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Nelly

Breaker shut down while firing by accident?

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Dear All,

 

I am sorry to bother you with all these questions but I started a firing on Sunday night. Glaze firing. Cone 6. The manual said it would take roughly 13 hours. I followed all the steps to a "t." In the past my glaze firings have been fine.

 

Yesterday, I left the kiln for all of an hour and when I came home, my renovation guy said he turned off the breaker as he could not get one of the reset buttons working in the bathroom outlet in my home.

 

By shutting off the breaker he inadvertently shut off the kiln. I did not realize this until I opened my kiln this morning and found my work totally under fired. I figured in the hour that I left that it must have completed the firing and was done since it was in the off mode when I returned. While he told me the story about the breaker I never put the two together until this morning and I saw the very dry appearance of my ware.

 

I figured I had one of two choices--pitch the work or fire it again at cone 6. I thought about going down a cone (cone 5) but thought no, this is not the right thing to do as I really didn't see the results at cone 6. At this point, I thought what the heck?? Experiment.

 

I did not repack the kiln. I left it as it was. The cones through the peep holes were totally upright this morning when I reviewed the work. The feedback from the controller said it reached 1900 and something. Thus it was short significantly from the temperature I was aiming for in cone 6 self-supporting large cones.

 

Here is my question...and know I did a google search on this before adding this to the forum...

 

Will the Orton cones react to this second fire??? Are they a one off thing or will they do anything over night as I check on them???

 

While I know my answer will be apparent to me soon enough, I just wondered if anyone knew can you fire Orton cones a second time and will they bend IF they never reached temperature initially??

 

If you have any experience with this, I would be interested. Yes, you could say I was lazy in not unpacking the whole kiln. But I had half shelves in place at the top and could see down to lower areas of the kiln. It was definitely under fired. Dry. Not quite powder on the surface but dry.

 

My guess is that the Orton cones won't do anything but I could be wrong. If I am right, I will simply be depending on the computerized read out to tell me when I have reached full temperature. I will be watching this carefully overnight and into the early AM (i.e., 7-8am tomorrow). Thus, I will clearly see the time it reaches the expected temperature. I will be sitting by the kiln watching the count down this time.

 

If no one has experience with refired Orton cones, I will reply to you all and let you know my experience. Know my cones are painted with iron oxide so their visibility is clear when they reach high temperature. I am not sure if this will happen this time.

 

Will keep you posted.

 

Nelly

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Refiring should be fine. No different than if a summer storm knocked out power while you were firing. The cone packs should be okay, too. Remember, cones react to heat work, not temperature. And, they do not tend to bend until getting near mature heat work. Like you underfired glazes, the cones are underfired . . . a little heat will cure them.

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Refiring should be fine. No different than if a summer storm knocked out power while you were firing. The cone packs should be okay, too. Remember, cones react to heat work, not temperature. And, they do not tend to bend until getting near mature heat work. Like you underfired glazes, the cones are underfired . . . a little heat will cure them.

 

 

Dear Bcicke,

 

Really?? So then not removing them was the correct thing to do. I am so glad. I have just checked the kiln and can see that the cones through the peep hole are still upright but I can clearly see the iron stripes and dots I put on the cone for easy identification. Thus, so far so good. Again, will keep you posted. Thank you so much for the reassuring advice. I thought someone might know the answer.

 

Nelly

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Guest JBaymore

Really?? So then not removing them was the correct thing to do. I am so glad. I have just checked the kiln and can see that the cones through the peep hole are still upright but I can clearly see the iron stripes and dots I put on the cone for easy identification. Thus, so far so good. Again, will keep you posted. Thank you so much for the reassuring advice. I thought someone might know the answer.

 

Nelly

 

 

All will be fine.... except................

 

If you paint stuff onto the cones, you have the potential to have changed the way they behave. That iron can affect the cones. Particularly in reduction (which you are not doing).

 

If you have trouble seeing cones .... get an arc welding mask glass filter plate. Works wonders.

