Dick White

The reason I asked for your firing schedule is I suspect a technical nuance is at play here. Cones deal in heatwork - time and temperature. Nothing new with that idea. If the ramp rate in the final 2 hours is aggressive (relative to the Orton table, which depending on who you ask, what book you read, or what kiln controller you have, medium speed to cone 6 is 120F/hr to 2232F), the cone bends at a higher final temperature, and vice versa, a slower ramp will bend the cone at a lower temperature. Nothing new with that idea either. Your ramp 5 is set for 200F/hr to 2200F, which is pretty aggressive. Putting that into the Orton cone calculation spreadsheet, that would give you a cone 5.5, and even the 20 minute hold doesn't quite get to 6. However, the nuance that isn't always seen is that as the elements wear with usage, the actual ramp rate attained by the worn elements falters (and in the most extreme case, simply can't heat the kiln in the final segment and the controller errors out). While the cone-fire programs in the Bartlett and Orton controllers have an adaptive feature that monitors the actual final ramp rate and adjusts the target temperature to produce a good cone bend, the custom ramp hold programs do not have that capability. In ramp hold, the controller will keep chugging until the programmed temperature is reached regardless of how long that might take (unless it determines the rate is futile and it errors out). As the elements wear, the final ramp rate slows down and the cone should bend at a lower temperature, but the controller keeps going until the programmed temperature, and now the cone is overfired. Going back to the Orton spreadsheet, a ramp of 100F/hr to 2200 with a 20 minute hold should give you a cone 7, which it did. So, my suspicion is that your elements are wearing out, the programmed 200F/hr final ramp rate is bovine droppings, it's actually only making 100F/hr, and from here, it will get worse. Check the resistance of the elements and be ready to replace them as they drop too far out of spec. In the short term, drop you final temperature to 2185F and that should give you a nice cone 6 when the kiln is chugging along at the best it can do.

The reason I asked for your firing schedule is I suspect a technical nuance is at play here. Cones deal in heatwork - time and temperature. Nothing new with that idea. If the ramp rate in the final 2 hours is aggressive (relative to the Orton table, which depending on who you ask, what book you read, or what kiln controller you have, medium speed to cone 6 is 120F/hr to 2232F), the cone bends at a higher final temperature, and vice versa, a slower ramp will bend the cone at a lower temperature. Nothing new with that idea either. Your ramp 5 is set for 200F/hr to 2200F, which is pretty aggressive. Putting that into the Orton cone calculation spreadsheet, that would give you a cone 5.5, and even the 20 minute hold doesn't quite get to 6. However, the nuance that isn't always seen is that as the elements wear with usage, the actual ramp rate attained by the worn elements falters (and in the most extreme case, simply can't heat the kiln in the final segment and the controller errors out). While the cone-fire programs in the Bartlett and Orton controllers have an adaptive feature that monitors the actual final ramp rate and adjusts the target temperature to produce a good cone bend, the custom ramp hold programs do not have that capability. In ramp hold, the controller will keep chugging until the programmed temperature is reached regardless of how long that might take (unless it determines the rate is futile and it errors out). As the elements wear, the final ramp rate slows down and the cone should bend at a lower temperature, but the controller keeps going until the programmed temperature, and now the cone is overfired. Going back to the Orton spreadsheet, a ramp of 100F/hr to 2200 with a 20 minute hold should give you a cone 7, which it did. So, my suspicion is that your elements are wearing out, the programmed 200F/hr final ramp rate is bovine droppings, it's actually only making 100F/hr, and from here, it will get worse. Check the resistance of the elements and be ready to replace them as they drop too far out of spec. In the short term, drop you final temperature to 2185F and that should give you a nice cone 6 when the kiln is chugging along at the best it can do.

