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Public Studio Vs. Lone Ranger


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#21 neilestrick

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Posted 10 December 2013 - 10:14 AM

The price of the Controllers shown above include a $50 FerroChrome Type-K thermocouple which will fail within a year or two, or you can have them sell you a controller upgraded with a Type-S thermocouple.

 

Norm and I disagree on the necessity of type S thermocouples, which is what makes this forum so great. If protected in a ceramic tube Type K's can last several years firing to cone 6 (depending, of course, on how often you fire), with perfectly adequate accuracy. I replace my thermocouples in my heavily fired kiln every 18 months or so, and have no inacuracy problems. 99%+ of all electric kilns use type K, without problem. Type K's are only $15. If you bump a type S and break it, you're out $250.


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#22 Bob Coyle

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Posted 10 December 2013 - 11:34 AM

Norm... off the subject but what is the function of the plywood "gasket" leaning against the open kiln in your pictures. My best guess is that it is used to prevent edge damage when loading and unloading. You sure couldn't use it while firing.  What is it really???



#23 JBaymore

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Posted 10 December 2013 - 11:55 AM

Neil,

 

Seems to me that not too many craft potter kiln manufacturers use protection tubes for their type Ks ;) ....... and most potter built gas kilns I've seen don't either.  I usually use them for clients, reminding them that it induces a slight lag in the temperature readout versus the temperture around the sheath.  One of the reasons that type Ks are the "workshorse" for the craft potter type electric kilns is that potters are notoriously "cheap"... and the extra cost for the benefits of the Type S are lost on them.  The benefits of type S are longevity and accuracy.

 

For cone 6 K-s are certainly absolutely OK for all but the most demading ceramic artist functions (except maybe for a nutzo level of crystalline glaze work). 

 

But for cone 10 (or higher) use......... K-s are not even rated for that temperature usage by the manufacturers.  They go VERY non-linear as you reach the top end of the firing.  On analog meters....... that fact made (makes) the top end almost useless for anything other than "is it getting hotter, colder, or stalling".

 

K's are ASTM rated for max use temps.  It is based upon the wire guage size of the thermocouple... and runs 8 gauge -2300F  14 gauge - 2000F   20 gauge -1800F and 24 gauge -1600F. So if you fire fast-ish to cone 8 .... you are already over the max use limit, and if you fire slow you are right to the very edge (2295F) at cone 9 just down.  Most people I know that say they fire "cone 9".... actually fire 9 down hard (which is really cone 10 or more).  While ewvery firing of a thermocouple takes its toll, each firing above the use limit "kills" some of the accuracy of the readings from that thermocouple... so the drift continues to add up.  (And if they are unoprotected, and fired in reduction, the life gets kicked out of them even faster.)

 

Type S-s deteriorate more slowly than K-s, so hold their accuracy over more time..... IF they are properly mounted in protection tubes.  So there is some payback on the high cost there.... IF accuracy is important to the potter.

 

As you say, most potters use K's because of the huge price differential and they just work for up to cone 9.  As long as they understand what they are buying and how that possibly impacts data acquired.... that is fine. 

 

best,

 

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


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#24 neilestrick

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Posted 10 December 2013 - 01:37 PM

John, I agree completely. I was speaking strictly in terms of electric firing, which most people fire to around cone 6 or cooler, where type K's are still plenty accurate. Those who fire to cone 9/10 in electric are often doing crystalline work or other unique firing types where yes, type S would be preferred. But for the vast majority of potters, the type K work just fine. If they didn't, type S would be the standard.

 

I'm surprised you haven't seen more gas kilns with thermocouple protection tubes. I rarely see one without a tube. They are standard equipment whenever I've built a kiln. The added benefit of the tube is that it protects the thermocouple from getting bent or cracked by a kiln shelf when loading. I see a lot of Skutt thermocouples die early due to blunt trauma injuries.


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#25 Bob Coyle

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Posted 10 December 2013 - 02:48 PM

 

I'm surprised you haven't seen more gas kilns with thermocouple protection tubes

 

Maybe you could make protectors out of a thin cylinder of paper clay... Anyone try this?



#26 neilestrick

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Posted 10 December 2013 - 02:55 PM

 

 

I'm surprised you haven't seen more gas kilns with thermocouple protection tubes

 

Maybe you could make protectors out of a thin cylinder of paper clay... Anyone try this?

 

 

I would bet that they would fail/crack after several firings if made from a regular paperclay. Tubes are usually made from a mullite/cordierite material like kiln shelves. It would be an interesting experiment, though.


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#27 neilestrick

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Posted 10 December 2013 - 05:15 PM

The exposed tip is the problem on that thermocouple, since that's the part that the reading comes from. You need a full tube to truly protect it, like this:

Attached File  accessories-tc-tube-950_0.jpg   3.51KB   0 downloads

 

The thermocouple should be pushed all the way up to the tip of the tube, so there is as little lag as possible.

