Operating a Small Gas Kiln
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- Опубліковано 17 лип 2024
- Welcome to the Potters’ Round Table lecture on Operating a Small Gas Kiln.
Gas kilns can produce some of the most beautify textures and colors in the entire ceramic spectrum. And firing a gas kiln can be an efficient and effective path to an atmospheric firing. There are many variables that can produce unpredictable results in kiln setup and kiln loading. In this video Phil talks about everything he has learned in setting up the kiln in three different locations and firing his gas kiln for over twenty years. If you are experiencing difficulty with your current gas kiln or if you are planning to expand your firing options to include a gas kiln, this video can give you some ideas that might help improve your results.
Show notes can be found at www.hfclay.com/the-potters-ro...
The Potters’ Round Table is brought to you by Washington Street Studios, a community pottery studio, gallery, and pottery school located in Harpers Ferry / Bolivar, WV. We exist to provide ceramic artists an affordable, fully equipped studio space for aspiring, emerging and established artists to share their creative energy and knowledge in an environment designed to support the ceramic artist. If you want to learn more about Washington Street Studios, visit our website at www.hfclay.com/.
At Washington Street Studios, we believe the sharing of creative energy and knowledge will improve the quality of our art and increase the appreciation of art within our community. We are striving to create an environment where the arts are shared and appreciated. We want to grow as a family of artists and contribute to our community.
This video is one of our steps to share our passion for the ceramic arts, creative energy and knowledge with other artists and art lovers. We also created an audio version to expand our audience. If you are looking for the podcast of our show search for the ‘The Potters Round Table’ on your podcast platform of choice or go to anchor.fm/thepottersroundtable.
Great info, thank you!
Thanks Dylan, I found this one useful as well! Phil did a relly good job explaining his process of learning the kiln.
Thank you sir!
You are welcome!
Thank you!! I use an updraft kiln and have the problem of hotter temps on the lower shelves. I will use the baffle system inside to mix air/fire better. Hopefully this will remedy this issue. Great info!
We're happy you found it useful, let us know if you have issues, we're happy to help!
Thank you! It helped me a lot to understand what's going on. Although my kiln is somewhat simpler (port-o-kiln). Your videos are very good!
Thank you Nicola, we enjoy making them. We are building a soda kiln at the studios and we are going to have a slideshow of the kiln being built! It should be one of our best. Thanks for the comment.
Great informative video
I am so glad you enjoyed it, another video is coming with my new internal chimney.
Thank you so much for this video! I have been searching for information on firing a gas kiln and how to deal with hot spots. I have the smallest Olympic gas kiln and haven't used it very often because I felt more comfortable using my electric kiln. Also, the reason I haven't used the gas kiln more is that I don't really know how to use it. There was a small manual that came with it that indicated the use of a baffle shelf 3" from the top of the lid it also said to place the bottom shelf 3 inches from the floor of the kiln. Other than that there wasn't any additional information on firing it. I got brave several months ago, bit the bullet and fired it. I did use a baffle shelf at the top, 3 inches below the lid of the kiln. The cone on the top shelf was overfired, the middle shelf was about right and the bottom shelf was underfired. I had larger pieces at the top and smaller ones on the bottom shelf. There were some pieces that looked more matured on one side than the other. It was very discouraging. Your video has given me new hope and I am anxious to try your modifications. I might add, I am firing with propane and not natural gas. I hope you will do more videos on firing the gas kiln as there is nothing else out there not even from the manufacturer. The books I have found on the subject are more technical. Maybe I have just looked at the wrong books. I would like information on how to adjust the rise of temperature, how much and when. Also I would like to know how and when to cover the top port. To me, firing the gas kiln is much more exciting. Sorry this is such a long comment. I am just so happy to find this place on UA-cam.
Check out our latest video 'Reduction Firing in a Gas Kiln' for more information and a general procedure for any and all gas kilns. It will tell you when and how to cover the exit flue. Any time the video refers adjusting the damper that tells you how and when to cover or uncover the exit flue. Best of luck on your future firings!
Be sure to share the channel with your friends and fellow potters to help us grow the channel.
I have had an Olympic gas kiln for more than 20 years, and it was so frustrating I gave up, with problems exactly like those you describe. Four burners. It cooled so quickly I lost a lot of pots to cracking. I finally wrapped the whole base in fiber at the end to slow it down. I wrote to the manufacturer and they offered no advice, saying you just leave the ports open. I also got uneven firing, variable reduction, burned a huge amount of gas. Three levels/rings. These videos have been very helpful, and I will try again.
