FrogBlog
How to Fire Pottery Without a Kiln
Pottery is a beautiful and expressive art form that has been practiced for centuries. While kilns are the traditional method for firing pottery, not everyone has access to one.
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Ceramic Kilns: What buyers need to know
When you are looking for the perfect kiln, you might think there is one out there that does it all, but kilns are made for specific purposes. The perfect ceramic or pottery kiln might be a poor choice for an enamel artist. The best knife oven would not necessarily be great for a glass fuser. In the next few weeks, we are going to take a look at several different categories of kilns and discuss what we think are important features to look for when you are deciding on your next kiln. Clay remains one of the busiest corners of the craft world, as recent pottery participation figures confirm. Let’s start with kilns for clay artists! Let’s Talk Ceramic/Pottery Kilns: Firing Temperature The first thing you should look for is firing temperature. First, we should point out that clay people use a measurement of heat called “cones”. For over 100 years, ceramic artists have used the pyramid shaped, ceramic pyrometric cones to measure heat in kilns. The cones are made from very carefully controlled clay compositions and they will bend at a specified temperature. We can thank Dr. Edward Orton Jr. for coming up with this very easy and accurate way to measure heat in the kiln environment. Of course, today we use digital controllers to keep track of the heat work in our kilns, but we still use the same cone ranges specified by Orton when referring to the various temperatures at which our clays and glazes reach maturity. So, which cone do you fire to in order to get your clay to maturity? Do you want the flexibility to fire all the way to cone 10, or are you strictly a low fire clay kind of guy or gal? Firing temperature is important for every kiln type, but in ceramic kilns there are many possibilities, and you don’t want to limit your creativity by purchasing a kiln that will only fire low fire clays if that isn’t your thing. Here are the temperature ranges that you should be familiar with: Low Fire – cone 09 to cone 1, or 1700º F to 2100º F. Low fire clays have the widest range of maturing temperatures, so knowing your preferred clay is important here. Mid Fire – cone 5 to cone 6, or 2167º F to 2232º F. High Fire – cone 8 to cone 10, or 2280º F to 2345º F. Most ceramic kilns will either be rated to 2100ºF (cone 1), 2300ºF (cone 8), or 2350º F (cone 10), so choose a kiln that is right for your clay of choice. (If you’re not sure which clay you’re planning on using, err on the side of a cone 10 kiln. This will give you the most flexibility.) Heat Source Now that you have your firing temperature satisfied, be sure you have the right heat source. Ceramic kilns will almost always have side firing elements. If you are looking at a front-loading kiln, you might want to include door elements so that you get heat evenly distributed coming from all sides. Most smaller front-loading kilns do a really good job of heat distribution with only the elements in the three stationary walls, but the larger front-loaders really do benefit from door elements. Round or octagonal kilns benefit from the perfect, even heat distribution that clay needs for a good firing. Power Supply Make sure you have the right power supply for your kiln. This is always important, but since ceramic and pottery kilns usually fire pretty hot, you will most likely need to have a 240v power supply. Always consult your electrician to see what size breaker you need for the kiln that you have your heart set on. There are a few 120v ceramic kilns out there, but they are very small, and typically are used to test glazes, or for jewelry projects like beads and barrettes. To get a large volume of space up to ceramic firing temperature requires more juice, so you are going to want to be sure you have an adequate power source for the kiln that you purchase. A good way to think of this is more space=more power. 120v and 240v kilns will have different power cords according to the amperage rating of the kiln. Again, consult your electrician once you have your kiln selected to make sure that the circuit for your kiln is the correct voltage, has the proper receptacle, and has the correctly sized breaker for the amount of power the kiln is pulling. For very large kilns, you might need a direct wired connection. You can find diagrams of the various outlet configurations here: https://kilnfrog.com/pages/what-type-of-plug-do-i-need Top Loading vs Front Loading Most ceramic and pottery kilns are round or octagonal in shape and load from the top. This is a very traditional design for ceramic kilns, but there is another option! A front-loading ceramic kiln makes getting larger pieces in and out of the kiln, especially in greenware, much easier! Front-loading ceramic kilns are typically larger and very well suited for the production ceramicist. Even if you are a hobbyist, the ergonomics of a front load kiln might be something you’d prefer. Round, deep kilns are