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SOfirst time event for old potter.

I packed kiln with mugs and bowls. Yes a different glaze but also same clay same ish design old tried and true glaze on half the mugs. some mugs had additions of clay molded pieces attached also.

Kiln and scheduled for usual ramping. c 6 firing finishing at 8.30 a.m. one top bung left out.

2 a.m. , I am an old potter used to manually turning up every hour, kiln temp. 480deg. Power out sometime between then and 6.30a.m...no alarm to awaken the sleeping potter..temp 350degC..reprogrammed kiln to go up to 1100 at150C/hr and then usual schedule of 80dc/hr to end and a 15 hold. top bung in.

Folk have said it's ok to go this fast , right? I never have before.

Result I have12 whole mugs out of 40. rest have a BEAUTIFULLY horizontal crack in middle of handle starting from underside of handle , not quite through the handle so it looks whole from above.Crack is sharp. Second cooling v. slow, finished firing sunday arvo, opened last night.

Occurring in both designs and both glazes

Bowls crack straight across bottom.

ah it's never boring!

 

20190520_185427.jpg

20190520_185506.jpg

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That's my thoughts. cold night top bung out.. occurred throughout the kiln....more good ones lower down. but still cracks bottom shelf top loader...

I usually fire first ramp 100degC to 600

then 150 to 1100. only change I did...

can't even repeat it to check.ha!

 

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Wouldn't want to repeat it!  I tried a slow fire to cone 5 yesterday and it was an hour shorter than my fast fire to cone 5, so I don't really know what I'm going to find when I get home from work tonight... I could open it up and see a bunch of nice pieces... Or open it up and start throwing things... Hopefully somewhere in the middle as usual hah.  36 mugs and a vase.

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Really interesting handle crack, sort of opposite of normal. Usually we see the highest stressed area crack first which would be the outside of the handle. These appear to have been influenced by the cup body itself. One thing, great handle attachments they were able to resist a rotational moment!

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I truly have not come to terms with this in my head except to say the handle shrunk significantly more than the body and exceeded the tensile strength of the clay pulling itself apart. Everything is so sturdy and well done that it is an interesting failure.

Edited by Bill Kielb

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My kiln load was a bust, total dookie, not a single piece looking good.  I thought the longer bisque might eliminate some issues with this glaze I am using, but instead it just over fired.  I knew when I was glazing it was going on pretty thin, and it was.  Gross thin zinc glazes yuck.  I'll try reglazing but I have some pretty low hopes.  

They can't all be winners, right?

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10 minutes ago, liambesaw said:

They can't all be winners, right?

I admire how pragmatic so many of you are when a clay-tragedy strikes.  If I get a crappy outcome, I am half heart broken. If I drop a bin and  shatter some of my best stuff, I want to crawl in a hole and have a pity party. The only thing that has helped was that I was taught---on a very philosophical/zen-ish level, by an artist I respected---that I should never  robe myself with the arrogance of thinking that my stuff is "precious". That sticks with me just enough to take some of the sting out when things go awry.   

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13 minutes ago, LeeU said:

I admire how pragmatic so many of you are when a clay-tragedy strikes.  If I get a crappy outcome, I am half heart broken. If I drop a bin and  shatter some of my best stuff, I want to crawl in a hole and have a pity party. The only thing that has helped was that I was taught---on a very philosophical/zen-ish level, by an artist I respected---that I should never  robe myself with the arrogance of thinking that my stuff is "precious". That sticks with me just enough to take some of the sting out when things go awry.   

Don't get me wrong, I see 36 mugs and a vase in terms of time and effort spent, but what can I do about it? Well, next time I'm not gonna use that schedule, that's for sure!  All I can do is learn and move on.  Yes there is a certain arrogance in wanting the things you make to be perfect.  The things you make are a reflection of you, so they should be important.  Nothing wrong with that, but at the same time there's nothing that can be done.  Shikata ga nai my wife would tell me, or c'est la vie, or it is what it is. My 5 year old would be quick to tell me "you git what you git and you don't throw a fit".

Anyway, back to the drawing board for me and Babs, let's see if we can't make our next firing our best.

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1 hour ago, Bill Kielb said:

I truly have not come to terms with this in my head except to say the handle shrunk significantly more than the body and exceeded the tensile strength of the clay pulling itself apart. Everything is so sturdy and well done that it is an interesting failure.

well I may learn something when I fire the 2 remaining mugs made in the same way. 

