Bill Kielb

Looks fizzy, under melted, over melted (toward drying up). I would definitely get the extended bisque going, I think everyone has mentioned time now helping with burning things out. You can spend lots of time in the 1500 - 1700 degree range and not worry so much about going into cone 04, 03, 02 direction which is usually an issue with holding at peak. The last 200 - 250 degrees should be in the 100f per hour range just to ensure even heating and a reasonable amount of heatwork to hit your planned cone. Bisque products are sintered so not necessarily a fluxed reaction. I would suggest trying an extended bisque on test tiles and for the test glaze firing truly hit the desired cone for clay and glaze, not exceeding the maximum cone for either. If that provides a mostly good result then a drop and soak can help heal any minor imperfections that might remain. Right now there are too many unknowns, maybe get rid of them one at a time holding other things constant such as cone fired to, and note the level of improvement.

Likely can be removed and replaced. Talk to your licensed contractor who is testing it though for a removal and remediation price, then anyone qualified can install new fiber to replace it. Hopefully it tests as fiber insulation, not asbestos containing.

You would need to provide a sample to a lab to analyze by microscopy. It’s usually best to contact a licensed asbestos contractor to collect and submit to an approved lab in your jurisdiction. They generally will follow protocols on collection so as not to disturb and contaminate the space the kiln resides in, provide chain of custody verification, and submit to an accredited lab for analysis.

A damper opened too far let’s out too much heat and let’s in too much primary air - cooling the kiln. A damper closed just right keeps the maximum heat in and provides just the right amount of air (10:-1) for combustion for the fuel to burn most efficiently. A damper closed that begins to smother the flame and builds pressure in the kiln while a jet begins to emerge from the spyholes is in reduction and most kilns are marginally powered so their temperature rise stalls or even falls. With proper gas pressure and coordinated damper operation you may be able to save a bunch of gas and some time as well. Folks usually find the best damper position and gas pressure combination throughout the firing (often every 30 minutes or so). Rarely does the damper position change by more than 1/4”-1/2” at a time once ideally found for each operating pressure.

If you have room for best centerline alignment adjust the height of either pulley until the belt tracks smoothest in the large pulley without rubbing the side of the groove, this should minimize your vibration as much as practical. If it’s still not acceptable then large pulley replacement is next. If that still wobbles excessively then the shaft is the next culprit that could be bent. Usually not likely though. Below, minimize the “offset” condition in the center picture so the belt rubs least along the side groove of the big pulley. If the wheel is bent excessively the other two conditions will be present and you will likely need to replace the large pulley and or in limited cases it’s due to a bent shaft. Of course definitely take the belt off and check for an excessive bend or flat spot for sure. Wheels are very slow spinning machines so everything should be rigid enough to not vibrate even when not balanced. Your first video showed a noticeable vibration in the motor pulley So I believe it vibrates excessively.

Just some ideas It’s pretty hard to tell from your video other than the large cast pulley appears to wobble but the belt tracks pretty straight so for large pulleys - this may be acceptable. What’s more interesting is the visible vibration at high speed. If the camera is just set in place then watching the motor pulley there seems to be considerable vibration induced in the image at high speed. This is really tough to diagnose from afar with a short video, but low speed assemblies like a wheel ought not to need much balancing and they are usually rigid enough not to require it and hence usually no visible vibration. So to that I would check: Belt tension, it’s not too tight - follow the manufactures guide! Too loose is bad, but too tight is not necessarily better Motor assembly and tensioning mounting bolts - they are all tight and nothing rocks in any direction if you wiggle it. This could be the motor pivot bolts or tensioner anchor bolts. Everything should be flush, perpendicular …….. as in bolts. / nuts / motor orientation and are seated and appropriately tightened so nothing can wobble in and out of its correct plane or orientation. That’s not to say over tighten the belt tensioner to achieve that. The assembly has to be sturdy, rigid, in plane but the belt tension should be appropriate with a bit of deflection when you press in on the middle of it laterally. If you can ………. post a video of the motor assembly while cycling through from low to high speed. it may reveal why the apparent vibration. Set the phone flat on the floor looking up, stationary and capture the motor and belt. You will not be able to hold the phone steady enough so it is important that it remain steady through the test. I could be totally wrong, but it is just a simple test. Late add, finally turned the audio in the clip on and there is a high and low spot. How tight is the belt and for how long? Is the belt perfectly aligned with the grooves in both pulleys? In the video, it appears the trailing side of the belt tries to climb ever so slightly out of the large pulley during each wobble which would explain the vibration. The easy thing to say is that pulley wobbles too much and that may be true, but if everything is adjusted and in plane it may become much more acceptable. on a positive note if I index the track of the top of your belt in the video, it’s stays fairly still in operation.

Ever try making the leading edge as sharp and smooth as practical and recruiting gravity to help. The rounded nature of glass seems to influence things quite a bit and the smooth rather sharp finish of metal seems to help remove the troublesome dribbles for many liquids. We have always tried to use smooth flow (laminar), gravity and a well finished leading edge to help with the dribbles. This has seemed to work well over the years for us https://youtu.be/BAwo5cKhCuM

This may help https://youtu.be/ElsovWpt61c. Gotta watch all the way through though. Looks like strong cone 6 is bright, less is muddy. The top shelf of the kiln can often be the coolest because of losses and element placement.

Generally recipes with 10% clay or more won't need bentonite. Your recipe has 20% EPK already which many find a bit high.

My sense is compression, especially for large items. Anytime something is stretched out compressing downward often does not put things back from which they came. Often if something is stretched away from itself it needs to be pushed back in upon itself to be compressed again. The physics or thermodynamics of a kiln really make it hard for a shelf to mysteriously overheat something. Energy flows downhill like water until the levels are even so I have never found the shelf to be at issue unless the piece does not slide smoothly along the shelf while changing size. Just an educated guess, and I could be totally wrong in speculating, but how do you compress? This may give you a new idea about compression https://youtu.be/jVNJELUpclk

Hmm, 1200 is cone 5-1/2 and with a fifteen minute hold probably a solid 6 or 6-1/2 so firing lower definitely something to try. Peak temperature is important in a bisque firing, but how long is super important as well to burn out all organics. Often especially for dark clays.

Polish potters often make their own with sponge / sponge rubber. https://youtu.be/BIrUcj3TC6Y. This may interest you, lots more videos out there. Some show hand making the stamps.

Looks great, nice choice should be no deflection for sure. I am curious how hot the paint will get, it ought to be fairly cool and also curious of wheel temp, my experience more room temperature than not. Here is a hood painted with high heat as well as some of the welded mounting hardware - has held up for five years now without an issue and these areas ought to be much hotter than you will experience.

Yes, although there can be similar compatibilities with respect to clays, there can also be differences as well. In general most everything is always tested first using test tiles to be sure they will work together. Clay and glaze are at the top of the “test first” list. The test is for compatibility in melt, glaze fit and then I would say aesthetics. As you explore pottery you will find that temperature is really a general guide and cones are more specific to how things melt and if they have fully melted, under melted or over melted. Post a picture of your glaze defect and you will likely get questions about what cone were they fired to? what cone was the clay bisqued to? How long did the bisque take?…….. The defect between compatible products often points to another need. So your description of the defect points to excess off gassing of the clay which leads me to ask, how long do you bisque and to what cone do you bisque to? Along with the usual, what cone is the published maturity of the clay and glaze?

@neilestrick had a couple models posted at one time - Grainger or Dayton brand that I believe he researched and was a less expensive replacement. He may weigh in here.

That would be a bearing. If it’s not overheating then it can run. It likely won’t run long without getting worse so replacement sooner than later. It seems you have no option so running with a bit of supervision to make sure it’s not overheating or the sound has changed and become worse is probably your best bet. It really does not have to run for the entire firing and if you have an alternative way to ventilate the space that could be your best option at this point.

Looks fairly clean and intact. Likely motor bearing then. My only thought - Can you tell where the noise is coming from?

Definitely screaming! Possibilities: rotor is rubbing, out of balance, loose, crud built up, bad bearing. Sleeve bearing or motor bearing going bad. I would definitely open it, examine closely and see if it can be cleaned and the rotor tightened. Generally not a good sign though. Even though this is a 2000f plus kiln these fans are supposed to be set up to draw a bunch of room air to keep them below 140 f degrees even at kiln peak temperature. Overheating will shorten the life of these significantly. Something to check especially if this is not that old and when you open it the blower wheel appears overheated and rusted.

A few things strike me: It looks fairly thick in the pictures, were your test tiles applied the same thickness? This glaze appears matte, is it sold as such? What cone is the glaze and clay and did you use witness cones in any of the firings. BTW the five minute hold at the end will drive this toward the next cone higher so not sure why it is there or if it’s something you have proven works for you.

Just to add, all the above is correct and I believe that circuit needs to be exclusive to the kiln, so not only breaker sized and wire sized correctly, dedicated for the kiln which means other receptacles are not connected to that circuit. So your electrician should actually do a number of things, including pulling a separate circuit for the kiln.

