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David Woodin

User Program, Does Anyone Use Ramp Rates Different Than The Orton Chart?

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Does anyone try to use ramps other than 27 F/hr, 108F/hr and 270 F/hr? when programing to cone 6.

I am sorry I didn't ask this question very well.  There are times I want to go slower than 108 deg F for the last 200 deg F. Recently I contacted Orton and they sent me a CD of their Cone Calc. program so now I know what to put in as a top temperature.  The feature Neil mentioned is great but only puts in the values for 108 F/Hr, but it will be like a regular cone program. A vary fire program doesn't sense how fast the kiln is going etc.

So I guess if anyone wants to know what the end temp is for various ramps, either ask Orton for the CD or I can put in the information you want to know. 

David

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It only matters in the last 200 degrees. If you use ramp rates other than the Orton rates for your final 200 degrees, you'll have to guesstimate what temp you need to achieve cone 6. I use different ramp rates than those, but I never use a temperature as my peak temp. Instead, I input a cone. To do that on a Bartlett V6-CF or L&L Dynatrol, simply hit the 'other' button and it will let you put in a cone instead of a temperature. You can do it on a Skutt, too, but I can't remember which button to use. I'm sure Paragon and other controllers can do it as well. That way the computer will  figure out how hot it needs to go to achieve the cone at the ramp rate I've chosen.

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So, a Newbie question Neil - what's the significance of the last 200 degrees? Should this be slower or faster than previous ramp rate? Is there a standard Firing schedule for Cone 6 glazes?

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200 deg F below the final top temperature is what most controllers use as the starting point for the last ramp of 108 F/hr ramp to final temperature.  For example Cone 6 down is 2230 F, so you start that last ramp of 108 F/hr at 2030 F.  But suppose you wanted  the final ramp for cone 6 down to be 80 F/hr?  My original post was asking if anyone considered using a different ramp.  There is a cone calc. cd that tells you.  A 80 F ramp for cone 6 down is A TOP TEMPERATURE OF 2218 F therefore the last ramp starts at 2018 F.  I find that this enhances the fired surface and seldom am bothered with pinholes, also it is easier on the kiln to be using a slower ramp rate. 

David

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Thanks for your reply David - I'm such a Newbie that this almost reads like Double Dutch to me. What I really meant was WHY is there a different ramp for the last 200 oF? I'm using a digital controller on a v small electric kiln and slow down to 80 oC between 500oC and 600oC then go flat out to the top temperature. I haven't got into the habit of using witness cones I'm afraid! What are the pitfalls in this? Should I be programming another ramp for the last 200o??? Does it make any difference if I'm firing earthenware or stoneware glazes?

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Slowing down the last 200 degrees allows the glazes and glaze ingredients to melt more smoothly than a more rapid increase. It can also help the kiln to even out heating from top to bottom. Makes no difference between stoneware and earthenware or porcelain glazes.

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Slowing down the last 200 degrees allows the glazes and glaze ingredients to melt more smoothly than a more rapid increase. It can also help the kiln to even out heating from top to bottom. Makes no difference between stoneware and earthenware or porcelain glazes.

 

Thank you Bciske, that's just what I needed to know.

 

Celia, if you ramp faster than the Orton ramp rate, and the cone goes down, there hasn't been enough "heat work" to actually mature the glaze.  Remember cones measure heat/work, not temperature.  So, to achieve a particular cone, the pots have to be heated to a particular temperature, gained over a particular amount of time.

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Celia, if you ramp faster than the Orton ramp rate, and the cone goes down, there hasn't been enough "heat work" to actually mature the glaze.  Remember cones measure heat/work, not temperature.  So, to achieve a particular cone, the pots have to be heated to a particular temperature, gained over a particular amount of time.

 

 

If the cone is down the cone is down right? and the heat work has been reached. I thought the slow down was because orton know that going 150deg/h till X temp or 60 deg/h to X temp for the last two hours achieves the cone/heatwork.

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My understanding is cone is down = melt temp reached. If the cone isn't down but it reached temp and cooled quickly the cone might not be all the way down. I could be completely wrong here, but I thought it was if the cone was down the cone was reached, that's the whole point of cones right?

 

I have been doing a lot of testing with user ramps. I dont even use the easy fire anymore I basically build a user program for each firing depending on the glazes I have used and how I want it to ramp.

 

If I am firing a slow cool set of glazes I just fire 550 straight to cone 5.5 then let the slow cool part of my schedule push my cones to cone 6. If I am doing a regular glaze firing for glossy glazes I usually just fire straight to like 1980 then do 150 an hour till cone 6. With no hold or no slow cool, but I have a little kiln, my temps are very accurate without any holds to build the cones up to correct.

 

Kilns are freaking amazing tools.

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Celia, if you ramp faster than the Orton ramp rate, and the cone goes down, there hasn't been enough "heat work" to actually mature the glaze.  Remember cones measure heat/work, not temperature.  So, to achieve a particular cone, the pots have to be heated to a particular temperature, gained over a particular amount of time.

 

 

If the cone is down the cone is down right? and the heat work has been reached. I thought the slow down was because orton know that going 150deg/h till X temp or 60 deg/h to X temp for the last two hours achieves the cone/heatwork.

