Jump to content


Photo
* - - - - 1 votes

Crack In Finished Bowl ?


  • Please log in to reply
46 replies to this topic

#21 bciskepottery

bciskepottery

    Advanced Member

  • Members
  • PipPipPip
  • 1,255 posts

Posted 01 November 2013 - 10:07 PM

Looks like dunting during cool down of the bowl, possibly compounded by thicker glaze pooling in bottom of bowl vs. glaze thickness on sides and/or thicker bottom vs. thinner sides.  Could also be a difference in glaze thickness from glaze on the outside of the bowl vs. glaze on the inside. 

 

Are you constructing the ware so that there are stress points that will crack (seems to be part of the look you are trying to achieve)?  If so, you might be setting the stage for these types of cracks/dunts when fired. 



#22 Babs

Babs

    Advanced Member

  • Members
  • PipPipPip
  • 534 posts

Posted 02 November 2013 - 01:39 AM

Being a peasant potter myself, I wsn't commenting on getting a pristine, smooth pot. I am also self taught so experiment is my method... If the edges of  of the cracks are sharp ie glaze looks like it is sharp then I think your pots are subjected to a rapid cooling at crucial times. Some one technical can tell you which temps the ware is sensitive to a rapid cool.

Love your pots.



#23 cgb

cgb

    Advanced Member

  • Members
  • PipPipPip
  • 42 posts
  • LocationMile High

Posted 02 November 2013 - 01:42 AM

Someone had asked me if the kiln was fully cooled down prior to the pieces being removed........I have no idea....but the pots are unloaded to an outside area immediately and that temp could be as low as 30 degrees, its outside.

I am rolling thinner than most ppls........very few pots that I construct.......have planned stress points. Brown pot photo above had many areas that could have cracked....but by some amazing miracle...........no cracks......maybe no mishandling in green ware, bisque or fired state...........I personally do not handle the piece through all the stages.......that is impossible.......my fees pay for that....

No, lol, I am not trying to create pots with serious cracks :) There is a sign in the studio (which is a gov taught facility ) "Careful with other's pots, the next pot cracked, may be your own"



#24 cgb

cgb

    Advanced Member

  • Members
  • PipPipPip
  • 42 posts
  • LocationMile High

Posted 02 November 2013 - 01:48 AM

Oh, its fine Babs...........I am in love with a very primitive look.........am in a studio taught by a very talented skilled woman.....but I like to go my own route....I think that's the whole wonder and joy of clay. I could try rolling a little bit thicker and see if that changes anything.....like fewer serious cracks........the other odd thing is that the pots once home develop new cracks or problems......more temp changes?......the gas fired pieces are removed to the outside air.....then I bring them home into the heat.......so.....

at any rate do you have your works and pots in the subscribers gallery...? I would love to see them....:)



#25 Babs

Babs

    Advanced Member

  • Members
  • PipPipPip
  • 534 posts

Posted 02 November 2013 - 03:28 AM

Yeh, didn't mean to offend, just trying to work out the reason. If part of your pots are sticking to dirty shelves then when the rest of your pot moves during firing, the stuck section cannot and so another area of stress as it expands during heating and contracts during cooling. Opening the kiln before it cools to about 200degs celsius will also crack ware.

Will get around to posting pots but that part of life gets neglected for the doing stuff.

Meant cracks, check out wabi sabi pots now that is seriously seeking breakdown.. ;)



#26 cgb

cgb

    Advanced Member

  • Members
  • PipPipPip
  • 42 posts
  • LocationMile High

Posted 02 November 2013 - 05:17 PM

wabi sabi? on this site or google, will try both :)))))) no offense taken....at all..........take care and hope to see your work soon!



#27 Babs

Babs

    Advanced Member

  • Members
  • PipPipPip
  • 534 posts

Posted 02 November 2013 - 05:50 PM

The Guru John who reads all we write and then shines a bright light of reason onto our problems prob knows where to find them online. But googling will get you there.

Still cracking after home  that's a lot of stress.  Had pots pinging for days but cracking is a whole different level of tension! Well done!  I see a pttery in action exhibition coming your way!



#28 cgb

cgb

    Advanced Member

  • Members
  • PipPipPip
  • 42 posts
  • LocationMile High

Posted 03 November 2013 - 12:26 AM

if I were able to make a distinctive tiny crack consistently in the same place on each piece that would align with  the deliberate chip during the Endo period............I really like the concepts involved in Hagi ware......I dislike completely perfect bowls, cups, etc.....I have always wanted an imperfection to show humanity.........to make a mark on time itself..........wabi sabi..............the idea of filling cracks with gold is very appealing.......the stress crack of use and years  showing the suffering and acknowledgement of the suffering by a precious metal.......beautiful......idea and implementation............



