How to Use a Kiln (Step by Step Guide for Firing Pottery)

Firing a kiln for the first time can be a little intimidating. If you are new to pottery, we have you covered.

In this guide, we will walk you through the process of setting up your kiln and firing pottery. We will also address some of the most frequently asked questions we encounter.

How to Use a Pottery Kiln (Step by Step)

Even if you have never used a kiln before, just follow these steps, and you should find success. To make it a little easier to follow, we will break these instructions down into major steps and then reduce each step into more detailed substeps.

Step 1 Prepare Your Kiln

An ounce of prevention is worth a pound of cure. Properly preparing your kiln goes a long way toward assuring you will have a successful firing, and your creations will come out unmarred by defects.

Vacuum Your Kiln

When a kiln is used, small amounts of brick dust and tiny particles of clay and glaze are generated. Even if a kiln has just been sitting, dust and debris in the air can settle inside it. There are a couple of issues this can cause.

The first is that dirty coils are less efficient and cost you more to heat. They also tend to develop hotspots that shorten their lifespan and cause them to burn out earlier than they should.

The other issue is dirt in your kiln can be stirred up when you fire clay and settle back on your pottery. It doesn’t take much to ruin the finish of what could have been a beautiful creation.

So, whether your kiln has been sitting for a day or a year, give it a good vacuuming. Be sure to pay special attention to the coils, and don’t forget the kiln lid if it is a top-loading kiln.

Perform a Safety Inspection

You can never be too safety-conscious. Inspect your kiln for any loose or missing hardware. Inspect every screw, nut, and bolt. The thermal expansion caused by firing can cause things to work loose and loose things to fall off, so be thorough.

Make sure that there are no electrical cords or flammable materials touching or too close to your kiln. Even the outside of some kilns can get hot enough to cause spontaneous combustion. So again, err on the side of safety and keep the area around your kiln debris free.

An often overlooked area when doing a safety inspection is the area above your kiln. Obviously, kilns generate a lot of heat. If your fire alarm is over your kiln and it is heat activated, you could find yourself in an embarrassing situation.

Even worse, if you are in an educational or commercial setting, you could activate the building’s sprinkler system.

Any alarms or fire suppression systems in a room with a kiln should be equipped with high temperature fusses or sensors.

You should also check and make sure your ventilation system is working properly.

Test Fire Your Kiln

The best time to find a hidden problem is before it ruins your hard work. For that reason, we strongly suggest you run your kiln through a test firing before you load it with ceramics or pottery.

Go ahead and load your kiln with shelves and any other kiln furniture you plan on using for your firing. Place a 04 Self Supporting Witness Cone on each shelf approximately two inches from the kiln wall. Be sure to place one next to the thermocouple.

Now set your kiln for a low fire cycle. Think like light bisque firings (Cone 04-06). If you are using a manual kiln, this would mean bringing the temperature up slowly over a number of hours.

For an electric kiln with programmable controls, just choose a medium-speed 04 ConeFire program. If your kiln has a downdraft vent, be sure the flue is properly set. Also, make sure your ventilation system is operating properly.

Now you can seal the lid on your kiln and turn the kiln on. Make a note of the time so you can calculate the time needed for your kiln to complete the firing process.

The elements in electric pottery kilns have relays that energize and shut off the various elements. Listen closely to the control box on your kiln. You should hear clicking coming from these relays as they energize and shut off power to the heating elements in your kiln. Observing the temperature reading, you should see the numbers beginning to climb.

As the temperature reading approaches your target temperature, the climb should slow, and you should once again hear the relays clicking. Relays can stick. If you don’t hear them drop or the temperature inside your kiln continues to climb, turn the kiln off and call a service technician.

If at any point you see smoke or smell burning plastic, turn the kiln off immediately and call for a service technician.

One bit of caution here is that it is normal for a new kiln or one with brand new coils installed to smoke slightly as the oils used in the manufacturing process are burned off.

Allow your kiln to complete its firing. For a manual kiln, be sure the kiln sitter shuts it down at the desired temperature.

