Table of Contents » Chapter 6 : Kilns » Chapter 6 : Selecting An Electric Kiln

Chapter 6 : Selecting An Electric Kiln

A little prep work before buying a new or used kiln can save you a lot of headaches! Information about buying a used kiln listed at the end of this page

Factors to consider:

  • Space where kiln will be located
  • The size and shape of your work
  • Power supply available
  • Price

Space/location-influence size of kiln

  • Plan on having 18-36 inches clearance around all sides of your kiln.
  • Your kiln should be located next to an external wall for proper kiln venting.
  • Given the gasses emitted during a firing, it is best to have it located in a separate room, (closets and small rooms are not appropriate choices)

Your work-influence size of kiln

  • What are the dimensions of the largest pieces you will want to fire?
  • What is the maximum volume of work that you will need to move through in a set time period?
  • How will your needs grow/change in the next 5 years?
  • What is your maximum desired firing temperature?

Power available-determines how manufacturer will wire kiln
(For more information see Understanding Electricity)

  • Voltage to your building _____volts
  • Amperage available _____amps
  • Single or three phase _____phase

If your voltage supply is 240 and your kiln requires 208 volts this situation will shorten the life of the kiln elements and switches. If you voltage is 208 and the kiln draws 240 volts the kiln might not reach its maximum temperature during the firing. The goal is to match the kiln to the power supply.

Extras available for kilns:

Kiln stand
You must have one! Kilns should not be operated directly on the floor.

Kiln controllers-for ease of use
Manual kiln controllers with kiln sitter require user to make all turn-ups. Combination of kiln sitter and timer provide backup to help prevent over-firing.

Computer controllers
Come with numerous variations for firing programs. Your own firing program can be entered into computer. Not very difficult to learn and use. It may be advisable to use a kiln sitter as backup to prevent over firing. Discuss with dealer.

Venting your electric kiln
Venting-for a safe working environment: In addition to the electrical requirements of the kiln, you will also need a standard 120-volt outlet to power your vent.

Hood vents: This system depends on hot fumes rising out of the kiln and collecting in the overhead hood. Because of air turbulence in the room (from people walking, open windows, etc.), not all the fumes will rise directly into the hood. For this reason, hood collection systems are unable to effectively remove all the fumes generated by the kiln, and a variable portion will remain in the working environment. Hood-style ventilation systems will remove a portion of the heat that the kiln gives off, making for some increased comfort in working conditions. This hood is excellent for assisting negative pressure systems in controlling the larger volume of fume that can be generated by luster, china paints, and some wax resists. Vent-a-kiln is the primary manufacturer of this style. Their web address is ventakiln.com.

Negative pressure system of venting: In most cases, these vents are superior to the hood style. Often a fan is located at the bottom of the kiln and pulls the air down through the kiln, helping to facilitate an even firing. The air is then led through dryer venting (metal, not plastic) to the outside, through a window or vent. Make sure that the draw of the fan is rated for the size of your kiln (if too powerful it will suck the heat from the kiln, if not powerful enough, it will not adequately vent the kiln). There are many manufacturers of this style, it may be best to use the manufacturer recommended for your kiln.

Extra insulating brick-for greater efficiency
Many kiln manufacturers offer the use of extra thick brick to aid in kiln insulation, which will provide a more efficient firing and a slower cool down. If you fire to a high temp, cone 6 or higher, or you use crystalline glazes that require a slow cool, you may consider this option.

Worksheet for buying and electric kiln
Worksheet to complete and discuss with supplier:

Basic considerations
Dimensions of available area for kiln in studio: ____L x ____W
Largest dimension of your work for kiln: ____L x ____W x ____H
Maximum firing temperature: cone ____
Available power: ____volts ____amps ____phase
Extras
Kiln controller: computer or kiln sitter w/timer
Energy efficient brick: yes/no
Pyrometer (not necessary for computer controlled kilns) : yes/no
Vent system what type
Kiln furniture whatever fits your needs
Worksheet to aid in comparison shopping
Kiln Manufacturer: ______________________
Kiln shape: round/oval/square
Kiln size ______________________
Internal dimensions: ___L x ___W x ___ D
External dimensions: ___L x ___W x ___ D
Kiln stand included: yes/no
Maximum firing temp: cone ___
Kiln rated for: ___volts, ___amps, ___phase
Kiln controller: computer or kiln sitter w/ timer
Energy efficient brick: yes/no
Vent system: style ________
Kiln furniture- posts size___”,
Kiln furniture-shelves: shape______, quantity_____

Price
Kiln base: $______
Extras: $______
Vent system: $______
Kiln furniture: $______
Total: $

 

Buying a Used Electric Kiln

Acquiring a used kiln can be an affordable way to set up a new studio or upgrade your existing space. All of these questions and inspections should be taken into account when purchasing a used electric kiln. They are not in any order of priority.

