Bill Kielb

Seems to work. Not sure I will depart from significantly below boiling point though as I am rarely looking to save a specific amount of time and like to be cautious with the wares.

So at 16 cu ft, maybe 750,000 btu or in the neighborhood of 90,000 btu per burner so your number 38 orifice is perfect at 11 INCHES of water column pressure. (Chart below) So …. Every 27.72 inches equals 1 psi. Of course your maximum operating pressure from the orifice chart is 11 inches which is 0.396 PSI. So ………. Your final regulator before the kiln orifices needs to be something that reduces the pressure to maybe 14 inches max or if you prefer psi, about 0.396 psi. If you feed these orifices with more than 0.396 PSI or 11 inches of pressure they will probably be way over design. This actually happens to many people as working with such small pressure is just not intuitive. The right way to do this is find out how many btu is stamped on the kiln nameplate, divide it by the number of burners, size your orifices for that output per burner (max) and install a regulator that operates in the right range. For propane that usually is 14 inches and actual operation is set to 11 inches or less. So if your kiln is 750,000 btu then all you need is the right downstream regulator capable of 750,000 btu, 0-14” and can also withstand your inlet pressure. …….. and a decent needle valve to hand operate your burners

No, 400c is a long way from cone 04. There is virtually the 100% reality they are not bisqued at this point as you are accustomed ……. so different than you are used to. Multiple bisque firings to cone for under-glazed pots are a common thing, usually with no noticeable effect for the decorator other than their underglaze is more permanent as intended.

At 400c they ought not to be very sintered nor fully dewatered. I. Would bisque them so they end up the same as your established norm. Not very likely all organics are burned out at this point. It may work with some cool result but why risk this load?

I think best bet is to search locally, maybe on the web by the manufactures name and model number on the relay. Oddly enough it was allegedly produced in Illinois (USA) which is where I am. Anyway Magnecraft, W389ACX-10 which is probably obsolete now but there are almost certainly equivalents produced. Hopefully someone local will weigh in on a local brick and mortar source.

Interesting reading some of the one star reviews. Dismissing the arrived broken, several that standout: glaze cracking after eight months, scratch easily with a fork, not dishwasher proof - glaze comes off. Glaze missing, color difference, glaze comes off on its own, foot ring sharp and scratch my table. There are many good reviews but it probably would be wise to be sure to test these as practical.

2166 is logical for cone 5 and 1044 ought to be 10 hours and 44 minutes, “CPLT” means complete and no errors so it appears the controller thought it made it. Max temp can be found in the “SFTY” setting p24 so theoretically the controller can go as high as that setting. But the piece severely under fired. I would still check to make sure type S is not errantly set (p 22) in the controller and it has a common type K. Apparently If someone hit the reset function the default is type R. It’s my only thought on why it is displaying 2166 and complete. If the kiln is stamped 1700 degrees it may not ever make cone 5 though just because it’s very underpowered…… or did someone change the elements and it is drawing more amperage (30a) / wattage (7200w) than the nameplate? Lots of questions……….

I believe this is your manual (below). If so the safety temp is not programmable. Your kilns nameplate should relatively match as well so worth checking it’s designed maximum. The only thing That strikes me is the controller is set for an S type thermocouple and you have a type k installed. When this happens kilns generally under fire considerably. Worth checking I think. If this is a cone 5 rated kiln. Then maybe suited to cone 04 work really. manual: https://paragonweb.com/wp-content/uploads/IM204_Sentry12ky_RH-CF_Manual_Oct2009.pdf

From my work with high temp heat exchangers probably not ideal. Depending on what you have it may soften quite a bit. Honestly many steel products melt as high or a higher temp. It’s always been too easy just to buy cone 10 rated stuff for me and some of the degraded heat exchangers made me stay away from trying it. Some interesting reading, 2nd paragraph onward might influence your decision. https://tubingchina.com/High-Temperature-Property-Stainless-Steel.htm

Nice, wonder how much time you will save. Maybe not electric but has to save some time.