 

best,

 

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

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If you have trouble seeing cones .... get an arc welding mask glass filter plate. Works wonders.

 

best,

 

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

 

 

I've always found those to be too dark at cone 6. I prefer the #5 braze welding mask. They're cheap, so worth trying both.

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Really?? So then not removing them was the correct thing to do. I am so glad. I have just checked the kiln and can see that the cones through the peep hole are still upright but I can clearly see the iron stripes and dots I put on the cone for easy identification. Thus, so far so good. Again, will keep you posted. Thank you so much for the reassuring advice. I thought someone might know the answer.

 

Nelly

 

 

All will be fine.... except................

 

If you paint stuff onto the cones, you have the potential to have changed the way they behave. That iron can affect the cones. Particularly in reduction (which you are not doing).

 

If you have trouble seeing cones .... get an arc welding mask glass filter plate. Works wonders.

 

best,

 

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

 

 

 

Dear John,

 

I have heard that. I know after a certain point, I just have to go on memory of where I saw the cones. But it does help in the beginning stages when I am starting to look at the cones in the firing. It is as though I develop a mental picture of their placement vis-a-vis the hole. A colleague of mine used to blow into a piece of long kiln furniture (stilts) to cool the peep hole and then look. I tried that but experienced back draft. Scary stuff. Lost a few eye lashes on that one. Now I use the painted cones and position them one behind the other on appropriate angles. But absolutely, I do need a welders mask or at least a pair of the glasses you can buy that rid your eyes of the harmful rays. Good advice. Good safety reminder.

 

Nelly

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Guest JBaymore

 

I have heard that. I know after a certain point, I just have to go on memory of where I saw the cones. But it does help in the beginning stages when I am starting to look at the cones in the firing. It is as though I develop a mental picture of their placement vis-a-vis the hole.

 

Interesting... I'd expect the issue in seeing them is actually toward the higher end of the firing. That is what many people experience. For the lower temps ...... maybe the brazing filters mentioned WOULD be better for you.

 

 

A colleague of mine used to blow into a piece of long kiln furniture (stilts) to cool the peep hole and then look. I tried that but experienced back draft. Scary stuff. Lost a few eye lashes on that one.

 

 

There is a well known phonomona of pyrometrioc cones called "freezing" (see Orton's info). This can be caused by just this kind of "blowing cold air onto the cones" approach to chill them so the color contrast with the background goes up. It causes the cone to not bend as the normal function would predict. This is not really a good practice. Also ... unless you keep the hole in the kiln wall very clean, when you blow in, you are in danger of blowing dust onto the glazes in the area of the spyport. Or if there is loose kiln wash or other debris on the shelf near the cones, blowing that around.

 

But absolutely, I do need a welders mask or at least a pair of the glasses you can buy that rid your eyes of the harmful rays. Good advice. Good safety reminder.

 

 

Just to be clear here, the harmful rays for the average part time or even full time potter using something like an electric kiln are VERY minimal. Not to say here completly ignore it.... but don't over play it either. The size (square inches / centimeters) of the radiating opening in an electric kiln is pretty minimal. The amount of actual time spent peering into that opening is pretty minimal even when looked at over the life of the potter. Particularly for those using computerized controllers... that minimize looking into the kiln watching the color and cones. Working at cone 6 makes it even less of a concern than for those that fire higher.... because the IR (and UV) goes up with temperature increase.

 

The eye hazard issue is far more significant for people like full time wood-firers, who spend a long time every firing looking into hot fireboxes often through very large stoke holes at kilns that are often held at elevated temperatures for rather long periods. THOSE people (like me) need to really think about this issue. Good eye protection and firing techniques in that case are far more important.

 

Of course full time hot glassblowers working at stuff like glory holes and batch furnaces are at pretty high risk of developiong issues. Plus add in the sodium vapor flare from hot glass......... and well........ they don't call them "glassblower's cataracts" for nothing.

