Bill Kielb

I think either is fine for a first time break in firing. I don’t have clayshare so I can’t speak to that video. The 04 firing in the first video is a nice soft test fire often used to season new elements. You can always practice a glaze firing later.

This video appears to be about a “break in firing” or first firing with a new kiln. My thought: Maybe good to post what are you intending to fire (bisque / glaze) what cone you are firing to, any other info, like it’s heavy sculpture work not fully dry or It’s already bisqued ordinary thickness mugs etc….. to avoid confusion.

Just some thoughts that might help here - nail down your approximate design heat requirements. One simple way to look at this is presently how much thermal energy does it take brand new out of the box electric. This kiln is a 16 kw so at 100% conversion efficiency, to make cone 10. 16,000w x 3.41 btu/w = 54560 btuh. That is totally sealed and converting 100% of your energy to useable heat. So estimating (approximate) Any gas burner you install will be 80% or less efficient which could range let’s say 60-80%. So minimum ballpark thermal energy range needed with no flue 54560/0.80 = 68,200 btuh min and 54560/0.60=90,933 btuh max.. But we know you need a flue so realistically 100,000 to 150,000 btuh will be necessary. From there you can begin picking approximate flue height, burner cfm, orifice sizes, etc… mostly from tables. To answer your question of approximate burner cfm: Burner CFM / secondary air cfm required from previous thread (table) Propane requires 23.82 cu ft of air for every cu ft of propane to completely combust (oxidation firing). 50% of which will come as primary and 50% secondary air. Previous thread here Maybe approximate your thermal needs or range first, then pick your other needs from tables.

Baso makes lots of valves, high pressure and thermocouple powered are attractive for minimal design. That kiln is 20” X 20” X36” h so not a lot of width for burners on each side and bag walls but height might be key. You may end up atmospheric through the bottom or single powered burner. Looks like a fun project. I did find this through Google. Not dimensional but appears proportional.

My experience they will very very likely grow as the clay shrinks in the next firing(s). For me, I would remake it

For the most part yes - My fault- I was trying to convey that observing the flame at the burner would be an important part of indicating sufficient Primary Air, however secondary air is directly influenced by the damper position. Both primary and secondary air are super important to efficient use of the fuel …… or for maximum heating. The damper will eventually influence the flow of primary air as the back pressure (when significant) will degrade the performance of the Venturi. This is often the reason to just leave the primary air adjustments (when present) alone and just go into reduction using the damper and sufficient gas pressure to pressurize the kiln down to the lowest spyhole or even lower attempting to keep oxygen away and maintain a uniform reducing environment. Enough back pressure in the kiln will eventually influence the primary air as well. The secondary air is often overlooked and misunderstood but is a super important part of the non powered burner process. I was trying to emphasize the difference in origination and importance of both.

Gas combustion made simple! At about 10:1 air / fuel you will get a nice blue efficient flame (natural gas, propane not so much), plenty of oxygen for efficient combustion. A nice blue base of the flame is a reasonable indication of an oxidizing fairly efficient flame so the answer to your question is basically yes it’s a decent indication enough primary air is coming in. . Venturi burners are sort of self calibrated within a pressure range of operation so the more gas pressure, the more primary air is sucked in by the Venturi effect. Your burners do not appear to have a primary air shutter and that is ok really. A nice blue color, devoid of yellow indicates you are operating within a reasonable efficient pressure range for this burner. About 50%:of the air for combustion comes from the primary air and 50% secondary air. The secondary air enters around the burner or the hole in the bottom of the kiln where the burner penetrates. when closing the damper there will be an absolute best position for a given gas pressure where you are losing the least amount of heat but still allowing enough secondary airflow through the kiln for all the gas to be burned efficiently. Close it more and flame efficiency drops, less secondary air comes in the holes around the burners. Folks often set their gas pressure - then find the point where performance begins to drop and open their dampers slightly more from there to get near that perfect balance. Every increase in pressure generally requires a slight opening of the damper so patience is key until you learn about where the damper needs to be for a given pressure for your kiln. Your stuff seems to be working as designed, I would’ suggest testing with a damper first, it seems you are close ……. before making changes to the original design. Meaningful fine tuning damper adjustments start about 1000 degrees btw. There always seems to be a lot of confusion with combustion Simple Bunsen burner pic below we use to teach primary and secondary air and a fuel air chart showing efficient mixtures you might find helpful.

