How to Choose a Kiln
Reprinted with express permission from Paragon Kilns!
1700 degrees F
2000 degrees F
2300 degrees F
2350 degrees F
Buy a kiln that will fire hot enough for the ware you will make. China painting or enameling kilns, for instance, will not reach ceramic temperatures.
Will you need a new circuit installed for your kiln? This may affect which kiln you choose. Have only a licensed electrician install your new circuit and use COPPER wiring, not aluminum.
208 volt wiring is becoming common in strip malls and schools. 208 volt and 240 volt circuits use the same wall outlets so you can't tell them apart visually. Call your power company if you are not sure about your voltage. If you fire a 240 volt kiln on a 208 volt circuit, it will fire slowly and probably never reach maximum temperature. 240 volt kilns do not necessarily fire hotter than 120 volt kilns.
Size: Hobby or Studio?
Generally, the larger the kiln, the lower the cost per cubic foot of interior. The 8-sided kilns are the most popular hobby size, because the cost per cubic foot is low. These kilns are large enough to fire most greenware, including Christmas trees.
One of the most popular sizes for dolls is the 6-sided S-11-9-3. Doll makers also like a 7-sided kiln or the 8-sided S-1613-3 or TnF 1613-3.
The larger the kiln, the more efficient your commercial operation. Loading time and electrical cost per piece of ware is lower in a 12-sided kiln than in an 8-sided or 10-sided Paragon.
Multi-sided or Square?
On a per cubic foot basis, the multi-sided kilns are less expensive than the 4-sided because they are easier to build. Ceramists usually buy the multi-sided models. Schools and potters sometimes buy the large, square, top-loading kilns because they are especially durable and slow cooling.
Top or Front Loading?
The popular multi-sided kilns are top loading. Front-loading kilns are preferred for enameling where pieces are removed from the kiln at 1450 degrees F. This would be difficult in a top-loading kiln since the heat rises when the lid is opened. Ceramists use the small front-loading kilns for testing and firing small pieces.
Firebrick or Fiber?
Insulation for ceramic kilns is refractory firebrick or ceramic fiber. The firebrick outlasts ceramic fiber while ceramic fiber heats and cools faster. So, each material has its advantages.
Heating elements are easy to replace in a firebrick kiln, because they are exposed in firebrick grooves. Most ceramic fiber kilns use elements embedded into the fiber. These elements are more expensive to replace along with the ceramic fiber.
2 1/2" or 3" Wall?
Most ceramic kiln walls are either 2 1/2" or 3" thick. The 3" wall kilns take slightly less energy to fire due to the extra insulation. However, their main advantage is that they reach a higher temperature than their 2 1/2" counterparts. They also cool more slowly, important when firing heavy pieces. If you intend to fire stoneware or porcelain, buy a 3" wall kiln. Paragon 3" wall kilns are called Energy Misers and their model numbers end in "-3"
S-Series Manual Fire
SnF Series Automatic
TnF Series Automatic
For most firings, the heat in a kiln is turned up gradually. This prevents the heat from shocking the ware and gives gases in the clay time to escape. The S, SnF, and TnF series differ in the way they control the heat.
S-series manual fire kilns operate without electronics or timers and they use infinite control switches to adjust heat output. For most firings, the switches are set on low to begin with and then turned up to higher settings.
A Dawson Kiln Sitter ® with a Limit Timer comes standard on the S-series. A small pyrometric cone is positioned in the Kiln Sitter (Pyrometric cones are small clay pyramids placed inside the kiln which bend to indicate when ware is fired to maturity. They are rated by number.) When the cone bends, it releases a trigger in the Kiln Sitter that shuts the kiln off. The Limit Timer is a safety backup that shuts the kiln
off in the event of a malfunction when the timer runs out.
SnF series kilns use switch-timers to change heat settings. A Dawson Kiln Sitter with Limit Timer shuts the kiln off at the end of the firing. The top switch of an SnF kiln adjusts the heat setting during the first phase of firing. The second switch is a timer that controls the firing time of the first stage. The third switch (if the kiln has one) is a timer that regulates timing on the second stage. As timers run out, higher heat settings are automatically switched on.
Owning a TnF-Series digital kiln is like hiring someone to watch your kiln for you. After the first few firings, you will wonder how you ever got along without one. Results are repeatable and consistent.
The heart of the digital kiln is the DTC Programmable Digital Controller board, small enough to fit in the palm of a hand. Replacing or upgrading one takes only minutes. It is backed with a reassuring warranty.
The DTC 800 series is a refinement of controllers that have been firing in Paragon kilns since 1988. The DTC 800 series uses improved circuitry and components for extended life and greater accuracy.
TnF kilns come with an improved thermocouple (temperature sensor) which is hermetically sealed in a protective metal sheath. Before updating, we tested it continuously for months. According to test data, temperature drift is only a few degrees after firing for 1,000 hours at 2300 degrees F. The new thermocouple is so sensitive that when registering around 80 degrees F., it will show the temperature rising when you hold the tip in your hand.
The controller comes in two versions: the DTC 800C for ceramics, and the DTC 800 for enameling, jewelry, heat treating, and glass. The DTC 800C uses two operating modes: (1)Cone-Fire and (2) Ramp-Hold. The DTC 800 operates in Ramp-Hold only.
Cone-Fire fires to a pyrometric cone number. You do not need to know cone temperature - just enter the cone number and firing speed (fast, medium, or slow.) New in Cone-Fire is the Fine Tuning feature. It matches the heat work of the controller to that of the pyrometric cone on the kiln shelf. For example, if you program the controller to cone 05 and the 05 shelf cone does not quite bend to maturity, you can adjust the controller to fire a little hotter next time.
The cone temperature of an actual firing will vary, however, depending on firing rate. The DTC 800C uses technology patented by the Edward Orton Jr. Ceramic Foundation to compensate for firing rate.
Ramp-Hold fires in up to eight segments. Each segment has an end temperature, speed, and hold (or soak) adjustment, so you can change the firing speed up to eight times in a single firing. Because each segment can control heating or cooling, even crystalline glaze firings are simplified.
Store up to six firings in memory - programs are retained even if the kiln is unplugged. The kiln temperature displays throughout firing and cooling in your choice of temperature scales, F or C. A safety switch near the display window shuts off power to the heating elements. Use the audible temperature alarm to remind yourself to close the lid from the venting position or to check the kiln when firing is almost complete. Error messages report possible mechanical problems.
Use "Delay Fire" to start the firing later to suit your schedule. The display shows time left before firing begins. You do not have to be present throughout the firing, but it is important that you are near the kiln before the expected shutoff time.
Furniture and Extras?
When estimating the price of a kiln, include the cost of the furniture (the shelves and posts stacked inside the kiln.) With furniture, you can stack multiple layers of ware. Without it, you can fire only the ware that will fit in the bottom.