a potential area of concern when you are trying to reduce your carbon footprint.  One thing working in our favor is that  our studio and kiln are located on a treed 5 acre plot of land.  A friend yesterday reminded me as well that propane does burn more efficiently and releases less particulates and pollutants into the air than, say, a wood kiln or even a salt kiln.

So working with what we have, we have tried to make some changes to help it fire more efficiently and use less fuel.  A big change we made about a year ago was getting some of those new nitride bonded silicon carbide shelves which are much thinner (and lighter) than regular kiln shelves and take require less energy to heat up. (When you fire a kiln, you heat everything in the kiln.. the pots, the shelves, the posts… everything. Anything extra you have means that much more energy consumed.)  So anyways, we did that and replaced the flat top with an arch and I was delighted to discover that the firing took a fraction of the propane it did previously.  Something else that we just did this last firing is reduce the pressure at the regulator on the propane tank. Again, much less propane was used. Brilliant. More firings for less and what fuel we did use what burned that much more efficiently.

NATIVE CLAY

Like propane and natural gas, the cost of raw materials has shot up.  Thankfully we dig most of the clay we use locally. We do this for a number of reasons. Besides the fact that it is very responsive and throws beautifully, it being so readily available and so close to the studio definitely works in our favor. Since we process it ourselves, it is a little cheaper plus we don’t have the additional expense of shipping it down from places like Ohio, Atlanta, California, and some other such places where clay is commercially processed and distributed from.  The environmental impact?  Well, one benefit is there is one less truck on the road and therefore less emissions released into the atmosphere.

OTHER THINGS

We usually have to travel away to do art shows and fairs, so for a number of reasons, we’ve lightened up the weight of our show display so when we do have to travel, its a lighter load and hopefully less wear on the vehicle, less gas, and less emissions.

Shows, Quality not Quantity –  What with the economy, rising show fees and travel expenses,  and the uncertainty of shows, like  many craftspeople,  we have been forced to be a lot more selective about where we go and what shows we do. Consequently that often means travelling less and sticking closer to home.  The internet has also made promotion to a broader audience without travel possible.

At home, I am trying to make changes as well. I switched (mostly out of necessity) from a large SUV to a Toyota Corolla which helps consumption, and switched out all my light bulbs for flourescents or compact florescents bulbs. My gasoline and electric bills have both gone down considerably as a result.  There’s always room for improvement though. I started the summer with plans for a big vegetable garden, but this year with things that come up, as they seem to do, the more invasive weeds just took over. But there is always next year, when I hope to have better luck with planting in raised beds.

So no matter what your lifestyle or how small your operation is, changes to our lifestyle and how we work are possible. Even small changes can have a positive effect on the environment.


Dec 5 2008

Bending cones and The Frozen Tank

Webb decorated bisque ware I love the look of pots all laid out whether they be green ware or pots  waiting to be loaded in the gas kiln, as these are.   The mugs almost remind me of a regiment of soldiers, or a tightly packed school of fish all swimming in the same direction.

I’ve been finishing up a gas firing this morning, busily trying to keep the gas tank from freezing up until the propane truck finally makes it here this afternoon.  We’re cutting it pretty close though.. down to less than 5% in the tank and I have the garden hose dribbling some water on it so I don’t lose gas pressure completely.   Thankfully though,  cone 9 is bending evenly top and bottom so we’re in the home stretch.

I made a little adjustment to the way my target bricks were positioned this time (an experiment) in hopes of making the firing more efficient.  Evidently it has had some effect because the last time the kiln was stacked similarly, I had a good cone or 2 difference from top to bottom .   I guess I’ll only know for sure once the kiln is opened.

Looking forward to this kiln opening. I have several pots in there with clay from our new clay deposit I mentioned in my last post.


May 14 2008

Firing Smarter by Upgrading

When we originally built our kiln in 2000, we used all recycled brick and built it around the size of shelves we already had. It was a flat top, built mainly of stacked arch brick for the walls and a fiber (ceramic blanket) and heavy sheet metal roof. Not fancy, but we had a kiln and didn’t have to spend much money to put it all together.

Cordite shelves beside new flat nitride bonded shelfIt took at least 7 years of painstaking tweaking and firing before I really got to know its ways. About 5 years ago a dog we had knocked over the entire stack of old brick we were using for the kiln door, breaking most of them!! (..sigh) Long story short, it has been a struggle from the get-go to achieve reduction with any reliability, if at all.

As I think I mentioned in my last post, the old kiln as it was is no more. The flat roof – gone. The danger of fiber bits falling down into pots if you accidentally brushed the roof of the kiln with your head when stacking/loading – gone. The flat top was replaced with a retrofitted sprung arch and we finally were able to get new brick for the door. Extra fiber and roofing tin wraps the outer walls now as well.

The other exciting change made was replacing the old severely warped cordite shelves in favor of 6 new nitride bonded silicon carbide shelves. As you can see in the pictures, some of the old shelves were warped an inch and a half to two inches in places (I put one of the new nitride bonded shelves beside the stack of old shelves to show the difference in thickness and flatness). As with a wood or soda fire, loading typically involved painstakingly “wadding” each and every pot for the firing with a mix of 60/40 china clay to alumina hydrate. It was the only solution I could see to prevent warping. I have several potter friends who have those zoomy Advancer shelves that run about $100 a shelf in the size I was looking at. The nitride bonded are a step down from the Advancers, but are a lot less cost prohibitive, costing maybe $20 or so dollars more than a comparably sized cordite shelf.

Thin, flat, and light nitride bonded shelf

These new nitride bonded shelves weigh all of 11 pounds (the old cordite shelves in comparison weighed 44 pounds!), so loading the kiln takes a lot less of a physical toll on me and I can load it independently. I still do wad some – little teeny wads – (vs using kiln wash or sprinkling alumina hydrate on the shelves), especially on those clay bodies I might be firing that might be a bit tighter than our native clay to prevent sticking, Loading takes a fraction of the time as does the preparation of the wadding itself. Now that I have flat shelves, the wads can be glued on in advance as well.

The new arch in combination with the new flat shelves gives me at least, I am guessing an extra foot of stacking space. Not only that but the kiln now reduces and fires more efficiently using about a third less propane per firing. With the rising price of propane ($264 for 75 gallons this last delivery), the upgrades to the kiln and shelves couldn’t have come at any better time. (Better for the environment as well.)

As an aside, we got our new shelves and brick from Larkin Refractory Solutions in Atlanta. Wonderful customer service and knowledgeable staff.