harder on the back to load and unload, and if your height challenged this can be even more difficult. Plus, the wider the kiln, the heavier the lid can be, making it an even tougher job. The trade-offs between the two loading styles run deeper than lid weight alone. Shape Kiln shape is another thing to consider when looking for a ceramic kiln. As I mentioned earlier, the traditional ceramic kiln is a round or octagonal shape that is tall enough for at least two or three layers of shelves. That being said, there are some great square top-loading and front-loading ceramic kilns out there. When you are considering what is the best fit for you it might be a good idea to lay out a typical load of your largest sized pieces and see what shape works best to utilize as much of your kiln space as possible. To Vent or Not To Vent… what are the options? Now we all know that kilns need to have adequate ventilation in their environment, but ceramic and pottery kilns also benefit greatly from interior ventilation systems. Usually referred to as a VentMaster, these internal vent systems give you many benefits in your firings: In the greenware to bisque stage, an internal vent system helps to get the excess moisture out of the kiln more quickly. During the glaze firing, internal vent systems get rid of excess moisture during the first portion of the firing, but also help your glazes to mature properly and develop more intense colors, especially in the red and yellow hues. If you are using glazes that have any toxic elements, this internal venting is essential to keeping your work environment safe. All of the noxious fumes inside the kiln are exhausted outside where they dissipate quickly and are not trapped inside with you! Vent systems typically have a vent hole in the floor of the kiln where the vent attaches. The vent then pulls a small amount of air through the body of the kiln via a vacuum effect and then exhausts that air through an exhaust vent hose which you direct away and out of your firing area. This could be done through an exterior wall or through a series of hoses through a window, or out a doorway, or even into another wider, better-ventilated space. Paragon and Olympic have the option of supplying a 240v Auxiliary Output Plug (AOP) on their controllers that will allow you to program when to turn your VentMaster on and off during your firing with the 12-key and smart touch controllers. In order to take advantage of this feature, you should specify the AOP option and the 240v VentMaster. Otherwise, the 120V VentMaster is simply plugged into a regular household outlet and turned on and off manually. Kiln Furniture Kiln furniture is an essential part of any kiln, but with ceramic and pottery kilns you typically have enough shelves and posts for several layers in your ceramic kiln. When we say furniture, we don’t mean sofas and chairs. Furniture is an industry term for stuff in the chamber to hold up clay ware. It means the kiln shelves, the posts, the stilts, the tile holders, or anything you need to support the items you are firing. All of our ceramic kilns have available shelf/furniture kits that include everything you need to set up multiple layers of pottery in your kiln, so don’t forget to add the furniture kit to your cart when selecting a kiln. Size And then there is size, and it does matter! Many people will tell you to buy the largest kiln you can afford, and there is a lot of wisdom in that train of thought. However, you don’t want to get a kiln that is so large that it takes you weeks to fill it up. That could get a bit frustrating if you are the type of person that loves to see results quickly. Of course, as you grow your skills as an artist, you might easily grow into a larger kiln. Speaking from personal experience, it takes a lot more planning to arrange work in a kiln when you work is 18-20 inches tall than when it was 6 or 7 inches tall. That’s where those half shelves that you see in the furniture kits come in handy! My last load of pottery had one half of my 22” tall kiln loaded with just two 18” vases on the bottom shelf, but the other side had three layers of shorter vases and bowls stacked up. Location, Location, Location Lastly, it is always good to keep in mind where you will put your new kiln when it arrives. Remember that ceramic and pottery kilns are usually reaching temperatures in the 2200-2350º F range and you should have a minimum of 12-18” of clearance from any combustible materials around your kiln. You should also have plenty of air circulation and ventilation in the space where you kiln will be located. It’s a great idea to have a portable fan that you can direct on your controller box to help keep it cool and happy. Also, think about where you will store your shelving, posts, and other kiln furniture in the vicinity of the kiln. Make room for the essentials like your shelf primer too! Hopefully this information will help in your decision making when considering a new ceramic or pottery kiln. If you need to talk things out, give us a call or shoot us an email. We are always happy to help you talk through your options and help you find the best fit for your needs.
