FrogBlog
Kiln Temperature Ranges for Pottery and Ceramics
Kiln temperature firing ranges refer to the temperature levels at which pottery is fired in the kiln. The maturity or the level of development of the clay and glazes is determined by these ranges.
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Observing a Kiln During Firing... What's Normal?
A big thank you to our friend Arnold from Paragon Kilns who helped answer these important questions about observing your kiln during firing. Gail also added some nuggets of information to help round out your knowledge! The heating elements hum when they turn on. The sound is generated because the elements vibrate in the brick grooves due to magnetism between the coils. So, it's totally normal! The sound actually diminishes as the kiln gets hotter because the elements soften. Notes from Gail: This is also true in kilns with suspended quartz wrapped tubes, but it's harder to hear since the elements are inside the tubes. Elements that are wrapped around ceramic rods probably won't hum much at all. The clicking noise of an infinite switch-operated kiln is also normal. It is the sound of an infinite control switch cycling on and off. When the clicking turns into a popping noise, the switch is probably about to fail. Notes from Gail: This isn't happening if you only have a digital controller. But, some kilns have an infinite switch in the lid with a digital control of the body. You'll be hearing the clicking on those. Digital Relays are another source of clicking. To turn on the elements, a digital controller sends twelve volts to the relays. The relays, in turn, act as switches and send full voltage to the elements. The relays click every time they turn on. A chattering noise, however, indicates that a relay is about to fail. Notes from Gail: This is why I'm a big fan of MDRs (mercury displacement relays) and SSRs (solid state relays.) They are much quieter and worth the money to upgrade in the long run! A crackling noise followed by a loud POP from the kiln's switch box usually means that a loose electrical connection has just failed. If you hear crackling, which sounds like sparks, turn off the kiln. The loose connection creates a tiny electrical arc, which overheats and burns electrical parts. Rapid arcing causes the popping noise. Whenever you change elements or have the switch box open for any reason, check all of the wire connections. Make sure they are tight... The power must be disconnected, of course. Tug on the wires. If a wire pulls out of a terminal, replace the terminal with a new one using a good crimping tool. Remove any dust before closing the switch box. When you replace elements, make sure the connections are tight. Notes from Gail: This happens in clamshell kiln lids occasionally, since the lid is constantly being opened and closed, the element connections an get loose. Don't despair, it's an easy repair. Why is there a gap between the kiln and the lid near the hinge? The gap under the lid of a cold kiln at the hinge is normal. As the kiln heats up, the firebricks expand, which causes the body of the kiln to grow taller and close the gap. The gap is designed to help prevent the front of the lid from rising at high temperatures. Notes from Gail: Yup! The lid on my kiln is rising at the front during firing. What is the cause? During firing, the wall bricks expand. This pushes the lid upward. If the hinge does not have sufficient play, the lid will rise at the front. If this happens, please do not put a weight on the lid to hold it down. That will only damage the lid. Instead, check for binding in the hinge. Notes from Gail: If this is happening, call the kiln manufacturer and ask them how to mitigate the problem. They'll walk you through an easy fix for your type of kiln. If this becomes extreme, it can crack your kiln lid so, it's important to take care of this issue sooner rather than risk a messy, crumbling lid. My front-loading kiln has a gap between the door and the firing chamber. Is that normal? There should be no gap between the door and the firing chamber at the side toward the door latch. There should be a gap, however, at the hinge side of the door. When the kiln is cold, you should see a gap of about 1/16 between the hinge side of the door and the firing chamber. As the kiln heats, the firebricks expand. Without a gap, the door will bind at the hinge and cause a gap at the side toward the latch. Notes from Gail: Some kilns have gaskets that fill the space and seal the door opening. If you have a gasket that is worn, it's easy to get a replacement from the manufacturer and should help alleviate the issue. New doors can also be purchased if needed. I am concerned about the light that appears under my kiln lid during firing. The light that you see under the lid is normal as long as the lid is not rising in front. The inner lid surface expands more than the outer cooler surface. Therefore, it bows inward slightly toward the firing chamber. This is normal. For this reason, you will see a thin line of light around the lid since the lid is no longer a flat surface resting on the flat firing chamber sidewalls. Surprisingly, there is very little heat loss from around the edge of the lid. Notes from Gail: If you suspect this is causing a cold spot during firing, call your manufacturer. If this becomes a serious issue, you can purchase replacement lids at reasonable prices for most top loaders.
