Bill Kielb

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.

One idea that comes to mind using underglaze, you can free form your initial design on greenware and bisque fire. The piece will contract a bit and your strokes will become more dense on their own. From there it is often enough, but if not then adding a second coat to cover often gets folks there. Stay between the lines to keep the original form true or judiciously accent and over paint the design to preserve brush strokes and depth. The second coat is a precision thing I know and not for everyone. The point though, when applied to greenware, just bisque firing it may get you the density you desire ……. or at least close, or maybe something to experiment with. I think the pot in the picture could be recreated on greenware and likely not need touch up and a second bisque.

Just a few things to suggest to start with. I would suggest laying out as best you can where the kiln will go. There likely is only one logical best place that you will place it. If you can do that, then roughing a circuit in for a future kiln and ensuring it Is 3/4” pipe (raceway) rough opening will allow you to pull the appropriate size wires when you get most any kiln. Now, where the kiln will go - probably adjacent to an outside wall, most likely in a corner so there is decent access to ventilation outdoors. You should not combine systems, this one is for the kiln. You should decide if you intend to remove the excess heat as well as all the fumes or a portion of the fumes as in counterflow systems you will likely need electric at or near the kiln for the ventilation accessories you have chosen as well. So maybe another rough electric opening in pipe to be pulled at a later date. Maybe another 3/4” rough opening so if you decide on full ventilation just about any wire size ought to fit. depending on your ventilation choice above you will likely need to plan on makeup air from outdoors as well. So just some things to start to think of

Yes of course simplicity is best. But I would suggest you re-read my original response directly addressing his post. Elaboration came as further requests were made. My first answer was intended to be reasonably brief but also a reasonable explanation to his question: “Is it correct to say that if a glaze/clay combination does not craze at cone 5, then it should not craze at a higher cone firing?” And his direct follow of working at cone 6. With due respect as well, I certainly apologize if I fell short of that goal in your view. Unfortunately my original answer was to the best of my ability an honest attempt to achieve that.

I really do not - just responding originally to the OP and your specific question. I have fired a bit and never did I notice firing higher cures crazing. That’s just an observation though. The reason I believe what I believe is outlined above but it’s just an opinion with a basis. Start a new thread, maybe you have something and firing higher is another tool to help with crazing.

Crazing to me is a result of the differences in the rate of growth or shrinkage. Once fired clay and glaze are the same size, so the clay has shrunk to what it will be and the rate of future expansion and contraction will be affected by its composition and its physical (and thermal) properties such as density etc…. Firing the body to its rated cone will provide the best chance of a fully melted body with repeatable characteristics. So the COE will likely be different for a cone 6 body fired to cone 4 or even cone 5. Our glaze on the other hand if able, may tolerate the difference in speed of expansion / contraction and not fail or craze as if pulled apart. As a glaze is fired higher will its COE change? Very likely yes. Will its physical characteristics change? Very likely yes. Glazes more resistant to wear as in surface hardness may fail more so in impact. I think the difference here for me, none of this is about the starting size and all about rates and whether the glaze can keep the clay body in a slight bit of compression without the glaze failing. So firing both to their rated cone likely gives the best repeatable representation of the match for both. Firing lower and assuming the next cone higher will improve the COE match between the clay and glaze is likely not really reliable in my view. So in the end, fire to rated cone, firing to lower cones is very likely not a good indicator for how these materials react when fired to rated cone.

I have not torn one apart but I would check the belt tension for sure and zero the pedal. The traction drive appears to be a part of the motor, so you might find complete rebuilt assembly. Here is the best in depth maintenance manual I stumbled across. https://cdn.shopify.com/s/files/1/0010/1931/4239/files/rk10-troubleshooting.pdf?14401615399485494650

If you absolutely do not find a spec, I would consider trying hypoid general purpose gear oil, likely in the 90w range and observe the heating in early operation. I would hope there are no significant swarf to speak of from machining operations and he was concerned about break in.

I think hard to generalize and no way to guarantee anything is craze free forever. I do think there is reasonable correlation though. Differences in the expansion rate of clay and glaze being the prime issue, followed by the long term reliance of the glaze to tolerate the slight inevitable difference. The fired COE is often a result of fully firing so a clay body or glaze not fired or fully melted may have a different COE than one that is. Just imagine a clay body or glaze under fired by two or thee cones, we would normally expect it to behave very differently than fully fired stuff because it is under fired. If both are under fired the same amount will their under developed COE somehow be even between them? While I think in the ranges you are working in, likely a decent indication, just firing hotter does not necessarily mean the glaze will have greater flexibility and could actually become harder and more prone to tensile failure. I think your logic is reasonable, but believe it’s always best to test the the clay and glaze combination fired to cone.