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Peepholes and Venting
Last week, we got an e-mail with a bunch of great questions about peepholes and venting your kiln when using powdered enamels--like EZ Fire enamels--dry on copper. So, we thought that we would give you some insights on venting for all kinds of enamels on glass, and metals too. Hopefully, this Q&A from Gail will help you in the future... it always helps me! Why does my kiln have a Peephole? Large peepholes (viewports), tapered for a wide view without heat loss, were originally designed for manual kilns so you could see when the pyrometric cones bent. With venting as their secondary function, peepholes allow oxygen to be drawn into the kiln’s chamber and serve as an escape passage for metal oxides, smoke, and water vapor. Do I need a Peephole Plug? Peephole plugs are used to stop air from entering the kiln, not to prevent heat loss. But a kiln shouldn't be vacuum sealed, so It is beneficial to have some air entering the kiln at all times, It is not necessary that the plugs fit tightly. What is the best shape for a Peephole Plug? Peephole plugs are typically made of a lightweight ceramic material that can handle thermal stress well. Many plugs are interchangeable with different kilns, and the type of plug that is chosen is typically based on individual preference. The plugs with a tapered shape are designed to fit in just about any hole. Should I leave the Peephole hole open or closed during firing? For plain old glass fusing and slumping, always fire the kiln with the plug in the hole as it helps the kiln reach temperature more easily. If you chose to leave the peephole out during firing to improve the oxygenation inside the kiln, be aware that this may cause a cold spot in the kiln. When firing dry enamels on copper, leave the plug in the hole until you reach the top processing temperature, then remove it for proper oxygenation of colors as you insert your trivets and fork. When you are firing red, orange, or yellow enamels you should remove the plug so that more oxygen circulates in the firing chamber, keeping the colors bright. When firing liquid enamels on glass, leave the kiln vented or plug out until your reach 1000F. Then place the plug back in the hole. SOME (not all) liquid enamels need oxygen to develop to their juiciest potential! If you want the kiln to cool faster, remove the plug. If you are doing a wax burnout, remove the plug. If you are doing a hollow core metal clay project, remove the plug. Are there fumes that come out of the Peephole that I should be careful of? That depends on what brand of enamels... SAFETY FIRST! OLDER ENAMELS MAY CONTAIN LEAD THAT CAN BURN OFF IN THE TORCH OR KILN and will require proper kiln ventilation of the area. Always do your research on enamels before you plan to use them.
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Kiln and Oven Troubleshooting
Happy New Year ! After reading dozens of "I am so excited for my new kiln" posts, I thought I would share some Kiln and Oven Troubleshooting advice that I got from our friends at Evenheat Kilns. Brick Cracking and Hairline Cracks Hairline cracks are common in all kilns and should not be a concern. Bricks expand and contract when heated and then cooled. The cracks will close as the kiln gets hotter. This is most prevalent in the kiln top or bottom. Kilns fired at the higher temperatures will experience more spalling and cracking of the brick. Kilns cooled down too rapidly will effect the amount of cracking. If you are repairing a broken brick, repair cement should be used to adhere the broken piece back into place. If a brick breaks under an element and is impossible to repair, an element pin can be used under the coil to prevent drooping. Fuse "Blows" or Breaker Trips Immediately when Kiln is Turned On Generally speaking, if a fuse "blows" or circuit breaker trips immediately upon applying power to the kiln, or pressing the start keys, it indicates a short circuit within the kiln itself. It's also possible that the fuses or breakers protecting the circuit are not sized properly. Check the wiring for any signs of arcing (visual and smell). If there is any evidence of arcing, call a qualified electrician to fix the problem. This must be fixed before you continue firing. Another cause of this issue, is that the electrical service to the kiln is wired incorrectly. Have a qualified electrician check the electrical service from the main service to the kiln. There have been incidences where the connections from the electrical pole outside to the main service at the house has been loose. Finally, it could be as simple as the circuit is overloaded. The easy remedy to this is just disconnect all other appliances on that circuit while operating your kiln. Fuse "Blows" or Breaker Trips During Firing Generally speaking, if a fuse "blows" or circuit breaker trips sometime after the beginning of the firing it indicates a problem with the electrical service itself. The causes are varied. Heat at the fuses or breakers will cause them to "blow" or trip at lower amperage levels. This heat can be caused by a weak or loose connection at the fuse or breaker or elsewhere in the service (heat travels well in copper). A fuse or breaker is not normally warm or hot. It should be very close to room temperature during normal operation. It's possible also that the fuses or breakers are bad, weak, junk etc. Replace only with the proper size. Do not install larger fuses or breakers to solve this problem. Something out of the ordinary made the originals fail. The problem must be corrected not bullied into submission. It doesn't work that way. In this type of situation, it is suggested that a qualified electrician be asked to check for circuit problems. Be Smart. Be Careful. Have Fun!