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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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My first big kiln! What should I be looking for?
I remember this like it was yesterday. I had been fusing for a while and I was ready to go to my first "big girl" 240 volt kiln. The truth is I really did not know what I was supposed to be looking for in a bigger kiln. I just knew I wanted more space and I had the money in my pocket ready to go. This was about 14 years ago, and I'm sure there were answers out there, but I didn't really know who to trust and what their motives might be. Here's my story... (without any bias to manufacturers). My first larger kiln was a 24"octagon with a 21" round shelf. I was so excited at the time that I didn't realize that a 21" round shelf meant that a only a 15" inch square would fit on the shelf. I knew that was not going to be enough shelf space for me so the problem was easily fixed a year later when I sold that kiln and purchased an oval. So, now I had an oval, which I loved by the way, but that one had a two piece shelf, making it harder to do larger pieces without the dreaded line. The full shelves were a $250 upgrade which seemed like a lot of money at the time. However, I really should have upgraded and not cheaped-out as it would have saved me alot of hassle. Lesson learned. About two years later, I then bought a new square one. This one had a 24" shelf and gave me a lot of utility. But again, I'd discovered there were issues I hadn't thought about. That kiln was very low to the ground and killed my back to load. Also, the lid was a bear to open and close from the front because again I didn't think I needed the lid lifter... so I'd have to stand on the side to open it. That added torque to the lid and a crack soon appeared. Again, I was being frugal and should have upgraded. After the lid was replaced, I sold that one too and continued my quest. By now you can see that the addiction was taking hold. My husband and my business partner may have been colluding behind my back to check me into the nearest 12-step kiln addiction program. But I didn't care. Within a few years I'd added a fiber kiln to the mix. My confession is that I've owned over 25 kilns in 15 years. It's given me a great deal of experience about what kilns work for what projects. It's also allowed me to have the experience to helping others determine what they need and what might not be a good fit. Let's face it, everyone's needs are different and dictated by the kind of art work they want to do. NO ONE KILN IS PERFECT FOR EVERY JOB, EVERY TIME, EVERY ARTIST! Next, I bought my first clamshell. I really liked that one but the shelf was only 20" square. Too small for my taste. More bad decisions, you'd think I would have learned!With all of that said... here's my checklist of what to think about when purchasing your first larger kiln. I wish someone would have shared this with me about 20 kilns ago. Think about what kind of work you might want to do in the future. Your choice might work for today's needs, but will it look for tomorrows needs? Think about your body. This might sound silly to you, but if you intend to use your new kiln a lot, you'd better be comfortable loading it, scraping the shelves, vacuuming it and lifting the lid. Whether the kiln loads from the top or the front changes how much bending and lid-lifting that involves. You will absolutely use the kiln LESS if you are not comfortable. Be smart, get the lid lifter, or the full shelf, or the clamshell, or the taller stand, even if it costs more. It will be worth it in long-term utility. Be honest with yourself. Will you change the relays every year or two without someone standing over you to do it? If not, then think about getting mercury relays, which never need to be changed. Yes, they're an upgrade, but in 14 years and over 25 kilns I've had a few relay failures. Two of my failure happened with full kiln loads and the relays stuck in the "on" position. It does happen and it's no one's fault. It's just like a blown out tire, it just happens. Think about how lazy or energetic you are. No one is judging you here! I can be lazy and I'll admit it. How much do you love to scrape shelves and vacuum? I don't love it, so I avoid it. The way to fix this problem and make it less irritating is to actually purchase extra shelves with your kiln. It's actually much less expensive and far healthier to use kiln wash than it is to use fiber paper. The more shelves you can rotate, the less scraping and coating it will feel like you are doing. Finally, really think about getting what you want. I cheaped-out on several upgrade items that would have made me happier with my kiln long term. Even if it hurts a little, get what you need so that you don't have