Thank you for your videos and podcasts they are super helpful and informative! I'm just wondering when you'll return to talk about the operation of the small gas kiln? I have a small downdraft gas kiln and I'm trying to figure out how to determine when the kiln is in reduction and how heavy the reduction needs to be. Thanks again!
We have discussed this topic several times. I'll get with Phil and hopefully we can put something together soon!
Hi, thanks for your email and question. Good timing! As it turns out, our topic for the January, 2021 Potters' Round Table presentation is going to be discussion of a general procedure for reduction firing in a gas kiln. In the meantime - the two features that I look for to confirm reduction are (1) back-pressure (caused by a partially closed damper) in the form of yellow flames out of any kiln openings (like peep holes) and (2) a "hazy" atmosphere in the kiln. The degree of reduction and the length of time for reduction depend somewhat upon the clays and glazes in use. Unless carbon-trapping is desired, it is not necessary to have reduction so heavy that a lot of soot is produced, and if reduction is carried out for longer than necessary to reduce the glazes and surface of the clay (judged by the fired appearance), then gas is being wasted.
Phil
@@WashingtonStreetStudios awesome, thanks so much for the advice Phil!!
Great Video - really useful as I have been given an old Olympic gas kiln just like this but with three rings instead of four. Are there still plans to do a follow up video on the firing procedure?
Jez,
Hi, thanks for your email and question. Good timing! As it turns out, our topic for the January, 2021 Potters' Round Table presentation is going to be discussion of a general procedure for reduction firing in a gas kiln. In the meantime - the two features that I look for to confirm reduction are (1) back-pressure (caused by a partially closed damper) in the form of yellow flames out of any kiln openings (like peep holes) and (2) a "hazy" atmosphere in the kiln. The degree of reduction and the length of time for reduction depend somewhat upon the clays and glazes in use. Unless carbon-trapping is desired, it is not necessary to have reduction so heavy that a lot of soot is produced, and if reduction is carried out for longer than necessary to reduce the glazes and surface of the clay (judged by the fired appearance), then gas is being wasted.
The January Potters Round Table will be on Saturday, January 9th at 2PM eastern.
The write up for the topic is:
Reduction Firing in a Gas Kiln
Working with a gas kiln can be pretty daunting. There are updraft, downdraft, propane and natural gas-fired, large and small gas kilns, but all gas kilns have certain features and controls in common. This discussion provides some general background information on gas kilns, an overview of the different stages and procedures in a reduction gas firing, and some of the common mistakes that are made and problems that can be encountered.
Hope this helps,
Phil
@@WashingtonStreetStudios Great - Thanks for such a generous and informative reply. I've been finding your videos really useful, they are an amazing resource, especially for the self taught potter like me. Look forward to the upcoming round table discussion!
Thank you! So helpful. Question , how do you provide air to the ring pilot burner. You show a diagram of it but not show photo or explanation. Thank you so very much.
No air, propane gas flows through the ring and once ignited provides a pilot light.
excellent presentation, I have a small gas kiln made by me very similar to the olimpic 2327, with ceramic fiber, two venturi burners but in a horizontal position, 6-inch space between the floor and the first shelf and on this the pots; I think that's how the turbulence you mention is created. I want to think that saves me from putting the deflectors on top, what do you think, thanks!
Salvador, the real question is 'does the kiln work?' If you are getting good and consistent results, then the kiln is working for you. The space does allow for gas / air mixture and turbulence. If the kiln is firing inefficiently or uneven, then you may want to add deflectors.
If it's working, don't change anything, just keep firing!
Your videos have been most valuable, thank you. I am in the process of building a small gas kiln, shooting for early summer to have it firing, and had a quick question. I will be insulating it with refractory ceramic fiber insulation and was wondering if you could recommend a rigidizer to coat and stiffen it? Either a recipe or a recommended brand that you might use. The only information I can find comes from diy blacksmith forge chat rooms. Thanks.
Deep Ashtray, Thanks for watching and the encouragement! If you didn't know, Phil passed away last July and I really wish he were still around to help with this question!
I have dealt with similar issues two ways. In both cases you need an exterior containment and reinforcement material. I've used chicken wire and / or metal fencing. This will be on the outside of the fiber, so it won't be subject to the extreme temperatures. I've done this with both a 'brick wall with a fiber wrap kiln' and a 'fiber-only wall kiln'. On top of the fencing / chicken wire you can coat the kiln with refractory cement, or a castable (we used old clay mixed with sand, straw, ground up soft brick and used wadding), or a combination of both.
