Rupsa Nath

Hi @Gusf, we dismantled the kiln completely and had to find a new place to install it. Due to Corona, we haven't managed to travel and install the kiln again. We hope to do so in these coming years and I will talk to Joe Finch for some guidance. I think our chimney on the kiln we had built before was too short and some potters have thrown around the idea that maybe the high firing bricks we got were not of good quality. I remember our temperature had gone up to 750 degree celsius eventually and the space around the kiln was hot. I have had the opportunity of firing in pre-fabricated gas kilns after that where you barely noticed the heat in the surrounding space even if the temperature was at 1220 degrees. So maybe we need to look into the issue of the brick quality as well.

Thank you everyone for your inputs. They have really helped us reassess our kiln placement and structure. We are currently moving our kiln at least 10 feet away from the house, and are going to make modifications to the existing model. Will definitely post again if we run into issues.

It seems obvious now that we need to move the kiln away from the house. Dangerous oversight on our part, which we will rectify immediately. We have been reading Olsen as well, and he too suggests a smaller burner port. We have it in mind to have a manufactured stand for our burners too. But since were just testing them out now, we thought of propping them up on bricks. @neilestrick: Do we need a damper only at the exit flue, or somewhere else as well? based on the size of the kiln and according to the calculation provided by Olsen, we got to a chimney height of about 15 to 16 feet high. Does that seem right?

@nielestrick: Actually the top of the kiln is a sprung arch made of insulating fire bricks, with more ceramic blankets on top and then those shelves. @Mark C: We presently have not added a damper yet. We are currently thinking of increasing the chimney height also.

Thank you for the response. I think adjusting the chimney height is what we can do as the next step to see if there is any difference.

Hi, This is the first kiln my husband and I built. The model we followed to the letter is of Joe Finch, as he explained in his book, "Kiln Construction: A Brick by brick Approach". We have fired this kiln 3 times so far, and every single time it has gotten stuck at 550-600 degree celsius. About the Kiln: The Gas Kiln has an inner dimension of 1 cubic meter. The wall is made of regular insulated firebrick + 4" ceramic blanket +outside layer of firebrick again for more insulation. It is a downdraft kiln with two burner ports on either side. Our chimney is about 7 feet tall and the exit flue is equal to the area of the burner ports. Burners: We initially did two firings with small burners (model S20) with a Btu of 30,000-83,000 per hour. And the next model (S80) we took for our third and last firing with a Btu of 120,000-336,000 per hour. I have attached a picture which has the list of burner models so you can see all their specs. Gas cylinders: In India for commerical firings, we get 19kg LPG cylinders, and we are using two of those simultaneously for our gas firing. To keep the pressure from falling too low, I douse the cylinders in room temperature water when they start to ice up in the bottom. For all the three firings we have done, the temperature always slowed down at 560 degrees celsius, and then stuck around 580 degrees celsius. The first time we kept firing for about 3-4 hours, but there was no progress, and the last time we stayed at the temperature for 1 hour before calling quits. I have added the firing schedule below for the first and third firing so you can see how the temperature had risen. All the numbers mentioned are in celsius. First firing (Sunny day, Third firing (Sunny day, not much wind) less wind) 1.30 pm 82.1 11.47am 215 1.51 pm 191 12.05pm 364 3.32 pm 279 12.09pm 400 4.42 pm 400.5 12.28pm 533 5.36pm 504 12.51pm 588.6 6.47pm 551 1.46pm 562 7.24pm 570 7.55pm 563 As you can see, we took less time to reach 550 degrees in the third firing with our bigger burners. But all three times, the temperature got stuck at around 580. I have added pictures of our burners position as well, and we made sure they were outside of the kiln to pull in the air and burn the oxygen. Based on these figures, do you think: - Our chimney is too small in height? - Burners are not enough? -Some other factor that is stopping the temperature from rising? Grateful for any advice and suggestions. Thank you!