Kiln Firing Checklist

What it actually takes to fire a kiln

Most people budget for the kiln and nothing else. Then the kiln arrives, and the list starts. The garage outlet is a 120 volt duplex and the kiln wants a 50 amp 240 volt circuit. There is no shelf in the box. The nearest wall is eight inches away and it is drywall. The pallet weighs 400 pounds and the driver is not coming past the curb.

None of that is unusual, and none of it is expensive to solve if you know about it in advance. The checklist above is built from the published specifications of the exact kiln you selected, so the numbers it shows you are your kiln's numbers rather than generic advice. Below is the reasoning behind each section, which is worth reading once before your kiln ships.

1. Electrical: start here, start early

The single most common delay we see is electrical. A customer orders a kiln on Monday, it arrives Thursday, and the electrician's first opening is three weeks out. Call an electrician the day you order, not the day the kiln lands.

What your electrician needs from you

• Voltage. Usually 240V for anything above a small test kiln, 120V for tabletop and jewellery ovens, and 208V in a lot of commercial and school buildings. 208V and 240V are not interchangeable for performance: the same kiln on 208V draws differently and fires slower.
• Amperage. The continuous draw of the kiln at full power.
• Breaker size. A kiln is a continuous load, so the National Electrical Code requires the circuit to be sized for at least 125% of the kiln's rated draw. A 48 amp kiln therefore wants a 60 amp breaker, not a 50.
• Wire gauge and run length. The gauge in a spec sheet assumes a short run. A long run from the panel to a detached garage usually needs the next size up of copper. Your electrician will work this out; just tell them the distance.
• Plug or direct wire. Some kilns arrive with a moulded plug, some with a pigtail, and larger kilns are hard wired with no plug at all.
• Dedicated circuit. The kiln gets its own breaker. Nothing else on it. Not the freezer, not the shop lights.

Common kiln receptacles

Does my panel have room?

A full size pottery kiln on a 50 or 60 amp breaker is a large appliance, roughly on the order of an electric range or a hot tub. In an older 100 amp service that is already running a dryer, a range and an air conditioner, the answer is often no without a service upgrade. That is a real cost and a real lead time, and it is much better discovered before the kiln ships than after. If you have any doubt, have an electrician do a load calculation first.

2. Where the kiln is going to live

Kilns get hot on the outside too. The skin of a firing kiln routinely sits well above the temperature at which wood and drywall begin to break down, and the air above one behaves like the air above a fire.

• Clearance to combustibles. Plan on at least 18 inches of open air on every side, including the back. Some manufacturers allow 12. Check your manual and use the larger number if you have the room. More clearance also means a cooler room and a longer element life.
• Overhead. Keep at least three feet clear above the lid, and nothing combustible above it at all. No shelving, no plastic sheeting, no low joists.
• Floor. Concrete is ideal. Over a wood floor you need a non combustible base, and cement board on top of the stand is the usual answer. Carpet, vinyl and laminate are never acceptable under a kiln.
• Stand. Top loading kilns sit on a stand that lifts them off the floor and lets air circulate underneath. This is not optional and the stand is often a separate line item.
• Dry and weather protected. A carport or an unsealed shed will corrode the metal and soak the brick. Damp brick can spall on the first firing.
• Access. You have to be able to reach into the kiln comfortably and open the lid fully without hitting anything.

Garage, basement or outbuilding?

Garages are the most common home kiln location and usually the best one: concrete floor, a door to vent through, and room to keep clearances. Basements are workable but harder to vent and harder to get a 400 pound crate into. Detached studios and outbuildings are excellent provided the electrical run is accounted for. A spare bedroom is almost never a good idea.

3. Venting

Firing clay burns off organics, sulphur compounds and carbon monoxide. Glazes can release fluorides and metal oxides. Glass firing and binder burnout produce their own fumes. In a sealed room with no vent, that all ends up in your lungs.

• A downdraft vent system is the standard answer. A small blower pulls air through the kiln and ducts it outside. It also improves firing consistency and element life because it gives the kiln a controlled source of oxygen.
• An overhead hood is the alternative, typically used on front loading and larger kilns.
• Cross ventilation alone, meaning an open door and a window fan, is the bare minimum. It is acceptable only in a detached space you are not occupying during the firing.
• Never fire a kiln in a space that shares air with a bedroom, and never sleep in a house while a poorly vented kiln is running.