Benzine I have had handles crack and pul away from mug body when handle has dried too fast, even waxed and wrapped handles in ceram wrap in hot weather. 

nothing like that in this batch.  Scratching my head on this one. Can't even sue power co. Outage due to lightning storm. in fact my heart dropped on reading the Fail message. Thought I may have cooked the power box of kiln..so that is  part of my placid acceptance of these mugs. Though not much u can do..

Ha Do you think Spooze will do the trick???:-))

.Drill out. succulents in I guess..

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28 minutes ago, liambesaw said:

Don't get me wrong, I see 36 mugs and a vase in terms of time and effort spent, but what can I do about it? Well, next time I'm not gonna use that schedule, that's for sure!  All I can do is learn and move on.  Yes there is a certain arrogance in wanting the things you make to be perfect.  The things you make are a reflection of you, so they should be important.  Nothing wrong with that, but at the same time there's nothing that can be done.  Shikata ga nai my wife would tell me, or c'est la vie, or it is what it is. My 5 year old would be quick to tell me "you git what you git and you don't throw a fit".

Anyway, back to the drawing board for me and Babs, let's see if we can't make our next firing our best.

Nice approach to things. My greatest learning comes from failure if I let my brain slow down enough to think through it and not be too distraught. Sometimes takes a day or two or three though.

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That's the challenge of making functional kitchen ware.  It really has to be perfect.  A small dimple and you can use it yourself, but it probably can't be sold.  It doesn't take much for it to be unusable.  My planters, on the other hand, are almost always usable.  My seconds, I either use myself, give away or trade for plants.  My plant collection features the worst examples of amateur pottery in the history of mankind.    I admire the level of skill it takes to consistently make salable dinnerware.  The downside is that I have a tremendous amount of freedom in the studio.  I just know I'm not really very good at it.  

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 hulk no crazing I can see and no clear glaze.

 

top and inside Alabama rain. mins version on some also cracked.

lower third a black satin matte. .

where are you seeing crazing hulk? I'll study them again.

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1 hour ago, Babs said:

top and inside Alabama rain. mins version on some also cracked.

Babs, did you test my low COE version of this glaze for dunting before using it? Like I mentioned when I posted the recipe it really is a low COE version of the original Alabama glaze. Is it a sharp crack across the bottom of the bowl? Could very well be dunting from a mismatch of glaze and clay if that's the case. Could you post the other glaze recipe that you used?

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yes min. I then used both your version and the original....on these mugs

AND I also used a glaze I have used for yonks on other mugs with the same cracking of handle.

I do wish I had studied the position of the survivors prior to picking them out of kiln..mind on other side....wjich ones were broken..

Edited by Babs

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In the pics, looks to me that the lighter part - Alabama rain - has crazing, however, you'd see it in real life it was. The test tile pic you just posted tells the tale, aah, an' that rutile!

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Babs, I have seen handle cracks like that from poor drying. It used to happen to me in the earlier years where I would put the handle on to a pot that was pretty wet, and figure they would dry together. .. .right!WRONG! The pot would dry slower than the handle because of all the open air around the handle as compared to the mug body. In the end, I would get hairline cracks so fine that I did not see them until after glaze firing. Then they would be cracked quite visibly, and when breaking off the handle parts they would show the glazed edges in the crack areas. If it had been in the glaze firing it would have been from the final firing itself. Take a look, let us know.

 

best,

Pres

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7 minutes ago, Pres said:

Babs, I have seen handle cracks like that from poor drying. It used to happen to me in the earlier years where I would put the handle on to a pot that was pretty wet, and figure they would dry together. .. .right!WRONG! The pot would dry slower than the handle because of all the open air around the handle as compared to the mug body. In the end, I would get hairline cracks so fine that I did not see them until after glaze firing. Then they would be cracked quite visibly, and when breaking off the handle parts they would show the glazed edges in the crack areas. If it had been in the glaze firing it would have been from the final firing itself. Take a look, let us know.

 

best,

Pres

may have hit on it Pres..I threw softer clay...hands aching... but winter here and all cold damp. etc but handles may still have been quicker on the dry. handle clay I usually and did apply firmer than the pot getting the handle.. larger bowls I threw a week ago just turned, but I'll make another batch of mugs after the weekend, ah never boring

nice to read someone else had similar cracking:-//

as said to Benzine, attachment on mug usual place of cracking...

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31 minutes ago, Hulk said:

In the pics, looks to me that the lighter part - Alabama rain - has crazing, however, you'd see it in real life it was. The test tile pic you just posted tells the tale, aah, an' that rutile!

yeh futile rutile and fickle nickel. who needs them!

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