Yes of course …. It really has nothing to do about old or new kilns. Kilns can go different speeds based on their size and how much power was built into them. The important point is speed. So dry everything thoroughly first. Next segment for bisque go 100-200 degrees per hour right up to your bisque temp minus 200 degrees. No waiting, no holding. Then 200 degrees below your bisque temp go about 100 degrees per hour til you hit that temperature and shut the kiln off. so from above So for bisque: cone 04= 1945 degrees - last segment begins 1945-200 or 1745 degrees Start: Room temp => 180 degrees hold until dry (skip this if everything is absolutely bone dry) 2nd segment: 180 => 1745 - go 100-200 degrees per hour as you kiln allows, don’t go faster. ( at 200 degrees per hour this takes about 7.5 - 8 hours) final segment: 1745 => 1945 - go 100-110 degrees per hour, shut off at 1945. (At 100 degrees per hour this takes 2 hours) Rates are a bit difficult but maybe think of them as driving a car, drive down Main Street at 20 mph, turn on the highway QQ and go 50 mph until exit A…….. try not to exceed the speed limit, it’s radar and camera monitored all the way.

The boiling point of water changes with the atmospheric pressure above it so in general at about 500 foot elevation (Chicago)I it boils at 211 degrees but at higher elevation say 1000 feet more like 210 degrees. There is also truth as they say that water boils easier on a cloudy day than on a clear one. Low and high pressure respectively. So I guess the point would be folks should dry their stuff with whatever risk is acceptable to them or has proven to be risk free. If you regularly fire your own things from a wet state to dry with no issue and watch steam coming out of the kiln, you are probably comfortable with doing it each time with whatever your schedule is. For many - 180 hold is conservatively safe for them. As to the boiling temperature of water, it varies. Teaching AC techs we always had the demonstration of evacuating the pressure in a flask of water and making it boil with the heat from our hand when we picked it up.

As much as I like down drafts, for your situation I still don’t have a good idea to make use of both fans. The range exhaust at 500-600 cfm on max is typical design for these things which is a great option to have to remove heat. For all practical purposes All pressure ductwork will leak a little, all of it, always, all the time. Do your best to seal it nicely, maybe foil tape all vertical seams, and joints including elbow joints to minimize to well below 1%. If this duct extends above the garage into an unheated attic space, you may need to insulate it to prevent winter condensation from forming and rusting out the ductwork. Looking at your southeast location, it may not be an issue. Save the downdraft for another day and improved design using a proper mixing manifold mounted on the kiln and next time enough dilution air to keep it running cool with that particular axial fan which uses its own exhaust to keep the motor windings cool.. If he watches the video above, that fan easily can serve two kilns and a full exhaust grill to ensure enough air is present for cooling the motor and ductwork. If that fan only draws air through a couple small holes it will be starved for cooling. The simplest application I have seen for this type of (axial) fan is a full open tee below the fan with the duct running down to the kiln. Even with such a large hole in the duct it will still draw several tenths of an inch suction at the kiln mixing plenum. You only need a tenth of an inch (-0.1” wc (suction)) at that point to perform like the store bought.

I think I mentioned this earlier but if not my apology. Just a couple questions: What size were the orifices you removed? what size were the orifices you replaced them with? If you remember just 1 PSI is likely going to be way too much pressure so an easy way for us to confirm is by the orifice size that was used and is being used. So if you can let us know, we may be able to save a bunch of aggravation on regulators, etc…

Looking closer he has one exhaust discharging and hopefully being picked up by the range hood. This won’t work so well especially for very light volatile particles as they will be ejected into the room before being completely removed. The fan for the kiln is axial and will need a bunch more room air to keep itself cool. The range hood on the other hand is great for heat and fumes and will cool itself with room air. Here is something to watch (old) that may give a better sense of the quantities we are talking about. https://youtu.be/etpa2Pc9Hug I would almost prefer just the range hood at this point. I can’t think of a good way to combine both of these really other than to pipe the kiln fan into the discharge of the range fan and install back draft dampers on both which will leak when one or the other is idle. And still the axial kiln fan will need a bunch of room air to keep it cool and not overdraw the kiln. Just my initial thoughts ………

No doubt many things can be done and are done. Reducing the atmosphere is a common thing. Drying evenly is usually key so adding less heat is usually a thing because it costs money in industry. As far as advising potters based on that, I worry that they would not understand the qualifiers nor have the equipment to do it effectively. My guess, it’s done daily in many industries. Typical potters, I would try and err on the conservative side of things. I am not sure what we are saving actually 40 minutes? Maybe it’s significant, it will be interesting to learn what you find. I can add that I made some speed dryers once. Large commercial cake transport with a computer fan inside and an adjustable inlet and outlet. Evenly dried things fairly quickly as most of the air was recirculated. Never made one for anyone else though for fear they would just go for max fresh air to speed things up.

Since boiling point is relative to the atmospheric pressure and the accuracy of most pyrometers is plus or minus and their ability to detect and read is not instantaneous and the thermal mass and lag of a kiln could be a thing and there is some differential built into most controllers ……… my guess is Bartlett could not find a practical reason to get close to boiling and so lowering the temp from 200 to 180 was still effective at drying things out, a bit safer and just not worth the risk of elevating it to theoretically save some time. I have seen folks come out of a 180 degree 4 hour hold on their massive sculpture and have it explode on them. Next go around was 180 at eight hours for the remade piece - no explosion. Its interesting theoretically, but with artists work at stake, we offer up infrared so their full size bust of their son graduating ranger school can dry slowly over a few weeks time, then encourage a long hold at 180 degrees and even help to tend the gas kiln and maintain a slow rate to their finished tested cone for color. Call me chicken I guess, not going there with others work or my own.

not sure this will help because I think the “best” way varies I have always used the same clay for the medallion as the base clay just so I knew their shrinkage was compatible. As far as medallions and impressions my observation has generally been those with lots of detail need to have a nice sharp stamp. If it’s round medallions you are trying to make, maybe better to slab cut them, impress your shape on a flat surface and then cut out the medallion to dry towards leather hard. If these are to be applied to a mug, then gently pre-shape them to fit distorting them as little as possible. My sense is the many techniques you are seeing are the result of the artists figuring out what is the best way for their wares and their clay and their preferred aesthetics. . As far as best stamp, I have had several cut for Madison Pottery. The first were too broad and required too much force to impress. In each rendition I reduced the width of the letters until I found something that looked good but did not require so much pressure to get the impression. Kind of a trial, observation, then maybe re trial until you find something suitable to work with. Hope that helps! Others here will likely tell you their favorite way.

Since it displays temperature I think it would be helpful to understand firing rates. If you understand basic firing in ceramics, you can apply it to any kiln, anywhere. First segment I would suggest the first segment to be the “make sure everything is dry”: So room temperature to boiling, we usually go very slow so any moisture can slowly leave the ware rather than converting a lot to steam suddenly which is the explosive part. So slow climb or a hold at 180 f for instance can allow this off gassing. This is particularly true for greenware, but also can be a factor for freshly glazed items. Now that out of the way, bisque firings generally rely on time and temperature so they are slower. Normally not more than 200f degrees per hour and range from approximately 10-12 hours. Glaze fires can go faster so often up to 550f degrees per hour and can be approximately in the 4-8: hour range. Approximating a cone and the last 200-250f. degrees of firing. (The final segment) With Orton cones, you will see an end of firing rate. The middle column is 108 f degrees per hour. This is a nice speed to mature glaze and clay so in the last 200 - 250f degrees make your kiln go 108 degrees per hour and it should heat to the appropriate cone. This is true for whatever cone you are firing, bisque temperatures as well. So as complicated as it sounds, most manual kilns are ramped up slowly to try and get the approximate 10-12 hour bisque as well as something like the 4-8 hour glaze. Kiln size and power all play into it which is why folks figure out for their kiln some schedule like 2 hrs on low, 2 hrs on medium, then high until shutoff but with a sitter their task is easier as the kiln will shutoff at a specific cone. It appears this kiln you will need to supervise and manually shutoff. So when you fire empty, I would suggest taking readings every half hour at your settings and observe the rates as you go. Record these. Toward the end of firing you will need a higher amount of power for a given rate of climb. Figuring out what gives you about 108-110 degrees per hour near cone six or 2232 - 200 or 2032. So from let’s say approximately 2000 degrees onward you want to be in that 108 - 110 degree per hour range and fire to 2232 for cone six. If you understand the why part, you will be able to craft your own best schedule for your kiln. Some folks do not like firing rates so they simplify it to a low medium high schedule. Both work effectively and take some observation. A change of 1 degree per minute = 60 degrees per hour, so 2 degrees per minute is 120 degrees per hour or almost perfect to get your cone to bend whether shooting for cone 04 or cone 6.

