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Glazes That Break

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I used fiber way back, there was a kiln lid kit made with fiber and a metal frame that attached to the kiln lid. It lasted for several years on the HS kiln. When I decided I needed to make some changes in my own kiln, I opted for a thicker lid. This has helped my cool down time quite a bit. Only problem is, as my sectional often gets a 4th section added lifting on and off was harder, at least until I added a second handle onto the lid to make it an easy two handed lift. Someday, maybe I 'll set up a pulley/cable lift for the lid.

 

best,

Pres

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Here's what I would try for manual slow cooling:

1. Get a pyrometer

2. Be there when the sitter shuts off the kiln.

3. Lift the sitter weight, push in the start button, and very gently lower the weight. The kiln will stay on if you do it gently.

4. Set all switches to 'Medium' and see how much that slows down the cooling.

5. It may hit a point where it's cooling slower than you need it to. At that point switch everything to low and see how that goes. You really don't need a  rate slower than 150-175F/hr.

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Of course a kiln without a setter, and color temp checking will help keep you in the ball park. Did so for years and still do at home here. However, it does take practice and you can lose sleep, besides being not so happy with a few loads in the early years. . . yes years.

 

best,

Pres

 

 

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16 hours ago, neilestrick said:

Here's what I would try for manual slow cooling:

1. Get a pyrometer

2. Be there when the sitter shuts off the kiln.

3. Lift the sitter weight, push in the start button, and very gently lower the weight. The kiln will stay on if you do it gently.

4. Set all switches to 'Medium' and see how much that slows down the cooling.

5. It may hit a point where it's cooling slower than you need it to. At that point switch everything to low and see how that goes. You really don't need a  rate slower than 150-175F/hr.

I woke up this morning thinking about this and came up with the same idea. The only thing I was missing was the cooling rate. Thanks

 

 

16 hours ago, Pres said:

besides being not so happy with a few loads in the early years. . . yes years.

 

Hmmm. . .  this is still my first year, I needed that. :(   ;)  :)

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Bad loads are part of testing. Usually it comes from a lack of good testing practices. Take time to make good notes and run good test and you will have quicker advances and happier openings. Don't jump to conclusions based off a tile and do and entire load in that glaze. Slowly scale up your test. Go from tile to small cup to budvase to an actual pot you plan to sell. This way you get to experience a few things about the glaze like how it keeps, how it applies, and how it fires over different surfaces and shapes.

 

 

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I usually had multiple glaze test tiles, pots, whiskey glasses, and small platters in those early years. Most of the time they moved me ahead with the glazes, but being able to have an a priori understanding of the kiln, not just knowledge, took much more time, and patience. It would have been much easier back then to fire with a setter, but then cool downs, would not have been as controlled. Cones only get you so far, pyrometers, I used, but they burned out also. In the end, color chart with matching temps, allowed notation that was repeatable. Today, I hardly ever chart. If you print a color chart out. . . make certain monitor is accurate, and chart is accurate. . . you can chart time/color/duration. This will allow for accurate firing until darkness falls, or less dramatically when heat/light color is not longer inhabiting the kiln.

 

best,

Pres

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I think I'm more critical with my work than those around me. I've fired my own mixed glazes and when they come out of the kiln I say to myself "boy this is ugly" then later on a friend or family member will say to me "I really love this glaze."  Surprises the heck out of me every time.

I do take notes and I have developed a chart for myself to keep a record of each firing. It has come in handy in ways I haven't expected.

I do test tiles with everything I mix, and sometimes will also fire a pot at the same time with the same new glaze. From this I've learned that sometimes what looks good on a test tile may not look good on a pot and vise versa. The pots are usually small 1# pieces that I've practiced throwing skills on and I'm not to concerned about chucking them out later on.

By months end I will have completed 24 firings.

A funny thing just happened while I was typing this post, I received a phone call from a friend who wants to have what she calls a "Flash Exhibit" at her doctor's office this Saturday. She's invited 5 other people to show and sell their work . I mentioned to her that I didn't think my work is ready for sale and she insisted that it is. I said I would get back to her this afternoon. I know one of the other people she contact (who is a painter) and will give her a call and see what she thinks.