Your flames look blue, so it seems enough primary air. Yes at 5000 ft you have less oxygen per cubic foot of air, so your burners will be derated a bit from what is shown in the orifice table. Of course your natural gas supplier may also have lower energy content per cu ft of gas as well. Not uncommon in mid altitude supplies. It would be nice to know about how many btuh with decent coordinated gas and damper. I would suggest finding the best balance for your damper and gas setting, there is always a balance when firing. Often finding the best damper position for a given gas pressure will be very slight movements of the damper so lots of patience is often required. At some point you will run out of secondary air to which the over cuts on the bottom burners will be too small. I would assume as designed this thing works so damper and max gas levels are something I would suggest you tweak now. Adding a flue pipe is a bit uncommon, typically this kiln would be installed in free air or a natural draft hood would be placed above so the existing hole in the top is probably optimal or close to optimal design for this kiln at present. Hoods use dilution air to keep them in the 500f degree or Bvent range. Direct connect stuff - not really great using metal at 2300 f degrees and not common for this type of kiln application. However if inclined, size (diameter) and height of the flue will influence the draft by stack effect - something you can look up in a table based on btuh and temperature difference. It really looks like you will get there just using a damper and proper gas pressure settings though so zI would focus there first.

Yes small metal pipe may help with the draft draw-great idea Babs Might want to just fire with a damper initially to see what this needs. Lots of updrafts just fire into a hood without a direct connect flue for simplicity.

Just under 3% less inspired ! But to your excellent point, when estimating burner output elevation needs to be corrected for as well as the heat content of your natural gas supplied. Both can combine to be very significant in mid and high altitude burner deigns. While as a percentage O2 is still just under 21% more space exists between air molecules so quite a different mixture and burner settings sort of like quite a bit different O2 absorbed with every breath! Your body can adjust or acclimate much more so than your burners. Good catch! This is definitely an important part of understanding what you have and designing for what you will need.

Well, I can tell you that you don’t have enough power to offset the shell losses. As to why, for me I would figure out just how many btuh the burners are producing? From there I would decide on the best way to get more. It looks like you have 1/2” or 3/4” csst gas piping so pressure drop will probably be significant. If you had a gauge and operating valve at the kiln then it would be easy to tell. One thing I would ask is did you ever fine tune using a damper? This is a fairly small updraft kiln and that hole in the top is gonna let a lot of heat out if it’s not just the right size. The more we know for certain the better, but I would test again and make very very very small adjustments to the damper to see what I could get this to (peak temperature) and figure out a way to know approximately how many btuh you were at. From there some logical decisions could be made and tested.

Just appears the element jumpers are mis wired.. wire per the schematic and you should be good to go. Confirm what I have drawn on the kiln in violet, then reconfigure jumpers so elements are in parallel. If my drawing is right, the current jumpers are jumping out the elements. Change to More like what I have drawn in red.

Yeah just a thought really. Not saying it is awful at 0.33, just it likely melts lower than cone 6 (under Katz):which potentially could be causing your holds to not be as effective. If true, reducing it might save on materials as well. Just something easy to try which may indicate reduction in fluidity is something to focus on here. Might not improve things as well. I have used the Katz numbers for several years now as a guide and thus far to good result but my premise is some glazes pinhole worse when more fluid. Firing them higher would be a good example of a glaze behaving counter intuitively as more fluid ought to heal, but in some cases because of the fired surface tension they behave opposite and respond to a drop and hold to heal. So less fluid condition and the glaze can overcome and heal these pinholes. Just an observational thought though. If it works, it also could save on expensive materials.

I am thinking this is bisque to 04 not 4. One thing strikes me in the recipe, boron is fairly high for cone 6. About 0.15 ought to get you cone 6, so this likely begins to melt much earlier. Might be worth an experiment or two reducing the Fritt a bit. Saves on an expensive ingredient and ought to reduce fluidity a bit which might be ideal. Definitely need to test to see if it affects the glaze positively or negatively.

