Emily Murphy's Page

This is a lesson for anyone out there using a pyrometer.

I've been using a pyrometer for the last 5 years and I have come to I love them! There can be problems with the cones in a soda firing and the pyrometer can be a great backup to the cones. Around c.6, the residual soda in the kiln can start to vaporize. Sometimes this soda can hit the cones and "freeze" them temporarily. Then all of the sudden, it "unfreezes" and the cones fall quickly. Then sometimes the soda can flux out the cones prematurely. Sometimes the cones on the top melt prematurely and the cones on the bottom freeze. And sometimes they are fine and go down when they are supposed to go down. By using both the cones and pyrometer, I feel like I am not firing totally blindly. Neither is perfect, but when used together, I have enough information to comfortably fire with.

There are 2 types of thermocouples that potters use, type J and type K. Type J is rated to about 2000' F, and type K is rated to almost 2500' F. The pyrometer is the same for both thermocouples, you just have to push a little button to switch from one type to the other. For the beginning of the firing, if you have it accidently pushed to type J when using type K, it will read normally. Then all of the sudden, your perfect firing seemingly goes crazy. For a couple of minutes, you think something is wrong, even though everything was going along just fine. Don't make any adjustments, don't play with the damper, don't turn up the gas or air. Just check the pyrometer and make sure that the setting for what type of thermocouple you're using is correct. Nothing has actually happened to your firing, it's just that the gadget wasn't working properly (user error). I teach people pretty regularly how to fire kilns and so I get to see that certain "mistakes" are common. This is one of those common mistakes.

I had been told by a couple people last month that they were having a problem at the end of their firings. After all the soda was in and the kiln was continuing to climb, something weird kept happening. The kiln dropped 15 degrees for basically no reason. Adjustments were made and the kiln started to climb back up. It was odd; I had never seen this happen before. Then it happened 2 or 3 times in a month. I chalked it up to firer error (just being honest here). Then I fired. I was having a great firing. I was within 2 degrees top to bottom from c.010 on. The soda went in at c.9 and the kiln continued to climb. Nearing the end, I thought I had about 20 minutes left before the kiln was to be shut off. I checked the kiln for what I thought was the final check, and it had dropped 15 degrees! What happened? This couldn't possibly be a firing error if it happened to me (hee hee). I managed to finish off the firing and the next day I talked with master kiln builder, Donovan Palmquist. His thoughts on this weird problem was that basically the thermocouples were fried. What was happening is that the pyrometer was acting totally fine up to about 2300'F. Then it was starting to freak out at about 2300'F. If the thermocouple is exposed to soda, then that can really cause trouble. I use a ceramic protection tube to encase the thermocouple so it isn't exposed to the soda, so I wasn't quite sure why there was suddenly any trouble. When I unbricked the kiln I discovered the problem. There was a crack in the protection tube, but it was in the first 9" so it was hidden by the brick. Once I pulled it out I found where the soda was getting in. New thermocouples were wired up. Problem solved! When I fired on Wednesday, it went up without trouble. Luckily I always keep a couple of extra thermocouples and protection tubes on hand for when these problems come up. (That was a lesson that I had learned early on in my pyrometer experience.)

One other way a misreading can happen is that the little prong end of the thermocouple that is plugged into the pyrometer might not be in quite all the way (it doesn't snap in, so it's not as easy to tell if it's in all the way). If it's not in all the way, it can give you a reading that is close to normal, but not quite right. Always check the wires and attachments when the kiln seems a little bit off. Wiggle them around until they "calm down" and settles on a number.

The moral of this story is to enjoy your thermocouples and pyrometer, but always be skeptical. It's a sensitive piece of electronics that you're using in and next to a very hot kiln. Before you freak out and make all sorts of adjustments, calm down and listen to your gut instincts with some logic thrown in.

For another very important studio lesson, check out Keith's tip from earlier this week.

You might have gathered from previous posts that I like tools. For years I limited myself to a the basics. Just a handful of adequate tools that did their job, but they weren't anything special. I wanted to be able to make pots no matter where I was and no matter what tools were available. After I felt like I was I had pretty much achieved that point, I started collecting tools. I have a thing for well designed tools. A tool that doesn't wear out in less than a year. One that is so comfortable to hold that it's basically an extension your hand. One that does something that no other tool can do quite as well. I still only really use a handful of tools on a weekly basis- but instead of being just adequate, they are a pleasure to use.