I have always been told this is a natural function of skin, predominately hands and feet and extended exposure to water. It definitely happens to me using city, well, lake, stream, and swimming pool water. The dead skin cells absorb water and expand, yet living cells beneath do not. End result - wrinkles. Today this is debated I believe (the mechanism not the wrinkles) … and there are diseases that can present other symptoms as well as similar symptoms. (See Raynaud’s disease) well water can be hard in general and often contains many more organics, not sure of any correlation there though. It is possible that city water is softer, occasionally if sourced from a river. “Chemicals” is a pretty broad description so anything is possible though, but in general well water is untreated and can contain lots more stuff than city water. For most of us I think quite common to see after prolonged exposure to water — city or well. If in doubt, probably take pictures, record what you can about time exposure, temperature, etc…. and see your doctor to be sure.

In my experience that is pretty much how they work. If you pull a lot of fresh air into your kiln you very likely will not have enough power to reach peak temperature. To me this is by design and does a decent job of capturing many fumes, but not all. Usually folks complain about the smell of wax burn off around 700 - 800 degrees. So by design they only pull a small amount of air balancing thermal load against essential exhaust. You can ramp up the exhaust a bit but the practical limit would be the air temperature entering the exhaust fan. So say 120 -130 degrees is practical at peak kiln temp using a mix of kiln air and room air. (Mostly room air) The more air you exhaust through the more power your kiln will need to reach cone.

Very cool idea, limit peak temp and get the drop and hold to heal.

Just a caution here KN95 and N95 masks will NOT protect you from asbestos fibers. Generally a respirator with an approved filter removing 99.97% of all particles 0.3 microns or larger and is well fitted to your face is required. Contaminating, your clothes, immediate and adjacent space(s) are really really important to protect yourself and others. Use appropriate caution testing first is generally the best way to know for sure.

It has a long history in the US starting in 1977 with a date of 1989 with which many consider a near prohibition for new use. In the UK, very likely sooner so I would Google for sure if you are curious of international participation. I would not assume though that the presence of a ban means it is not asbestos or asbestos containing. One thing I do know is we always presume it is and test to rule it out. The only test I am aware of that is accurate would be a bulk sample to an accredited lab where the sample is analyzed appropriately. Current (international) asbestos ban article http://ibasecretariat.org/alpha_ban_list.php

Fans and clay studios - bad mix. Two very popular ways to get this done, place the pot on an unused wheel rotating very slowly and a fan blows on the pot while it’s revolving. Old habits die hard - folks would set their ware on top of an operating kiln (usually along the edge not where it could be screeming hot). Oh, and third I have chattered things nearly right after throwing (10 min.) by drying with a heat gun while still rotating slowly on the wheel until stiff enough to chatter. Dry evenly inside and out, don’t overheat. None of these are great for the ware, but as a way to move the demonstration along ….. the bowl below was thrown, dried and chattered nearly all at once. Definitely dried out enough to demonstrate chattering.

+1 for caring! My experience - this is likely a joint failure, not necessarily glaze related. I like you, worried about the same things and once I had a similar handle crack decided to knock the handles off on a handful of my bisqued mugs and even several glazed. What I found was some handles were attached so securely that the parent material or clay would fail and the joint material remain intact on only the best made joints. From that point on - I spent quite a bit of time on making sure to compress these joints very firmly during construction to be sure the material around and the joint itself was every bit as dense as the parent clay. When I did this, the joint would be as strong as the parent clay which was the best that could be done for that joint. If I needed a stronger joint for extra rough use, then it became larger but always paying extra attention that the joint was fully compressed and attached well. A few more well compressed attachments later, knocking the handles off revealed the parent clay material would now fail before the joint actually would. From that point on I never had a failure, and often when tested by impact, the side of the mug would fail and not the joint. Good glaze helped, but glaze is too brittle to save a weaker made joint. Never had a critical joint fail after that. Typical well made and well attached joint below. This joint is fairly large but these are very custom mugs. It takes significant force but the cup will fail before this joint will. Always compress critical joints so the material is uniform strength was the lesson for me.

So it looks like you are intentionally firing short of peak cone temp, using a hold at the top to get near to the actual heat work without reaching the actual cone peak temperature and adding a drop and hold for healing?