This is the way I learned this particular pinhole theory but to my knowledge and what I have been taught, like fired COE, the fired characteristics cannot be obtained from the glaze formulation and measuring at temperature for just one composition has its own complications. + one from me realizing kilns generally don’t have powered cooling cycles so they cool at their rate (thermal mass being significant here) and you simply establish holds along the way. Multiple holds can give you step control though so closer to a defined rate of cooling. To my knowledge alleviating the surface tension issue involves trial and error though. Some of the randomness to multiple trials could be the different natural rates that things are actually cooling. So if your kiln cools very quickly at top end, then your holds could be more material and reliable. Hopefully I am wrong and someone here has the magic, but from my experience testing is necessary. Pinholes can have other causes though so you may want to explore those cures as well. I will add that temperature differences from shelf to ware or outside of a ware to inside of an open shape always seemed highly unlikely just because ceramic conducts heat pretty quickly, generally much faster than typical heating and cooling rates it is subjected to. Still, if you find a solution based in that theory then it works for you. I believe you need to test to find the best answer for a glaze combination. One solution I really liked was to fire short of peak temp using a hold to still make cone heatwork and doing a drop and hold from there. In my experience glazes can pinhole more so at higher firing temps. So firing one cone lower with a fifteen to 20 minute hold drives the heatwork to the desired cone but without the peak temperature. Something maybe worth trying with your established drop and hold from there. Finally, if this reads crazy complicated, it’s just me not being able to adequately simplify, someone likely will have a simple fix.

Just realized, harder to do with LED Christmas lights these days!

Just thinking, if it melted the sitter cone then it made it to that temperature - almost without doubt. You might want to triple check the sitter cone Orton cones- “Cones and Bars from 05 to 3 are dark red because of the iron that they contain.”

So what turned the kiln off? Did the safety countdown timer turn it off too soon or did the cone melt in the sitter? If the sitter, then check it was not cone 05 instead of 5 (likely), sitter calibration ( that’s a lot of mis calibration, confirm everything else first before drastically recalibrating). You made it to red heat, that’s 1000f + so no stove oven would ever get near there. If all the above is not helpful, then testing the elements is likely next. The good news, it made it to red heat and something shut it off. First task, what shut it off?

I can second the cone 5 experience it did not like to go to cone 6 for me without pinholes with our clay. Also needed to apply it fairly thick, else it was just sort of some ugly. Just a reminder: it is NOT listed for food surfaces when we tried it. Took lots of firing tests to get one family bragging rights trophy fairly pinhole free. Also as it aged it became more black chrome than bright chrome.

The good news those appear to be silicon carbide elements which tend to have decent life ……. But the somewhat bad news is they have very different resistance readings as they heat up. Hopefully I am wrong and it’s just the picture and they are standard coiled kiln elements. If silicon carbide: my best thought, It may be necessary to run this kiln up to temperature and measure the hot resistance by actually measuring the amperage the kiln is drawing at top temperature. And if it makes top temperature then you will already know it is still serviceable or what temperature it can make. Place cones in this firing for sure and a pyrometer would be very useful. If you are or have someone technically familiar with kilns and electric, it may be easiest to safely temporarily wire this kiln and fully supervise the firing. At peak temperature the amperage would be measured and wattage can be compared with the nameplate as well as hot resistance of the elements will be able to be derived from the amperage measured. Sorry - I am at a loss for an easier method here, unfortunately silicon carbide resistance can change significantly when heated as well as aging. Maybe someone here has an easier way, this is the only definitive way I am aware of. Hopefully I am wrong and they are really traditional elements which means measure the resistance cold. The Nova 1 manual seems to match your kiln shape and indicates 1/2 of the element with the fiber is a part number, so my thought would be when worn the entire fiber and element group would be replaced and installed 1/2 section at a time.

Good question! Someone here likely firing regularly on their own tanks has that figured out.The recent propane kilns I have tweaked or instructed on have all been 1000 gallon tanks. Propane does provide about 91,000 btu per gallon though so we could back into an estimate from the data. All the more reason to reduce shell losses as much as practical. Less BTU, less gallons.

