PVC Arch Forms
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After years of building arch forms for kilns, the idea came to us:
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"Why spend money on plywood to build this form that in an anagama must be burnt out and wasted? Instead, why not build it out of PVC and lath so it can be disassembled after construction, recycled and used in our water system?"
The technique we use starts with the prime measurements, the size you want the cross-section of the kiln to be. In an anagama style kiln with an arch that is not straight, but tear-drop shaped, measure the ribs to be about 2 - 3 feet apart front to back.
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1. Measure the width you desire the kiln to be at the point of that rib.
Mark that off on a beam of the kiln shed taller than the height of the kiln
2. Drive a nail at either end of the width. Suspend a chain from the two nails, letting the chain be pulled down in the middle by gravity to a point that is equal to the desired height of the kiln at that point. You will then have a chain suspended in a perfect arch, only upside down
3. Remove the chain from one nail and measure its length.
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4. Use this measurement to cut a length of PVC pipe. I suggest 3/4 " for medium sized kilns, 1/2" for small kilns and 1" for large kilns that are 6ft across or larger.
5. Drive an 18" piece of #4 rebar into the ground about 8"-10" at either side of the kiln interior opposite each other where you want the arch to spring across.
6. Using a rebar quick twist tie to attach the PVC to the rebar stakes |
7. You now have a model of your arch.
8. You can now use this as a visual guide to raise the majority of the arch
9. When the arch nears its zenith, when bricks begin to approach being vertical or want to start to slip it is time to use the same rebar quick twist ties to attach lath or thin strips of wood over the p.v.c. ribs to create an enclosed arch form. Resembling an upside down boat.
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10. When the brickwork is finished, simply use wire cutters to free the lath from the PVC and the PVC from the rebar stakes, pull the rebar stakes and set the floor bricks. 
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