 

The main culprit for hazards to the eyes from kilns is IR radiation..... direct radiational heating of the aqueous humor and the retina. There is actually very little UV produced by kilns, even at cone 9-10. Some.... but not much. The electromagnetic inverse square law applies to the intensity of radiational transfer, so the distance from the IR/UV source makes a huge difference. So simply backing away from the spyport a little bit has a huge impact on the possible "dose".

 

Do not use plain cheap sunglasses to filter out the glare to see the cones! They mainly filter out the visible light spectrum not the long and short waves that are the issue. This causes your pupil to dialate more than it would if you looked directly into the kiln. This allows more of the IR and UV to penetrate into the innner eye structures. If you use "Cheap Sunglasses" (bows to ZZ Top) this is actually worse than using nothing. If you get something for protection, get a pair of decent "kiln glasses" that filters BOTH UV and IR.

 

 

best,

 

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

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I have heard that. I know after a certain point, I just have to go on memory of where I saw the cones. But it does help in the beginning stages when I am starting to look at the cones in the firing. It is as though I develop a mental picture of their placement vis-a-vis the hole.

 

Interesting... I'd expect the issue in seeing them is actually toward the higher end of the firing. That is what many people experience. For the lower temps ...... maybe the brazing filters mentioned WOULD be better for you.

 

 

A colleague of mine used to blow into a piece of long kiln furniture (stilts) to cool the peep hole and then look. I tried that but experienced back draft. Scary stuff. Lost a few eye lashes on that one.

 

 

There is a well known phonomona of pyrometrioc cones called "freezing" (see Orton's info). This can be caused by just this kind of "blowing cold air onto the cones" approach to chill them so the color contrast with the background goes up. It causes the cone to not bend as the normal function would predict. This is not really a good practice. Also ... unless you keep the hole in the kiln wall very clean, when you blow in, you are in danger of blowing dust onto the glazes in the area of the spyport. Or if there is loose kiln wash or other debris on the shelf near the cones, blowing that around.

 

But absolutely, I do need a welders mask or at least a pair of the glasses you can buy that rid your eyes of the harmful rays. Good advice. Good safety reminder.

 

 

Just to be clear here, the harmful rays for the average part time or even full time potter using something like an electric kiln are VERY minimal. Not to say here completly ignore it.... but don't over play it either. The size (square inches / centimeters) of the radiating opening in an electric kiln is pretty minimal. The amount of actual time spent peering into that opening is pretty minimal even when looked at over the life of the potter. Particularly for those using computerized controllers... that minimize looking into the kiln watching the color and cones. Working at cone 6 makes it even less of a concern than for those that fire higher.... because the IR (and UV) goes up with temperature increase.

 

The eye hazard issue is far more significant for people like full time wood-firers, who spend a long time every firing looking into hot fireboxes often through very large stoke holes at kilns that are often held at elevated temperatures for rather long periods. THOSE people (like me) need to really think about this issue. Good eye protection and firing techniques in that case are far more important.

 

Of course full time hot glassblowers working at stuff like glory holes and batch furnaces are at pretty high risk of developiong issues. Plus add in the sodium vapor flare from hot glass......... and well........ they don't call them "glassblower's cataracts" for nothing.

 

The main culprit for hazards to the eyes from kilns is IR radiation..... direct radiational heating of the aqueous humor and the retina. There is actually very little UV produced by kilns, even at cone 9-10. Some.... but not much. The electromagnetic inverse square law applies to the intensity of radiational transfer, so the distance from the IR/UV source makes a huge difference. So simply backing away from the spyport a little bit has a huge impact on the possible "dose".

 

Do not use plain cheap sunglasses to filter out the glare to see the cones! They mainly filter out the visible light spectrum not the long and short waves that are the issue. This causes your pupil to dialate more than it would if you looked directly into the kiln. This allows more of the IR and UV to penetrate into the innner eye structures. If you use "Cheap Sunglasses" (bows to ZZ Top) this is actually worse than using nothing. If you get something for protection, get a pair of decent "kiln glasses" that filters BOTH UV and IR.