regrets. Of course there's a disclaimer! I am part of the kiln establishment now, selling kilns to other artists. But here's my truth, I represent four different kiln companies and doing this allows me to better represent my artist clients and get them the kilns they need, configured the way they need them. I'm not sure if I should be proud or ashamed of the number of kilns I have owned from each of the companies I represent. I'm joking a little saying that, but owning kilns from each manufacturer has made me more than just familiar with how those kilns work, it's made me educated about how each company builds their kilns, and where each company shines. So here's the recap of what to consider: Think long-term about your artwork needs! Think long-term about your physical needs and how they might change! Think long-term about your nature and how you want to spend time! Think long-term about your budget and what you'll really need to make you happy on #1-2-3! I love teaching my students and talking to artists about their needs everyday! I love helping fellow artists get what they need to do their best work! Thanks for letting me do what I love! Your kiln gal, Gail Explore some of our best-selling large or x-large kilns: Olympic Kiln - MAS1823HE Paragon Kiln - CS-19S Jen-Ken Kiln - AFG JK2 27-11
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The Power of A Small Multi-Use Kiln
I love my big, very capable kilns, but so many times they just are not the right solution for my smaller projects. Having a smaller multi-use kiln for making jewelry, firing metal clays, making drawer pulls or glass bracelets, small ceramic projects, pulling vitrigraph stringer, bead annealing, and enameling is just a must in my studio. I'd be lost without my little wonder of a kiln! Here are some kilns that I really like as they do A LOT for the money... It's definitely hard to choose which one is best. It really just depends on what smaller projects you like to do and how much flexibility you need. The Evenheat Copper Kiln I love this kiln because of its front loading capability. It makes for easy access and loading. It allows you to do all of the above except vitrigraph and bead annealing. The really nice thing is that this kiln pulls less watts then most other kilns, while still making the temps we need. If you have power challenges in your studio, this kiln plugs into any household 120V receptacle, so you'll have an easy time getting the "juice" you need. The Copper excels at ease of use. It is built entirely of firebrick to offer the metal clay artist the opportunity to explore materials in the higher temperature ranges. Many clays require temperatures up to 2200F and the Copper has the capability to get you there. The Copper also finds use in china and porcelain painting, ceramics, and glass. The Copper is stock equipped with our easy to use Set-Pro control with preset metal clays programs as well as allowing for custom programming. The Copper sits comfortably on table tops and includes a stand. The Olympic HB86E This kiln is a rocket, because it heats very quickly! The reason this kiln is special is because it's super powered, going really fast up to temp and having the ability to hold that temp for long periods. That is especially important when pulling vitrigraph stringer. This nifty little kiln is truly multipurpose! We use it to fuse, anneal beads, fire Metal Clay, as a vitrograph, and to make bracelets. You can even fire small ceramics. The top and bottom are removable for the ultimate in versatility. This little wonder does it all! It is important to note, that when the bead collar or blank collar are added, the maximum temperature on the HB86E reduces to 2000°F. If you are a fan of Vitrigraphs and want to have your own set up, but don't want to deal with ladders or a permanent shelf, Here's a very cool solution that goes perfectly with an Olympic Kiln HB86E!! Olympic Vitrigraph Stand The Paragon Caldera Digital This is one of Paragon's best sellers because it literally can do anything! It's used in a lot of studios as a dedicated vitrigraph kiln because it fires fast and stays there! You can order extra collars for bead annealing, enameling, or just depth! You can also order extra bottoms too! This kiln is a sold workshorse that has a great reputation. You can make jewelry from the amazing silver, bronze, and copper clay, fire ceramics, porcelain, or stoneware jewelry. When you are ready to try something new, fire china, decals, try enameling, and glass in Paragon’s digital Caldera kiln. Glass compatibility and glaze color tests are fast and easy. The Caldera fires rapidly to 2350°F/1287°C. What will you do with your multi-use small kiln? Your Kiln Gal, Gail
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PREPARE YOUR LOVED ONE (YOUR KILN) FROM STORM RELATED DAMAGE!