The reason I asked for your firing schedule is I suspect a technical nuance is at play here. Cones deal in heatwork - time and temperature. Nothing new with that idea. If the ramp rate in the final 2 hours is aggressive (relative to the Orton table, which depending on who you ask, what book you read, or what kiln controller you have, medium speed to cone 6 is 120F/hr to 2232F), the cone bends at a higher final temperature, and vice versa, a slower ramp will bend the cone at a lower temperature. Nothing new with that idea either. Your ramp 5 is set for 200F/hr to 2200F, which is pretty aggressive. Putting that into the Orton cone calculation spreadsheet, that would give you a cone 5.5, and even the 20 minute hold doesn't quite get to 6. However, the nuance that isn't always seen is that as the elements wear with usage, the actual ramp rate attained by the worn elements falters (and in the most extreme case, simply can't heat the kiln in the final segment and the controller errors out). While the cone-fire programs in the Bartlett and Orton controllers have an adaptive feature that monitors the actual final ramp rate and adjusts the target temperature to produce a good cone bend, the custom ramp hold programs do not have that capability. In ramp hold, the controller will keep chugging until the programmed temperature is reached regardless of how long that might take (unless it determines the rate is futile and it errors out). As the elements wear, the final ramp rate slows down and the cone should bend at a lower temperature, but the controller keeps going until the programmed temperature, and now the cone is overfired. Going back to the Orton spreadsheet, a ramp of 100F/hr to 2200 with a 20 minute hold should give you a cone 7, which it did. So, my suspicion is that your elements are wearing out, the programmed 200F/hr final ramp rate is bovine droppings, it's actually only making 100F/hr, and from here, it will get worse. Check the resistance of the elements and be ready to replace them as they drop too far out of spec. In the short term, drop you final temperature to 2185F and that should give you a nice cone 6 when the kiln is chugging along at the best it can do.

The reason I asked for your firing schedule is I suspect a technical nuance is at play here. Cones deal in heatwork - time and temperature. Nothing new with that idea. If the ramp rate in the final 2 hours is aggressive (relative to the Orton table, which depending on who you ask, what book you read, or what kiln controller you have, medium speed to cone 6 is 120F/hr to 2232F), the cone bends at a higher final temperature, and vice versa, a slower ramp will bend the cone at a lower temperature. Nothing new with that idea either. Your ramp 5 is set for 200F/hr to 2200F, which is pretty aggressive. Putting that into the Orton cone calculation spreadsheet, that would give you a cone 5.5, and even the 20 minute hold doesn't quite get to 6. However, the nuance that isn't always seen is that as the elements wear with usage, the actual ramp rate attained by the worn elements falters (and in the most extreme case, simply can't heat the kiln in the final segment and the controller errors out). While the cone-fire programs in the Bartlett and Orton controllers have an adaptive feature that monitors the actual final ramp rate and adjusts the target temperature to produce a good cone bend, the custom ramp hold programs do not have that capability. In ramp hold, the controller will keep chugging until the programmed temperature is reached regardless of how long that might take (unless it determines the rate is futile and it errors out). As the elements wear, the final ramp rate slows down and the cone should bend at a lower temperature, but the controller keeps going until the programmed temperature, and now the cone is overfired. Going back to the Orton spreadsheet, a ramp of 100F/hr to 2200 with a 20 minute hold should give you a cone 7, which it did. So, my suspicion is that your elements are wearing out, the programmed 200F/hr final ramp rate is bovine droppings, it's actually only making 100F/hr, and from here, it will get worse. Check the resistance of the elements and be ready to replace them as they drop too far out of spec. In the short term, drop you final temperature to 2185F and that should give you a nice cone 6 when the kiln is chugging along at the best it can do.

Ron, I think the only acknowledgement we will get to infer that there was a problem is this 2 sentence paragraph buried midway down the the page on the About Us/History page on their website,
"In 2018, Pacer Corporation changed ownership and operations management. Under a new name and business philosophy, Pacer Minerals, LLC has improved mining practices, modernized ore sorting techniques, & restructured quality control procedures."
I don't see a current materials analysis on their public website, apparently one must request that. Whatever numbers are in circulation were "published" by someone else after getting it from Pacer, hence the 3 slightly different analyses dated 2020 and 2021 in Min's chart. You mentioned that you could get another independent analysis if we could ship you some current samples. Send me your address in a private message in the upper right corner of this page and I'll send you some.