#29 cgb

cgb

    Advanced Member

  • Members
  • PipPipPip
  • 42 posts
  • LocationMile High

Posted 03 November 2013 - 12:36 AM

Babs, thnx again.........I think I had the lock or accidentally made the lock......deliberate fissures in bowl......and you gave me the key.....wabi sabi :)))))))



#30 cgb

cgb

    Advanced Member

  • Members
  • PipPipPip
  • 42 posts
  • LocationMile High

Posted 03 November 2013 - 01:00 AM

extra wabi, perhaps not enough sabi......... :))))))))))))) early in the year I tried a yunomi.....that simple form so difficult

no cracks ............the vase has a very mediocre color.........too washed out......not enough glaze

Attached Files



#31 Frederik-W

Frederik-W

    Advanced Member

  • Members
  • PipPipPip
  • 291 posts
  • Locationa distant moon of Uranus

Posted 03 November 2013 - 06:53 AM

I would also say that your bowl rim is quite thin, and that you are probably pushing the limits for that type of clay for that thickness. The crack is consistent with the normal force on the rim - i.e sagging outward and down and a rim would tend to tear like that if it is too thin and not "elastic" enough.

Do you perhaps work your clay when it is a bit dry and beyond its stretching limit? It can cause small hairline cracks that become worse during firing.

Some clays can handle a lot of thermal shock (Raku clay) and is resistant to cracking.



#32 Babs

Babs

    Advanced Member

  • Members
  • PipPipPip
  • 534 posts

Posted 03 November 2013 - 03:50 PM

Good luck with your pots.

A kiln of your own where your thin pots are not placed i within a stack of heavier wares and all the rest discussed would be the way to go. Small single phase kilns are available.

Yeh upright and contained shapes tend to be more forgiving . Know your clay limits and techniques reqired then go bend them!!! Clay is an unforgiving medium and it has a memory....

Great images.



#33 cgb

cgb

    Advanced Member

  • Members
  • PipPipPip
  • 42 posts
  • LocationMile High

Posted 03 November 2013 - 06:21 PM

I would also say that your bowl rim is quite thin, and that you are probably pushing the limits for that type of clay for that thickness. The crack is consistent with the normal force on the rim - i.e sagging outward and down and a rim would tend to tear like that if it is too thin and not "elastic" enough.

Do you perhaps work your clay when it is a bit dry and beyond its stretching limit? It can cause small hairline cracks that become worse during firing.

Some clays can handle a lot of thermal shock (Raku clay) and is resistant to cracking.

er which one, the first complaint.......yeah, but check out the brown one, with the glaze streaks....deliberate......its thinner......no working dry :)



#34 cgb

cgb

    Advanced Member

  • Members
  • PipPipPip
  • 42 posts
  • LocationMile High

Posted 03 November 2013 - 06:28 PM

Good luck with your pots.

A kiln of your own where your thin pots are not placed i within a stack of heavier wares and all the rest discussed would be the way to go. Small single phase kilns are available.

Yeh upright and contained shapes tend to be more forgiving . Know your clay limits and techniques reqired then go bend them!!! Clay is an unforgiving medium and it has a memory....

Great images.

Thank you again :) Rules bending is one of my favorite aspects of life and clay.........have to wait until spring for gas kiln.......maybe longer....have a beautiful day....oh, and splash of shino did exactly what I wanted.........firery

Attached Files



#35 Babs

Babs

    Advanced Member

  • Members
  • PipPipPip
  • 534 posts

Posted 04 November 2013 - 03:01 AM

Rich stuff there, who knows what you'll dream up over winter!! Big wabi sabi soup bowls, held in hand kind!! friend who made semi circular pots then inverted them, picked them up with a couple of finger s and thumb when they were still a bit soft ___ personal soup/rice bowls  nice! Had to empty them before setting them down, no prob for the hungry..  Left rims unglazed and fired them inverted, luscious interiors.

Good luck.



#36 oldlady

oldlady

    firing an electric kiln to cone 6

  • Members
  • PipPipPip
  • 673 posts
  • Locationharpers ferry west va and pinellas park fl

Posted 10 November 2013 - 07:49 PM

MAY NOT BE white glaze, just a thick area of one of the glazes you used.  did you hold the bowl upside down while glaze dripped off?


"putting you down does not raise me up."

#37 cgb

cgb

    Advanced Member

  • Members
  • PipPipPip
  • 42 posts
  • LocationMile High

Posted 10 November 2013 - 09:47 PM

I do not recall, most likely not held upside down............one of the glazes was chun



#38 Babs

Babs

    Advanced Member

  • Members
  • PipPipPip
  • 534 posts

Posted 10 November 2013 - 10:25 PM

Thick drip of  glaze, many glazes become more opaque when applied thickly



#39 cgb

cgb

    Advanced Member

  • Members
  • PipPipPip
  • 42 posts
  • LocationMile High

Posted 11 November 2013 - 02:18 PM

ahhhhhhhhhh........too bad it looks like it was left in a room that was being painted.......I usually apply thin, thin, very much so..........well perhaps next time I can get a piece that does not have a major problem :)

Thanks for writing Babs......



#40 Babs

Babs

    Advanced Member

  • Members
  • PipPipPip
  • 534 posts

Posted 12 November 2013 - 08:34 PM

Major problem!! I think it brings the white froth on waves to mind, bit of surf up on yur pot!! Just shows you again that you are not in control! :D  






0 user(s) are reading this topic

0 members, 0 guests, 0 anonymous users