 

 

best,

 

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

 

 

Dear John,

 

Well if that post didn't scare me enough into buying proper lenses nothing will!!! I need my eyes. I am academic when I am not a potter. Thus, I do not want cataract eyes or should I say, I do not want any unnecessary eye issues down the road. I did look up the Braze #5 last night when it was posted. It is now the first thing on my list for when I call my supplier and if they do not have something in this vein (I do know they carry the usual glasses for kilns) I will go to welding supply house. Again, this is a really important reminder about a safety issue that I am sure can be over looked.

 

Another one that I feel is seriously not considered enough is the use of grinding machines. Perhaps I will put that in another forum.

 

Just know I am most thankful to you for mentioning the glasses to me. If is a good reminder in setting up my shop. I DO need these.

 

Thank you every single one of you.

 

Know the kiln is on the climb down now. It reached full temperature at 2pm and then started the down ramps. So, the kiln reached full temperature at about 9 hours. I then had subsequent ramps entered in for soaking. It is now cooling off.

 

As I have said, I am using the "Frog Pond" glaze firing schedule. If anyone would like to see this schedule just let me know. I think it is okay to post it given that it is commonly available on-line. I got my copy directly from my clay supplier.

 

Again, thank you everyone.

 

Nelly

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Info on IR exposure to the eye:

 

http://whqlibdoc.who...S_25_(chp3).pdf

 

best,

 

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

 

 

 

Dear John,

 

Thank you so much for this article. Do know that this morning when I spoke with Ian at Tuckers, he said "yup, you need the googles." Thus, I have order the ceramic welders googles with the #5 lens.

 

What was interesting for me in this article was all the incredible hazards that can be brought on by these rays. "Skin issues, cataracts, interoccular pressure in the vitrious humor etc." I wear glasses now, the last thing I need is something more to happen to my eyes. So this was really a good wake-up call on this front. And the part about glass blower injuries going down over the years was also of interest to me. I found that statistic quite interesting given the IR they are exposed to frequently but then again, maybe as the article pointed out, they now pay attention to this work relate hazard.

 

Now, I must let you all know about the firing.

 

Who ever wrote in the cool and calm, collected manner "Yup, all is well" was absolutely right.

 

Here is what I saw:

 

1. First half shelf one-nice clean firing. Despite the repeated coats of PC glaze to make the saturated gold color, it was okay. It can be refired and I can see the gold definitely ready and coming through.

 

2. Second shelf--Again a large platter, nice firing. I am wondering if this is my medium heat zone. It looked good. The saturated iron glaze worked beautifully as a back drop for some simple landscapes I do.

 

3. Third shelf- large platter that I did with a commercial white glaze and some rutile wash underneath followed by some further smudging of rutile on top. It has an old world glaze quality to it. Matt cream with some irregular ruffled edges. Nice orange edges. A good piece.

 

4. The fourth shelf was a piece that I knew had cracked but I wanted to try to experiment with it anyway. It turned out okay. It will go into my shards bin for sure.

 

5. The best piece was on the bottom. Imagine some slip poured on the leather hard platter done with iron and black mocha diffusion. After it was bisqued, I marked off 3 different squares with painters tape and did a clear/sepia looking glaze followed by wax resist. The whole piece was then dipped into saturated iron. What happened was the squares were clear with a sepia tone against the iron colored glaze. Nice clean peek a boo square where the mocha diffusion came through were evident. In addition, the iron from the slip that was in the surrounding area of the boxes came through to make some interesting textural gestures. This was the one I liked the best. I will likely refire this once as there is one spot that I has a bit of an open area but all and all the mocha diffusion looks very interesting. It is like seeing three old antique pictures against a saturated iron brown background with slight texture.

 

As you all predicted, the cones DID BEND. All worked out well. I couldn't believe it.

 

I have to tell you, I love this forum. It is like being in a studio again where I can ask questions at whim!!!

 

Sometime over the summer, I will get a camera that takes digital images to show you some work.

 

I know you aren't supposed to write in capitals on any e-mail correspondence but THANK YOU EVERYONE.

 

Nelly

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