If this doesn't address your question adequately, let me know and I'll see if I can find some additional help, and please post pictures when you've built your kiln!
@@WashingtonStreetStudios I'm very sorry to hear of Phil's passing. All I know about him is through these wonderful videos. He was certainly generous with his knowledge, which has enriched my pottery to no end.
The kiln will be built from a repurposed water tank, which I now have set up as an updraft kiln lined with soft brick left over from an old electric kiln. My plan is to replace the soft brick with fabric, build a more efficient firebox and turn it into a downdraft kiln. Sodium silicate is supposed to work as a rigidizer but has a temp limit, and the products on the market are mostly geared toward forges so I was asking around to actual ceramicists for ideas. Thank you.
@Deep Ashtray, I would try this: Colloidal Silica Rigidizer - Coating for Refractory Ceramic Fiber Products - 1 Quart, found it on Amazon for ~$35 a quart.
@@WashingtonStreetStudios Thank you, I'll check it out :)
Hi there, I can't seem to find the show notes at the link you provided. Are they available still? (Assuming the notes include the slides presented)
Some of the early shows didn't have notes provided. Sorry.
thank you - there is no one around here who can help build, but I'll work my way through....
Where are you that no one is around?
hola! otra vez aqui, In the photo they show of the burners of this oven, there are 5 burners, what type are they, dimensions, I think there are many that depends on their size
Sorry, I don't know the exact dimensions, this is an Olympic Gas Kiln from ~40 years ago. There are five burners.
Hey I fire electric to gas even during bisque. I have almost the same set up that I learned to do over the years. Adding the post flame deflectors may be something I might try. You did not mention the temp or cone difference between the top and bottom after your changes. I am still running a hot bottom much of the time.
I'll check with Phil and get you a response.
Even with the modifications, we still get a half cone to a cone difference in temperature between the top and the bottom of our Olympic updraft kiln (bottom hotter). I think that this is about the best that can be achieved with a small updraft kiln where there isn't the possibility of manipulating or redirecting the flame path like there is in a cross draft or a down draft kiln. The bottom will tend to be hotter because of being closer to the burners and the air supply, but it may also tend to be slightly less well reduced than the top because of slow or incomplete mixing of the secondary air with the gas.
Phil
@@WashingtonStreetStudios - Ok thanks so much! For the last 5 years using only up drafts I am about the same. I fire a high cone 5 middle to reach a 5 top and bottom 6. It works out as I run different glazes on each shelf. To close up my kiln I have it up on blocks and slide out the burner then slide in a cinder block with a half shelf to cover the hole as in my kiln I only have one. If you have 4 holes maybe you can pack the holes with fiber in some way to have the kiln slow cooler.
Thanks for the comment and the tip!
Are gas kilns good for beginners? Right now my home is fully powered by solar power only so i don't have the means for an electric one. But i have plenty of room to make an area for a gas kiln on the backyard.
Gas kilns can be used by beginners and they can be purchased with programmable controllers. Manual gas kilns can be a little tricky, and there will be some loss of pots in the beginning. You will have to decide if you will bisque fire in your gas kiln or will you single fire your pots. Once you learn how to work it, it's just like electric, it gets hot!
@@WashingtonStreetStudios Awesome, thank you for the reply. I'll check those gas kilns with controllers to see which one fits my needs. Thank you!
I've been using half shelves instead of whole shelves in the firings I've done. I have left about an inch between the shelves. Does this make a difference in the firing? Also, could half shelves be staggered to accommodate the sizes of various pieces being fired? Would the spacing between the shelves affect how the heat is distributed? Thanks for your help. I love this channel.
I've sent the question to Phil and I will post his response when I receive it.
Thanks for your questions. The spacing and arrangement of the shelves definitely affect the heat distribution, along with how the shelves are loaded (how tightly spaced the pots are) because these affect the path that the flames can take through the kiln. Tightly spaced pots and closely spaced shelves tend to block the flames and can result in cooler areas. Although the details of shelf arrangement and pot spacing depend upon the specifics of the kiln design (for example updraft vs. downdraft, catenary arch vs. "box"), anything that you can do to provide open pathways for the flames will favor more even heat distribution and temperatures. And you definitely can stagger shelves to accommodate different sizes of pots.