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The Importance of Keeping a Firing Log
In 1905 Spanish philosopher George Santayana wrote these well-known words “Those who cannot remember the past are condemned to repeat it.” And, for anyone that uses a kiln on a regular basis that quote can have significant meaning. That is why we recommend that EVERYONE keep a kiln firing sheet or project log. We cannot stress this enough as it is the easiest ways to learn about your kiln and recall exactly what glass, metals, materials, molds, and most importantly, firing schedule you used. Over time, a properly kept log is critical to keeping track of what you’ve done. It will help you learn the particulars of your kiln plus it will go a long way towards avoiding future mistakes. In many ways, a firing or project log is the most underappreciated tool in your studio. All too often, the enthusiasm to fire overcomes the need to keep records of the firing, resulting in unusable comments. This is an enormous mistake. The firing or project log is one of the most essential tools you have. The combination of your kiln, the materials you select, and the designs you create are exclusive to you. No one else can precisely duplicate the conditions in your kiln, so it’s up to you to keep records that are detailed enough to allow you to repeat good firings and avoid repeating bad ones. Some people suggest that a printed log like the Bullseye Kiln-Glass Project Notes, or the Joy of Fusing Project Log, while others favor a simple notebook. Digital logs are also a popular option. It really doesn't matter which log you chose as long as you document, document, document! Some firings will require minimal notes while others might demand several paragraphs, pictures and/or sketches. Most importantly, keep you log in your work area. Use it religiously and enter essential information about each firing. As you become more knowledgeable, you may find that many of your firings are similar and require minimal entries. But regardless of your experience level, don't stop logging your firings, as your log is a priceless tool! Check out some of our best-selling glass kilns: Evenheat Studio Pro 17 Jen-Ken Vitri Barrel Vitrigraph Kiln Olympic 126 Lite
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Applying kiln wash should be easy, right?
We all know that kiln wash and shelf primer does not melt at high temperatures which enables it to form a protective barrier between kiln shelves and glaze or glass. But, did you know the secret to smooth and bubble free kiln wash is to warm the shelves prior to its application?
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Feeling Like I'm on Grey's Anatomy... Kiln Surgery... STAT!
