FrogBlog
Ask Arnold: Arnold's Firebrick Repair Toolkit
Kiln Pointer from Paragon: Arnold's Firebrick Repair Toolbox ------------------------------------------------------------------------------------------------------------- Contents A Firebrick Repair Toolbox Book Recommendation: "Clay: A Studio Handbook" Reader Response Firebrick Repair Toolbox ------------------------------------------------------------------------------------------------------------- A Firebrick Repair Toolbox Ever since I left Paragon and became an independent kiln technician, hunting for tools has been my biggest waste of time. So I have sorted my kiln tools into four tool boxes (along with a vacuum cleaner and air compressor). Recently I put all of my firebrick tools into one box where I can find them instantly. Here they are, going clockwise from left to right in the photo: Plastic or Aluminum Foil Tray: It should be large enough to dip firebrick pieces into kiln cement. This is much faster than applying the cement with a putty knife. You have to work quickly, or the cement will begin to set before the repair parts are pressed together. The faster you work, the better the bond. Kiln Wash: Apply to the firebrick kiln bottom and the Kiln Sitter cone supports. Kiln wash looks like kiln cement. IMPORTANT: Keep these powders separated and clearly marked. Spray Bottle: Spray a little water onto firebrick parts that you are cementing together. This helps the cement to adhere to the firebricks. If you work fast, you won’t need the water at all. Plastic Cups: If you don’t have these, you will constantly hunt for a container to mix the cement in. Clean and reuse indefinitely. 2” Paint Brush: Thin kiln cement to coffee cream consistency. Then brush onto surfaces that you want to harden, such as the top of sidewalls in a top-loading kiln. Immediately wipe off the cement with a rag. Paragon Liquid Kiln Cement: I like the liquid kiln repair cement, because it’s fast and convenient. This is the very same cement used in the Paragon factory. Scrap Firebricks: Cut pieces to replace broken sections in a kiln. Paragon Dry Kiln Cement: This is for when you run out of liquid kiln cement. You can also mix the powder to the exact consistency that you want. Rag: For wiping off kiln coating and for general clean up. Repairing firebricks is messy. Paint Mixing Stick: For mixing kiln cement and kiln wash. Stir kiln wash constantly as you use it. DeWalt DWHT20542 Multi-saw: This comes with a coarse blade and a hacksaw blade. Use it to cut firebricks. I found this at Home Depot. You can find other brands, of course. 3M Sanding Block: Medium grit sandpaper works well in shaping firebricks. 3M Sponge Sanding Block: Sand the edges of firebrick lid grooves to remove loose debris. You can cut the sponge to the size you need. Marinade Injector: I found the “Good Cook Flavor Injector” at Tom Thumb. Use it to inject kiln cement deep into the cracks in firebrick kiln walls and floor. I will cover this in detail another time. HEPA Vacuum Cleaner and HEPA mask (not shown): Wear the mask when working around firebrick powder. Vacuum firebrick parts before cementing. Book Recommendation: "Clay: A Studio Handbook" Vince Pitelka, well-known for his teaching and his contributions to Clay Times, here tells you more than you ever thought you needed to know about pottery. He shares a lifetime of knowledge. Click here to see much more about Vince's book Reader Response Last week I wrote that I left Paragon in August, 2019 to become an independent kiln technician in the Dallas - San Antonio, Texas area. The day after I left Paragon, I was replacing elements at a school in Fort Worth. I also wrote that doing something creative helps one to forget the daily news. A few of the responses from readers-- “Many thanks, Arnold, for your Kiln Pointers and also your paragraph on facing world events,” wrote Ruth Canham of Nahiku Art Glass in Hawaii. “I don’t know how I would have made in through the last couple of weeks without having my kiln to keep me busy. First, I took on the challenge of trying strip construction with reactive glass. After that I went on to making whimsical birds. It’s kind of freeing in a weird way to have the galleries closed. Time to play.” ---------- “Thanks for sharing the electrical knowledge,” wrote Alexander Riedel. “Many are terrified of electricity when it can really be very simple if you know what to look for and how to do it