Pottery/Sno Industries Kiln Firing Instructions and Element Replacement
I am a first year teacher at an elementary/ middle school. I have two Sno kilns that I am trying to learn more about. The larger kiln is a model P27, ser. 581 with 240 volts and 45 amps. The smaller kiln is a model C19S, with ser. 1272, 230 volts and 19 amps.
Both kilns were donated, are not in the best condition, and do not have operating manuals. The larger kiln has been having a lot of issues and I think it needs all new elements. However, I am not sure what kind of elements to get since I do not have the operating manual. Is there a way to buy some kind of 'standard' elements or do you know of a similar model for either kiln? I am also aware that Sno Industries is not in business anymore...and I have not had any luck finding a manual on-line.
I was also wondering if you could give me some advice on how to slow-fire the smaller kiln. This kiln has a kiln sitter with no timer and the switches for the elements are only on/off switches. What is the best way to slowly heat up this type of kiln? Should I only turn on one set of elements and then increase heat every hour or so by turning another set on? There are three sets of elements.
Thanks for you help!
Thank you kindly for your question. Yes, unfortunately, Sno Industries went out of business many years ago, however, their kilns are still in service today. Although I have yet to find a manual to place in my collection for use in questions like yours, I will gladly help you in replacing the elements and firing the kiln.
Many kilns have interchangeable parts, and this includes elements for Sno kilns. My suggestion is to remove one of the elements and carefully measure the length. Since you know the voltage and amps required, you can contact Paragon for replacement elements. They will be able to match the element length with the voltage and amp requirements so that you can replace the elements and have a kiln that will fire appropriately.
I do not believe these kilns were designed to fire to cone 10. I will keep checking for you, but you should be able to fire to cone 6 with no problem. Therefore, I am including instructions on firing the kiln bisque to cone 05 and glazed to cone 6. You can fire the kiln to any bisque firing or glaze firing lower cone by inserting the appropriate cone in the sitter. I would also include a cone pack inside the kiln just to assure you are firing to the correct maturing temperature.
Bisque Cone 05
As always, the first time you fire using the schedule, keep a log of the firing, watch the internal cones for maturity, and make any changes you need to make to the schedule once you have a good idea how your kiln fires.
Remember that even if two kilns of the same model are being fired, each will have their own firing schedule. This is because each kiln will fire according to how well their elements work, how loaded the kiln is, and even how dry the pottery is and how thick the ware is. The schedules listed below should be used only as a guide. Your cones are the true test of what is going on in the kiln.
Although the kiln has a cone sitter, please use stationary cones inside the kiln until you know that the sitter works appropriately if you choose to use it. Also, although you use the maturity cone as a stationary cone inside the kiln, use a cone 1 cone higher in the kiln sitter if used. This is because the rod that sits on top of the cone puts some pressure on the cone. When firing, the cone will begin to bend prematurely if the cone is the same as the stationary maturity cone, therefore, under firing the kiln.
Now that we have the essentials down, let's get to the firing schedules.
For convenience, the knobs will be labeled as follows:
B - Bottom
M - Middle
Bisque Fire Schedule Cone 05
Insert a cone 04 into the kiln sitter if used. Place a cone 05 on the center shelf in the center, aligned with a peep hole for viewing. Leave all peep holes open and prop the lid with a fire brick or one of the cone plugs.
Hour Ramp Up or Down
0 B1 - M1
2 B2 - M2 - T1
4 B5 - M5 - T2
6 B7 - M7 - T5 Close lid - Plug Lower Peep Hole
8 - Finish B10 - B10 - T10 Plug Upper Peep Hole
10 approximate The stationary cone should be bent and the cone sitter should turn the kiln off. At hour 10, look at the cone inside the kiln and see if it is beginning to bend. If so check every 15 minutes until the cone bends to the correct maturity. If the kiln sitter does not shut off within 5 minutes of the stationary cone bending, manually turn off the kiln.
Glaze Fire Schedule Cone 6
Insert a cone 7 in the kiln sitter.
Place a cone 6 on the center shelf in the center, aligned with a peep hole for viewing.
Leave all peep holes open and prop the lid with a fire brick or one of the cone plugs.
Hour Ramp Up or Down
0 B1 - M1 - T1
2 B2 - M2 - T2
4 B3 - M3 - T3
5 B6 - M6 - T3 Close lid and plug lower peep hole.
7 B10 - M10 - T10 Plug upper peep hole.
11-14 approximate The stationary cone should be bent and the cone sitter should turn the kiln off. At hour 11, look at the cone inside the kiln and see if it is beginning to bend. If so check every 15 minutes until the cone bends to the correct maturity. If the stationary cone bends and the kiln sitter does not shut off within 5 minutes of the stationary cone bending, manually turn off the kiln.
During both of the above firings, stay with the kiln beginning at hour 8 for bisque and hour 9 for glaze so that you can get a good determination as to when the stationary cone begins to bend. From there, the cone will continue to bend quickly and could be matured in as little as 15 minutes. So watch carefully and record the number of hours it took to reach maturity so you have something to go by the next firing.
As you learn your kilns disposition, you will probably adjust the firing schedule to meet the characteristics of the kiln itself. You will also probably change the firing control for different types of glazes and techniques. This is perfectly fine. Just remember that during a bisque firing, the crucial period for breakage is temperatures below about 1150 F when chemical waters are still in the bisque. After the kiln slowly reaches this temperature, you are safe to bring up the kiln in just about any manner for the pieces in the kiln, i.e. thin or thick pieces require different ramp procedures.
During a glaze firing, it is good to bring the kiln up to the same temperature standards as the bisque firing so that the glaze can release chemical waters also. It also helps the glaze spread over the surface of the clay during the first part of the melt. There are many other reason too lengthy to list here, but if you find that you need more information on glaze firings, you can contact me again.
I hope this helps you. If you have further questions, please feel free to contact me at any time. At your service and good luck!
Ms. Ti Phillips
Earth Stoke 'N Fire Pottery Studio and Artist Retreat