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Cones And Soaking Times Theory


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#21 neilestrick

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Posted 09 November 2013 - 05:38 PM

I understand the concept of heat work. What I don't understand is what's the merit of soaking for an extended period of time to reach a certain cone as opposed to just raising the kiln to that temperature more quickly. Given that there are merits of this  approach, how far can you push it and why? I know that Stephen Hill's firing schedules make a lot of use of soaking.

 

I know that I can test all the stuff for 10 years but at 69, I need more of a shortcut

 

Firing to a lower temperature and soaking can add richness to a glaze, and can also extend element life. I noticed a 25% increase in element life when I started soaking cone 6 for 40 minutes to get to cone 8, instead of firing all the way to cone 8. Two things cause wear on elements: high temperature and cycling on and off. In my very unscientific test, firing hotter wore them out faster than cycling to hold temp.


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#22 Chris Campbell

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Posted 09 November 2013 - 05:39 PM

Docweathers - in the book Mastering Cone 6 Glazes, John & Roy illustrate how various glazes change when they are allowed to soak. For myself, I like to know the whole kiln has reached temp, not just the area near the thermocouple. Soaking gives me more even firings top to bottom.

Mart - I always say that every potter should help to fire a wood kiln at least once ... Just to hear how it speaks to you, to give your full attention to a process, to finally feel why they call it FIRING a kiln. Then go home and give your electric kiln a hug. : - )

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#23 Wyndham

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Posted 09 November 2013 - 06:01 PM

neil, you're right about the wearing out of elements. The closer they get to their max temp about 2385 or so, the shorter the life. I wonder about the dimishing return on longer firing at lower temp for better life span vs wearing out of relays over a prolong firing, something to consider.

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#24 JBaymore

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Posted 09 November 2013 - 06:01 PM

Then go home and give your electric kiln a hug. : - )

 

:lol:  :lol:  :lol: With the complexities of firing noborigama, sometimes I very much feel that way, Chris.  :lol:  :lol:  :lol:


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#25 Bob Coyle

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Posted 09 November 2013 - 07:37 PM

well yes, firing glazes requires dealing with multiple variables beyond time and temperature, but for any given gaze there should be an optimum ramp that gives the best results at the least cost which might be found by heat work calculations rather than pure trial and error.

 

I bisque fires some pieces for a woman who said that her mentor uses a 16 hour cycle up to cone 014.  I asked here how thick the pieces were that he fired and she said they were ordinard pots and mugs. I told here I would not do it unless she let me fire them with my regular 5 hour bisque cycle. She was very uneasy with this but guess what? They turned out fine anyway. I can't imagine the wasted time and energy  this guy has been using.But by god, I suppose he can say he never lost a pot!

 

We are much better at predicting weather since we developed computers than when grandpa felt his joints acting up. I see no reasone why firing ceramics should remain a black art.



#26 neilestrick

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Posted 09 November 2013 - 10:39 PM

neil, you're right about the wearing out of elements. The closer they get to their max temp about 2385 or so, the shorter the life. I wonder about the dimishing return on longer firing at lower temp for better life span vs wearing out of relays over a prolong firing, something to consider.
Wyndham


The 40 minute hold I used to do to get from cone 6 to cone 8 did not really make the firing any longer than actually firing to cone 8. And with zone control the relays were cycling some anyway. So I don't think it hurt them much at all. Plus relays are cheaper than elements. I think the greater killer of relays is heat. I see a wide range of relay life depending on how the control boxes are designed. Some do a better job of shielding them from the heat of the kiln than others.
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#27 JBaymore

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Posted 10 November 2013 - 10:40 AM

Good post, Norm.

 

Too many folks do not understand the huge number of variables that are involved in each step of the pottery making process (not just firings), and then wonder why, when they THINK they did everything the same, that the results differ.  It is the variables that they do NOT control that get them... and in many cases they do not even realize that those variable are there.

 

The tools we have available help us control some of these variables. 

 

best,

 

..................john


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#28 Wyndham

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Posted 10 November 2013 - 01:53 PM

Well as you describe, this is about how i fire.Attached File  2-vase.jpg   97.03KB   0 downloads



#29 Bob Coyle

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Posted 11 November 2013 - 11:38 AM

Pazu:

 

I have designed a kiln firing program that uses an Arduino UNO with a thermocouple module  to control a solid state relay. The user interface on the PC is based on  VB 6 . The software reports theoretical and actual heatwork, and total KW hours. It graphs the time/temp and produces a report  of the ramp and all of the above info including a printout of the graph.

