Thursday, June 11, 2009

Element Design --- Answers to Questions -- Part 5

I was thinking that this thread has gotten out of hand by being so technical --- and no pictures --- which is why I shortened it but here are the answers to Dan and Alex's questions.

When I got Papa Bear I had discussed my needs with L&L and they sent this large 29 inch diameter kiln with 18 gauge elements, and the elements had almost no stretch to them. The kiln fired fine for a few firings and then it would not get to temperature quickly enough. I will mention that zinc crystalline glazes are quite caustic to elements and kilns so this was a new problem for them and that they have been really open to learning and overcoming the problems that we have. But anyway the kiln was underpowered and I just started using it for earthenware and bisque. It now will not even do that so something had to be done. The kiln was rated for less than 40 amps and that was not enough to make it useful.

I did not want to learn about element design because it hurts to try to keep all that stuff in memory at one time. But I have this kiln that is totally useless, and I wanted to bring it up to useful.

My smallest kiln, Baby Bear, has 137 firings on one set of elements so I know that there is a way to design elements so that they last a long time, but I don't know how to do it. I'll get a picture today of the elements of Baby Bear. There are twice as many element holders in Baby Bear as a normal kiln.

These new elements for Papa Bear, 12 gauge Kanthal A1 wrapped around a 3/8 inch mandrel and 8 ohms cost 72.00 each and the kiln needs 8 of them so a good part of this is wanting elements that last a long time. But it is also important for the kiln to be nimble -- able to reach temperatures quickly (both up and down) -- say at least 200F/hr at the end. Eventually this figure will not be able to be reached and we will have to replace the elements, but we want to be able to use them for as long as possible as 576.00 is 576.00.

By the way, if you have a newer Bartlett controller and you press 5 while the kiln is firing, it will tell you how fast you are going. Mini tidbit but impressive for onlookers.

It is true that my work requires more precision than most, but the principles apply to anyone who fires to cone 9 or 10 --- your elements will wear out at some point. Ray Gonzalez, who is the tech person at UF, says that kilns fired to cone 6 and below rarely need element changes.

One thing that is a good question is whether the kiln manufacturers should design their kilns for us. I say no, it is not their responsibility. They have to compete with one another and they have to make the best product that they can within those parameters, but they make "hobby kilns" and we have to adapt them to our purposes.

It's true that the L&Ls are made like a tank. If you stacked boxes of clay on top of an L&L stand, you would be able to go until the stack fell over. That stand could probably hold 500 pounds or more. Every other kiln that I have had has had a less robust stand, and I have had a few. Not that the stand does not still work, but I did get a feeling of confidence the first time I held an L&L stand.

Tonight I will go over the math stuff again but I am the cook today for the community and it basically takes all day to shop and cook. I cook every other Thursday. Yesterday was Anne's birthday and she requested black bean soup with amarillos and tostones and salad so that is what it is. Maybe a photo of the whole meal tonight if I can remember.


1 comment:

Alex Solla said...

Now it all makes sense. I was just trying to figure out how much was simply a kiln not doing what you need, as opposed to intellectual noodling with Ohms and Amps. Makes perfect sense now.

I keep looking at the DaVinci models for all the reasons you mentioned. I want a kiln that ramps up wicked fast when I need it to, is built like a tank, and can do it for years on end. So, when $6K fall out of the sky, that's where the money will go.

I'm excited to hear how your new elements fare.