safely. “From my experience working on industrial foundry ovens,” Alexander continued, “it’s always something incredibly simple when it comes to electrical problems. It just takes a while to chase it down: a loose connection, limit switches slipping from loosening, fouled relay contacts, a wire or nut that loosened from expansion/contraction, overheated or broken elements. I also really enjoyed the quote about the studio being a place away from reality.” ---------- “The nose told the story,” wrote Fujie Robesky. “Great detective work. Good to hear you’re still working in what you obviously love.” ---------- “The Kiln Pointer email was a breath of fresh air!” wrote Andy Reeves ---------- “No telling what changes we will see from all this," wrote Pattie Necaise about the virus. “I think there will be good changes. We just might value people more than things.” ---------- “It was good to hear from you, like hearing from an old friend, although we’ve never met. Thanks so much for the many pointers through the years,” wrote Colleen Gilligan Gilbert of Cypress, Texas. “I work at a non-profit that serves adults with intellectual disabilities, and I help them earn a paycheck by making and selling fused glass,” she explained. “We have three big Paragon kilns--two Ovations and a Pearl-44. We got the first Ovation on my first day here over 10 years ago. We have used the heck out of these kilns, firing them every afternoon. “Right now it’s very quiet here, as all our folks are staying away from our Learning Activity Center for their own health and safety. I continue to do paperwork, and look forward to the hustle and bustle of their return.” The Rain in Mesquite This morning before dawn, I sat in my sunroom listening to the rain. It drummed softly on the steel roof and splashed into a puddle outside. I felt like I was in the steel-roofed A-frame that I built in Leilani Estates near Pahoa, Hawaii. The rain fell in sheets there. The rain cleanses the world and sounds comforting. Thank you, Arnold Howard Mobile 972-333-1437 www.instagram.com/arnoldhowardkilns www.facebook.com/arnoldhoward
Read moreFrogBlog
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.
Read more
When the Kiln Lid Flakes...
Great information about kiln lid repairs from our friends at Paragon... At Paragon, they coat the inner lid surface of all kilns to reduce brick dust. Sometimes the refractory coating is too thick so, it will blister and flake off when the kiln is fired. An especially thick coating looks like a network of peeling cracks similar to a dried mud puddle. This cracking is due to the difference in expansion between the firebricks and the coating. Conversely, correctly applied kiln coating will look like it disappeared after the kiln has been fired. The good news is that cracked lid coating is easy to repair. Just lightly remove the blistering coating with sandpaper and apply a new coat of liquid kiln repair cement. Keep in mind that the natural tendency is to apply too much lid coating because it just looks better than a thin layer. If done correctly, you should still be able to see the firebrick pores under the coating! First, shake the container very well! Then, pour some of the coating into a bowl. Make sure to stir it just before you apply it to the firebricks. Apply the coating with a large, soft sponge. Moisten the sponge with water; then squeeze out the excess... this is a very important step! Dip the sponge into the bowl of kiln coating. Wipe the coating over the lid surface. Do not let excess coating run into the element grooves of the kiln. Applying a light coat will prevent this from happening. If the coating drips along the edges of the grooves, remove by wiping a cotton swab or rag along the groove. Many people have asked us... "What is the difference between kiln cement and Liquid Kiln Coating? Can a lid be coated with a thin mixture of kiln cement?" The answer is YES! Kiln cement thinned with water will work as a lid coating. Liquid Kiln Coating is simply a mixture of kiln cement, fine brick dust, a gumming agent, and water. The great news is that lid coating lasts for several years. So, it's not something you need to worry about on a daily basis. But, if you start getting kiln brick dust on your work, maybe it's time to re-apply. Some kilns such as the Paragon CS-14S allow you to upgrade to a fiber top, which helps to keep your kiln cleaner and reduces the chance of debris in your pieces.
