My mailbox kiln/bead annealer

I explained in a previous post how I built a digital controller for an old Paragon kiln that I’d inherited.  When I first set up my torchworking station in March of 2013, (to brush up on my skills before attending a class at the John C. Campbell Folk School) I tried to use that Paragon for a few days to anneal my beads.  I placed the kiln shelf on the tallest posts I had (to minimize the depth) but it was still difficult to place the mandrels into the kiln without running the risk of having then touch the elements in the side walls.  I quickly decided I needed a dedicated bead annealer, and started shopping around.  I really hated to spend $500 or more on a benchtop annealer, so I started looking for instructions on building my own.  I found several threads on wetcanvas and lampwork etc (art forums), but the die was cast when I found Dudley Giberson’s amazing website (Joppa Glassworks, Inc).  Mr. Giberson is well known in the studio glass world, and in addition to manufacturing burner heads for glassblowing furnaces and pipe warmers, he sells a number of papers he’s written with detailed instructions on building glass working equipment, including bead annealers and digital controllers.  He sells a wide range of kiln elements and other kiln components, and has even put together a few DIY kits for those who want to build their own annealers.  I decided to follow his instructions for a mailbox annealer, based on a large “rural” metal mailbox, and ordered his encased element kit.  I went to my local home improvement store for additional hardware, sheet metal, wire, a switch, a metal utility box and extender ring, and a power cord. All I needed after that was insulation, and I found a seller on ebay who was selling 2″ thick fibrefrax in 10square foot pieces.  I didn’t keep all the receipts, but I’m guessing I spent about $150 for the annealer.

The tray attached to the mailbox, with the door before attaching the hinge.

The tray attached to the mailbox, with the door before attaching the hinge.

Along with the component kit I bought Mr. Giberson’s build instructions.  Once I’d received all the parts I set aside a weekend to put it together, and following his instructions made it a fairly easy build.

The bead door consists of a tray made of three sheet metal pieces, snap riveted together and then attached to the bottom edge of a rectangular cutout in one of the long sides of the mailbox with sheet metal screws.

 

The door is a strip of sheet metal (edges folded over and hammered flat), hinged to the upper edge of the cutout with a piano hinge. I screwed a scrap piece of metal bar (no idea where I got it) to act as a handle.

I followed the patterns in the instructions to cut out pieces of frax to line the inside of the mailbox.  The body and floor are insulated by friction fitting pieces of frax into place, but the frax on the side and end doors are held in place by wire pigtails, a clever approach that I’d never heard of before.  (You really have to buy the paper, it’s great.)

frax

The element is attached to the top arch of the mailbox, routed inside quartz tubes which are then held in place with ceramic donuts.  The element tubes pass through the center of the donuts, and the donuts are mounted onto the shell with more wire pigtails.  The electrical connections are housed in a circuit box mounted to the back (small end) of the mailbox.

isulatorsGiberson includes two unique tubes of cordierite, also called “wall tubes”, that are 1″ in diameter on one end, and 1/2″ in diameter at the other.  I drilled 1/2″ holes in the metal, slid in the tubes, and then fed the free ends of the element through the center holes of the tubes.  I then mounted the electrical box to the extension ring, with the 4″x4″ piece of marinite (fiber insulator board that came in the kit) sandwiched the between the two.  I drilled holes in the marinite, mounted bolts in the holes with washers, and then mounted the wiring and free ends of the element to the bolts.  That allowed me to make the essential electrical connections without electrifying the metal shell of the kiln.

Even though I built the kiln to plug into a digital controller (and eventually built a controller just for this kiln), I added a 15A household switch to the power box so that I could turn the kiln off even if the controller was powered up.  It’s certainly optional, since you could turn off the controller, or unplug the kiln.

Once I finished all the connections it was time for the moment of truth–I plugged the kiln into my controller, programmed it to get to 960 F (annealing temp) and pressed “run”.  The controller cycled the power on and off (the kiln made no noise at all), and the kiln ramped up to process temperature beautifully.  It reaches annealing temperature in about 45 minutes, although it could probably go faster.  I bent two c-shaped pieces of sheet metal to form legs for the kiln, but I found that they don’t need to be very tall, because even at full temperature the outside of the kiln is only about 150F.  You could probably just rest the kiln on a couple of bricks if you wanted to skip that step.

I strongly recommend buying Mr. Giberson’s construction paper, but I’ll pass on a tip of my own.  The most intimidating part for me was bending the sheet metal to make the tray, the bottom shelf of the bead door.  For anyone with a bending brake it would be childs play, but I don’t have one, so I made do with a couple of pieces of angle iron.  I clamped one over the edge of my workbench, positioned the other on top with the angled edge lined up carefully with the bottom iron, and then slid the sheet metal pieces in between the two.  With a lot of patience and careful positioning I was able to clamp the metal tightly and accomplish crisp bends.  If you try the same be sure to study the instructions until you clearly understand how the parts fit together.  I was frankly surprised with how good the finished product looks.

I’ve turned out several hundreds beads with this kiln so far and it’s performing beautifully.  Here are a few more photos of the build to help you visualize it.

 

pigtails door frax door close
Pigtails that hold the insulation in place on the door, from the outside. The insulated door in operation. Stainless steel rods held in place by the wire pigtails keep the insulation in place on the door.