How to Build a Kiln Arch
- 1). Build the wall of the kiln on which to place the arch. The top edge of the walls should be flat and level. Use the dimensions of a specific design if possible to get the right curvature. If you do not have a design, measure the gap between the walls, subtract 2 inches and mark this length on a sheet of plywood. Draw a straight line from point to point.
- 2). Place the plywood so that it is on-end and hang a chain or heavy rope from both ends of the line. Use enough length to create the curve you wish and trace this curve onto the plywood. Since you reduced the width by 2 inches, you can later nail on the 1-inch strapping on both sides and the mold will still fit.
- 3). Cut out the marking with a saw to form part of the arch-form. Mark and cut as many as you need. Depending on the length of the arch, you may need more than two to support the weight of the bricks. Use a hammer and nails to attach the wood strapping (1 by 2 inches) to the ribs of the arch-form. Use enough length to connect all the plywood ribs you have cut. Place the ribs at even distances every few feet. Nail them on with small separations between rows so the bricks don't fall through.
- 4). Lift the completed arch-form into place using blocks to get the right height. It should be sitting snug between the walls with the bottom of the plywood ribs level with the top of the wall. Dry-fit your arch-bricks on top of the mold building up from each side. Find the right size key brick to complete the arch. A key brick is the last brick that is placed in the arch.
- 5). Try several combinations until the arch has a good fit with the mold. Remember to place the bricks on one edge (not the end or face), horizontally along the length of the kiln. The thinner edge of arch bricks should always face inwards. Write down the order and type of brick you used to make the dry-fit arch.
- 6). Build the arch using the same combination. Use a minimal amount of mortar between bricks.. Start at the sides and make sure each row is staggered. Staggered rows will eliminate vertical seams going from side to side and strengthen the arch. Use a brick saw to get the right sized bricks needed to stagger each row.
- 7). Build both sides up until you get to the final row on top. Lay the last bricks (key-bricks) into place to complete the sprung arch of the kiln. Carefully remove the arch-form by taking out the blocks underneath and lifting it out from under the arch. This will let the arch settle and the mortar dry. Let the mortar dry completely before testing the kiln.
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