Read more
The Importance of Spare Parts
This is one of those stories that you don't believe... until it happens to you! A few years ago, we had a visiting instructor with a full class of students teaching at our studio when the kiln just decided it wanted to be a rebel. There was a tiny waft of smoke, and then a error signal from the controller. Part of me wanted to freak out and run around the room with my arms waving while screaming expletives at the top of my lungs as this was the only kiln we had that was large enough to fire the student projects. Luckily, I quickly realized that I had an audience so, after a few deep breaths and some positive self-talk, I turned the kiln off and unplugged it. My first diagnostic step was to use my nut driver to unscrew the box where I saw the little smoke puff. And, yes... I know it's not an extra part but, everyone must have a 1/4" nut driver on hand in your kiln room. So, I opened the box and I see a small area that looks burned. It's the connector that attaches the kiln element to the electrical feed that runs to the relay. There's also a ceramic insulator that looks like it's seen better days, and a dead bug. To make a short story short...the bug wiggled in, couldn't get out, and in it's frenzy, wiggled around the wire and caused a short when the wire touched the side of the box. This action killed the bug, and fried the connection. I know what you are all thinking... and, yes... we have big bugs here in Texas. This is not common, but it can happen. Thankfully, kilns these days are made pretty "smart" so the controllers sense when a problem arises and shut the program down. With that said, all I needed now was a new ground connector and a new ceramic insulator. I went to my local hardware supply and picked up some hot tub ground connectors as a temporary measure and found some unglazed bisque beads to serve as my insulator. A few moments later I was up and running again. (I know... who the heck has unglazed bisque beads?) We learned the importance of having spare parts on hand; Just like with a car, occasionally your kiln will hit a bump, or a bug in the road, and need a minor repair. You CAN do it, if you have some spare parts available. Here's what we recommend having on hand: An Extra Set of Relays Call the manufacturer of your kiln and ask them to send you a full set of relays for you kiln... some kilns use one and others can use up to three. That is why you need a full set! The best part is they are cheap. They usually run about $50 each and are worth their weight in gold. They do have a lifespan rated in "clicks." So, keep that in mind as age is less of a factor than usage. You just can't run your kiln with them. You can find an example here on our website. In the time since this happened, kiln manufacturers have introduced Solid State Relay Systems. As we just discussed, mechanical relays wear out and fail at some point but, that is not the case with solid state. Solid state means there are no moving parts, nothing to wear out and nothing to replace. Mercury relays are also an alternative but, they are more costly and include hazards associated with handling mercury if it breaks. Ground Connectors Since you're already calling the manufacturer for relays, ask for a few of these too! Again, cheap but worth it. Ceramic Insulators You guessed it! Since you're asking for relays and the ground connectors, make sure to ask them to add a ceramic insulator. (Now you sound very knowledgeable and they will be impressed!) Extra Side Element & Element Pins Elements can be finicky so, these are a must! The side elements are usually longer than the top element, but these could be MacGyver'd to be smaller if you needed to replace your element on top and just couldn't wait to for it to come. These typically run about $30 each. Have a spare on hand, you'll sleep better at night. I know I do! Thermocouple This is truly for the die hards! These run somewhere around $45 dollars depending on the company. Again, your kiln won't run without it. Check out some of them on Kiln Frog. Electrical Tape Duh! Everybody loves tape! Pliers, Phillips and Flat Head Screwdrivers, Wire Strippers, Set of Nut Drivers, and a Flush Cutter These are basic tools you should have in your kiln survival kit. Pack these along with a shot of tequila for calm steady hands! An Ohm Meter Another weird, but handy tool to help you determine whether electrical amperage/voltage are getting to your elements. (Using this is a whole other conversation.) They come with directions and there are smarty pants types on YouTube who can walk you through it. Trust me, you'll need it at some point in your kiln life. The phone number of someone who knows what their doing If you need help, no problem! Or, sometimes it's just nice to talk to some for reassurance.. that's what we do! Kiln Frog's "Kiln Repair Directory" is a great resource of over one hundred kiln repair technicians across the US. When you call them and they tell you to get all this stuff, you'll look like a genius because you already have it.
Read more
For the LOVE of Vitrigraph
Did you know you can make your own stringer for use in kiln-glass work? Vitrigraph is a special hot glass technique that involves pulling hot glass through a hole in the floor of the kiln. These glass stringers are fine strings of glass that can be used to create your own unique curved forms you can’t find elsewhere. Bullseye Glass TechNotes 2 describes the vitrigraph equipment and processes developed at Bullseye in the early 1990s by Narcissus Quagliata and Rudi Gritsch, in the process creating a whole new vocabulary for fused glass. Here are some quick vitrigraph tips: Glass Feedstock Any scrap pieces of compatible sheet glass or coarse frit can be melted down to make lines or “stringers.” Avoid glass granules smaller than coarse frit, as they produce a seedier stringer due to the greater amount of air trapped between the smaller particles. Loading The Glass Load the glass into the pot outside the kiln, while it is at room temperature, and then place the loaded pot into the kiln so that it is supported. When working with frit or extremely small pieces of scrap sheet glass, place a small square compatible sheet glass the same color as the feedstock over the hole to prevent the glass from falling out. Then fill the pot with the feedstock. As we just stated, loading the amount of glass needed for a run of stringer while the pot is cold, and then cooling between runs is the best option. However, if time forces you to do continuous melts, or if it becomes necessary to add more glass to the pot during the melt, here are a few things you need to keep in mind... Always, turn the power off before adding more glass. Use extreme care when filling the pot as glass scraps or frit which miss the pot and land on the electrical elements can damage them. Finally, glass scraps or frit that melt against the refractory brick will corrode it. Vitrigraph Pot Avoid pots with hairline (or larger) cracks, as these will widen as they reach molten glass temperatures. In our experience, unglazed Italian terra cotta pots are the most durable. Avoid re-firing a used pot. The risk of cracking is far greater than the minimal expense of a new pot. As mentioned above, watch out for cracks. They widen and eventually break on firing. If you want to see in a vitrigraph kiln in action, Bullseye Glass has a great video in their Kiln-Glass Education Online. In the lesson, you can see how they transform a Paragon Caldera kiln into a vitrigraph kiln and how to safely hand-pull stringers. Most importantly, have fun and enjoy the process! It's a good one! Check out vitrigraph kilns on Kiln Frog!