Don’t open the hot kiln. The thermal shock of opening the kiln lid too early can cause damage to your kiln brick, kiln shelf, and other parts of your kiln. Allow your kiln to cool down naturally.

Once your kiln has cooled slowly to near room temperature, you may open the lid and remove the kiln shelves and cones. Be sure to wear loose-fitting clothing and heat-resistant gloves as the kiln furniture can retain a great deal of heat.

Inspect your kiln furniture and the firing cones closely. Cracked shelves can indicate hot spots within your kiln.

Each cone should be bent twenty degrees or slightly more but not be leaned over and touching the shelves or still standing straight. Cones leaned over too far indicates that that area of your kiln is overheating. Cones that are only slightly deformed or still straight tell you that you have a dead zone in your kiln.

This could be because the heating elements in this area are burned out, or the relay controlling them is worn and needs replacing. In either case, you will need to consult with a service technician to correct the issue.

If the cone next to the thermocouple is bent completely over, it is a strong indicator that the thermocouple needs to be replaced.

Step 2 Load Your KIln

Assuming that everything went well with your test firing, you are now ready to load your kiln and begin firing clay.

Positioning Kiln Furniture

How you set up your kiln prior to firing greatly impacts how successful your efforts will be. Kiln furniture and how it is positioned is often an overlooked element but should be considered carefully.

It is best to position your shelves with at least one element radiating between shelves.

If you are using half shelves, leave a quarter to half-inch gap between them. It is also best if you can stagger their height slightly to help improve the natural airflow within your kiln.

Load Your Clay Ware

First and foremost, never fire a wet clay body.

Doing so will not yield good results and can be dangerous. There have been cases of kilns being damaged and people suffering severe injuries from damp clay exploding.

When positioning pieces to be fired, Be sure to maintain proper clearances inside the kiln. You should always have at least two inches of open space from the kiln lid and thermocouple.

You should also always maintain a minimum of one inch of clearance from the kiln floor and walls. Most kiln elements are located in the walls and require space for their heat to radiate

Try to spread the mass as evenly throughout your kiln as possible. The one exception to this is if you know you have an area in your kiln that fires cooler. Then you should load that area a little less densely than the rest of the kiln.

Lastly, you should place Self-Supporting Pyrometric Cones throughout your kiln to monitor how your kiln is firing clay. Electric kilns will ideally be firing evenly throughout the firing chamber.

Things rarely work perfectly. You will likely find that some areas have high temperatures while others will suffer slow firing.

Step 3 Program Your Kiln

If you have a manual kiln, you will have to set your temperature controls to the desired temp for the clay you are firing and set your timer or Kiln Sitter with an appropriate guard cone.

If you have a programmable controller, then you may have several options at your disposal. Every major kiln manufacturer has its own controllers with its own features. This makes it a little difficult to give detailed instructions on how to properly set your kiln.

It must also be considered that we have no way to know what type of clay you are firing, whether you are even firing clay, and what point in the creative process you may have reached.

Most better kilns give you some options that equate to firing to a specific cone or a way to program ramp/hold sequences.

If possible, using cone firing settings will be the simplest and most foolproof way to set up your kiln. They are also the most commonly used setting used by most potters.

Ramp/hold settings, in the majority of cases, are reserved for specialty glaze firings like high fire glazes and working with glass, metal clay, or other non-ceramic pieces.

Our best advice is to follow your manufacturer’s suggested programming sequence for the particular materials that you are working with. If your guidebook is no longer available, most companies have tech support or YouTube videos posted to walk you through the programming of your kiln.

Once you have completed programming your kiln, you can close the kiln lid and begin firing.

Read Next: Best Home Ceramic Kiln

Step 4 Unloading Your Kiln

Now comes the moment that you have been waiting for. Opening your kiln and seeing the fruits of all your labors.

A word of caution here. Do not get in a hurry and open your kiln too soon. It is completely understandable to be anxious to see your finished works but fight the urge.

