Where do I begin fixing up my manual kiln?
Before we dive deep into repairing/updating the kiln, we need to talk about the parts (if you’re already a pottery nerd and know the parts you can skip a couple paragraphs. Throughout this post I am including pictures of my kiln & what I’m currently working with- this is specifically for my Skutt 231 kiln sitter model and may not apply to your kiln (if ya have one)! Skutt has a fantastic resource page that contains manuals dating back to the 70’s, you could find the one belonging to your kiln here.. I highly recommend checking this out if you bought your kiln secondhand and it did not come with the original manual. For those of you without a kiln, I commend you for reading this!
The basic parts I’ll be referring to:
The kiln itself: This refers to the overall piece of equipment. The unit in which we load ceramic objects to transform the clay and or glaze chemically with high heat. Oh, and for my kiln her nickname is Calvin.
Kiln Sitters: (From The Ceramic Shop) "are the control boxes on electric (or manual) pottery kilns that utilize pyrometric cones to dictate a kiln’s firing. Prongs within the kiln sitter extend to support a pyrometric cone or rod. Once the kiln reaches a specific temperature, the cone will start to bend, causing a lever to drop, switching the kiln off. While kiln sitters have become less common with the advent of digital controllers, they are still found on many manual kilns -- and like any piece of hardware on a kiln, these items sometimes need to be repaired or replaced." These are found in manual kilns and are the mechanical control to end the kiln’s firing cycle. It can be controlled by time and/or temperature depending on the kiln. In my case it is temperature alone. The sitter turns off the kiln when the bar or cone (description below!) drops/slumps causing the sitter to drop, the clasp to raise up dropping the falling weight.
Cones: Aka Orton cones; much like negative (ie. 05, 04, 03) and positive (ie. 5, 6, 7) numbers, this is a form of measurement when referring to firing temperatures in clay and glaze chemistry. For example, “cone 05” refers to about 1850 degrees F, “cone 6” refers to about 2250 degrees F. More info on this here. For my kiln, I can use bars and cones within the tube assembly.
The tube assembly: (according to Clay Planet’s website) the tube assembly goes through the kiln wall to hold the cone/bar inside the kiln with a kiln sitter. This houses the cone supports.
Cone supports: These slide into the end of the tube assembly on the interior of the kiln-it holds the cones and when brought to its peak temperature, the cones bend, triggering the kiln sitter release claw to fall, shutting off the kiln automatically.
Elements: (according to the big ceramic store) “...a piece of (coiled) wire that is designed to resist the passage of the electricity. As electricity is forced down the wire, the "resistance" impedes this movement and subsequently causes the wire to heat up. Think of it as heat caused by electrical friction.” This wire wraps around the interior of the kiln and is held in place by fire bricks.
Fire brick: The porous refractory bricks that make up the interior wall of the kiln. They not only hold the elements, but insulate heat created by the elements. (Yes the elements and bricks look a mess in this photo, I'll be fixing them!)
When I picked up Calvin (yes, as in Calvin Kiln ba-dum-tiss), formally known as Norbert, I noticed the fire bricks that hold the elements were in relatively good shape aside from a couple damaged ones at the top. So, in the back of my mind I knew I’d be ordering more to properly hold the elements and insulate all that heat they’ll be producing. When I reassembled her at home and took a closer look, I noticed the tube assembly on the interior of the kiln no longer held cone supports-in fact I had no idea where they were… They may have fallen out during the move and perhaps went unnoticed! But that aside I knew I had to replace the entire assembly. I came to this conclusion because I believed if I tried to insert new cone supports, that they would most likely fall out; and if they fell out during the firing, my kiln could misfire and we REALLY do not want that. I’ll be showing pictures to compare the old and new assembly in the next blog post! So, for you realists out there wanting to pick up a used kiln you may be waiting for the cost of these repairs on Calvin. In my case, I ordered from an online shop that had the items I need in stock.
Thus far I have ordered these things for the kiln, aka The Prescription:
Fire bricks- 1 peep hole and 5 straight (there are four types for my kiln as pictured) (~$82)
x24 kiln element pins- I got ones that have a hooked end-more on this in the next post (~$20)
Tube Assembly- Since the current one's bottom is blown out & I'm missing cone supports (~$50)
Considering I purchased the kiln for $150, I've now invested about $175… Not terrible! I am praying I can get a good test fire out of this girl and perhaps a few bisque and glaze firings before I need to replace the elements. Out of all the repairs, that alone could cost another couple hundred. Currently waiting for the last of my bricks to arrive. The rest is here, and we have begun some repairs.
As for getting electricity out to the garage, that has also been completed (Thank GOD). Electrician came last week and put a 110 and 220 out in the new space for me. 110 will be for the wheel, lights, heat gun etc. 220 is for the one and only Cal. NOW THAT WAS PRICEY. If you don't have a 220 close to the location of your kiln, you'll be paying a pretty penny. Again for you realists, wanting this to be your reality too, it cost me a little over $800. That has been a big sting, but it'll be worth it in the end. As for Cal, it would be ideal if we could get the new bricks in there before her maiden voyage firing in my garage, but we may just go for it. I'll let you know how it goes next time! Until then, let's get muddy.
Fantastic resources for manual kilns (basic breakdowns):
Skutt’s Youtube Channel:
From Earth Nation Ceramics on Youtube: