Dick White

If the kiln is over- or under-firing consistently across all cones, you can do a thermocouple offset to fool the controller into firing cooler or hotter. If just a few cones in a particular range are off, you can do a cone offset which does the same tom-foolery but only for a particular cone, not a general shift of all temperatures as with the thermocouple offset.

For better or worse, the commercial purveyors of premixed glazes have co-opted a general glaze chemistry term as a specific glaze name. A flux is simply any of the alkaline metal or alkaline earth oxides that assist glass (alumina and silica oxides) to melt at lower temperatures. The Mayco and Amaco glazes that are named one or another variety of "Flux" (e.g., Honey Flux, Light Flux, Dark Flux) are actually just cone 5 glazes that are designed to be applied over a cone 6 glaze, causing it to melt at the lower cone 5 temperature so as to stream down over the cone 6 base glaze and interact with it as they melt together. Nobody knows what Mayco and Amaco put in their proprietary glazes, but there are some recipes developed by others that have similar effects, and published for public use. Search Glazy.org for "Flux Glaze;" there are several recipes to try. Or you can try some layering of other glazes, such at the Strontium Crystal Magic series that Bill mentioned. These are not represented as direct substitutes for the commercial glazes named Flux, but they do make interesting runny effects.

Further to Min's answers to your stated questions - 1. Don't buy a hydrometer. Contrary to popular wisdom, hydrometers are useless. Do a forum search for some of the other threads where we have discussed using a 10 or 100ml syringe and a digital scale to accurately measure specific gravity. 2. Not glazing the interior of a pot increases the risk that the pot itself will fail due to unequal tension/compression of only one side of the ceramic being glazed. 3. What Min said.

The picture of the electrical rating plate is a bit fuzzy, but looks to me like 24 amps. Thus, in the US national electric code, that would require a dedicated heavy duty 30 amp circuit, not an ordinary household plug. I don't know about the Aussie electric code, but it is probably similar. The circuit requirement includes not just the plug and receptacle, but the wiring back to the mains and the breaker. Since you will probably need an electrician to install the special circuit, you have a choice to hardwire it or have the electrician install an appropriate plug on the power cord.

Pike's Purple is a cobalt/magnesium combination. Cobalt and titanium will come out green. There is no titanium in the usual Pike's Purple recipe. Are you certain you mixed it correctly?

@MinI'm not surprised at that answer. Yes, our newer controllers preheat at 180F. But I have 2 ancient ones (with the 8-segment numerals) that preheat at 200F. I guess the notion of "more heat work" by running longer at a lower temperature can be explained by considering the meaning of "heat work" as allowing heat to penetrate to the interior of the clay mass. We conventionally think of heat work at cone temperatures (faster ramps require a higher final temperature to bend the cone, slower ramps achieve the cone bend at lower temperatures) as how heat penetrates the body to attain maturity all the way through. But why not also use the word "heat work" to model temperature penetration to attain complete drying?

Gearing up the Ohm's Law calculator - you want the total amperage of the kiln to remain 60 amps but at 240V vs. the original 208V. There are 3 sections, so each will pull 20 amps. Using the calculator to convert that to watts and resistance, gives us 4800 watts and aggregate resistance of 12 ohms per section. If the 3 elements in each section are wired in series, they need to be 4 ohms per element. When you order the elements from L&L, ask/confirm the design resistance of each element and the connection requirements (parallel vs. series) for the elements they are providing. It is possible they have a different plan now than in 1996.

Are you wedging the clay before rolling your slabs? It is a misconception that clay is perfect straight out of the bag. The pugging process during production of the clay body introduces spiral tension/compression rings in the block, which if rolled straight into a slab could result in latent fractures along those rings.

As noted by Neil above, you can drill new holes where you want the thermcouples to go. Measure carefully so you know where to start the hole through the metal shell to ensure it comes out the other side in the right place. Regarding new bricks, be aware that L&L has changed the size of the hard ceramic element holders several times over the years. Your kiln from 1996 has the original smallest size channels and thus can only hold the smallest diameter elements. When you order from L&L, they will ask you the serial number (which is the manufacturing date) so that they can send the proper size. Also, regarding the reuse of the top-mounted control box with the Robert Shaw switches, yes that could possibly be used - if you are facile with basic metal working. The Bartlett controllers (either the V6-CF or Genesis) require a rectangular hole through the face of the control box so that the faceplate of the controller is on the outside while the circuit board and connectors are on the inside. You'll have to cut that hole yourself - after ensuring there is enough space inside for the controller, transformer, fuse, 3 relays, and the existing three 250 volt 25 amp sockets for the jumper wires to each kiln section. When I was rebuilding my J230 of a similar vintage, I didn't think I could cram all that in, so I built a new box with a metal enclosure box I got from the big river in South America dot com. Even then, there was some cutting and drilling required. dw

