Jump to content


Photo
- - - - -

Real Time Preheating Question


  • Please log in to reply
28 replies to this topic

#1 Isculpt

Isculpt

    Inexperienced but eager

  • Members
  • PipPipPip
  • 391 posts
  • LocationSouth Carolina

Posted 24 June 2014 - 09:04 PM

I have a one-year-old electronic Olympic kiln.  I use the preset programs, always going with a slow bisque combined with a long preheat period -- usually 12-18 hours preheating at 200.  Tonight I need to rush this load a little, but I don't think it's ready for 200 degrees!  I'd like to dry the work a little faster than it can dry by just sitting in my studio (withits humidity of 85%).  It seems that PRE pre-heating the work at maybe 125 for 12 hours before I use the actual preheat program, which is 200 degrees, would be safer than jumping the temperature on the sculptures straightaway to 200. 

 

Is my logic, um, logical? And if it is, can anyone tell me how to do this?  I can't find anything in the instruction manual that tells me how to set the temperature to 125 degrees for a period of time.

 

Jayne



#2 Benzine

Benzine

    Socratic Potter

  • Members
  • PipPipPip
  • 1,655 posts
  • LocationThe Hawkeye State

Posted 24 June 2014 - 10:11 PM

You normally hold 200 for over twelve hours?!!! How thick/ wet are you wares generally, upon loading?

In my classrroom, I'll do a preheat for about four hours, which is normally adequate.
"Anything worth believing, is worth questioning"

#3 Isculpt

Isculpt

    Inexperienced but eager

  • Members
  • PipPipPip
  • 391 posts
  • LocationSouth Carolina

Posted 24 June 2014 - 10:27 PM

Benzine, My sculptures tend to be a bit organic....which is another way of saying that they decide what they're going to be as we go along.  Let's say I build a person's head, then add hair, then add feathers, then add....., well you get the idea.  The attached image of a sculpture that stands about 25" high is a good example of that.  Even though I've cut open the head and scraped it out to try to make the walls 1/4" thick, the individual ropes of hair and in this case, feathers, makes it impossible to keep to that 1/4" thickness. 

 

Also, it's VERY humid here, so nothing is every really dry.  AND, I don't have the patience to wait the 2 or 3 weeks that some folk recommend for sculptural work.  I did read yesterday's posts about using a kiln to dry wet work, but it didn't really address this kind of work........

Attached Files



#4 Mark C.

Mark C.

    Advanced Member

  • Members
  • PipPipPip
  • 2,975 posts
  • LocationNear Arcata Ca-redwood rain forest

Posted 24 June 2014 - 10:52 PM

I would keep it under 212 degress no matter what kind of work as steam is steam no matter what the work is.

The question is really hold it under 200 until the moisture is gone and that will be a direct relationship to thickness and dryness.

Your work demands a long slow preheat k.

If its paper clay it can take a bit less time I think or any clay with an aditive that loosens it up.

How tight is this clay body?

Mark


Mark Cortright
www.liscomhillpottery.com

#5 Babs

Babs

    Advanced Member

  • Members
  • PipPipPip
  • 1,080 posts

Posted 24 June 2014 - 11:35 PM

Thank you Jayne :)



#6 Isculpt

Isculpt

    Inexperienced but eager

  • Members
  • PipPipPip
  • 391 posts
  • LocationSouth Carolina

Posted 25 June 2014 - 12:05 AM

Mark, this is a raku clay body.  I chose it because I wanted a clay that was strong enough to survive my mistakes!  Also, the intention is to pit fire (well, trash can fire) my work....one of these days.  (My last pit firing was with an earthenware clay and it ended up broken into 8 pieces.  I really don't want to stand by a fire and hear that many pops and cracks every again!!)

 

Okay, I think I hear what you're saying, Mark.  I just thought that if I slowly raised the temp to 200, there would be less likelihood of fissures.  

 

 

Babs, you make me laugh.



#7 Benzine

Benzine

    Socratic Potter

  • Members
  • PipPipPip
  • 1,655 posts
  • LocationThe Hawkeye State

Posted 25 June 2014 - 08:40 AM

Jayne, Your sculptures tend to be a bit awesome...