Nice to see you are on the way! I found this old firing data and its profile from an updraft kiln It’s a simple Reduction profile but also fun to see the data of one of these in action along with rates it can achieve in reduction. It might give you a better idea of how these are often fired by hand. This one is in the 9 hour range and they are trying (more or less) to follow the profile pictured by manually adjusting gas and damper as needed every 15-30 minutes. There kiln hasa bit more capability than the profile below which was specifically created for a Geil downdraft car kiln.

Really good to have the combustion background, definitely half the battle. Now some stuff that may help with your background and hopefully allows you to work through the design and tuning. In the end It’s pretty simple basic combustion stuff The split between primary air and secondary air is about 50% Knowing that will allow you to figure reasonable over cuts around the burners where secondary air will enter, if not 1– 2 inch clearance is fine. Too small is generally the mistake. An ideal ratio air / fuel will be approximately 10:1 (oxidation) Reduction will be a dirty flame, producing lots of carbon monoxide and ……… pressurizing the kiln so very little air is drawn into the kiln through the over cuts. Reduction is achieved by closing the damper and and pressurizing the kiln from top to bottom. Very slight adjustments will establish this. Slightly pressurizing the kiln (very slight) will be enough to keep secondary air from coming in the over cuts which drives the kiln into reduction. (Very dirty flame - no soot needed, too rich and decreases reduction) Never go into early reduction below the PEL of the gas 1500 f or better. #60 is pretty small as most propane kilns are regulated down to inches, but at .#60 (for now) you likely will operate this in the 1-2 psi range, here is one of my favorite orifice tables https://www.gordonpiatt.com/wp-content/uploads/2021/07/Propane-Orifice-Chart-7.E.80.6-Rev-3-05.01.pdf easy to figure just what pressure you will need after you figure how much Btuh you need as well. Total guess, start at prox. 300,000 btuh, work your way down as practical.The kiln will be easier to fire and adjust in firing using low pressure. Inches of wc pressure Design your flue by table p41 here can help or 4” - 5” is likely reasonable and allow you to tune the height in the end. https://www.selkirkcorp.com/literature/Chimney_Venting_Sizing_Handbook.pdf Higher increases draw but also makes damper adjustments more sensitive. For an updraft kiln placing the thermocouple as near the kiln as practical in the flue likely give a decent reading of the average temps. Gas kilns are fired supervised by cone so watching when cones bend will be more important than peak temperature. Firing rates 500-600 f degrees per hour are generally considered fast for clay, but once in reduction your flame will have much less energy so 100 -200 f per hour will still be fast. Reduction has its nuances, but simplified, very dirty flame, slightly pressurized kiln not allowing any oxidation. Reduced pieces can and often are reoxidize by plain old air going past them if the kiln is not kept slightly pressurized while in reduction. Onlya handful of metals are affected by reduction. without an O2 meter, you fire by eye, reduction flame poking out spyholes Really nice example reduction flame below from an updraft. Firing with someone who is used to reduction firing is generally a patience saver.

Hmm, I don’t not know if I fully understand. Underglazes are not glaze and often consist primarily of clay and stain. Many do not really melt so unglazed they are very matte but more sintered than melted hence durability or longevity would be difficult to guarantee. For a gloss finish it’s common to apply clear gloss glaze over the underglaze. For matte appearance with reasonable durability it’s also common to use matte clear glaze over the top of the underglaze. Any clear matte will cloud to some extent because of the diffraction of light. Thin application definitely better than thick as far as glaze clarity. As far as a glaze that works for you and your clay and the desired finish you will likely need to test. If you look on Glazy.org Marcia’s matte https://glazy.org/recipes/19734. Was created to be very dry ( but easily adjustable) and melt over fairly heavy underglazes. It has great reviews, but it may not work for your clay, desired aesthetic, etc…. Sadly clear glazes often tend to take testing to meet an artists needs. There are many matte glaze recipes though - which one works for you will require testing.

I like all the ideas. For anything a bit uncertain I favor a rough opening done in pipe so it can be pulled later but the number 6 takes care of that. I would suggest terminate in a 4X4 box for working room for now. Cover plate typical below. (Duplex drywall ring typical) a single gang box would be tough to work in when you install the receptacle.