 

The KW hours of the run is based on user input of volts and amps. There is no real time reading of the actual electrical params. On my  120V test kiln I get a 5 volt drop during the ON cycle and just type that value in.

 

As far as load weight is concerened, it would be easy to add some set of params to the program that set the hold time but I'm not sure it would be worth the effort of weighing each piece and kiln shelves to try to get some optimum soak.

 

If you are handy with a soldering iron, I'll send you the Arduino script and the software setup and you can have a go at it.

 

The total cost of the custom controller I put together is around $80 , but I salvaged a few of the components from an old PC.



#30 JBaymore

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Posted 11 November 2013 - 12:19 PM

Bob,

 

Ah... VB6....

 

How are you dealing with hysteresis on the temp overshot in your code?

 

best,

 

......................john


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#31 Bob Coyle

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Posted 11 November 2013 - 02:20 PM

 

How are you dealing with hysteresis on the temp overshot in your code?

 

I'm not John. I have not put any logic in the code to damp overshoot.  I could but I'm not sure the gain would be worth the sweat. At lower temps I get sometimes a 10deg F or more overshoot, but when the duty cycle is more on than off it only amounts to 2-4 degreesF. I can live with that.  (the reading is with a 100 point average over 100 milliseconds)

 

Any ideas?



#32 Bob Coyle

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Posted 11 November 2013 - 03:03 PM

The reason I chose Arduino is that there is a ton of support and add on gadgets that plug right into the board. Then all I have to do is modify the existing code for the gadget to get it to talk to my computer. It has a real simple programming development environment and the board only runs around $25.

 

you can buy clones cheaper but none of them seem to work under the dreaded WINDOWS 8!

 

The board has plenty of digital I/O and has 6 analog inputs, so you could control multiple relays. The only down side is the the A/D is only ten bits, but I think that is enough since the thermocouple reading has more slop than that.

 

Anyway, Keep us informed on how your project is going.....$60 for a kiln...some folks have all the luck.



#33 neilestrick

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Posted 11 November 2013 - 05:41 PM

The Evenheat looks like it's in good, shape, although it needs a stand. For the money it's the best deal. That $65 thing is scary. Run away. The Skutt looks good, to, although the Evenheat is a lot cheaper. The Gare looks exactly like an Evenheat. I'm wondering if it si truly a Gare, or if Evenheat built them for Gare. Without seeing the inside I can't make any judgement calls on it.


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#34 docweathers

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Posted 11 November 2013 - 06:52 PM

I have completely outfitted both my welding and pottery shop from craigslist this includes two kilns, a wheel, steel shelving, extruder  plasma cutter, TIG welder, drill press, vice, steel workbench etc.etc. I have gotten top-quality equipment very cheap because craigslist is a buyers market. I can't ever remember having something sold before I get there. If I spot something that I like, I usually wait a couple weeks after the posting date. By then most sellers realize that they have gotten 95+% of the traffic they're going to get on their item. At that point, I will typically, in person, offer them half of their asking price, and I have an open wallet full of hundred dollar bills clearly visible. I can usually get what I want for less than two thirds of the asking price sometimes at my original half offer.

 

After a couple of weeks they have a guy in front of them who clearly has money to spend and if they can't sell it to me they know their other use for it will be as their headstone.

 

I have gotten everything at prices that someday, when it's time to sell all of this stuff, I will lose very little money.


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#35 karencopeland

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Posted 18 November 2013 - 01:13 PM

I have an old kiln that has a kiln sitter. I would like to increase the amount of crystal formation in the glazes I am using, some are Steven Hill glazes and some are standard ^6 "dip" glazes. Would there be a recommendation to soak the kiln, at what setting and for how long, after the kiln sitter has turned off the kiln? I have put in cones to see how the kiln tends to fire in the past and the kiln sitter turns off the kiln but the test cones on the shelves do not indicate that a full ^6 has been reached. That said I have gotten some beautiful results, not too runny. Reading thru all these posts I think I may have made a mistake by putting a ^6 indicator cone in today! But I would still like to try out the "soak". Any guidance would be appriciated!






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