Sunday, March 26, 2017

Keeping your eye on your kiln

 I had to work on Friday and that left Mark here for the cone 6 firing that I was working on. Most of the time we will program the kiln to come on in the wee hours of the morning. Then it is usually finished around lunch time.
This time I asked him to turn it on as I was leaving and make sure we vented the hot wax out of the kiln before dropping the lid. We use hot wax, or paraffin to coat the bottom of the pots before they are glazed. It keeps most of the glaze off the bottoms and what is left can be easily sponged off.

 Mark let the wax vent off by leaving the lid and peep holes open after that he closed the lid, closed the peep holes and let it fire. It was going along as it should until it hit 2183 degrees. Our computer program is set up to hit 2190, then cool to 2175ish and hold 15 minutes. He looked and it said, 2183, he went back and it said, 2183. Here is what we did not know, how long it was holding at 2183. He tried to call me at the school, but because I am all over the building I missed his called, he called again, he called again, and finally I heard my cell phone go off. Here is what is going on. My reaction was, shut it off. I knew the glazes would be matured, my hope was that they had not been sitting there at 2183 so long that the glazes had become runny enough to over fire or that we had over fire the clay body.
In the morning, I took a  quick look.
Then shut the lid.
Then I slowly let the kiln cool.
560.
500.
480.
400.
350.... I started opening the lid, 325, open more 300 degrees I opened the whole lid and let thing cool to around 200 degrees.
I did lose a few pieces, such as the one at the top of the post, and 2 more that were the same combination.
I lost a few pots to the clay sticking to the top shelf. That was more my own fault for using an older shelf and not applying a fresh coat of kiln wash.
But, all in all the black glaze, with the top glaze that we have been working to salvage for over a year, worked. It melted, stayed on the pots and over all we like the results. Here's what we think happened, the kiln stalled when one of the thermocouples failed.  We looked back to find out when we bought this kiln and turns out we bought it almost 8 years ago. So yep, time to do a little maintenance. After which another fire to see if we can replicate the results.
It could have been worse, so much worse, I feel very lucky.
Remember when you are firing that computers can fail, your eyes are the best source to see that your kiln has finished it's job.
Whew.
M
  

Tuesday, March 21, 2017

Little sister, making pots and glazing tiles

These two jars could be related.
 Mark is making a few jars and playing with shape and design.He is using a white stoneware body. There are a couple of thoughts on glazing, but let me get back to you on those.

We both seem to have a lot of different things going. I am working on tiles, and glazing pots.
The same but different.
When I start any new glaze combination, or tile, I need to commit the glazing to my memory bank. That is what I have been working on lately and it goes like this; what glaze goes first, what glaze works on top and what glaze works better under, and will this make a good liner glaze and if so, what works best with it.
I find it helps to think with a pencil in hand. I write directly on the pot. The pencil line or note will burn away during the firing. I write on pot bottoms if I remember before I apply wax. Otherwise right on the pot works too. I do make notes as well and if it is a test piece I write that note with black stain or pencil that is made of a stain that can I can read later.

We have been working off and on with a variety of test for the cone 10 gas kiln and the cone 6 electric fired kiln, since glazes can look alike in the bucket we have added a new way to identify the cone 6 from the cone 10 glazes. I know, if you have read this far stay with me it's really quite easy.  We bought some very bright pink duct tape to placed on the lid and on the bucket where we can write the name of the glaze and cone 6. This is important because uncovered glazes can look the same no matter if you are using 6 or 10 glazes. A quick look at the side of the bucket can save you a surprise later. Although, I have made some surprises that look great and were added to our mix. I have also figure out a mistake and had to wash 3 boards of pots. Wash, dry, reglaze equals frustration for that lost of time. Lesson learned.

Here are two of the tiles that I was glazing this morning.
It made me think that one was the big sister and the small one little sister.

I am also playing with a new camera that is one a different phone.
So here is Happy, the giraffe, I hope he makes you smile.

Don't forget the spring kiln opening in April.
We hope to see you here.


Sunday, March 12, 2017

You can't all make bowls

As you all know I am still teaching one day a week at the Community College.
One of the things I do is load kilns.
I load the bisque kiln and some days I am loading a glaze kiln as well.
There are these times when everyone is making bowls.
I can't tell you why, maybe it is the alignment of the stars, the moon or a combination of both.
The problem with everyone making and glazing bowls is shelf space in the kiln. What do I put around all the bowls? How do I get them all in? It has become a  puzzle for me to figure out.

In our own studio we know for every serving bowls on a shelf we need 10 mugs, 4 to 6 juice cups, and maybe an odd item or two.
We also know, that in order to fire well using gas the kiln needs some mass around the bowls.


I just grabbed a picture from a firing done last year, as you can see that there are many like items on a shelf, but in order to get good heat flow through the kiln, we will vary sizes. If I packed a shelf with nothing but beer mugs, 3rd from the top, I could block some of the pots from getting the heat and later the reduction that is needed.You can see that along with the mugs are salt jars, a juice cup or two and some spoon jars.
Looking above or below you will find like items staggered with unlike items. Again this helps the kiln heat all the pots, and helps those pots get an even reduction. Or, as even as possible.

In the electric kilns we fire I use as much space as possible filling all the nooks and crannies I can.

I was trying to find a picture for you and ran across a picture of the large gas kiln that we are not firing right now.
You can still get a feel of how much you will need other pots to fill a kiln.

When we plan a load to fire we usually work off a list, knowing that filling the kiln in the most efficient way to work. We work towards a goal. Mugs, oil lamps, lamps, crocks, juice cups, bowls....jars, creamers, trays... and so it goes.
How do you map out your work, even if you are not making pottery you need a plan to get a job done.
Are you just making bowls all day, or do you have a lot more on your list?