FrogBlog
Pottery vs. Ceramics | What's the Difference?
In the world of crafts and fine art, the terms "pottery" and "ceramics" are often used interchangeably. But, what’s the difference between pottery and ceramics? Today, we’ll look at what separates these two terms, their main uses, and even the different types of clay used. Are you ready? Let’s get started!
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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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Kiln Q&A
Learning from others is at the heart of the kiln community. So, I thought everyone would enjoy some Q&A as we just love to share knowledge and information! When using or buying a kiln... this extra insight not only saves you time but, often money, too! Can a small test kiln accurately duplicate the firing of my larger pottery kiln? A digital controller on a test kiln can duplicate the firing of a large kiln. Find a test kiln that has a simple 3-key controller. It won't have all the features of the more expensive 12-key controller, nevertheless, it can slow the cooling to whatever speed you want. Keep in mind that most 120-volt kilns are rated to 2000 F so, make sure you use one that is rated to 2300 F. Examples for great small test kilns are the Paragon Caldera Digital and the Olympic HB86E. I need a small kiln that can be moved often. What do you recommend? Since you are going to move the kiln frequently, we would suggest a fiber kiln. They are lighter than firebrick kilns. However, you can move a small, tabletop firebrick kiln without damaging it, you just need to be extra careful. Whether you get a fiber or firebrick kiln, its a good idea to save the carton and foam packing from the original shipment. The packing is designed to protect the kiln. Also, be sure to place a sheet of foam packing material between the kiln body and door or lid whenever you move a kiln for extra security. Is there a reason to buy a ceramic shelf instead of a fiber shelf? A ceramic shelf is recommended for activities like pattern bars, pot melts, high fires, or any there techniques that requires temp to be held at 1450F or above. A fiber shelf will be marred by these activities and won't stay smooth as the glass moves. Can a kiln be safely operated on a wooden work table? Yes, but it's not ideal! You will need a liner to buffer the heat. We recommend a concrete board, i.e. hardy-backer or Duraboard, or at the minimum, a double layer of ceramic tiles. It is easy to find at your local hardware store, and it's fireproof so it will protect the table and the area. Metal is always the preferred surface for a kiln table or cart. I'm curious how hot a fiber kiln gets on the outside vs. a conventional kiln? A fiber kiln reflects heat internally and a brick kiln absorbs the heat, so a fiber kiln will not be as hot on the outside. With that said, at a full fuse (1480F) the kiln might be 200-300F degrees on the outside. Is it worth the extra cost for a solid state or mercury relay on a new kiln? Glass fusing kilns are much harder on relays than ceramic kilns because of the very long glass annealing times that are typical with glass. (The glass is cooled slowly during annealing.) The same holds true for heat treating, crystalline glazes, bead annealing or any kiln that is holding temp for a long period. With that in mind, we think the optional mercury relay or solid state relays are well worth the money. They cut down on maintenance and help you elements last longer too! How much heat is lost through a kiln’s bead doors when mandrels are inside? With bead mandrels extending out past the bead door of a kiln, there is some loss of heat, but it is minor. In our opinion, not enough to make a difference. The kiln's digital controller and thermocouple will sense any differential and accommodate for this by firing the elements when needed to make up for any heat loss. Do I need a top load or a front load glass kiln? Top load kilns offer the most size for the cost. They can fire most glass projects but they are not good for projects that require manipulating the glass during the firing as the artist is subjected directly to the heat when the lid is opened nor are they recommended for bead annealing. Front load kilns are better for bead annealing and manipulating glass during the firing. They are also easier to load with large glass projects on the kilns shelves. What type of kiln is best for copper enameling? Copper enameling is best done in a front-loading kiln. This is because the copper pieces are removed while red-hot. When you open the door of a front-loading kiln and remove the piece with an enameling fork, you are comfortably out of the way of the rising heat. Removing an enameled piece from a top-loading kiln is more awkward and can be dangerous. Before opening the kiln to remove the piece, always turn off the power to the elements, which may mean turning the kiln off if your kiln did not come with a power interrupt switch. To enamel another piece, you can turn the power back on after you have closed the kiln door. To check out an example take a look at the Paragon SC2. How is depth measured in a kiln? The interior depth is always front-to-back for a kiln with a door and top-to-bottom for a kiln with a lid. For outside kiln dimensions, depth is the distance from the front to the back. For glass, do I need elements in the top and sides or only the top? Glass does not like temperature variation. Though top elements offer even heating across a flat piece of glass, top and sidewall elements are recommended for firing tall or deep pieces with molds. Side elements offer more even heating of the sides of drape molds or deep castings. Basically, the deeper you want to slump, the more side elements become necessary. How do I get a wide ceramic kiln through a 32” doorway? Many top-loading ceramic kilns are sectional. You can disassemble them and carry the sections through narrow doorways or downstairs. It can take some time for a beginner to disassemble and reassemble a sectional kiln. If the kiln is front-loading, you can temporarily remove the door handle and the back element cover. If necessary, you could also remove the door itself. Please have a kiln technician remove and reinstall the door for you if you do not feel comfortable with the project. An example of a kiln that is structured in sections is the Olympic 2827HE. Have more questions? Call us... as always, we are happy to help!