Your burgundy glaze is likely a chrome-tin red. Grey or green is unavoidable for a chrome-tin in reduction. If you still want a red in reduction, you have to go for a copper red.

The flame should be drawn in only in the bottom holes. There is too much leakage around other areas of the kiln (the seams between sections, the peeps) for the inflow to be concentrated solely at the top holes. But having the top holes helps even out the inflows.

The easiest way I have discovered to process it is... don't. Head on over to the big river in S. America dot com and order cosmetic grade zinc oxide in 4 lb bags. It is already finely ground. Upon opening, store it in an airtight jar.

What @PeterH said. Neph sye is a known bad boy in the glaze chem world. It is very high in sodium, which is why it is popular. It is also slightly soluble. Sodium is an alkaline deflocculant, which results in hard panning. The sodium slowly leaches out of the neph sye and at some indeterminate point deflocs the glaze slurry and it hard pans.
Also understand clay is the only material that can be flocculated to create a suspended glaze slurry. Materials such as feldspars or feldspathic materials (neph sye), other minerals such as whiting, etc., or frits do not respond to the alkaline or acidic conditions in the slurry to deflocculate or flocculate, respectively. Only clay responds to the deflocculation/flocculation process. A recipe with little or no clay, such as your recipe with a mere 5% EPK, needs a few additional percent of bentonite (a super clay) upon which to cause flocculation (if needed) by adding a mild acid such as epsom salts. And then after some time, the alkaline sodium leaches out of the neph sye and neutralizes whatever acidity in the slurry has been keeping the clay suspended, and boom, without warning it all falls down. The bentonite is not enough to stop this from happening. Dig it out and remix it with some epsom salts or vinegar to neutralize the excess alkalinity and restore the suspension.
As for the Magma product that folks above recommend, it does not chemically flocculate the slurry. It is an artificial gum additive that mechanically suspends the glaze solids. It is unaffected by the soluble leached sodium from the neph sye. It also has other attributes, so read the cautionary statements on the label. Otherwise, it floats bricks.
 

What @PeterH said. Neph sye is a known bad boy in the glaze chem world. It is very high in sodium, which is why it is popular. It is also slightly soluble. Sodium is an alkaline deflocculant, which results in hard panning. The sodium slowly leaches out of the neph sye and at some indeterminate point deflocs the glaze slurry and it hard pans.
Also understand clay is the only material that can be flocculated to create a suspended glaze slurry. Materials such as feldspars or feldspathic materials (neph sye), other minerals such as whiting, etc., or frits do not respond to the alkaline or acidic conditions in the slurry to deflocculate or flocculate, respectively. Only clay responds to the deflocculation/flocculation process. A recipe with little or no clay, such as your recipe with a mere 5% EPK, needs a few additional percent of bentonite (a super clay) upon which to cause flocculation (if needed) by adding a mild acid such as epsom salts. And then after some time, the alkaline sodium leaches out of the neph sye and neutralizes whatever acidity in the slurry has been keeping the clay suspended, and boom, without warning it all falls down. The bentonite is not enough to stop this from happening. Dig it out and remix it with some epsom salts or vinegar to neutralize the excess alkalinity and restore the suspension.
As for the Magma product that folks above recommend, it does not chemically flocculate the slurry. It is an artificial gum additive that mechanically suspends the glaze solids. It is unaffected by the soluble leached sodium from the neph sye. It also has other attributes, so read the cautionary statements on the label. Otherwise, it floats bricks.
 