Just my experience and a suggestion or two High heat paint is fine, use it on many kiln repairs in much hotter places. The outside bottom of the kiln is usually pretty cool. Just a suggestion I would support across the center span to keep the bottom from cracking. I would also use tall 4”-5” urethane castors so it rolls easily over little humps and bumps. Maybe Big box store castors - prox 15.00 each

This may help or this may confuse you. We use the UMF to understand our glazes chemically. So in your example above the boron went from 0.58 to 0.67 a significant change even though the same weight of each compound was used. The relationship under UMF is relative and is a comparison of atoms. Here is a quick how to calculate UMF that may shed some light. https://www.youtube.com/watch?v=HyLjAg1_8_4

If you look at orifice tables they are generally in inches so most burners are designed for inches of wc because natural gas has a bunch of energy and even with a really small pressure one can achieve lots of btu with a tiny orifice. At 1/8” diameter I can get 100,000 btu with only 9” of. Pressure. (About 1/3 of a psi) That same orifice at 2 PSI will be 144,000 btu. Propane tanks are relatively high pressure so they can hold a reasonable amount of liquid propane in a small bottle and operate in low temperatures.. My advice: follow the design tables that we have used for the last hundred years. Will it improve adjustability, definitely, just use a metering hand valve to control your burner like most kilns. When you adjust the hand valve you are essentially dropping the pressure across it from zero to 1” to 2” etc…. That’s WAY harder to do with 30 psi on one side of it than with 11”. BTW you need a valve so you can adjust the kiln output as needed. In the beginning, small flame gradual warming, at the end more heating. This is just firing, a kiln doesn’t cycle on and off maintaining a temperature as if it were an oven. People hand fire it according to their schedule. It never starts out full on and just roars through the firing. Set your regulator at 11” and adjust downstream with the hand valve. This way as tank temperature and pressure changes you will always have a steady 11” to your kiln and your last hand setting will remain consistent. Are burners in general sized for inches of water, YES - Stoves, heaters, grills, dryers, fire places, kilns, Venturi burners, basically gas appliances. Can you pipe high pressure propane - YES. Is it more dangerous than low pressure if there is a leak - YES, without a doubt. If you run low pressure do you need a larger diameter hose? - yep, follow the tables. Can you cram PSI through burners sized for inches? Yep, the head loss (friction loss) goes up enough so the burner puts out more but the head loss becomes really high. Are orifices designed to operate in inches that way for a reason Yep, always have been. Do most propane appliances have a regulator built into them? YEP PSI to inches of water column. Are inches of pressure misunderstood by many - in my experience, YES Call Ward for sure, he is used to this - once inches of water column is understood, generally the mystery goes away. here is a very generic video you might find interesting https://www.youtube.com/watch?v=T-QhRrQA21g Orifice table (inches of water Column) Finally, for CSST it looks like 3/8” inside diameter at 10 feet is fine for 100000 btu but check with your hose provider based on 11” of water column what diameter hose

I still think pictures of the failures would help folks formulate a more informed opinion or basis for other questions. Post some if you have any.

It’s just molar math. A mole of something contains 6.022 X 10 (raised to the 23rd power) of something. Atoms, molecules, particles. Since the components such as silica, Alumina etc…. Contain different grams per mole relating everything to moles is the great chemistry unifier to grams. Now the mixture of each substance can be compared accurately. Use the formula amounts, they are there to make everything relatable to grams. The formula weight for 3195 = 339.82 and the formula weight for 3134 = 195.57. The formula amount ends up to be the actual how much of a component is present even though the two formulas vary significantly by weight and have different portions by percentage. Your logic is good, but I will say once your glaze is melted you are depending on gravity to make the glaze move. Melting it a bit earlier can give gravity more time to pull this glaze down or for it to break and flow across ridges. But glazes are stiff for other reasons. A popular one being how much Silica and alumina are present. Thick applications help because they help gravity pull everything downward. If the fired viscosity is stiff though, it wont be enough to move it and melting earlier only provides more time for it to perhaps move slowly. Reducing the silica and alumina Will definitely affect the viscosity but also can lead to glazes with less durability. If your glaze is melting now and you melt it one or two cones earlier and it still will not move, it’s likely too stiff and additional boron will not necessarily make it runny. Lots of testing using lots of care when making runny glazes is always good advice, else ruined kiln shelves, wares, basically heartache ….. Look at Glazy runny glazes and observe the commonality. Cone 6- 10 and then: Low silica, low alumina, both, high R2O values, None of those chemistry traits are great for durability though.