We have seen 10-year-old kilns with firebricks still in pristine condition and one-year-old kilns that looked like they had been dropped from a roof. You can tell at a glance when a kiln has been cared for. Please follow these guidelines to make your kiln last:
Vacuum the kiln interior regularly using the brush nozzle of a vacuum cleaner. Be gentle when you touch the firebricks with the nozzle.
Apply kiln wash to the kiln's firebrick bottom. But keep kiln wash away from the walls and elements. (In a glass kiln, you could also use glass separator to coat the bottom.)
If possible, do not fire moist greenware. It should be bone-dry and warm to the touch. If you must fire moist ware, wait until all signs of vapor have disappeared before heating past 200 degrees F. The moisture at higher temperatures is not good for the firebricks and can cause the ware to explode.
Do not lean too heavily against the firebrick walls while loading and unloading. Some people use a small stepladder to reach into a deep kiln. You can also cut a piece of plywood to fit across the wall that helps protect the wall during loading.
Lower the kiln lid (or close the kiln door) gently. Slamming the lid can crack the lid the first time it happens. Fully disengage the lid support before lowering the lid. Forcing the lid downward can break the bricks near the lid hinge. From time to time, check the condition of the lid support.
Keep the lid closed when you are not using the kiln. This keeps dust out and prevents the lid from dropping while you are away from the kiln. Do not store anything inside the kiln.
The kiln stand should be level and rock-steady. An unleveled stand can stress the firebricks. A stand that rocks can cause the kiln to move when jarred, knocking over ware against the sidewalls inside the kiln.
During loading and unloading, do not touch the sidewalls of the kiln with anything. Do not allow a shelf to bump into the firebricks. The extra time and care you spend loading and unloading may add years of life to your kiln.
If glaze, glass, or other materials drip onto a kiln wall or the kiln bottom, repair before the next firing. Otherwise these materials will remelt and embed deeper into the firebricks. Remove the contaminant by scraping gently with a putty knife. If you remove kiln wash from the kiln bottom, apply a fresh coat to the bare spot.
Do not be concerned about small cracks that appear in the firebricks. The cracks are normal and act as expansion joints. During firing, they close tightly.