Some questions to ask yourself: is it mainly in an area of a particular thickness of underglaze. Maybe thickness and moreso a specific color? When you did test tiles did you replicate the thickness and color? Often Wash applied underglaze react just fine, solid color applied underglazes can require a clear that melts a bit better. The mug below relies on the rough texture of this very defect for its outside decoration. It was fired to bubble then in the end down fired with a lowfire clear to make it a bit sturdier. The simple sugar bowl below required about a summer of testing before I realized the overglaze needed to be able to melt better and develop a clear matte and gloss that covered the very solid red and solid black on that pot. Try and make your test tiles match your desired application exactly Just to add a note to add since someone is asking, the mug above is my creation, the bowl below was thrown and glazed by me and hand painter in underglaze by my Marcia - Marcia Grant under Madison Pottery where we collaborate on many pieces together.

I can tell you that we opted to use it, but when a glaze spill did occur a bit of effort was needed to remove instead of just popping it off, re-coating and moving on. Overall in a studio environment for us it was good ………….. but expensive comparatively. In my first post I mentioned “Flaky is a big complaint, Lees will not flake and the various good recipes you will find generally the feature folks like, not too flaky, can be touched up relatively easily and can be removed with reasonable pressure / scraping.” .

I have experienced various clears failing to fire smoothly over various underglazes which at first appear bubbled but are often the result of the clear not melting evenly. Usually dependent on color and thickness of the applied underglaze and also a bit brand dependent. I am with @Pres this is very difficult without a picture of the defect. Please post some examples if possible. Folks here will likely have some good explanations.

Hmm, yeah, this would confuse anyone. The truth be told in a bisque firing it’s really good to ventilate your kiln to help remove or oxidize the organics being burned out. The problem is how much? As the more you ventilate, the more energy it takes to heat. Sort of like leaving a window open in your house and heating it. Anyway the truth is a very small amount of ventilation is a great compromise. For bisque, at some point, all the organics are gone so there is no need. In glaze firings a little bit of oxidation brightens up the glaze colors for similar reasons. Your kiln manual provides the most consistent advice and some ventilation (a tiny amount) will also improve the life of your elements by removing harsh corrosive gasses, especially during the bisque. After 600c though most everything is burned out so closing the bottom vent is appropriate for sure. closing the top vent will likely save energy as well as kilns are really not super air tight so there will always be some infiltration. That kiln should be piped to exhaust the fumes outdoors. The height of that pipe will affect the draw as well. The bottom port of that exhaust allows air in the room to move up the pipe and a very small amount of kiln air to be mixed in and the room air helps keep the exhaust pipe relatively cool, say 100-200c degrees I personally would make sure it’s piped outside so folks would not breath in the fumes and not plug the bottom port of the vent after 600c just to ensure there was some ventilation. My experience - the kiln manufacture seems to have the most reasonable approach.

Yes, you can do a new element cold but like all cold things it tends to harden and stretch at each cold bend. If you can safely do it hot, it bends like butter else do it cold. I would consider it temporary and likely to fail first.

Have you looked on Glazy.org for a recipe? https://glazy.org/search?keywords=Blue rutile&base_type=460&cone=30&photo=false&production=false or are you looking for a pre made commercial glaze?