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4 hours ago, RonSa said:

 I mentioned to her that I didn't think my work is ready for sale and she insisted that it is. I said I would get back to her this afternoon. I know one of the other people she contact (who is a painter) and will give her a call and see what she thinks.

hmmm, not sure I'ld feel comfortable going with someone else's opinion, who's not a potter or has an understanding of ceramics, to judge when your work is ready for sale. It's your name and reputation, you can't take the pots back after they're sold. If it's a confidence thing then fine, that's another issue. One of the things that is helpful is to have someone knowledgeable critique your work. It's hard to listen too sometimes but it is helpful. (I had a prof who looked at my work one semester and said "got anything else?" crappy critique but I got the point) The organizers agenda doesn't have to be yours.

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1 hour ago, Min said:

It's your name and reputation, you can't take the pots back after they're sold.

I get you Min, its the same thing I've preached to other woodturners for years. Thanks.

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You will find out straight away there is no accounting for taste.Believe me when I say this from experience

You may have the ugliest pot you ever made in every way and someone will think its the best thing they ever saw.

I know this to be a truth.

Edited by Mark C.

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23 hours ago, RonSa said:

I think I'm more critical with my work than those around me. I've fired my own mixed glazes and when they come out of the kiln I say to myself "boy this is ugly" then later on a friend or family member will say to me "I really love this glaze."  Surprises the heck out of me every time.

I do take notes and I have developed a chart for myself to keep a record of each firing. It has come in handy in ways I haven't expected.

I do test tiles with everything I mix, and sometimes will also fire a pot at the same time with the same new glaze. From this I've learned that sometimes what looks good on a test tile may not look good on a pot and vise versa. The pots are usually small 1# pieces that I've practiced throwing skills on and I'm not to concerned about chucking them out later on.

By months end I will have completed 24 firings.

A funny thing just happened while I was typing this post, I received a phone call from a friend who wants to have what she calls a "Flash Exhibit" at her doctor's office this Saturday. She's invited 5 other people to show and sell their work . I mentioned to her that I didn't think my work is ready for sale and she insisted that it is. I said I would get back to her this afternoon. I know one of the other people she contact (who is a painter) and will give her a call and see what she thinks.

Trick is to smash those ugly pieces quickly before too many people see them.

Edited by C.Banks

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I ordered a pyrometer today, until that comes in I'll have to guess

I'm glaze firing today ( ^6) and I placed an extra shelf above all the pots and I have a test tile with Neil's modified  GW1214 base glaze. I plan doing as Neil and Marcia suggested with an1/2+ hold at the medium setting. I'll also turn off the down draft vent.

My question is this, should I expect the witness cones to look different than previous firings with this setup if all other things are equal as before?

 

On 12/10/2017 at 4:09 PM, neilestrick said:

3. Lift the sitter weight, push in the start button, and very gently lower the weight. The kiln will stay on if you do it gently.

4. Set all switches to 'Medium' and see how much that slows down the cooling.

On 12/2/2017 at 8:07 AM, Marcia Selsor said:

Do this at your preferred temp. say 1800 or 1900 and watch it for 1/2 an hour or more. then shut it off.

1 hour ago, C.Banks said:

Trick is to smash those ugly pieces quickly before too many people see them.

:lol:

I do that to many pots but sometimes I like the form but not the glaze. I tend to hold on to those as a reference until I can repeat the shape with a more pleasing glaze.

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The cones may drop more, depending on how slowly it cools from the peak. I cool at 175F/hr from 2232F, and that drops at least 1/2 a cone more. If you want to avoid that, crash down to 2000 before starting the cooling cycle.

Edited by neilestrick

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I just opened the kiln and was surprised how warm it still was. The extra top shelf was almost to warm to pick up and this is 19 hours after the kiln shut off and in a room that fell to 57°F overnight.

I fired to an intended ^6 and found the kiln fired up to a perfect ^7, too hot for my work IMO. This clay was on Standard 630 C/6 clay.

Bad news one pot bloated, I'm guessing from the heat? Luckily it wasn't important and it was only one pot.
Good news is my floating blue looks better.

Next time I'll set the switch to somewhere between medium and low and use a pyrometer.

Thanks everyone for your advice, I learned a lot.

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