What @PeterH said. Neph sye is a known bad boy in the glaze chem world. It is very high in sodium, which is why it is popular. It is also slightly soluble. Sodium is an alkaline deflocculant, which results in hard panning. The sodium slowly leaches out of the neph sye and at some indeterminate point deflocs the glaze slurry and it hard pans.
Also understand clay is the only material that can be flocculated to create a suspended glaze slurry. Materials such as feldspars or feldspathic materials (neph sye), other minerals such as whiting, etc., or frits do not respond to the alkaline or acidic conditions in the slurry to deflocculate or flocculate, respectively. Only clay responds to the deflocculation/flocculation process. A recipe with little or no clay, such as your recipe with a mere 5% EPK, needs a few additional percent of bentonite (a super clay) upon which to cause flocculation (if needed) by adding a mild acid such as epsom salts. And then after some time, the alkaline sodium leaches out of the neph sye and neutralizes whatever acidity in the slurry has been keeping the clay suspended, and boom, without warning it all falls down. The bentonite is not enough to stop this from happening. Dig it out and remix it with some epsom salts or vinegar to neutralize the excess alkalinity and restore the suspension.
As for the Magma product that folks above recommend, it does not chemically flocculate the slurry. It is an artificial gum additive that mechanically suspends the glaze solids. It is unaffected by the soluble leached sodium from the neph sye. It also has other attributes, so read the cautionary statements on the label. Otherwise, it floats bricks.
 

What @PeterH said. Neph sye is a known bad boy in the glaze chem world. It is very high in sodium, which is why it is popular. It is also slightly soluble. Sodium is an alkaline deflocculant, which results in hard panning. The sodium slowly leaches out of the neph sye and at some indeterminate point deflocs the glaze slurry and it hard pans.
Also understand clay is the only material that can be flocculated to create a suspended glaze slurry. Materials such as feldspars or feldspathic materials (neph sye), other minerals such as whiting, etc., or frits do not respond to the alkaline or acidic conditions in the slurry to deflocculate or flocculate, respectively. Only clay responds to the deflocculation/flocculation process. A recipe with little or no clay, such as your recipe with a mere 5% EPK, needs a few additional percent of bentonite (a super clay) upon which to cause flocculation (if needed) by adding a mild acid such as epsom salts. And then after some time, the alkaline sodium leaches out of the neph sye and neutralizes whatever acidity in the slurry has been keeping the clay suspended, and boom, without warning it all falls down. The bentonite is not enough to stop this from happening. Dig it out and remix it with some epsom salts or vinegar to neutralize the excess alkalinity and restore the suspension.
As for the Magma product that folks above recommend, it does not chemically flocculate the slurry. It is an artificial gum additive that mechanically suspends the glaze solids. It is unaffected by the soluble leached sodium from the neph sye. It also has other attributes, so read the cautionary statements on the label. Otherwise, it floats bricks.
 

What Peter just said. Show us pictures of 1) the electrical rating plate on the side of the kiln, and 2) the plug and receptacle you have the kiln plugged into.

Ron, that's interesting. We know that NTYAL was run out of business for that reason. Geologists tell us that talc deposits and asbestos deposits are sometimes close together and sloppy mining practices can result in asbestos contamination of the talc output. It was alleged that NYTAL was thus contaminated, though Vanderbilt (the company that owned the mine) denied it. The cost of litigation to prove their case was too much and so they cut their losses and shut the mine. The AMTAL mine in Texas was purportedly clean, and so it became a major North American source for our talc. Your sources are now suggesting it wasn't so clean after all. We do know from the business world that Daltile, the huge wall and floor tile producer headquartered in Dallas, TX, was a significant customer. A few years ago, Daltile bought the mine from AMTAL, supposedly to improve their vertical integration controlling everything from raw materials sources to sales, but at least they continued to service the rest of the AMTAL customer base (including us mere potters). However,  in 2021, Daltile reduced the customer list to exactly one, itself, and the North American ceramics world has been scrambling ever since.
So, what your sources are suggesting, it was not merely Daltile buying out one of its materials suppliers to improve its own profitability, but AMTAL was happy to sell its looming liabilities. Interesting.

I have 3 electric kilns in my personal studio. The small test kiln is the only one bought new, the others were acquired in roundabout ways. All have been renovated and Bartlett Genesis touchscreens added for total control. I also manage the community studio of the local park system where, because of a political issue at headquarters they owed me a favor, which I used to buy 4 new L&Ls to replace the Skutt dogs. Although we don't do any fancy firing, the Genesis touchscreens are foolproof for the kiln volunteers to run. At my other part-time gig, I am the studio monkey for the ceramics program at one of the campuses of the community college. There we have 4 L&Ls for bisque and cone 6 oxidation, and a Bailey gas kiln for cone 6 reduction. I am the only one there knowledgeable about the gas kiln, so several times a semester I spend the day tweaking the gas and air dials and the damper every half hour. I have it down now to even temps up and down and uniform reduction throughout in 7 hours. But that took me five years to perfect.

