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Please Help: What Causes Pinholes Etc In This Cone 6 Firing Set-Up?

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Hello!

 

Could anyone please give me hints on where to go next best to figure out where the following problem comes from?

 

Here are three examples of first tests made by me and my friend with glazes we found in recepy books and online, all for cone 6.

We are using an electric kiln at one workshop where we can only program a ramp with three steps and so we tried the following firing programme, while skipping the step 1 and the last one (so we had no hold on cooling and just had the kiln switch off after the 15min hold on the top temperature).

here the original firing programme: http://digitalfire.com/4sight/firingschedule/plainsman_cone_6_electric_standard_firing_schedule_114.html

 

I suspect we need a slower cooling. We can program the kiln to cool down with a constant temperature, but we can't add any hold into the programme. Any idea what would be a good temperature then?

 

We now also try to apply some of the glazes thinner.

 

Several texts I have read on the troubleshooting issues mention to lengthen the firing programme, but give no specifics about which step and how much to lengthen. Some say to use higher temperature, but doesn't give a hint in terms of how much higher etc.

 

Any advices would be highly appreciated!

Best wishes,

Martin

If you skipped step1, this meant the kiln went as fast as it can to step 2.  That would not be a good idea as the kiln could have been going at 500 deg per hour or more  and anything could have happened to the glaze as it tried to adhere to the pot.  I am wrong as to what I said about this glaze.  It does have a lot of flux and doesn't fit in cone 6 limits.  I fired it using EPK instead of OM4 ball clay to cone 06, it was a very dry white surface no blemishes, than fired to cone 4 still a dry white surface, then to cone 6 still white but not quite as dry a surface, cone 8 still dry off white matte.  Please post the firing schedule used.

David

 

 

Hello David,

 

the 1st step in our schedule is identical with the second one in the linked schedule, so we start from 0 and go with 166°C/hr to 945... Do you think that's too fast then? I'm sure it won't take too much more energy if we drop it slower, but again, it's a wild guess for me in terms of how much to drop it.

 

Thank you!

M

 

Thanks for the information.  I don't think that is the problem although most people want to make sure all the water is out of the glaze, therefore the first segment is used.  I never could get this glaze to become a good surface even firing to Cone 8, too dry.  I am afraid it is your clay.  To be sure try a small like 100 gram batch of the glaze I gave you if you have the materials, make sure it is dry before firing that fast.  If you don't have the frit tell me what frit you use and maybe I can redo the glaze for you.

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Hello!

 

Could anyone please give me hints on where to go next best to figure out where the following problem comes from?

 

Here are three examples of first tests made by me and my friend with glazes we found in recepy books and online, all for cone 6.

We are using an electric kiln at one workshop where we can only program a ramp with three steps and so we tried the following firing programme, while skipping the step 1 and the last one (so we had no hold on cooling and just had the kiln switch off after the 15min hold on the top temperature).

here the original firing programme: http://digitalfire.com/4sight/firingschedule/plainsman_cone_6_electric_standard_firing_schedule_114.html

 

I suspect we need a slower cooling. We can program the kiln to cool down with a constant temperature, but we can't add any hold into the programme. Any idea what would be a good temperature then?

 

We now also try to apply some of the glazes thinner.

 

Several texts I have read on the troubleshooting issues mention to lengthen the firing programme, but give no specifics about which step and how much to lengthen. Some say to use higher temperature, but doesn't give a hint in terms of how much higher etc.

 

Any advices would be highly appreciated!

Best wishes,

Martin

If you skipped step1, this meant the kiln went as fast as it can to step 2.  That would not be a good idea as the kiln could have been going at 500 deg per hour or more  and anything could have happened to the glaze as it tried to adhere to the pot.  I am wrong as to what I said about this glaze.  It does have a lot of flux and doesn't fit in cone 6 limits.  I fired it using EPK instead of OM4 ball clay to cone 06, it was a very dry white surface no blemishes, than fired to cone 4 still a dry white surface, then to cone 6 still white but not quite as dry a surface, cone 8 still dry off white matte.  Please post the firing schedule used.

David

 

 

Hello David,

 

the 1st step in our schedule is identical with the second one in the linked schedule, so we start from 0 and go with 166°C/hr to 945... Do you think that's too fast then? I'm sure it won't take too much more energy if we drop it slower, but again, it's a wild guess for me in terms of how much to drop it.

 

Thank you!

M

 

Hi Martin

I tried firing the glaze at your temperature rate and there was no problem except that  cone 6 was started but not down and probably it needed a 23 minute soak.  The glaze is a dry white and not a good glaze.  I also wonder if maybe one or more ingrediants was contaminated, this can happen in an open studio, it has happened to me in the past.

Hope you have a chance to try the glaze I sent you.