 

Love that wood loading ring!


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#28 Chris Throws Pots

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Posted 10 December 2013 - 06:51 PM

Hi Peachy and All,

 

Like Weeble, I'm the studio manager at a non-profit, community-based clay and print studio. We have 14 wheels, a large handbuilding area with a slab roller, an extruder and 3 PK Skutts which are rarely cool silmultaneously. We have a raku kiln and an off-site wood kiln. Our clay studio is roughly 2000 square feet. We mix 15 glazes from our own recipes (12 that we always have, 3 that rotate to keep things fresh). All clay fired by us must be purchased through us. Glaze chemistry and firing costs are built into the price of clay. People participate as either renting members or students. All participants can access the studio during open hours... I aim to have 30-35 during the academic calendar and 25 during the summer when we have summer camp programming all day every day. All open studio hours are scheduled in 4 hour blocks and are hosted by a studio assistant. Assistants trade 4 hours of work for a set of keys to the studio and waived studio rental dues. We offer wheel throwing and sculpting classes and have recently started doing more advanced workshops including woodfiring weekends and one-off lectures. We partner with the public school system for some afterschool classes and a local college for 3 undergrad and 1 grad level course per year. Every month we have about 100 renters and adult/college students accessing open studio hours, and another 40 or 50 coming in for youth programming and drop-in nights.

 

We have A LOT happening at our studio, and while accidents happen, most accidents can and should be prevented. In my studio, most are. Participation in a class at my studio is not just about learning how to throw, trim and glaze. As a teacher I put a lot of emphasis on learnign the studio as well. I build in bits of studio etiquette to the curriculum. I encourage other instructors to do the same. I rarely bring it up that explicitly, but I find that being able to navigate the studio in a manner respectful to the space and the other people here is as important as developing a skill set for throwing or sculpting. When someone walks through our door for the first time, they are often new to clay; it's a foreign thing; it's intimidating. I find overwhelmingly that students want very much to do the right thing, want to learn the bigger process. And they don't want to piss anyone off by wrecking someone else's work. Additionally I am selective when hiring studio assistants, and make sure to train them thoroughly on studio operations and etiquette before asking them to do anything. If a studio assistant sees a student or member doing something that would be detrimental to our equipment or someone else's work they use it as a teachable moment and help that person; nothing punitvie, just learning. 

 

I bring all this up because if you haven't already, I'd strongly encourage you to give feedback to the studio where you took the class. As the studio manager here, I want to hear what's going on. Sure I love positive feedback, but hearing about areas for improvement is equally as important. My worst fear (as it relates to my job) is that someone leaves a class with a bad taste in their mouth and doesn't give us a chance to remedy the situation, or at least learn from the situation.

 

With all this in mind, I very much enjoy my small, incomplete home studio set up. I have a wheel and shelving, but transport everyhtign into work to fire. I've been based out of the community studio for 7 years, first as a student, then as a studio assistant, now as the studio manager and an instructor. There are times when I have my own work to attend to and don't necessarily want to stop to help someone with a throwing technique or process a credit card for their rental dues. That said, there are plenty of times when I relish in the fact that I don't always work in a silo and can work amongst a diverse group of clay people to with whom I can share conversation and bounce idas off of. For me, these times when I'm glad to be in the community atmosphere tend to be when I'm doing experimental work. I like to be alone for production. I have a three season porch on which my wheel lives. From May to October I can sit at the wheel with the company of my morning coffe or evening beer and Netflix playing on my laptop. But it's December and for better or worse I'm doing all my work at the community studio until spring. So I tend to snowboard more in these months than I do make production volumes of work.

 

C


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#29 JBaymore

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Posted 10 December 2013 - 07:39 PM

Norm,

 

Those insulators on the thermocouple you mention are not "protection".   That is a "bare wire" type with ceramic insulators.  It does not protect the thermocouple from the kiln atmosphere in any significant way. 

 

A protection tube is sealed on one (or both) ends, and runs right thru the kiln wall.  In some cases they are open to air on the cold face side... and in some cases they are sealed there too.  In industry sometimes they are filled with an inert gas.  Protection tubes come in many materials... depending on the use temp and atmosphere.  Sometime they come with a terminal block for the connection on the back end.

 

The goal is to have the protection tube as thin as possible in wall section and as close to the actual thermocouple tip as is possible so as to minimize the lag time.

 

You can make a "quick and dirty" one by making a plaster mold of something like a wood dowel ith the rounded end, and casting a porcelain one.  Pre fire it to maturity and install.

 

best,

 

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


John Baymore
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Professor of Ceramics; New Hampshire Insitute of Art

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