Expert: Ti Phillips – 10/16/2013
First time in 6 years that I have had this problem of glazes running to shelves and allot of very small busted bubbles in the glaze. I have an older small Duncan kiln. 15 in high interior. It is really taking a long time to stop firing. 7-8 hrs at glaze firing.Even my bisque fired projects sound just like a .bell when tapped. very load. I fire with combination of glazes. Full dip first, second just the top rim. Beautiful colors. Just starting a website.
Thank you for your recent question. Your problem most likely lies with the elements in your kiln. Although the kiln is firing for 7-8 hours, it is still not reaching maturing temperature. This causes glazes to run and creates bubbles in the glaze surface. The bubbles happen when the glaze begins to melt and gases are released. If the kiln does not reach maturing temperature, the glaze will not smooth out and the bubbles will burst and set.
Bisque ware will sound like a bell when under fired.
I am assuming your kiln elements are at least 5 years old. If so, then you will need to check them first to determine if they are going out. If they are, they are simple to replace.
To check the elements, you can first start with a empty kiln firing. Using three cones, cone 06, 05 and cone 04 to determine where your kiln is firing as far as maturing temperature. Place the three cones in the center of the kiln in the order listed above from left to right. Fire the kiln to cone 05 maturing temperature. If you do not have a kiln sitter, then you will have to watch the cones through the peep hole. Record the amount of time it takes for cone 05 to bend. If it is more than 5 hours, your elements are failing. Cone 06 and 04 are used to determine if the kiln is firing appropriately. If cone 06 is bent with it’s tip laying horizontally, and cone 04 is just starting to bend, then the kiln is firing correctly provided it is not firing over 5 hours.
If you find that your kiln elements are failing, you are welcome to contact me again for assistance in replacing them.
I went to your website. It is nice to see a photo of you. It helps to make conversations more on a personal level. I hope this helps you. If you have further questions, please feel free to contact me again and I will be glad to assist you. I am always at your service.
Ms. Ti Phillips
Earth Stoke ‘N Fire Pottery Studio and Artist Retreat