Read more
How to Load a Kiln
Loading a large kiln can often be intimidating. After talking with our friends at Paragon Kilns, here are answers to some of their most frequently asked questions... Do you recommend 3 or 4 posts under a shelf? It is recommended to support shelves with three posts instead of four. Sometimes four posts can cause the shelves to wobble unless the bottom of the kiln is perfectly even, the shelves are flat, and the posts are exactly the same height. It is best to position posts fairly close to the kiln walls and away from the center of the kiln bottom. This places the weight of the kiln load close to the kiln stand and away from the unsupported kiln center. How do you load the top shelf so that the ware fires to the correct temperature? On top-loading kilns, placing a shelf too close to the top of the firing chamber can lead to over- or under-firing. To help combat this, try using two half shelves, instead of a full shelf, stagger the height of the shelves. Another option is to mount the top shelf low enough so that element grooves show between the kiln lid and top shelf. How does one prevent posts from sticking to the kiln shelves? When you unload a shelf out of the kiln after a firing, a post occasionally sticks to the shelf and then drops onto the shelf below. To help prevent this from happening, dip the ends of the posts about 1/8” – 1/4” in a mixture of kiln wash. Only a thin coat is needed. How important is placement of posts inside a kiln? When possible, posts should line up vertically from one shelf to another throughout the kiln, especially with large kilns and heavy loads. Vertically aligned posts increase the stability of the load and reduce stress on the shelves. Do you need to fire a top-loading ceramic kiln with an empty shelf in the top of the kiln? It is not required but, a shelf placed in the top of the kiln will prevent brick particles from falling onto glazed ware. This is also useful if the lid is cracked. Some people like to place a shelf in the top of the kiln to prevent the incoming air of a downdraft vent from affecting glazed ware. Keep in mind, it would be better to fire the kiln without the blank top shelf, since the shelf uses up more electricity. What kind of gloves can you wear to handle kiln shelves? You can find thin, leather-lined mechanic’s gloves at home improvement centers, or try batting gloves! They are both thin enough for you to load and remove shelves inside a kiln. They will also help to protect your hands against sharp bits of glaze or glass. Always wait until the shelves have cooled before removing them from the kiln. Is it okay to continue using cracked kiln shelves? You should not fire cracked shelves. They could break during a firing and ruin a load of ware by causing other shelves to collapse. Is there a way to repair a broken kiln shelf? Unfortunately, there is no way to repair a broken kiln shelf. However, all is not lost, as you can still use the shelf pieces. Use a tile saw to slice the shelf into horizontal sections. Place broken shelf pieces under pottery that is decorated with runny glazes or pieces that have too much glaze. If the bottom of your kiln is uneven, place the broken shelf pieces in the bottom of your kiln to support posts. Use the shelf pieces as smaller shelves to place around tall pieces. Silver clay and enameling: Place hot pieces onto the broken shelf. It is a good fireproof surface. Lay the broken shelf across two half-shelves for even support of a piece with a large base. Is it okay to fire freshly coated shelves with a glaze or bisque load? No problem! When loading a kiln for bisque firing, just allow the shelves to dry beforehand. What is the difference between loading ceramics in a front-loading kiln and a top-loading kiln? Smaller, lighter pieces are usually loaded in the front of the kiln near the door or on the bottom. This is because these are the cooler areas of the front-loading kiln. Load heavier pieces near the back wall of a front-loading kiln as that is where they will get more heat. The cooler areas of the top-loading kiln are usually the bottom and sometimes the top so, load lighter, smaller pieces in those areas. Explore our selection of Shelf kits in various sizes and shapes by clicking here!
Read more
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!
Read more