I have 3 electric kilns in my personal studio. The small test kiln is the only one bought new, the others were acquired in roundabout ways. All have been renovated and Bartlett Genesis touchscreens added for total control. I also manage the community studio of the local park system where, because of a political issue at headquarters they owed me a favor, which I used to buy 4 new L&Ls to replace the Skutt dogs. Although we don't do any fancy firing, the Genesis touchscreens are foolproof for the kiln volunteers to run. At my other part-time gig, I am the studio monkey for the ceramics program at one of the campuses of the community college. There we have 4 L&Ls for bisque and cone 6 oxidation, and a Bailey gas kiln for cone 6 reduction. I am the only one there knowledgeable about the gas kiln, so several times a semester I spend the day tweaking the gas and air dials and the damper every half hour. I have it down now to even temps up and down and uniform reduction throughout in 7 hours. But that took me five years to perfect.

I have 3 electric kilns in my personal studio. The small test kiln is the only one bought new, the others were acquired in roundabout ways. All have been renovated and Bartlett Genesis touchscreens added for total control. I also manage the community studio of the local park system where, because of a political issue at headquarters they owed me a favor, which I used to buy 4 new L&Ls to replace the Skutt dogs. Although we don't do any fancy firing, the Genesis touchscreens are foolproof for the kiln volunteers to run. At my other part-time gig, I am the studio monkey for the ceramics program at one of the campuses of the community college. There we have 4 L&Ls for bisque and cone 6 oxidation, and a Bailey gas kiln for cone 6 reduction. I am the only one there knowledgeable about the gas kiln, so several times a semester I spend the day tweaking the gas and air dials and the damper every half hour. I have it down now to even temps up and down and uniform reduction throughout in 7 hours. But that took me five years to perfect.

You have several things running in different directions here, so it can be confusing. This kiln needs a 4-wire circuit. Easy enough, Sparkie checks the old circuit and maybe it is an old 4-wire job. Maybe it is also sufficient gauge to support 35 or 40 amps as required by the 125% rule. Maybe there is already a 40 amp breaker on it. If so, the circuit is good to go for this kiln. Your remaining problem is the cord on the kiln needs to be replaced. Unlike extension cords and household appliance cords, kiln power cords are made with high temperature type SEO cable to accommodate the heat buildup of long-duration full amperage current when the kiln is running on high for several hours to finish the firing. The stove cord you linked to is not quite up to that spec, but since it is rated for twice the amperage your kiln will pull, it probably will do ok.
On the other hand, if the existing circuit in the wall is not sufficient, Sparkie has some work to do, and there are some choices to be made. The replacement circuit only needs a 40 amp breaker and 8 ga. 4-wire cable for this kiln. But you said you might step up to a bigger kiln in the future, so future-proof the circuit now. The biggest plug-in kilns (which are actually quite common among hobby potters) draw 48 amps and require a 60 amp breaker with 6 ga. wire (though possibly 4 ga. if the run back to the panel is really long). So, ask Sparkie to install the 6 ga. cable and put a 40 amp breaker in the panel. The cable will be a bit more expensive and seemingly overkill for now, but you will only be paying for the labor once. When you upgrade in the future, all that will be needed is a new breaker and receptacle, the expensive part of pulling the cable will already be done.

