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How Long Do Thermocouples Last?

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I've been reading Clay and Glazes for the Potter by Daniel Rhodes as well as Mastering Cone 6 Glazes by Hesselberth. Reading these and watching my own firings got me to thinking...


How long do thermocouples last?

Mine has been fired 125 times. I think it's (I don't have my kiln log in front of me for exact numbers) 55 cone 04 slow bisque, 55 cone 6 slow glaze, 15 cone 05 fast glaze (transfers).




How do you know when your thermocouple is starting to have issues?


In my last couple of firings I have had a couple of pieces develop pinholes. I'm trying to remedy this issue since I have never had it before these 2 firings. I am using the same glazes as I have been. I know it might be my bisque firing as well. To fix pinholes at what temperature should I add a hold to burn out the issue? Just a hold at the end temperature?


It could also be that my thermocouple is drifting because it needs to be replaced. The cone 6 before this load did not look over fired but this cone looks a little towards the over fired range. It could just be where it was placed or something. If I run a test load through at cone 5 should I add a hold at the end temp? If so for how long?


In this last load I also had a couple Amaco Blue Rutile pieces in there and they seem more brown than blue than they usually are. This can also happen if I have the glaze too thin so am not sure if Blue rutile runs brown if over fired.


Thank you for helping me answer these questions.

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Thermocouple life will depend greatly on how hot you're firing, as well as your firing schedule, and whether or not they are in protection tubes (which are a worthwhile investment). If they're starting to drift that's a good sign they're due for replacement, or if they're starting to look pretty crispy and flaky, or starting to bend. You can either try compensating with hold times and such, but you'll be better off just replacing them.

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Thanks Neil!


I'm going to run a test load with 5, 6 and 7 cones on each shelf and see what they say then if I am getting hotter than I should I will pull it and put in a new one. I already have one here just never installed one before and want to make sure I actually need to at this point. Trying to learn every aspect of this business called pottery.


Again thank you so much for all your kiln wisdom!



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I'm having a similar problem. My thermocouple died two firings ago. It was replaced by the only chap in Jhb who works with kilns He replaced it with the same type K for K. I ran a bisque which fired fine. I then ran a glaze (results in a post under Studio Opperations). This was a disaster. My shelves buckled or cracked throwing pots against pots. The glaze ran and ran sticking everything to the shelves. One shelf buckled and fused to the large bowl on the shelf below.


We called the chap and had him come out to check the kiln and he has said that the replacement was correct and that the firing was wrong. How this could be I don't know as I've fired the same way as always without any issues.


So I'm firing a single pot today, with cones to check. But if this is not a "successful" firing, what is my next step?

I'd be very grateful for any advice.


Have a good Sunday

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DO you keep a log of your firings ie what you turn up your energy input to/hr , temp reached , temperature range, length of hours on, final shut off time.? When bungs went in etc. and how the pots were if anything odd happened.

I used a manual kiln till recently and recorded the above by the hour until shut off.

Of course being human, I left it for a few hours over my life time. I never left it to turn itself off by kiln sitter.

This is the only simple way for sure way to know that your kiln is behaving as normal.

I also checked that when the 500deg C came around there was a faint glow starting to happen in the kiln. The cones were watched as they emerged from the gloom.

I guess I started when I, still don't, had little trust in myself or machines. The human factor is all around.

I feel for you Andrea being an isolated potter.

Do you have any books available.

Temperatures can be "guessed" at by the colour of the interior of your kiln. It is pos. to see the glaze melt as well.

I would also, prob not recommended, flick my meter if it seemed a bit off in case the local red dirt was invading it.

You bought a new thermocouple and it was connected to your existing pyrometer? No help around I'd be disconnecting and reconnecting that in case it is in fact slightly loose.

The thermocouple and pyrometer may have to be recalibrated, that's a different chappie who recalibrated pyrometers, not necessarily a kiln chappie, no gender bias intended there.

Keep posting. Better advice will come your way.

ALso when you said your thermocouple blew... what happened?

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My platinum one lasted over 10 to 15 years it's also an oxegen meter.my cheaply made type k ones last a few years at cone 10

I always have new ones in stock. Mine are all 12 inch long as I have thick walls and fire to cone 11.

I have replaced a few of the platinum ones over the years via Axner repair.

Digital meters are the way to go vs analog ones

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