Fingers Crossed

My big kiln has had a number of difficulties in the last month or so.

First I began blowing bubbles in and through a lot of pieces. I had not changed any of my practices (however unscientific they may be) and could not see what was happening. I tried a number of tests: firing slower, firing lower, venting the kiln, firing on batts instead of the sand, testing the temperature distribution round the kiln.

The last showed that I had hot perimeters in the kiln, very unusual. I checked with the manufacturer who suggested I take the elements out of the ceramic tubes and space them out at the ends. They forgot to mention that they are wired in a single run of 6 metre long length, through 6 tubes. I got the heating of the elements OK on the first one's ends so they were evened out with the rest of the element. Then the problem was to heat the bend of the element and straighten it so it would pass through the second tube. Well, I wasn't up to it. The element broke.

Now the question was whether to try to buy the appropriate amount of wire and wind it myself and then insert it into the tubes, or hire someone else to do it. I decided on the latter. After some consultation we decided to establish the elements in three pairs for each phase. This means the element tails are at the back and I only need to replace one pair instead of a complete run of 6. Much cheaper to repair if needed.

Fired away confident that all was well. And it was. Until the third firing when things seemed a little odd, as the kiln seemed cooler at one end than in the centre and other end. On the fourth firing it was clear that one phase of the kiln was not working. So another large piece lost.

The people came and repaired a broken element, since there was a loose connection that caused the element wire to overheat and then break. Fixed. Not quite. fifth firing was fine, but sixth firing showed only one phase was firing. Now not only the original problem phase but the centre too.

Well, the company has a couple of people who are knowledgeable about glass kilns and they were away in Inverness, and of course, there is a holiday too. So the kiln sat idle for just over a week waiting for repair.

Today the man came and found two other wires leading from the main connections to each of the phases had corroded and failed. Well, they hadn't replaced them when doing all the other work on the elements and wiring. Certified as working as of 11:30 this morning.

Now it has somebody else's tests in it so at least if there are problems, it will not be mine. Then, of course, the first firing after repair has been fine. It has only been later when problems arise. I wonder when I will trust the kiln again.

Oh yes. The bubble problem was an accumulation of dust from sieved thinfire over four years. The sand bed becomes less porous with lots of dust and so does not let the air from under the glass as well as a mix with less dust.

Bubbles

Sometime you want to have bubbles in your pieces. Sometimes you don't. But you never want what I am getting recently. Large burst bubbles.

Kiln forming is often an unpredictable art, but mostly the variations should be small. Withing the last month my big kiln has begun blowing big bubbles. Like this one.

Most often these seem to come from underneath the piece but sometimes between layers. This is a piece I put in after I thought I had diagnosed and fixed the problem:

This has bubbles coming from under the piece and from between the layers. My practice has not changed as far as I can tell, from the past when there was no problem. I have checked on the density of the sand bed beneath the glass, by compacting it tightly. I have been very careful about level screeding of the bed. I have fired on both unfired and fired thinfire. I have fired smaller pieces and still got bubbles (see the piece at the top). I need my big kiln. I need to find out what is happening.

So I went back to basics and did a "Know your kiln" test from Bullseye . This showed me that the temperatures in my kiln are different than at the beginning of its short live (five years old now). The chamber is much h0tter at the back than at the front, rather than just a little. I phoned and found out that the elements are loose inside the ceramic tubes. This probably means that with me leaving the lid open when not in use, the elements have slowly compacted to the back of the kiln. This means that I have to take the top off the kiln, and remove 8 square metres of fiber blanket to get to the tubes that hold the elements. I then have to lift each of the 20 tubes and stretch the elements back into some sort of even-ness. I expect this will be a 2-4 day job, when I could be doing other things.

Even when this is done, I am not sure it will cure the bubble problem, as I am getting bubbles at the front and at the back both. Still, the elements must be sorted. And in the spirit of eliminating problems one at a time, I will get to the bottom of this!

Verrier Glass Studio

Let me introduce you to my studio. It is a large one in the WASPS Hanson Street building in Glasgow. I will tell you about WASPS at some point in the future. I am on the ground floor and the official entrance is from the elevated ground floor. As you can see from the photo below, you go down stairs to get into the studio. The advantage is that the glass windows on the right slide open to give access to the car park outside. The windows are about 3.5 metres high, giving an enormous amount of light into the studio from the south. The disadvantage is that the low sun (56 degrees North) when we get it, is directly into your eyes. So you have to bring the shutters part way down for shade (in the Winter!).

Studio entrance

As you come down the steps, you get closer to the work benches - which, as you can see, I did not tidy up for this picture - and the glass storage underneath high level storage for all sorts of things. I finished these shelves only about 3 months ago, so they are not yet full of all my stuff. You can just see a pair of lobster panels in the far window. These are salvaged from our kitchen remodelling - my work no longer fitted into the new black , white and blue scheme.

At the back of the studio are two of my kilns. The others are in another part of the building. So these are my big (2.2metres by 1.03metres) and my smallest (.5 by .5 metres) kiln. The other two are about 1metre by .5metre and are in a special kiln room shared with ceramic artists.

This image shows some painted pieces sitting in the kiln just before being removed.

This final photo is taken toward the entrance from the main floor of the studio. It shows the current progress toward a display area for the studio, and possibly for other glass artists in the building. It shows a few pieces in cases along with shelves of supplies. The large structure to the right of the shelves is a piece called "Internal Landscape" which was prepared for the travelling exhibition "Cutting Edge". It is four sided, with lighting in the drum below the glass. It is based on the turning of things inside out. The projections are reminiscent of the polips in our digestive system, projected into a landscape under stress.

Enough "artistic" description. These photos give a flavour of the environment in which I work.