Wanted to share this great tip from our friends @ Jen-Ken Kilns: It's that time of year again, it's storm season in various parts of the country. During this time, we start getting "those" calls... "My kiln was fine and now it wont come on!" "I was firing, and all of the sudden I smelled something electrical burning!" "My display just flickers and beeps!" These are just a few of the typical issues. Over the years, we've seen the pattern and we've found the one common thread. It's storm season. We take so many calls like this a year, and every time we trace the symptoms back to one thing: LIGHTNING! When lightning strikes nearby, it sends a very HIGH VOLTAGE SURGE throughout the entire electrical system in your house. Unfortunately, you just can't plug your kiln into a surge protector to prevent the surge from zapping your kiln. The circuit board is the most expensive part on your entire kiln, and a good power surge will knock it out faster than anything else! It can also cause other problems, like burning out relays, and damaging your transformer. We know you love your kiln, and we want you to protect your baby! SO WHAT CAN YOU DO... If you have a digital kiln, PLEASE UNPLUG IT when it's not in use. Just like your computer or other expensive electronics, your kiln needs protection especially during storm season. Also, never fire a kiln when lightning is nearby. If your kiln is firing and a storm comes up, end your program as soon as you can and unplug the kiln. Don't just hope for the best! Don't let your kiln be the victim of mother nature! If need us, as always we're here to help. All the Best and Happy Firing, Jenn The Jen-Ken Tech Girl Explore some of our favorite Jen Ken kilns: Jen-Ken - AF3P Vitri Barrel Vitrigraph Jen-Ken - AFG ProFusion Fiber 26 Jen-Ken - AF3P 15/6
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What I'm Supposed to Do Before Firing My Kiln..... and other things I'm probably forgetting to do!
Most of us are so excited about what we're putting into our kilns, that we forget we need stop and inspect the kiln carefully prior to each firing. Caring for you kiln is an easy task that, if you pay attention to the small things, can save you down time and lots of maintenance dollars. Doing these simple steps every time can help your kiln last a really, really, really long time! Before EVERY firing... Look. Take a gander inside of your kiln and make sure nothing has taken up residence. You think we’re kidding, but sometimes, especially if your kiln lives in your garage or basement, insects or even a critter could have taken up temporary quarters if you left the top open. If you have house pets and the kiln is in an area that your pets can access, make sure that none of your little friends have left you a liquid present near the kiln. Moisture and electricity don’t mix, and really smell up the joint! Avoid installing kilns in a damp area. This could cause corrosion on the plug. Even if there is no critter present, sometimes droppings around your kiln can be a telltale sign you have guests in the vicinity. Check for anything out of the ordinary. Vacuum. Turn off the power switch! Then, vacuum all brick areas on the inside of your kiln! Make sure there is no loose fiber paper, blanket or other refractory material that is unneeded in the kiln. Extra burnout of unnecessary fiber smells crummy and may contribute to devitrification. This includes the inside of the lid, around your elements on the side, and the bottom. Your vacuum should have a HEPA filter, to protect you from inhaling dust. Ideally you would use a shop VAC with a separately purchased HEPA filter. Make sure you are using a soft brush attachment. You are vacuuming because you must remove all kiln brick dust, sand, and residue that could settle into your glass during the firing. Clean. Make sure the area is really clean - remove all flammable or combustible materials such as curtains, plastics, rags, paper, packing materials, etc. from the area surrounding the kiln. Inspect. Make sure all the coils/elements are in their designated place and tuck everything in where it belongs. Make sure the elements and their respective channels have no glass, glazes, or metal fragments, crustings, etc. Push all loose element pins back into place. Inspect your thermocouple for any signs of damage and replace immediately if needed. Tighten screws in the lid band, if necessary. Check for cracks. Check your shelf for cracks before firing. This may prevent the possible disappointment of the shelf breaking mid-firing. Sand any rough spots on the bottom or shelves and recoat with kiln wash. It is not necessary to kiln wash between each firing but a sufficient coating should be maintained. Power Up! Turn the power switch back on and make sure your kiln registers an appropriate room