Carbon monoxide detection is cheap insurance in any space with a kiln, and mandatory in any space with a gas kiln.

4. Kiln furniture: the part nobody budgets for

With rare exceptions, a kiln ships empty. No shelves, no posts, no wash. You cannot fire pottery in an empty kiln, so the furniture kit is not an accessory. It is part of the purchase.

• Shelves carry your work. They are sized to the kiln, so a shelf for one brand's 23 inch kiln will not necessarily fit another's. Full rounds and half rounds let you stack flexibly, and most potters want a mix.
• Posts set the height between shelves. You want a range of lengths, not all one size, and you want an even number of each so shelves sit level on three posts.
• Kiln wash is a refractory coating painted on the top of each shelf so that a glaze run releases from the shelf instead of welding to it. Re-coat as it chips. For glass work you use a shelf primer or fibre paper instead.
• Stilts and setters hold glazed pieces off the shelf during a glaze firing.
• A furniture kit bundles the right shelves and posts for your specific model, which is almost always cheaper and less error prone than buying the pieces individually.

Heat treating ovens, knife ovens and burnout furnaces generally do not use kiln furniture in this sense, so the checklist leaves this section out for those models.

5. Firing supplies and monitoring

• Pyrometric cones. A controller reports temperature. Cones report heatwork, which is temperature and time together, and that is what actually matures clay and glaze. Put a witness cone on a shelf in every firing until you know your kiln. It is the only way to find out that the controller and the kiln disagree.
• Know your controller. A digital controller fires a programmed schedule. An older kiln sitter is mechanical and uses a small cone bar that bends and trips the switch. They behave completely differently, and a kiln sitter needs the right cone bars on hand.
• A firing log. Date, program, cone number, what came out. Six firings in it will tell you more about your kiln than any manual.
• The first firing. New kilns want a break in or bisque out firing to cure the elements and drive moisture out of the brick, run empty and slow. Your manual will give the schedule. Skipping it shortens element life.

6. Safety gear

• Heat resistant gloves rated well above the temperature you will be reaching into. Welding gloves are not a substitute.
• Eye protection with an infrared rating for looking into the peephole of a hot kiln. Staring into a cone 10 kiln with bare eyes is genuinely harmful.
• A dust respirator for mixing kiln wash and handling dry clay or ceramic fibre. Silica dust is cumulative.
• An ABC fire extinguisher within easy reach of the kiln, not across the room.
• Carbon monoxide detection in the space, and smoke detection nearby but not directly above the kiln, where normal firing heat will set it off.

7. Spares, and why they matter more than you think

A kiln is a simple machine with a few parts that wear out predictably: elements, relays, thermocouples. When one fails it fails mid firing, and a load of greenware or a kiln full of commission work is sitting inside it. A $40 relay you do not have is a two week delay. A $40 relay in a drawer is a twenty minute repair.

• Relays are the most frequent failure on a digital kiln. They are a consumable with a click count.
• Thermocouples drift and eventually fail. A drifting thermocouple under fires or over fires your work long before it dies outright, which is exactly why you keep using witness cones.
• Elements last hundreds of firings and then go all at once. A spare set is the difference between a weekend repair and a month of downtime.
• Emergency parts kits bundle the common wear parts for your specific model.

8. Delivery day

Full size kilns ship freight on a pallet, and freight is not parcel delivery. Know this before the truck arrives.

• Standard freight is curbside. The driver brings it to the end of your driveway on a liftgate and that is where their responsibility ends.
• Getting a crated kiln from the curb into the garage is a two person job with an appliance dolly, and more than that for the largest models.
• Measure your doorways and your path. Add the crate, which is bigger than the kiln.
• Inspect before you sign. Walk around the crate, photograph any damage, and note it on the delivery receipt before the driver leaves. Signing a clean receipt for a damaged crate makes a freight claim very difficult.
• Someone has to be there. Freight carriers call ahead to schedule, and missed appointments get re-delivery fees.

Firing checklist FAQ

Specifications shown in the checklist are taken from each manufacturer's published documentation. Electrical figures, including any breaker size we derive from the NEC 125% continuous load rule, are provided for planning only and are not an electrical design. Installation must be carried out by a licensed electrician in accordance with your local code. Always follow the manual supplied with your kiln.