I suspect the electric power of the kiln (7,200 watts/30 amps in a kiln <3 cu.ft) would go to cone 4-6 easily, but the controller is set at the factory to match the original intention for the kiln usage, i.e., glass slumping that goes only to 1700 degrees. There are secret ways to get into the controller settings known only to Paragon technicians when they are building a kiln.

@Min Interesting! They haven't replied to my request, but when/if they do it will undoubtedly be the same as you received. So, let's go with that. 2020 or 2021 is probably recent enough, it is well after the management change. If we look at the long history and do the numbers: pre-2000ish had 69% silica, 17% alumina, 10% potash, 3% soda (for 13ish% KNa flux) and other miscellany. Ron Roy's average for the early century bags (which is not much different from the numbers @Kaolinwashergot in 2017) had 72% silica, 15% alumina, 7.5% potash, 3% soda (for 10ish% KNa flux) and other miscellany. The new numbers are now almost exactly back to what they were over 20 years ago (and, what pisses me off, what they have been consistently advertising as unchanged during that 20 years of despite different independent material analysis). Actually, the KNa flux now is slightly higher than 20 years ago 14.5% vs. 13.2%, which goes a long way to explaining why my glazes with fair amounts of Custer are now running off the pots. Time to recalculate them again (or more likely, just go back to the old recipes). And no, I don't mix my own clay bodies, just glazes. But they do in the ceramics program at our sister campus. I will let them know if it matters , And now back to work...

Interesting. The company may have been reorganized, but that was 4 years ago. This change in glaze behavior is more recent than that. I too emailed them for an analysis. Most other sources of ceramic material have their analysis somewhere on their website (usually deep, you have to dig and know what you are looking for), but nothing to be seen here. My local supplier does not carry Mahavir, or I would have been using it all along.

Is anyone having (or aware of) recent issues with Custer feldspar, or aware of any recent independent data on the material content of it? Those who have been in the rabbit hole for awhile may remember maybe 10 years ago, Custer-based glazes suddenly were underfiring. It was a wide enough problem that some folks with access to the necessary resources (e.g., Ron Roy) had samples tested by independent laboratories and found that the potassium content was significantly less than previously, and less than advertised as Pacer Corporation insisted there was no change. Those of us who mix our own glazes and know about such things, recalculated our recipes and got on with our lives. Recently, however, glazes mixed with our last bag of Custer have been running all over the kiln. There has been some slight noise in other clay groups wondering why their glazes with Custer in them are responding differently. We have a pretty smart group of peeps here - does anybody else have any insight?

My understanding of the physics (fluid dynamics) behind the downdraft vent is that the box under the kiln (L&L calls it the bypass collection box, Skutt calls it the plenum cup) has an opening on the opposite side from the hose connection so that the fan at the output on the far end of the system can pull a significant volume of room air through the box and thus create a venturi effect to draw the kiln fumes down through the holes in the base of the kiln. The L&L collection box has an adjustable "sliding valve" to regulate the amount of room air drawn through the box (thus adjusting the venturi suction across the holes in the kiln base) while the Skutt plenum cup just has a hole. This flow of room air also serves to cool whatever fumes are being drawn out of the kiln and up through the fan. The system does not apply direct suction to the holes in the kiln. Because air flows seek the path of least resistance, the hole in the pipe of your vent will both increase total air flow at the fan and reduce suction at the base of the kiln when everything is in good condition. However, it introduces the necessary cooler room air at some distance after the fumes leave the kiln. Also, your design with the fan in the middle of the duct run provides the appropriate negative pressure from the kiln to the fan, but applies positive pressure after the fan, blowing the exhaust into the stove hood in hopes that it will be picked up. As Bill notes, this may not work, but also as the duct work corrodes over time (it will, count on it), the positive pressure will blow the stinkies back into the room long before they come out by the stove hood. The design of the Skutt and L&L systems places the fan right on the outside wall of the room so that the whole system remains under negative pressure until being exhausted to the outside. Then, any minor leakage in the duct work will draw air in, not push the fumes out.