Phil
@@WashingtonStreetStudios Thank you for your answers they are very helpful. I have one last question. At the beginning of the firing, I've read that the flame should be a candle flame for a while. I am not sure what a candle flame looks like. Would the bar that lights up from the pilot light be lit up and the burners not lit or would the burners also be lit? When I tried to adjust the burners to what I thought was a candle flame, I got a lot (and I do mean a lot) of soot or carbon. My kiln was black inside. Is this normal for a candle flame. I am sorry if I am a bother by asking so many questions, I have had absolutely no one to help me with my questions. I will definitely become a supporter of your channel because you have already helped me tremendously. Thank you.
@@WashingtonStreetStudios There is a manual for these kilns online and they specifically advise half shelves with a gap between.
Jim Barribeau, Thank you for your response! Staggering shelves is nearly universally encouraged by manufacturers and operators of all varieties of kilns.
You mentioned a typical firing lasting for about 5 hours. Is this a glaze firing? What cone? And what rate of temperature increase?
Glaze firing, cone 10, 400-500F per hour.
@@WashingtonStreetStudios thanks for the info! I want to try fast firing like that but was concerned about a fast temperature increase. Is your clay body specially suited for that or would say a common b mix clay manage that?
Love the info on your videos! Keep it up
Potter House, We don't have a special clay for this, we even use our reclaim, which is a combination of many clays! It is important that all the water is out of the clay. The pots must be bisque fired. And they must be left to dry, 24 hours minimum, 48 hours preferred, after glazing. I light the pilot flame and turn on the gas until it ignites. I run the kiln on low flame until I see the heat waves coming from the top of the kiln. Give it 10 minutes to dry the interior of the kiln and then flame on! Phil passed away in July, and he always did the firing. I've fired the gas kiln twice since he passed and got to cone 10 in 5-5 1/2 hours with good results. Best of luck!
@@WashingtonStreetStudios thank so much for your response. I'll give it a go and see what happens. My condolences.
I hope someone at your place can help me. I started to fire my Olympic 1823 gas kiln (the smallest one) today and had some problems. At the beginning I left only the pilot bar on to warm up my ware. After an hour I turned the main burners on low. I did notice some soot but it has been my understanding that soot is normal at this stage. I had the lid propped open about 4 inches and the peeps open. I noticed kind of a strange sound coming from the piolet burner and saw lots of flames coming out between the burner and the air adjusting plate. I had this plate open about 1/2 in. I had to close it up completely to not have the flame coming out but assume it was still burning inside. I don't know how to deal with this. I turned everything off because I don't want to blow up or cause a fire. I do fire with propane and I do have a low pressure regulator on my propane tank. The tank I have is a big one that we use to power the whole house since we don't get natural gas where I live. I don't know if this was caused by the way I loaded the kiln or what. I would greatly appreciate any feedback. Is this a dangerous situation? Once the kiln has cooled down I plan to take it apart and clean the pilot bar of any debris and check the orifices. I am assuming the correct orifices are installed as they are the ones that came with the burner when I purchased the kiln and I did specify propane. If anyone out there can help me solve my problem, please do. Thanks
Hello, sorry it took a while to respond. I had to think this through a litttle bit!
There are a couple questions I have from the start, first, is there some space at the bottom of the kiln for the air to mix with the gas? we have about six inches at the bottom of the kiln for the air and gas to mix and ignite to produce the most heat. If you don't have some space, that could explain flames coming out from the bottom.
Next question, is there anything blocking or restricting the flue? We put a 10" circular shelf about 1.5 inches from the flue to help keep heat in the kiln and we use soft bricks as dampers to cover the flue. In an earlier firing, I had the shelf too close to the flue (less than an inch) and we couldn't get to temperature. we also experienced the backflow of flame you are describing. Basically, the gasses couldn't escape the kiln.
Next question, what is your line pressure going in to the kiln? We have a regulator for line pressure and a flow valve into the kiln. I keep the pressure at 5 psi or less and the flow valve barely open, and that gets me through the entire firing. If the flow or pressure is too high, the kiln chokes up and stalls. We have our primary air on the burners open about 1/2 inch and have never had to change them.
Is it windy? I put cement blocks around the base of the kiln, slightly higher than the floor, as a wind block and they are great for steps to load the kiln. We have three large tanks ganged together to feed our gas kiln and soda kiln.
If you have any pictures, that would help. send them to washingtonstreetstudiosinc@gmail.com.
