12:00 am - 12:30 am
Studio Testworth, Neverwhere DC
The brick used to make most consumer kilns is fragile. It is made by mixing refractory materials with wood pulp and then firing it to burn out the wood pulp. Air is the best insulator so all the little pockets left behind help your kiln retain heat and make the kiln much lighter.
Unfortunately this process weakens the breaking strength of the brick so odds are you will occasionally chip your brick. This normally happens when you are loading shelves and ware into your kiln.
Most chips and dings will not affect the performance of your brick. The areas that will need attention are your lid, element grooves and slabs (kiln floor). It is very difficult to patch brick in areas where gravity is working against you such as sidewalls and the underside of your lid.
Most manufacturers coat their lids with refractory cement designed to seal the brick so bits of brick dust do not fall into your ware during the firing. Sometimes trying to patch the underside of your kiln can actually create more problems if the patch does not hold. Since many lids are coated on both sides it is often possible to remove the lid hardware and flip the lid over.
The element grooves are designed to hold the element in place so it does not want to droop down when the element heats up and softens. If you break out an element groove usually the best thing to do is go ahead and replace the brick. Often times kiln owners will postpone brick replacement until they are ready to replace their elements. A good way to hold the element in during this period is to form a little fence using element pins. This is definitely a temporary fix but it can usually get you by until you are ready to replace elements.
The floor of your kiln can get worn of time. Small bits of melted glaze or glass may need to be chipped out leaving chunks missing that can affect the stability of your shelf posts. This is one area where patching can be very effective. Most kiln manufactures make a kiln patch using a binder with brick dust. Just use a spackling knife to apply the patch and let it dry before you fire the kiln.
The process recommended for replacing brick will vary between manufacturers. The brick will also vary since most manufacturers groove and cut them differently. You will also notice that brick types within the same model will vary. Check with your supplier or manufacturer to verify the brick you will need.
The hardware of your kiln includes your lid prop, lid lifter, handles, section buckles…basically anything that is attached to the outside of your kiln.
Keeping all of these components maintained properly is important to extending the life of your kiln and your safety.
When things heat up they expand and when they cool down the contract. All this movement coupled with the strain of normal everyday use can cause things to loosen over time. It is a good idea to periodically inspect the screws holding all the components to the kiln and make sure they are still tight.
Most kiln companies use stainless steel components that resist corrosion, but they are not impervious to it. Kilns that are located near the coast can be particularly vulnerable to corrosion due to the salt in the air. If you live near the coast it is particularly important to locate your kiln indoors where salty moist air will not condense onto the metal parts.
The stainless bands that surround the majority of kiln models will loosen over time. A loose lid band can slip. This can be particularly unsafe when it is your lid band which holds a heavy brick lid over your head while you are loading your kiln. Follow your manufacturers instructions since procedures vary between manufacturers.
Relays are the components that physically cycle the elements on and off to your kiln. If the kiln is firing too fast or too hot the controller will tell the relays to turn off and if it is firing too slow or too cool the controller will tell the relays to turn on.
Most kilns will have at least two relays. Relays have a limited life that is determined by the number of times they cycle on and off. Excessive heat can shorten the life of relays so make sure your kiln room is well ventilated.
There are many different types of relays. The most popular are mechanical relays. When they fail they can fail in the on or off position. If they fail in the off position the elements they control will not receive power which will most likely trigger an error code by your controller and shut down the firing.
If the relays fail in the on position the kiln will often complete the program but may never completely cool. If your relays fail in the on position turn off the breaker to your kiln and unplug it from the receptacle.
The likely of more than one relay failing in the on position at the same time is very slim therefore the risk of losing ware or damaging your kiln is slim. Most kilns divide the power between 2 or more relays so if one sticks it will not over fire the kiln.
It is very important that you use only manufacturer recommended relays for your particular model when replacing them. The relays are located inside the control box. If you choose to replace them yourself it is very important that you disconnect the kiln from the power source first.
Thermocouples are the temperature sensing probes that protrude into your kiln chamber and feed information to your controller. Just like elements they can degrade over time.
Again, it depends on the temperatures you are firing too and the amount of combustibles they are exposed to that determines how long they will last. If you are only firing your kiln to glass fusing temperatures (between 1400 F and 1500 F) you may never need to change your thermocouple. If you are firing cone 10 crystal glazes and holding at high temperatures (over 1800 F), you may only get 20 firings out of one.
There are many different types of thermocouples but the standard is the Type K. Check with your dealer or manufacturer to be sure which one you have before you order your replacement.
When your thermocouple is approaching the end of it’s useful life you will notice that your kiln will fire a little hotter each firing. If you are firing ceramics you will want to use a pyrometric cone to monitor your thermocouples accuracy. These are available through most ceramic suppliers. They can recommend the type of cone you will need when you purchase your clay and glazes.
Place the pyrometric cone on a shelf about 2 inches from your thermocouple, brick and any ware you have on that shelf. When the cone bends over and touches the shelf, you should change your thermocouple.
It is not uncommon for people to accidently hit their thermocouple when loading the kiln. If you ever bend or crack a thermocouple, replace it right away.
Some thermocouple are exposed and some of covers. Both have their advantages. If you have an exposed thermocouple you can see how much it has degraded. If it begins looking like the image to the left it is a good idea to change it.
Exposed thermocouples can flake, so it is a good idea to brush it off with an hold toothbrush every once in a while.
Replacing your thermocouple is something most kiln owners should learn. It can take as little as 5 minutes and usually only requires a screwdriver. Learn to follow your manufacturers instructions for replacing the thermocouple for your model and you can save a lot of time and money.