temperature for the inside of the kiln. Regular MONTHLY maintenance check up… Do a Lid Check Up! During every firing the kiln lid expands and contracts. All this action will make it necessary to tighten the lid band occasionally. Carefully, using the correct tool, tighten the band, being mindful not to strip threads. Most kiln lids are manufactured with a protective coating on the "hot side" or inside. This coating was applied to optimize the heat insulation of the lid, as well as to prevent brick dust from falling into the kiln. Of course this cannot be completely prevented. Because of all of this expansion and contraction over the years, cracks may appear in the lid. Most cracks are cosmetic in nature and will have no impact on your firings. Sometimes, a small crack can become a problem that can be repaired with kiln cement. If a lid crack is creating a structural problem, then it’s time to call in the kiln repair person, or call the manufacturer. Structural problems will be handled in short order by most manufacturers during the warranty period. If you are in the warranty period, DO NOT ATTEMPT TO REPAIR THIS without calling the manufacturer, as this could void your warranty. Do a Body Check Up! The only things inside of your kiln should be your elements, pins, brick, kiln furniture/posts and kiln washed shelves. Turn off the power to the kiln and remove anything else (glaze, slip, clay, glass, silica sand) from the sidewalls before firing. We are doing this for the same reasons we vacuum the lid. Leaving this material in the kiln will damage the sidewalls and possibly the heating elements. Remove the material with a small screwdriver or knife. Be careful not to gauge the brick. It's possible that small pieces of brick will break free from the sidewall. Most cracks are cosmetic in nature and will have no impact on your firings. On occasion, a small crack can become a problem that can be repaired with kiln cement. Be as neat as possible and be mindful not to get cement on the heating elements, as this could destroy the element. If a sidewall crack is creating a structural problem, then it’s time to call in the kiln repair person, or call the manufacturer. Structural problems will be handled in short order by most manufacturers during the warranty period. If you are in the warranty period, DO NOT ATTEMPT TO REPAIR THIS without calling the manufacturer, as this could void your warranty. Visually Inspect The Elements! Rusty, bulging, and thinning or thickened areas of your elements mean wear is happening. Elements don’t last forever, so expect to change your elements at some point during the life of your kiln. Element wear is based on the number of firings you do, and the environment or climate where the kiln resides. Just like tires on a car, mileage equals wear. In a kiln, the hours firing are equivalent to miles. The more hours you fire, the wear you’ll see on your elements. The thicker the gage of the element coil wire the more resilient the element will be. Keep in mind that each manufacturer has taken great care to size the element coils for the amount of amperage that they will carry to get the job done well. If you find it necessary to change out your elements, make sure you speak to the manufacturer to determine the appropriate element size for your kiln. Please refer to your operator’s manual for the discussion and photo's of "Element Replacement". Perform an Electrical Check Up! Perform an Electrical Check Up! Periodically inspect the power cable, receptacle, and plug for any signs of discoloration or heat. Make sure all connections in the receptacle and plug are tight. Check plug regularly for corrosion or dark spots. If corrosion or discoloration occurs, replace the plug and receptacle. Touch the plug and receptacle regularly to make sure it is not hot. If it does feel hot, check for loose connections and corrosion. Do not continue firing until the problem is fixed. Replacing the cord set or the receptacle may be necessary. If an electrical problem occurs and it becomes necessary replace any part of the plug assembly, then it’s time to call in the kiln repair person, or call the manufacturer. Electrical problems will be handled in short order by most manufacturers during the warranty period. If you are in the warranty period, DO NOT ATTEMPT TO REPAIR THIS without calling the manufacturer, as this could void your warranty. ***Don't take any of these check up steps for granted!*** The long life and resale value of your kiln depend on these steps! Now that I've reminded you....my work here is done! Go fuse, fire, slump, rake, drape, and drip to your hearts content! Your Kiln Gal, Gail... Special thanks to our friends at Paragon and Jen-Ken Kilns for the use of their pix!
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