Kiln Parts and Functions

Have you wondered what parts make up a kiln and what each of them does? If you have, then this article is for you. 

Here, we will explore the various parts of the kiln and give a brief explanation of the roles they play. Bear in mind that there are many different types of kilns on the market, and not every design will have every part listed here. 

Lid

Top loading kilns, whether they be gas or electric, will have a lid. As you would expect, the purpose of the lid is to seal the top of the kiln and prevent heat loss. They are generally lined with a layer of fire brick or ceramic fiber material as an insulator.

Some lids may also have heating elements mounted in them and supply top-down heating.

Lid Latch

This one is very easy to explain. A lid latch is used to secure the lid in the closed position, whether to seal it during firing or to prevent debris from getting inside the kiln.

Door

Where top-loading kilns have a lid, front-loading kilns have a door. These are also lined with an insulating material and have a heat-resistant seal around their edges.

Their purpose is to allow easy access to the firing chamber and to prevent heat loss during firing cycles.

Door Handle / Latch

As you might expect, the purpose of a door handle is to make it possible to open and close the door on a front-loading kiln. This is where one difference between front-loading and top-loading kilns comes into play. 

Where the lids of front-loading kilns have a separate latch, the doors of front-loaders have the locking mechanism built into the door handle assembly.

Chest / Kiln Section

Many top-loading kilns are built with a modular design that makes it possible to expand them. Each of the sections is called a chest or kiln section. The ability to separate your kiln into sections also makes moving and cleaning it much easier.

Chest Handle

Many top-loading kilns are divided into sections that can be separated to make moving and performing maintenance easier. Each of these sections will have a set of handles used to lift it off the kiln and reset it later. 

Ring Latch

A ring latch is a lever-type latch that is used to secure kiln sections together and sometimes as a lid or door latch on a kiln. They consist of a lever mechanism with a ring mounted through it. The ring will usually be placed over a hook, and when the lever is lowered, pull the separate sections firmly together.

Slab or Kiln Floor

The kiln floor, often referred to as the slab, is the very bottom of the kiln’s interior. This is the area where kiln furniture is stacked, or large pieces often rest for firing. In many of the better kilns on the market, this area is one of the best-insulated parts of the kiln. 

Kiln floors are normally made of fire brick or ceramic fiber blocks.

Kiln Stand

A kiln stand is exactly what it sounds like. It is a set of legs that lift the kiln up from the floor and allows air to circulate around the kiln.

Some kiln stands are nothing more than a set of legs that attach to the kiln body. Other kiln stands involve a frame that fully supports the kiln’s lower section. These are the type of frames that are generally found on quality kilns.

Stand Feet

Stand feet are the very bottom of the kiln stand where contact is actually made with the floor. In most cases, these will be made out of rubber or silicone and are designed to provide a firm footing that prevents the kiln from sliding and protects the floor from being damaged.  

Lid Lifter

Lid lifters are usually found on larger top-loading kilns and are intended to make opening the heavy lids on larger kilns easier. They can take many different forms, including lever arrangements, spring-assisted lifters, and gas-assisted support struts.

Kiln Section

Some larger kilns are designed to be separated into individual sections that can be stacked and removed to adjust the size of the kiln, make maintenance tasks easier, or make them easier to move. Each of these modules is referred to as a kiln section.

Kiln sections are most commonly found in top-loading electric kilns and will include the outer body, an area of bricks, and the heating elements themselves. These sections must be properly mated for a kiln to function properly.

Bricks

KIln bricks are the insulating material that reflects and retains the heat produced inside the kiln. In modern kilns, bricks are most often made of refractory (high temperature) ceramic material.

However, you will occasionally still see clay kiln bricks used in larger kilns by craftsmen who produce more traditional types of pottery.

Bands

Bands are a very important feature of a kiln that requires careful attention. Normally made of stainless steel, their purpose is to hold the fire bricks securely in place and prevent them from moving. 

They are attached to the bricks using worm screws. Thes screws must be tightened periodically as the bricks naturally break down over time. It is very important that you keep the bands in your kiln clean and dry. Even though made of stainless steel, they can be attacked by the salts and sulfur compounds used in many glazes.