A manual kiln will teach you everything you need to know about firing a kiln, because YOU are totally responsible for everything that happens - what switches to turn on, when to turn them on, when to turn them up to the next level, how to load it so the witness cones are visible so you can turn it off at the right time, yada yada yada. There are lots of potters who have only manual kilns by choice. At the same time, there are lots of potters with modern digital controller on their new kilns who think that having pushed a particular button means that is what happened, and are shocked to learn that didn't actually happen. So, work with this one.
As for the wiring, as Neil and I have noted, this one will require an older form of 240V power with 4 wires vs the usual 3 in most current 240V situations. The required amperage of the circuit is fairly narrow for any kiln. If you get a newer kiln, you will probably get one that is bigger, which will need higher amperage. The trick for this is have the electrician install wire suitable for 60 amps, but set a smaller circuit breaker appropriate for this kiln plus an outlet appropriate for the power cord you get. Then when you get the newer bigger kiln, all you have to do is swap in a bigger circuit breaker and change the outlet. The newer kiln won't need the 4th wire (the neutral), so just cap it off in the box. It's ok to run less power on bigger wires, but not ok to run more power on smaller wires. So, pay the sparkie to do it once with the big wires.

You say you have a 240V hookup for it. Be aware that the old A88B kilns used a 4-wire 120/240V hookup in which the neutral is essential. Also, kiln circuits need not only correct voltage, but also correct amperage of 125% of the nominal amperage shown on the electrical rating plate. But perhaps the hookup you have is correct? If so, carry on.
 

You know you are going to have some amount of water in the slurry. I start mixing my dipping glazes at a rate of 1 liter of water per 1 kg of dry recipe. That typically will yield a specific gravity of around 1.5, which will be adjusted as needed after mixing and sieving. For recipes with soda ash, I  will boil half of the water in a small electric teapot, and dissolve the soda ash with that in a small bowl. It will take a few minutes of stirring and waiting until it is all dissolved, and then put that in the bucket with the rest of the water before adding the dry materials.

You know you are going to have some amount of water in the slurry. I start mixing my dipping glazes at a rate of 1 liter of water per 1 kg of dry recipe. That typically will yield a specific gravity of around 1.5, which will be adjusted as needed after mixing and sieving. For recipes with soda ash, I  will boil half of the water in a small electric teapot, and dissolve the soda ash with that in a small bowl. It will take a few minutes of stirring and waiting until it is all dissolved, and then put that in the bucket with the rest of the water before adding the dry materials.

You know you are going to have some amount of water in the slurry. I start mixing my dipping glazes at a rate of 1 liter of water per 1 kg of dry recipe. That typically will yield a specific gravity of around 1.5, which will be adjusted as needed after mixing and sieving. For recipes with soda ash, I  will boil half of the water in a small electric teapot, and dissolve the soda ash with that in a small bowl. It will take a few minutes of stirring and waiting until it is all dissolved, and then put that in the bucket with the rest of the water before adding the dry materials.

Oh no, Babs, don't fail on us now, we love you and need you. So, what did I ever write about elements and glazes... where do I begin...
A cursory review of the infamous Orton cone tables shows 3 columns of temperatures for each of the basic types of cone. The first column of temperatures is for a slow ramp over the last 2 hours into the final temperature, the middle column is for a medium speed ramp into the final temperature, and the third column is for a fast ramp into the final temperature. A slow ramp will bend the cone at a lower final temperature than a fast ramp, as a fast ramp must continue to a higher kiln temperature before the heatwork has penetrated the ceramic and the cone bends. Elements, as they wear out, produce less and less heat, which means the kiln will heat slower and slower (i.e., take longer and longer), particularly at the higher temperatures of mid-fire and high-fire clay bodies and glazes. A Bartlett or Orton kiln controller (Skutt controllers and the L&L DynaTrol are private label Bartletts, and the Paragon Sentry line is a private label Orton) that is programmed using a custom ramp-hold sequence to finish at a particular ramp rate to a particular temperature will continue to fire to the assigned temperature regardless of the actual ramp rate the elements can achieve in their weakened state (until the elements are so weak they just can't manage any increase in the kiln temperature, and then you get the dreaded E1 failure). Thus, if you are running a program with a set point of 1222℃ at 60℃/hour expecting it to produce a nice cone 6 per the Orton chart - but your elements are so worn that they can only manage 15℃/hour at the end - the kiln still will go to 1222℃ because that is what is programmed, but at the slower rate because that's all the kiln can do. Looking further in the Orton cone table, 1222℃ at 15℃/hour is cone 9, seriously overfired. (I'm just pulling these numbers from the table for the purpose of discussion, your studio practice and kiln condition may be different.)
All that said about custom ramp-hold programs, there is the other side of the Orton and Bartlett controllers - the cone-fire method. You enter a speed and a cone number via the keypad, and the controller knows what to do. The cone-fire method on both these controller types contains some hidden adaptive programming that monitors the actual ramp rate in the final segment in real time. If the kiln is lagging, the controller will adjust the set point down using a proprietary algorithm from Orton so that a proper bend of the cone will occur at an appropriately lower final temperature. Using the above example, if you have set a cone 6 medium speed firing, but the elements are so worn they can only manage 15℃/hour at the end, the controller will stop at 1185℃, 37 degrees early, for a perfectly bent cone 6. Similarly, if you set a fast firing and your elements are still sufficiently robust to accomplish the higher ramp rate, the controller will automatically proceed to a higher temperature.
Note that this adaptive behavior is only available in the cone-fire method. If you are using custom ramp-hold programming, you need to watch your cones and adjust your final set point to match the cone behavior. And when you install new elements that can actually maintain the ramp you set, you need to watch your cones and adjust your final set point to match the cone behavior. But alas, I repeat myself.
Keep calm and carry on. Especially carry on .