There's a sinking feeling that I get in my gut when one of my kilns behaves oddly. It's akin to the car making weird noises as you are driving down the highway. Thoughts of dread begin to fill your mind and you start to concoct scenarios of doom. Mainly, "ON NO, I HAVE TO OPEN THE CONTROLLER BOX!" It's funny because I've owned a lot of kilns over the last 14 years and changed a lot of relays, transformers, thermocouples, etc., but still that feeling of dread comes over me as though it was my first time "opening the box." It's like a big mystery. What's in there? What's it going to look like? ...and the biggest question of all.... WILL I SCREW IT UP? You'd think that I'd approach this with confidence and bravado thinking, "I've done this a million times. I've got this!" But, sadly, NO! Anyway, if you feel the same way too, know you are not alone. The inside of the "box" is intimidating. Although it's pretty simple once you know what all of the wires are for and how the electricity needs to move, it's still a little daunting. So here's my story of the week regarding my kiln surgery. I have a 36" Profusion Fiber kiln. I love her, and her name is Jenny! (Yeah, I know I'm a weirdo.) I loaded some simple 2 layer plate tiles into the kiln for an easy full fuse and got a FTL error. The glass never got fired at all and the kiln only went to 600F. So why the FTL? (That's failure to cool, for those of you who don't know all the error codes.) Apparently, you get a FTL code after a FTH (failure to heat) code. Now that seems illogical, but that rant is for another blog. So my task was to figure out why the kiln wasn't heating. No heat = no fusing = no fun for me! There are only a few reasons why a kiln won't heat; dead or stuck relay(s), broken or fried element, not enough current/volts getting to the kiln, etc. The thermocouple was telling me the correct temps, so we could rule that out easily. I'm not as religious about changing relays as I should be on this kiln. I changed them all out exactly 3 years ago. So, it clearly was time! Luckily, I'm not a hypocrite! I did have a stash of relays that was reserved for this event, so I was ready when the time came. (I might be lazy, but I'm not a hypocrite!) So I set aside yesterday afternoon for this planned outpatient kiln surgery! I took out my drill with the 1/4" nut driver attachment, my phillips head bit, and my long nose pliers. I unplugged the kiln and set a small bowl next to my chair. The bowl is for all the screw, nuts, and parts that come off, and will need to go back onto the kiln. It just helps keep things in one place and makes sure things don't roll away and escape from you. (I learned this from experience of not doing the bowl thing and being on my hands and knee on the floor looking for a damn screw.) I pull up a comfy low chair and found a stool to rest the box on since It was still going to be attached to the kiln. NOW I AM READY FOR SURGERY! All I needed was the trippy Grey's Anatomy music and someone telling me, go for it! As you can tell from these pictures, there is A LOT going on in there. The kiln has 4 relays with 4 element connections, power jumps from one relay to the next, connections to the pilot lights, etc. There are 6 prongs on each of the 4 relays, and each prong has something attached to it. That's 24 connections to take off and reconnect correctly, and in the right order. That wouldn't be so bad except that this all has to be done in a tiny space. I'm not the largest lady in town, but I'm not small and delicate either. My hands are normal size, but in that box I felt like my hands were baseball mitts. Each relay is color coded to an element. So the red wires go to one relay, the whites, the blacks, and the blues, each to their own relay. That's really helpful so that you know you've got it all correct. Of course that escaped me the first time I did this, but you learn. Each relay is held in place by 2 bolts, each with their corresponding nut. That's a challenge, removing the relay from its spot, then disconnecting all of the crimped connections, then attaching all the connections correctly to the new relay, and then bolting the new relay back in place securely. That's what you do, just four times, in a small space, bent over, with reading glasses on, while you struggle to hold the long nosed pliers that are wiggling the tightly crime connectors on and off. See.... it's simple... a breeze.. ARE YOU KIDDING ME? The TRUTH is that none of this in mentally taxing. I didn't need special knowledge, JUST NERVE! I had to remember that this was just a giant toaster, and I am a resourceful girl! Yes, I started out intimidated, but that soon gave way to a wave of confidence and accomplishment. My last step was to take a picture of the inside of the box and send it to the folks that built the kiln to assure I hadn't missed anything. They got back to me quickly and pointed out one mistake, which was easily fixed in 15 seconds. The kiln companies are there to help, so utilize that help. NOW I AM READY TO GO! HERE'S WHAT I LEARED, THAT YOU CAN LEARN FROM TOO... Fear is the enemy, not the relays! Have the right tools and get them together in one place. Get a stash of relays so that you will be ready when the time comes. Schedule a quiet, uninterrupted "appointment" time with yourself to do this task. Go slowly and take a break if you need it. DO NOT wait until the kiln doesn't fire, or do this the night before a show. Ask for help from your kiln manufacturer. Reward yourself for job well done! Good luck! If I can do it, you can too! Your Kiln Gal, Gail Some important kiln parts: RelaysAdhesive Electric Kiln Parts
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