What temperature do you want to fire to?
Not all kilns are made to fire to ^10. Check the specification for each kiln you find. There is usually a metal plate near the switches or control panel that will have the Make, Model #, Serial #, Voltage (V) and Amperage (A) and maximum temperature. If you can’t find any information on the Internet, you may have to contact the manufacturer to get the details about the maximum temperature.

Is very old kiln worth buying?
How old it is doesn’t matter as much as how many firings and to what temperature most of those firing were. Replacement parts for kilns are available through the manufacturers and their distributors. Both of these sellers often have technicians or staff that can help you with diagnosis and repair procedures. If the kiln is discontinued or the company is no longer in business, finding parts can be difficult. Wires, switches and relays are used in a lot of other electrical equipment and can be found through electrical supply companies. However, elements are often designed for each kiln specifically, so finding replacement elements for discontinued kilns could be difficult. Clay Art Center in Tacoma Washington will make custom elements for electric kilns.

Look for a kiln locally.
Get the word out to friends and family that you are looking for a kiln. Post an ad on Craigslist.org, check local ceramic suppliers, schools, art centers, etc. Search within a distance you feel comfortable driving to pick up a kiln. Shipping is costly and could damage the kiln. Depending on the condition and cost of the kiln it could be worth driving several hours for the right one. The lid and floor of most electric kilns come apart and two strong people can move the main body into a truck.

Make sure you match the voltage and phase of the kiln to your studio.
Most residential home power is 240V single phase. Many schools have kilns that use 208V three phase (this is more efficient). It is important to match your power source (voltage and phase) with your kiln. If the kiln you find has the same phase but the voltage is wrong, you can change all of the elements to match the voltage of your studio and use that kiln.

Inspecting the kiln.

Questions for the seller.

– Does the kiln work?
If the kiln is not working and the seller doesn’t know what is wrong, I would recommend finding another kiln unless you have prior kiln repair experience and feel comfortable troubleshooting.

– How many times has the kiln been fired?
Some kilns keep a record of this in the circuits. All of the elements and thermocouples have a finite amount of use before they malfunction or break and must be replaced. Most thermocouples last from 100 to 150 firings before they start to “wander” and give inaccurate readings.

– What temperature was the kiln usually fired to?
The higher the temperature, the harder it is on all the components of the kiln (bricks, elements, relays, kiln sitter, etc).

– What condition are the bricks in?
New bricks will be smooth and off white in color with small pores throughout. Look for cracks, discoloration, missing pieces, fused or deformed bricks. The more cracks, missing pieces and discoloration to the bricks the less efficient it will fire. If long sections (4+ inches) of the element channels in the bricks are broken, the elements will not work as well (uneven firing) and will need more frequent maintenance (pinning) and replacement. Replacing broken bricks is doable, but time consuming and a pain.

– What condition is the lid in?
It should be smooth without large cracks or pieces of brick missing. The lid is held together by kiln cement and compression from a metal band around the outside. Check the clamps that hold the metal band together to see how secure it is.


What condition are the metal jacket and screws in?
Is there any visible rust or stains? It is not horrible if there are some rusty areas or stains. It can just help you get an idea of how much the kiln has been used and what kind of firings it has gone through. Most kiln jackets are stainless steel and will last a very long time. Are the screws that hold the controller and or kiln sitter anchored into the metal jacket?

What condition is the kiln sitter in?
Is the sensing rod straight and full sized inside the kiln? The sensing rod should be the same diameter on the inside as it is on the outside at the claw (about 1/8 inch).

Test the elements
Other than a visual inspection looking for collapsed elements, excessive corrosion, discoloration and reduced wire size, it is difficult to tell what shape the elements are in unless you turn the kiln on. If you really want to get into it and see what kind of shape the elements and relays are in you can run this test on a computer controller kiln:

– Ramp/Hold
– Segments 1
– Rate per hour 9999
– Temperature 750 F
– Hold 30 minutes

This will cause all of the elements to turn on full time. If the kiln is in good shape, in about 10-15 minutes, the kiln should be at about 400 F, you can open the lid with a glove and see all of the elements glowing red-hot. The top and bottom elements of most kilns have “hotter” elements so they will be brighter. If some parts of the elements look duller than others or some are not glowing at all, there are problems with some part of the kiln’s heating system. The possible costs and time to repair these problems can vary greatly. It could range from a few minutes and a couple of dollars for a shorted wire, to several hours of work and hundreds of dollars for new relays and elements.

Hooking up the kiln
Once you know the power demand for your kiln you need to get a certified electrician to run a connection from your circuit panel or sub panel to your kiln. It can be fairly costly if the distance from your kiln to the panel is 50 feet or more. Determine a safe location and follow the manufactures specifications for the minimum distance to a combustible material.

Happy firing! – Essay by Steve Belz