Good luck, I hope this helps.
@@WashingtonStreetStudios Thanks for getting back to me. I really appreciate it. I'll try to answer your questions. I had the kiln set up with a bottom shelf 4 inches from the bottom of the kiln and then another shelf where I placed a kiln post over the burner as explained in the video Operating a Small Gas Kiln. Above that shelf (which had nothing else on it, I placed another shelf 3 1/2 inches above it. I had a baffle shelf about 1 inch under the opening at the top of the kiln. We have a very large propane tank that fuels the whole house. The handiman who helped me get my kiln set up put a low-pressure regulator off of the big tank. There is also another low-pressure regulator that is connected to the gas line going into the place where my kiln is located. There is a gauge also on the gas line pipe inside my shop that registered about 1 PSI. I attempted to fire the kiln this past Sunday and the flames coming out of the pilot burner were really bad so I shut the whole thing down. The next day my son came over and helped me disassemble the kiln. He blew out the burners with the air compressor and there was a lot of soot that came out. When he blew out the horizontal bar attached to the piolet burner there was a whole bunch of black soot. He cleaned the piolet bar with still wool and cleaned each of the holes in the piolet bar with a fine wire. When we lit the pilot, it worked great and both burners came on at the same time. The flames looked great. I am thinking now that the flames coming out of the burner (between the adjusting plate and the burner) was caused by the soot or carbon buildup in the horizontal pipe. Now I am wondering why I had such a buildup of soot and carbon. I did have the kiln on low for about 3 hours. Now by low I mean I only had the pilot bar lit. Could that have caused the buildup of soot? All of the burner adjusting plates were at about 1/2 inch below the burner. I haven't fired the kiln since we cleaned it out with the compressed air. I checked the orifices and they are for propane which is what I originally ordered. Sorry for this long reply but I definitely want to get to the bottom of my problem. I have never had any trouble reaching the higher temperatures in the past and am hoping that cleaning the soot out of the pipes did the trick. I am just clueless as to what to do in the future to avoid this happening again and wonder what I did wrong to cause it in the first place. Maybe it was having it on low for so long but I have read that some people leave the kiln on low all night. Some of my pieces are handbuilt and have thicker walls. I have had pieces explode in the past where fragments landed on the burners and caused backpressure. I try to avoid that ever happening again. If I try to fire it on low again, should I turn on the main burners and keep them on low? I do get soot when they are on low. Okay, I'm done. Hope you can give me some suggestions to help with my next firing. Thanks for your help.
I would definately lower the baffle shelf to leave at least 1 1/2 inches. If the gases can't escape, the soot will build up. But that's my only real suggestion. Phil passed away last July, and he probably could have helped.
@@WashingtonStreetStudios I'll definitely lower the baffle shelf. Sorry to hear of Phil's passing and glad for his videos. They have been very helpful. Thanks again for your help.
Hello sir how are you sir I want your help regarding the thermocouple for gas kiln
Today unfired gas kiln with 900 degree temptarture glaze in gas kiln.
When I start to fire gas kiln the temperature have been 25 degree than after 6 hours temperature was 225 degree
When I saw the glaze test piece in kiln it was melted
Hassan, do you fire with pyrometric cones? If you are not familiar with pyrometric cones watch this video: ua-cam.com/video/4iqiC752MFc/v-deo.html
Using cones is the only accurate way to know the 'heat work' within a kiln. Heat work is a combination of both time and temperature.
Thermocouples measure temperature and they need to be tested to make sure they are working properly. It sounds like your set up is not working very well and this could be caused by several different components (faulty thermocouple, thermocouple not properly installed in the kiln, wires not properly connected or damaged) and most of these issues need to be resolved with help from the manufacturer. Can you tell us what is in your setup? What equipment? Pictures would be good as well. You can send them to washingtonstreetstudiosinc@gmail.com.
@@WashingtonStreetStudios sir I did not use cone but I used test sample of glaze .
If you give me your email I will send my kiln pictures
@@WashingtonStreetStudios how I can make pyrometric cone ?
washingtonstreetstudiosinc@gmail.com
Please redo the lecture. The visuals were essential, but useless because the videographer did not realize that only you could see the visuals.
Thanks for the compliment of calling me a videographer! This was one of my early videos and I've learned a lot in the last year. I'll see if I can improve and re-release this video. We will also put it in the queue for a re-recording, but I will say it's a rather long queue.