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Different Shrinkage Of Glazes In One Piece


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#21 Min

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Posted 17 March 2017 - 08:33 PM

  In the glaze fire: the most important firing schedule in this case would be the last 120F: which I would slow down to 60F an hour with a short hold. Getting the clay mature is the most important issue in this case: and then find a glaze that matches the peak temp and the body.

 

Nerd

 

Unless I misread what Infinite said I don't think it can be fired at that speed. Sounded like the only option was full on after hitting 600C. Before then only 4 ramp options, 60C being the lowest. I was suggesting slowing down towards the end of both the bisque and glaze but I don't think it can be done with her kiln. 



#22 Infinite

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Posted 18 March 2017 - 02:02 AM

Hi Min,

 

you are correct.

 

(I'm sorry to all of you if my messages aren't as clear as they should be due to my not-so-perfect English -_-)

 

Yesterday I also contacted my local supplier from which I bought the clay. They said that I bisc fire too high and that 985 should be the best temperature for the glaze to stick onto the bisc...

 

I also contacted my former teacher from art school and he advised also to rise the final temp, and said that most commercial glazes will hold when overfired (his experience) but that the colour can change.

 

So being the stubborn curious Dutch woman I am, I've made a testbatch with several mugs and glazes combined with the yellow matt glaze, just to see what happens (learningprocess) but now i'm firing upto 1120 (1140 is the limit temp of the clay) degrees celcius.

 

to be continued....


Form is the possibility of structure -tractatus logico; Ludwig Wittgenstein-


#23 High Bridge Pottery

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Posted 18 March 2017 - 08:42 AM

What the supplier is saying isn't related to your final glaze problem. You can bisque to a lower temperature so the clay is more porous and sucks up more glaze. If you have no problems with applying glaze then keep doing the same thing. 

 
The glaze may be fine up to 1120, the odds are probably on your side but I don't know if it will fix the issue that it doesn't fit the clay.

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#24 Min

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Posted 18 March 2017 - 10:59 AM

Did your supplier recommend another glaze to fit that clay or did they say your current glazes should fit when fired to clay maturity temp?

 

I would put the test pieces on scraps of clay and/or don't glaze within a few cm's of the bottom outside of the pots. You might get running glazes so the scrap saves glaze melting onto your kiln shelves. The matte glazes might be okay as I think they are underfired gloss glazes since they are matte without a slow cooling kiln. May see blisters. Also, if any survive without shivering I really would do the testing I mentioned a few posts ago with freezing/boiling.

 

"So being the stubborn curious Dutch woman I am..."  

 kinda think you have to be stubborn to succeed in ceramics, so many things that can go wrong. If you aren't stubborn it would be so easy to just give up. I know I can definitely be stubborn, obstinate, headstrong, willful, pigheaded, contrary, strong-willed, well you get the idea. ;)



#25 Infinite

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Posted 19 March 2017 - 08:49 AM

Just opened the kiln and to my surpise and relieve everything was still in one piece and looks good zo far! I'm so happy ^_^

No cracks so far, colour looks ok, no runny glaze on the kiln shells. I've used a white shiny glaze on the inside of the cups as reccomended in this topic (thanks) and added 'rutiel/rutile'.

 

 

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The mugs are currently in the sink, undergoing a boiling-water-tea-test.  :)  fingers crossed :)
 
Big kiss on the cheek to you guys!

Form is the possibility of structure -tractatus logico; Ludwig Wittgenstein-


#26 Min

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Posted 19 March 2017 - 01:26 PM

Glad it seems to be working out  :)






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