 

My understanding is that if you fire faster than the Orton ramp rate the cone will fall, but the heat WORK is not done.  Luckily my kiln wont fire that fast  :)

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Celia, if you ramp faster than the Orton ramp rate, and the cone goes down, there hasn't been enough "heat work" to actually mature the glaze.  Remember cones measure heat/work, not temperature.  So, to achieve a particular cone, the pots have to be heated to a particular temperature, gained over a particular amount of time.

 

 

If the cone is down the cone is down right? and the heat work has been reached. I thought the slow down was because orton know that going 150deg/h till X temp or 60 deg/h to X temp for the last two hours achieves the cone/heatwork.

 

On the Orton chart it says "heating rate deg F/hour (last 200 degF of firing)" or" Heating rate deg C/hour ( last 100 degC of firing)"  I decide on what  user ramp I want to use, usually less than 108 deg F/ Hour and as long as I use this ramp for the last 200 deg of the firing than the results are very close to what the cone calc. program says it should be,  this also allows me to forget about a cool down firing unless I want to enhance a matt glaze surface

David

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Too much information for me after 4 hours in the golf course and a couple of glasses of wine! I'm not dim, but I need to go back to basics on this and sit and think about it carefully. I do know that cones measure heat work but as I'm not in the habit of using them except in the kiln sitter as a back up, I haven't really got my head round the significance of it all. I think I've generally been ok using the digital programmer and final temperatures because I'm mostly using transparent glazes which I think don't need too much subtlety! No doubt as I get into more complex glazes I'll need to sit down and read this up and get my head round it all.

Thanks for all the info!

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David, does the CD give the temps for firing to cone 4? I'm looking for the temperature I need to reach if I fire the last 200oF at 72oF / 40oC per hour.

 

Ideally I'd like to know what temp to reach if I fire at this rate and have a 30 minute hold, but any info will be useful.

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Cone is cone, whether you got there at 500/hr or 100/hr. That said, just because the heat work has done its job on the cone doesn't mean it has done its job on the pots. The interior of lidded or closed/narrow forms, or pots that are thicker than the cone may not have had the heat penetrate through if you fire really fast. In addiiton, glazes will react differently to different rates of climb. In general, glazes look richer when fired more slowly at the end because they spend a longer time at high temps, and have more opportunity to flow and mingle. Most glazes have a broad range during which they are fluid, so the longer they spend at the high end, the better the effects. I formulate my glazes so that cone 6 is pretty near the top of their range. That way if it underfires a little bit it won't really matter, and I get good flow. The down side is that if the glaze goes on too thick it can run off the pot. The last 200 degrees is important because below that the kiln just isn't hot enough to have an effect on the glaze melt.

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David, does the CD give the temps for firing to cone 4? I'm looking for the temperature I need to reach if I fire the last 200oF at 72oF / 40oC per hour.

 

Ideally I'd like to know what temp to reach if I fire at this rate and have a 30 minute hold, but any info will be useful.

cone 4 @72 deg F ramp is 2118 deg F top temp. a 30 minute hold is -45 deg F. ( reduce the top temp by this much) or 40 deg C  ramp to 1159 deg C top temp. 30 minute hold -25 deg C cone 4 down 90 deg.

David

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I forgot to ask: are these temperatures for self-supporting or large cones?

I noticed something odd about the numbers for the firings with and without a hold. Let's say I fire two identical kilns, starting at the same time from the same temperature, both at 40 oC / h. Kiln A fires to 1134 oC with a 30 minute hold, and kiln B fires to 1159 oC with no hold. At the point in time when kiln A starts its hold, kiln B still needs to fire for 37.5 minutes to reach its top temperature, by which time kiln A will have shut off already. So the temperature of kiln B is always greater than or equal to that of kiln A, yet they both fire to cone 4.

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The figures I gave you are for self supporting cones or large cones mounted @1 3/4 ". Large cones mounted with 2" mounting height deform approximately 2 deg C lower.  As to your other question All the figures are based on the last 100 deg C of firing, a 40 deg C ramp to 1159 deg C should bring cone 4 down Its starting point is 1059 deg C.  A 30 minute hold means you subtract 25 deg C from the 1159 deg C = 1134 deg C is its top temp., its starting point is 1034 deg C. So with a hold you fire longer at a lower temperature.

David

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Thanks for clarifying the type of cone.

 

I agree that you'll spend less time within the last 100 oC if you fire without a hold than with a hold, but overall, you fire for longer and at a temperature at least as high as the firing with a hold. I had time to kill while waiting for my laundry, so made a graph comparing the two firing schedules.

 

KDOSn3R.png?1

 

Assuming the ramp rates are fixed at 40 oC / h to the left of the diagram for both schedules, I would conclude that the red curve fires to a higher cone than the blue curve.

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I don't think you took into account that the last 100 deg C of the firing start at different temperatures. Without hold 1059 deg C with hold 1034 deg C plus 30 minutes of hold.  If this doesn't explain it than send an e-mail to Orton and they will answer the question.  There is also a curve they are fitting this data to.

David

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I don't think you took into account that the last 100 deg C of the firing start at different temperatures.

 

I don't see how this would make a difference, since the cone doesn't know when the last 100 oC of the firing begins, so to speak. But let's agree to disagree. Thanks again for posting the data from the Orton CD.

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