David

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I tried firing the glaze at your temperature rate and there was no problem except that  cone 6 was started but not down and probably it needed a 23 minute soak.  The glaze is a dry white and not a good glaze.  I also wonder if maybe one or more ingrediants was contaminated, this can happen in an open studio, it has happened to me in the past.

 

Hi Martin

Hope you have a chance to try the glaze I sent you.

David

 

 

Hello David,

 

I have to say I'm really amazed by all the great help and care in this forum (which I registered to just recently). I will definitely try the recipe you posted and let you know how it went. I can confirm the glaze is dry on white clay pots and I wasn't sure whether it wasn't somehow relating to the firing programme. I live in Germany, but I recently got 3134 and 3110 so I will be able to work with few glazes I wasn't able to mix with mostly american recipes.

 

Have a great day!

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Here are actually few results with the first test glazes we did with my friend and applied on our very first pots. We actually like the coral looking results on the outside, but we definitely need to get some good liner and more knowledge about why the glazes came out this way to work the way we want...

 

post-71183-0-45749600-1444773201_thumb.jpg

 

post-71183-0-50092900-1444773203_thumb.jpg

 

post-71183-0-01448300-1444773207_thumb.jpg

post-71183-0-45749600-1444773201_thumb.jpg

post-71183-0-50092900-1444773203_thumb.jpg

post-71183-0-01448300-1444773207_thumb.jpg

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Here are actually few results with the first test glazes we did with my friend and applied on our very first pots. We actually like the coral looking results on the outside, but we definitely need to get some good liner and more knowledge about why the glazes came out this way to work the way we want...

 

attachicon.gifdungeontt-teapot1.jpg

 

attachicon.gifdungeontt-teapot2.jpg

 

attachicon.gifdungeontt-teapot4.jpg

How thick do you apply the glaze, any binders or suspension materials? The clay fires from cone 5.5 to 9. you are firing at the low end.  Fill one of your test pieces with water and place it on a napkin look at it the next day, it may leak at the temperature you fire to.  It has a high water absorption even at cone 9.  Does any glaze fit properly?

David

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Here are actually few results with the first test glazes we did with my friend and applied on our very first pots. We actually like the coral looking results on the outside, but we definitely need to get some good liner and more knowledge about why the glazes came out this way to work the way we want...

 

attachicon.gifdungeontt-teapot1.jpg

 

attachicon.gifdungeontt-teapot2.jpg

 

attachicon.gifdungeontt-teapot4.jpg

How thick do you apply the glaze, any binders or suspension materials? The clay fires from cone 5.5 to 9. you are firing at the low end.  Fill one of your test pieces with water and place it on a napkin look at it the next day, it may leak at the temperature you fire to.  It has a high water absorption even at cone 9.  Does any glaze fit properly?

David

 

 

Hello David, I will test that! Since I'm really new to pottery, how do I generally find out the ideal firing range for clay body? They only inform about the max temperature in the shop...

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Here are actually few results with the first test glazes we did with my friend and applied on our very first pots. We actually like the coral looking results on the outside, but we definitely need to get some good liner and more knowledge about why the glazes came out this way to work the way we want...

 

attachicon.gifdungeontt-teapot1.jpg

 

attachicon.gifdungeontt-teapot2.jpg

 

attachicon.gifdungeontt-teapot4.jpg

How thick do you apply the glaze, any binders or suspension materials? The clay fires from cone 5.5 to 9. you are firing at the low end.  Fill one of your test pieces with water and place it on a napkin look at it the next day, it may leak at the temperature you fire to.  It has a high water absorption even at cone 9.  Does any glaze fit properly?

David

 

 

Hello David, I will test that! Since I'm really new to pottery, how do I generally find out the ideal firing range for clay body? They only inform about the max temperature in the shop...

 

Hi Martin,

The clay I use says cone 10,  I fire to cone 9 down with cone ten starting in a gas kiln.  I use the same clay for electric kiln firing and fire it at cone 7 and the clay doesn't leak water at cone 7 but will leak at cone 5 and 6.  This will not help solve the blistering problem you now have which could be caused by the bisque firing program, not taking enough time between 1000 deg F and 1200 deg F, which will help burn out all the organic material. 

David

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Hi Martin,

The clay I use says cone 10,  I fire to cone 9 down with cone ten starting in a gas kiln.  I use the same clay for electric kiln firing and fire it at cone 7 and the clay doesn't leak water at cone 7 but will leak at cone 5 and 6.  This will not help solve the blistering problem you now have which could be caused by the bisque firing program, not taking enough time between 1000 deg F and 1200 deg F, which will help burn out all the organic material. 

David

 

 

Ok! I will ask at the workshop, how they have the bisque firing set up. The bisque is done the same for everyone working there and the second firing is the only one I can set myself.

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