Though modern technology has led to the creation of ceramic and glass kilns with far greater safety features than early potters could have ever imagined, there’s no getting around the fact that kilns operate at extremely high temperatures and therefore pose severe dangers when used incorrectly or with negligence.
And a kiln’s heat isn’t the only safety concern: toxic volatiles are often released during fuel-burning (carbon dioxide), when firing soluble metal salts (sulfur dioxide), and during reduction firing (carbon monoxide). Overexposure to these volatiles can lead to blood oxygen levels falling, a rise in blood pressure, lung irritation, and in the case of carbon monoxide, drowsiness, fatigue, and even death.
In order to ensure the health and safety of yourself and others, as well as the longevity of your kiln, it is critical to familiarize yourself with the precautions and upkeep requirements that accompany kiln ownership.
In this guide we’ll outline the safety tips you need to know before, during, and after firing so as to help you develop good habits that will lead to smoother, safer kiln use.
Before you even begin firing, there are a few simple but crucial steps you won’t want to forget. Here are some things to get sorted before creating your glass or ceramic masterpieces:
Even though kilns are built with a significant amount of insulation, their outer surfaces can become hot enough to seriously burn bare skin. Whenever handling any part of the kiln, kiln mitts or gloves should be worn. Additionally, be sure to buy dark glasses from a safety supply house - long-term viewing inside a kiln can cause serious eye damage due to the radiant heat. IR and UV protective glasses will not only keep your vision safe, they will allow you to see your cone packs more easily. Note that regular sunglasses are not sufficient and may melt when exposed to a kiln’s heat.
If bought new, your kiln will come with a manual; be sure to follow it closely. If you buy a used kiln, be sure the previous owner includes a manual or visit the manufacturer’s website to obtain proper installation instructions. Observe building and safety codes, never use an extension cord, and make sure your kiln is located in a dry place to prevent electrical shock and corrosion.
All kilns need to be properly vented either outdoors or to the outside so as to limit the user’s contact with toxic and irritating gases. While there are several venting methods to choose from, if installing a venting system, it is recommended you use a licensed heating, ventilation, and air-conditioning (HAC) contractor, as they will have the equipment for installing and accurately testing the adequacy of a system’s ventilation. Here are the three main types of systems:
Updraft kiln vent system: An updraft venting system removes vapors as they rise. It consists of a hood with a fan mounted over the top of the kiln, and may be custom built by a HAC contractor or purchased ready made. If using a hood, it is important to note that you should always turn it prior to loading your kiln so as to prevent ceramic glaze dust exposure.
Downdraft kiln vent system: This system draws unwanted fumes from the base or bottom of the kiln. In order to create this effect, a hole is drilled into the top of the kiln and on the bottom of the kiln, a collector or plenum is added to the bottom of the kiln, and an electric fan, located nearby, draws off fumes. This can also be done independently or with the help of a HAC contractor.
Crossdraft kiln vent system: The most basic type of venting, a crossdraft system relies on fans placed near the kiln to move air from the surrounding area out through a nearby open window or door. If using this method, be sure to prop the lid open during the carbon burnout period and leave open the top peephole if there is one. While this is the easiest and cheapest method of ventilation, it removes the least amount of unwanted kiln exhaust.
A kiln needs at least a foot of clearance, so double-check that you’ve given your machine suitable space and that you’ve removed any potentially combustible materials from the surrounding area. Additionally, nothing should ever be left on top of a kiln during firing. Before starting your kiln, make sure that the power cord doesn’t touch any portion of the kiln that gets hot, and keep a fire extinguisher near by. Finally, be aware of any fire sprinkler systems located in the kiln room that might be triggered by high firing temperatures. To make sure they are high enough, test them by setting your kiln to peak temperature with the ventilation system turned off and all doors and windows closed.
Once your pieces are in the kiln, here are some tips for safe firing:
If it is necessary to open your kiln during firing, caution should obviously be practiced for all models, but while a front-loader or clamshell allows you to stand to the side, a top-loading kiln results in heat escaping straight up and potentially into your face. When opening a top-loading kiln, be sure to avoid standing directly in front of it and wear protective gear.
Even for short periods of time, it is important to shield your eyes from radiation. Never touch a heating element during firing: Even if you are wearing gloves, heating elements will cause an electrical shock if touched. To further avoid electric shock, never insert metal instruments into the kiln while it is firing.
Due to the fact that trapped heat will be let out quickly and intensely when they’re removed, peephole plugs should be removed with caution.
Once your projects have finished firing, there are still a few essential steps you’ll want to take. Here’s what you should keep in mind:
Even after your kiln has been turn off, it will remain hot for hours. Don’t open or touch it until it is fully cooled and handle it only while wearing gloves or kiln mitts. Unloading the kiln should only take place when your pieces can be easily touched by hand.
Though it may sound obvious, it is very important to unplug your kiln before performing any maintenance, repairs, or work on the electrical components, so unplug it after firing every time, just to be safe. Additionally, don’t unplug or plug in an electric kiln unless the circuit is off.
Especially for kilns insulated with firebrick, frequent and thorough cleanings are crucial so that no foreign matter will be exposed to the heating elements and short them out.
Finally, here are some general rules all artists should live by to ensure the wellbeing of themselves, others, as well as their kiln:
Keep your kiln away from kids and pets.
Never allow your kiln to exceed the temperature rating listed on the serial plate.
Fuel-fired kilns need to be attended during the beginning of their warm-up period until the flash point of the fuel has been reached.
Don’t place anything in the kiln you are unsure of. Firing unknown materials is risky; some items may melt, explode, or release toxic fumes when fired.
Kiln upkeep is extremely important. Be sure to regularly check electrical components and immediately replace any that are damaged, discolored, corroded, or brittle.
Additionally, make sure kiln lids have braces that are secure and not corroded.
Never wear loose-fitting clothing around a hot kiln.
Avoid eating and drinking in the studio. Toxins and dust are easily ingested when you handle food and kiln working materials in the same space.
Always wash your hands upon leaving the studio so as not to risk tracking or exposing toxins and dust to other locations or people.
In a similar vein, consider dedicating a pair of shoes to studio use only.
Don’t smoke while your kiln is firing. Smoking has been proven to increase the rate at which many toxins are ingested.
We hope you’ve found this guide helpful! Please contact us with any questions you may have - we’re always glad to help - and happy firing!
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