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The Fear of Buying your First Kiln
Don't sweat it! We've got you covered.From glass to pottery, heat treating to annealing... we have handled thousands of questions that revolve around buying your first kiln. So, we thought we would share our favorite nuggets of advice from some of our most frequent questions.Q1: I am considering buying my first kiln. The choices and information seem overwhelming as they all look so similar. How do I know which one is right for me?It can be an instant information overload. We think that choosing a kiln becomes simpler when you narrow the search with these factors: The size of the electric circuit in your studio... your kiln choice will be limited by the number of amps available. The size of the kiln... estimate how much firing chamber space you need. For glass and clay, you may also want to consider the shelf size, too! Front loading or top loading, a choice with real consequences for ergonomics, capacity, and price. Max firing temperature. After you reduced the kiln selection search with those four factors and make a list of models that you are considering. Then, compare those kilns and manufacturers in greater detail. This process will make everything better, promise!Q2: I’m nervous about ordering my first kiln... and, have so many questions. Do you have any pointers that will help? We totally understand that ordering a kiln can be complicated. But, it doesn’t have to be. Here is a great checklist to help you avoid any issues: Is your dealer knowledgeable about firing? This can be as important as the price of the kiln. What about warranty repair? Make sure you understand how the manufacturer handles the warranty. If comparison shopping, have you asked about the cost of crating or residential delivery? Are you paying extra for the stand as some are not included? Do you need to order a kiln shelf? Most kilns do not include them. Do you have a covered, well-ventilated location for the kiln, protected from the weather? Is the area free of flammable materials? If you are going to use the garage, plan on parking the car in the driveway during firing. Is the kiln room large enough? You will need 12" of additional clearance on all sides of the kiln during operation. We do not recommend small, enclosed rooms such as closets. Will the kiln fit through the doorway? Measure to be sure. Sounds crazy but, we know of cases where doorways had to be torn down to move the kiln into the firing room. Are you sure about voltage and electrical phase? 240 and 208-volt outlets cause confusion because they look the same. Check with your electrician, if in doubt. Ordering a kiln of the wrong voltage can be very difficult to remedy! Will you need special wiring? Figure this into your budget before ordering the kiln. Q3: How will putting a kiln in my garage affect my homeowner’s insurance? Our friends at Paragon shared this info regarding homeowner’s insurance: Some insurance companies simply don't insure kilns. No matter what you tell them, they won't change their minds. Other insurance companies need extra information--i.e., the kiln is UL Listed--before they will OK the kiln. If they need more information about safety, we will be glad to supply it from the manufacturer. Still, other insurance companies have no problem with kilns and don't even care if you have one. A properly installed and operated electric kiln is very safe. Do not leave it unattended during operation, and disconnect the power when not in use. Keep flammable materials out of the firing room. If you fire the kiln in a garage, remove cans of paint and gasoline. Store them in a separate building such as a garden shed. If you follow these basic rules and the others listed in the manual, your kiln will be a source of joy rather than of worry.As always, if you need help or have questions... call us! We are happy to help!
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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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