I've never done it, but some things to consider - The preheat segment on a Bartlett controller is 180-200F, depending on the age of the controller (some of the older models I have preheat at 200F, the newer ones at 180F). If 240F is right, why does Bartlett keep it lower than boiling? With an electric kiln w/ controller, there may be some thermocouple offset programmed in, so the apparent temperature showing on the screen may not be the actual temperature of the atmosphere in the kiln? It takes time for the temperature to penetrate the clay body, so the surface may be already dry and hotter than the interior which is still cool enough that it doesn't turn to steam? A principle of phase change is that evaporation leaves the surface from which it evaporated cooler, so 240F may be the perfect atmospheric temperature to balance the evaporating moisture and surface temperature of the ware? dw

Well, actually, it can be kludged to do that. I didn't feel like paying $180 for the feature, so I built one with $20 of parts to control the shared vent for both my bigger kilns. The wire from output 4 triggers a standard relay that turns on the vent power cord. I ran the wires from both controllers' output 4 to the relay, so now whichever kiln turns on first starts the vent fan and whichever kiln turns off last stops the vent fan. But one must be adventuresome to open the box and do that. dw

If you need something to turn your vent off at the end of the firing, Skutt has the EnviroLink switch that connects to output 4 of the Bartlett controller.

As Min suggests, the feldspar doesn't add much for electric firings. I use that recipe in 5 different studios that I am associated with (including my own personal studio). 50% alumina hydrate (cheaper than alumina oxide), 25% EPK, 25% calcined EPK. If you are completely set on adding the slight amount of feldspar, the G200 that John mentioned was one of the more common potash spars available in the US at the time. It is no longer available (the mine ran out), but the reality is that any locally available feldspar, soda or potash, will suffice. dw

The CMC will burn out early. Clay body is the term we use for the raw clay that you made the piece with. The raw clay molecule has 2 forms of water in it that must be dealt with carefully during the first 1000 degrees of the first firing, whether bisque that will be fired again with glaze, or single firing that will go from zero to cone 6 in one firing.

Single firing is usually no different EXCEPT that it is really just a bisque firing to glaze temperature. The raw clay body needs to be fired slowly during the early stages so that it does not explode or fracture. Bisque schedules usually provide for this; glaze schedules for previously bisqued ware just charge ahead, damn the torpedoes. The glaze work itself is just fine, it's the clay body that you need to worry about.

The elements of the US version are all the same, 11.4 ohms. However, because the middle and bottom elements are wired in parallel, for a service person taking a resistance reading across either of these two with everything in situ will include the other, yielding a reading of half, or 5.7 ohms.

According to Wikipedia, the standard mains voltage in Taiwan is 110V, or 220V when measured across both poles of the split-phase service. The US version of the Skutt 714 is designed for 120V mains. Something to note about the design of the 714 is that it is actually two stacked but electrically separate 120V kilns. It requires a 4-wire (two 120V hots, a shared neutral, and ground) NEMA 14-30 plug. One 120V side of the line powers the top element and the other 120V side powers the middle and bottom elements (which are wired in parallel). It is designated as either 120/208V because, in the US, 208V service in commercial locations is also 120V from either line to neutral/ground. So what does this mean for Didiho? In the best of circumstances, the kiln when used in Taiwan will have about 10% less heating power than in the US simply because the standard mains voltage is 110V vs 120V. If the Diag function (which measures across both lines without regard to the neutral) is getting only 217V with no load and 207V under load, that suggests the power supply from the utility is lagging or the household usage is overloading its capacity. This yields a performance loss of at least 20% from the nominal US design. Further, as the elements wear through usage, the heating power will decrease, until at some point it simple can't finish the job and the dreaded E-1 error appears. You can't fix the utility supply problem, but you can check whether the elements are worn past their prime. The three elements for the 714 are all the same, with resistance specified as 11.4 ohms. You can use a digital multimeter to test the resistance of each element. If the resistance measures more than 12.5 ohms, the element is worn out and should be replaced.

If the cone fire program is overfiring (as indicated by actual witness cones on the shelves), you can adjust the thermocouple offset to make it fire cooler. If you can't find instructions for that in your manual or it seems daunting, call Skutt support and they will guide you through it.

Peter, those are some interesting articles. There is mention of Fe2O3 (RIO) having a similar effect as tin. I wonder if it can be substituted for the tin to obtain the copper red, and if so, how much? dw

Can you upload a picture?