Peep plugs

Peep plugs often look like a series of cabinet knobs running up and down the outside of the kiln. These were originally used to allow the potter to peep into the kiln and monitor the firing process. 

Before electronic controllers came into use, potters would place one or more pyrometric cones in their kilns in line with the pep plugs. 

During firing, they would pull a plug and look to see if the cone had bent properly. If it had this signified that the wares inside had received the proper amount of heatwork to have fully matured. The potter would then shut down the kiln manually.

In modern kilns, peep plugs are primarily used to vent fumes from the kiln and to allow the kiln to cool faster. This last bit has to be done carefully because if the kiln is cooled too quickly, the thermal shock can cause ceramics to crack and break. 

Thermocouple

A thermocouple could be thought of as an electronic thermometer. In simplest terms, two different metals are bound together and when heated, the difference in their potentials produces a very small current. 

This current can be read and be used to determine the temperature they are being heated to. The higher the temp, the greater the current. 

In a kiln, they are normally weird into an electronic controller that reads the temp and automatically adjusts the current being fed to the heating elements in an electric or the solenoids in a gas kiln. 

Controller

Controllers are the brains of a modern kiln. First emerging in the early 1990s, they made it possible for us potters to have control of firings in ways we had never even imagined.

When they came on the scene, it became possible to take command not just of firing temps and time but to create custom programs with firing rates, holds, dwell time at different temperatures and even control the cooling rate of our wares.

All of the controllers that we are aware of operate on 24 volts. This means that the incoming power must first pass through a transformer that steeps it down. The controller itself takes readings from the thermocouple in the kiln and, depending on its programming, energizes or turns off the relays that act as switches for the heating elements in the kiln.

While controllers have all but eliminated the use of kiln sitters, it is still best to use pyrometric cones to make sure that the thermocouple and controller are functioning properly.

Kiln Sitter

Kiln sitters were the best method of monitoring the firing of a kiln before the advent of electronic controllers. They are still found in many older kilns and as an option on many newer models.

The basics of how they functioned were that a pyrometric cone of the desired firing temp was placed in the sitter before the kiln turned on. The potter would then manually control how fast their kiln heated. When the selected heat work had been achieved, the cone would bend over and activate a rod on the kiln sitter that turned off the power to the kiln.

Relay

A relay is an electromechanical switch that, when it receives power, is opened or closed depending on the type of relay. These are found inside almost all controller units and are used to turn the heating elements inside the kiln on and off.

Like any mechanical device, relays can go bad, so it is always best to use pyrometric cones inside strategically throughout your kiln during firings to watch for dead zones.

Heating Elements 

Heating elements, as the name implies, supply heat inside an electric kiln. These are resistance coils. When electricity passes through a resistance coil, the electrical energy is transformed into heat energy due to the resistance of the heating element material makeup and the interference of the magnetic fields created within the coil. 

Burner

In a gas kiln, instead of heating elements, you have gas burners much like what are found on gas grills or gas stoves. While most potters use electric kilns today gas burners do offer a few advantages. 

They do not require electricity, so they can be used off-grid. Since they produce actual flames that use oxygen, they can be used to create low a low oxygen atmosphere. This type of firing, referred to as reduction firing, can be used to create some stunning effects.

Flue

Flues are found primarily on fuel-burning kilns such as gas, wood, and coal-fired kilns. In the simplest of terms, they are gates that allow more or less airflow through the kiln. In some types of kilns, this is used to control the temperature of the firing.

Outside of industrial kilns, you are most likely to find a flue on a gas kiln used in a commercial pottery shop. On these kilns, if the flue is on the top of the kiln, it is called an updraft kiln as the flue allows or restricts the flow of air out of the top of the kiln creating an updraft.

If the flue is located on the bottom kiln, it is a downdraft kiln as air is pushed out of the bottom by pressure creating a downdraft. Downdraft kilns are generally considered to be more efficient than updraft kilns.

Hardware

Hardware is just a general term for all of the little minor pieces of a kiln. These could include screws, nuts, bolts, pins, terminal connectors, hinge pins, receptacles, and the like.