Bison trimming tools fit my definition of a really great tool. At first, I was quite apprehensive. They are definitely on the expensive side. ($58 for the one below.) But I had been feeling frustrated my trimming tool situation and decided that I would try to solve my dilemma problem several years back during NCECA in the exhibition hall. I had been using Dolan tools for a couple of years. They were quite nice, (the nicest trimming tool that I had ever used up to that point) but I was wearing through them on a regular basis. My main clay body is pretty gritty which was causing a lot of wear. I stopped by the Dolan booth to ask their advice. They said if I was actually wearing through them, there wasn't much to do. So I headed over to the Bison booth where they had a wheel set up with leather hard pots to trim. I sat down at the wheel, picked up a trimming tool and starting trimming off ribbons of clay. It definitely wasn't like any other trimming tool that I had ever used. It sliced into the piece with almost no effort. After less than I minute I was hooked. I knew that I could never go back to using any other trimming tool. This sounds dramatic, but I'm serious! This is the tool I ended up bringing home with me from the conference:
I've had the large loop tool for about 4 and a half years and have never regretted shelling out the big bucks. It's sharp, comfortable and the loop is the perfect shape for me. I just love how the sharp edge cuts into the leather hard clay. Eventually, I decided that I needed to add a second tool, a small loop tool for smaller pots and detail work. I ended up picking up a small loop tool at NCECA 2 years later. Again, I fell in love with my new Bison tool. I now have two trimming tools that cover most my trimming needs.
Bison trimming tools are quite different than other trimming tools. They are made of tungsten carbide and are quite brittle but will later forever if cared for properly. Here's some info about the material they are made from from the Bison website:

All tools are made having tungsten carbide cutters. Tungsten carbide is not related to steel in any way. Nor is it 'springy' or bendable in the fingers. Do not twist the end to see how strong it is.

All tools are entirely non-ferrous, and there should be no contamination of porcelain from any oxidation from the tool.

Tungsten carbide is a very hard, dense material. As a consequence, it is somewhat brittle in applications where these unsupported slender sections are extending out from the end of a little stem. One must take care to keep them from spills, falls, or being jumbled in a tool box when traveling. Keep them safe.

One should not tap the tool against things to dislodge a gob of clay, nor should one allow others to do so. Just as with our pots... do not drop them.

I have actually dropped my large loop tool once onto my concrete floor. My heart stopped for a second, but somehow it didn't break. I am very careful with these tools, making sure they always has a safe resting place when I put them down.

I think that I will need to get my large loop sharpened sometime this year. You can send your tools to Philip Poburka, the maker of these fine tools to get them sharpened. It's $10.00 for medium or large tools, or $7.00 for smaller and miniature tools plus return shipping. I will plan it so the repair will coincide with a vacation. I don't want to be without them!

The Bison tools and the Mudcutter are definitely three of the most expensive hand tools that I own. Part of the reason why I wanted to review them was to share my experiences with you to help you judge if it's worth the money for you. Most of my tastes in tools aren't so expensive. At some point soon I will be writing a review of a tool that I absolutely can't live without... and it only costs $1.85 (usually marked down to $1 at NCECA).

One of the great things about being a potter is to be able to make a pot to fulfill a need that I have at home. I can make something that is 'just right' instead of 'good enough' for the job.

We were in need of a compost jar. I had many parameters in mind when designing it. You might think that it just looks like a regular old jar, but it is oh so much more...
You might remember that we live in the middle of Chicago and you probably don't think about Chicago and composting going very well together. (Actually, you probably don't think about Chicago and compost at all...) Well, here's how we do it... We're friends with our next door neighbors (neighbor Eric is a potter and we work at Lillstreet together.) and they have a great yard and a compost bin on the other side of our scrappy fence. So we just reach over the fence and dump our compost in their bin (the bags make this especially easy). It's all very quaint and neighborly. We chat over the fence, share homegrown veggies and compare grilling tips.
It might sound a bit silly, but this is another one of those things that makes me happy to live where I live. When we moved to Chicago 9 years ago, I didn't think that my city life would have much in common with my life growing up in New Hampshire. But it does. We grow vegetables and herbs (on a porch instead of in a garden), go to the farmer's market, we compost our food scraps and have truly great neighbors.

I've been meaning post this picture for a while. There is a Buddhist Temple a block away from my apartment. They always put on the most amazing visual displays for their celebrations. This was up in their front yard during the month of May to celebrate Buddha's birthday. Complete with neon lights. I passed by this every day for a month on the way to my studio (which is only a 6 block commute). How lucky am I?
Everyday inspiration for an urban potter can be a little different from that of a country potter. I think this is a nice illustration of one of ways it can differ. Not as many trees, but more neon lit Buddha statues.