Wait For the Temperature to Drop

Opening your kiln too soon opens you and everyone in your kiln room to inhaling clay molecules or vapors from your glaze firing. There is also the very real risk that all of your hard work will be wasted due to thermal shock.

Thermal shock can cause your ceramics to crack or glaze to craze. The first firing or bisque firing often results in broken pieces when rushed.

While this second effect is actually sought after in some art forms, be aware that pottery or ceramics with crackled glaze are not considered food safe.

If your glaze firing has resulted in a crazed finish, the tiny crevices can trap food particles and provide a haven for microbes that can cause severe illnesses.

Wait until the temperature inside your kiln has dropped below 125 degrees Fahrenheit (50 degrees Celsius). Even better is to wait until it returns to the ambient temperature of your kiln room.

Remove Your Fired Pottery

Now you can carefully remove your fired clay from the kiln. Again, don’t be in a rush and pay attention to what you are seeing in your kiln.

It is easy to become overwhelmed with inspecting your artwork. The thrill of holding a freshly fired work never goes away. If you want to improve your craft, though, you must learn to observe each firing.

Inspect each piece as you remove it and note where it was in your kiln. Look for signs of uneven baking that could have resulted from heating elements that got too hot or didn’t reach temperature evenly.

See Also: How Hot Does a Pottery Kiln Get?

Inconsistent finish in a bisque firing or glaze that didn’t flow evenly are two danger signs.

Also, pay attention to each firing cone that you placed in your kiln. Make a note of its rating, where it was located in your kiln, and how far it has bent over.

Step 5 Update Your Firing Log

What you learn from today is what helps you improve tomorrow. Just as importantly, it can help you diagnose possible problems early before they become major issues.

Be sure to keep a firing log. Diagram where each piece was located, its size, and shape. Include the sizes and type of kiln furniture that was used and how it was arranged. Record the details of your firing cones and any issues you noticed in your fired clay or glaze.

Over time you will learn how your particular kiln likes to be loaded, where it is a little hotter or cooler, and what furniture it likes arranged how.

These may seem like minor details, but when viewed together, they will begin to tell you a story that will make it possible to steadily improve your results with each firing. They will also make any developing issues stand out where you can have them corrected before you waste an entire kiln of work by firing clay in a failing kiln.

FAQ

How long does it take to fire clay in a kiln?

It normally takes 20 to 25 hours to fire clay from freshly formed to finished work. Most pottery or ceramics are fired twice. The first firing or bisque fire will normally take 8 to 10 hours. Then glazes are applied, and a glaze firing is run. This can take an additional 12 hours.

Factors such as the size and type of your kiln, Hoe full it is, and the type of clay or glazes used can greatly impact these times. The times listed include average cooldown periods.

What is kiln firing in ceramics?

Firing means bringing clays and glazes to a high heat. The purpose of kiln firing is to bring them up to or near a fusing point where they will physically change and mature. This results in pottery that is non-porous, food-safe, and very durable.

A kiln is a large high temperatures oven that is used to heat the clay sufficiently and hold it for a proper amount of time for these changes to take place.

How much does it cost in electricity to fire a kiln?

According to the Energy Information Administration, the average cost of electricity in the United States is 14 cents per kilowatt-hour. However, prices can vary widely from $0.04 per kilowatt-hour in Washington to $0.39 per kilowatt-hour in Hawaii. Your costs locally should be listed on your electric bill.

To calculate the cost of running your kiln:

1. Find the wattage of the kiln on the information plate next to where the power cord enters its body.
2. Divide the wattage by 1000 to convert it to kilowatts.
3. Multiply the results by the cost per kilowatt listed on your most recent electrical bill.
4. This will tell you how much it will cost on average for each hour your kiln’s heating elements are actually energized.

Remember that most kilns do not continuously energize their heating elements. They cycle on and off. If your kiln has an electronic controller, you should be able to read the actual burn time from your controller’s readout. For manual kilns, you will need to listen for the relays to drop in and out to get an accurate time. The total firing time multiplied by 0.7 is widely considered a good working average.