Oh no, Babs, don't fail on us now, we love you and need you. So, what did I ever write about elements and glazes... where do I begin...
A cursory review of the infamous Orton cone tables shows 3 columns of temperatures for each of the basic types of cone. The first column of temperatures is for a slow ramp over the last 2 hours into the final temperature, the middle column is for a medium speed ramp into the final temperature, and the third column is for a fast ramp into the final temperature. A slow ramp will bend the cone at a lower final temperature than a fast ramp, as a fast ramp must continue to a higher kiln temperature before the heatwork has penetrated the ceramic and the cone bends. Elements, as they wear out, produce less and less heat, which means the kiln will heat slower and slower (i.e., take longer and longer), particularly at the higher temperatures of mid-fire and high-fire clay bodies and glazes. A Bartlett or Orton kiln controller (Skutt controllers and the L&L DynaTrol are private label Bartletts, and the Paragon Sentry line is a private label Orton) that is programmed using a custom ramp-hold sequence to finish at a particular ramp rate to a particular temperature will continue to fire to the assigned temperature regardless of the actual ramp rate the elements can achieve in their weakened state (until the elements are so weak they just can't manage any increase in the kiln temperature, and then you get the dreaded E1 failure). Thus, if you are running a program with a set point of 1222℃ at 60℃/hour expecting it to produce a nice cone 6 per the Orton chart - but your elements are so worn that they can only manage 15℃/hour at the end - the kiln still will go to 1222℃ because that is what is programmed, but at the slower rate because that's all the kiln can do. Looking further in the Orton cone table, 1222℃ at 15℃/hour is cone 9, seriously overfired. (I'm just pulling these numbers from the table for the purpose of discussion, your studio practice and kiln condition may be different.)
All that said about custom ramp-hold programs, there is the other side of the Orton and Bartlett controllers - the cone-fire method. You enter a speed and a cone number via the keypad, and the controller knows what to do. The cone-fire method on both these controller types contains some hidden adaptive programming that monitors the actual ramp rate in the final segment in real time. If the kiln is lagging, the controller will adjust the set point down using a proprietary algorithm from Orton so that a proper bend of the cone will occur at an appropriately lower final temperature. Using the above example, if you have set a cone 6 medium speed firing, but the elements are so worn they can only manage 15℃/hour at the end, the controller will stop at 1185℃, 37 degrees early, for a perfectly bent cone 6. Similarly, if you set a fast firing and your elements are still sufficiently robust to accomplish the higher ramp rate, the controller will automatically proceed to a higher temperature.
Note that this adaptive behavior is only available in the cone-fire method. If you are using custom ramp-hold programming, you need to watch your cones and adjust your final set point to match the cone behavior. And when you install new elements that can actually maintain the ramp you set, you need to watch your cones and adjust your final set point to match the cone behavior. But alas, I repeat myself.
Keep calm and carry on. Especially carry on .