 

That long of a preheat, still seems excessive, even if you work is a bit uneven, in regards to thickness.  I've seen some "heavy" unevenly thick Middle School work go in the kiln, but it always comes out just fine, sometimes to the chagrin of the creator, who didn't really want to have to deal with painting it...."Man, work!"

 

If the humidity is high in your area, what about creating a drying chamber of sorts.  Create a sealed chamber, hooked to a dehumidifier.  I've seen people post their method, for creating such a device.  It would save you time on your preheat.


"Anything worth believing, is worth questioning"

#8 Isculpt

Isculpt

    Inexperienced but eager

  • Members
  • PipPipPip
  • 391 posts
  • LocationSouth Carolina

Posted 25 June 2014 - 10:55 AM

Thanks for the compliment, Benzine.  I'm afraid that I've kinda screwed that piece up!  I usually add copper carbonate to get dark tones to enhance the texture, but I've been experimenting with other glazes.  Yesterday I chose Stoneware Wash from Mayco as a paint on and rub off wash, and it went too dark.  Arrrgh!  Now I'm trying to figure out how to pull it back from the edge!  

 

Benzine, That's a good idea about using a dehumidifier.  I'll search for posts on the subject... 

 

I followed Mark's lead and went ahead and set the kiln to preheat at 200 overnight.  It hasn't hurt the work!! Yaaay!  So maybe I'll follow your lead and take a chance on shortening the overall preheat that I had planned on doing.  I'm going to try checking for steam via a mirror as has been mentioned here on the forum.  Unless there is a better way?



#9 neilestrick

neilestrick

    Neil Estrick

  • Members
  • PipPipPip
  • 2,752 posts
  • LocationGrayslake, IL

Posted 25 June 2014 - 11:32 AM

The cost of preheating is so low you might as well do 12 hours just to be safe. If I put freshly trimmed pots into the kiln I usually do an 8 hour preheat to get them dry.


Neil Estrick
Kiln Repair Tech
L&L Distributor
Owner, Neil Estrick Gallery, LLC
www.neilestrickgallery.com

neil@neilestrickgallery.com

#10 Isculpt

Isculpt

    Inexperienced but eager

  • Members
  • PipPipPip
  • 391 posts
  • LocationSouth Carolina

Posted 25 June 2014 - 12:09 PM

Thanks for the validation, Neil.  Is the mirror trick the best way to know if the moisture is all out?



#11 Benzine

Benzine

    Socratic Potter

  • Members
  • PipPipPip
  • 1,655 posts
  • LocationThe Hawkeye State

Posted 25 June 2014 - 12:11 PM

Jayne, have you fired the piece with the wash yet, or it just went dark after wiping off the wash?  If it hasn't been fired, you may just need to really saturate the surface, and keep wiping.  


"Anything worth believing, is worth questioning"

#12 oldlady

oldlady

    single firing an electric kiln to cone 6

  • Members
  • PipPipPip
  • 1,022 posts
  • Locationharpers ferry west va and pinellas park fl

Posted 25 June 2014 - 10:00 PM

I am sure the experts will disagree, but I have been using the mirror for 35 or more years.  a clear piece of glass from an 8x10 picture frame is my current choice.  all peephole plugs are out and the lid is cracked 1/2 inch until about 1000 degrees.  I hold the glass at an angle at each peephole and the edge of the lid to check for steam.  lid stays up until there is none.  lid down, peeps plugged and we're off.

 

I get steam at over 900 degrees sometimes.  remember that I single fire clay and glaze on each pot.  even though I have consistent thickness in each piece, they are only as dry as air in a very humid location can get.  and there are 9 or ten shelves tightly packed.

 

though you may fire less mass,  your work is thicker and might take more time.  I think, maybe.  experts chime in here, please.


"putting you down does not raise me up."

#13 Isculpt

Isculpt

    Inexperienced but eager

  • Members
  • PipPipPip
  • 391 posts
  • LocationSouth Carolina

Posted 26 June 2014 - 02:55 AM

Benzine, the Mayco stoneware wash looked great before the piece went into the kiln.  The dark color was in each tiny, tiny groove on the feathers with the high areas between grooves wiped clean and showing the white clay.  As you can see by the photo, it didn't come out that way.  I'm guessing that the stoneware wash has to be really scrubbed off, and the feathers couldn't take that kind of abuse even after bisque firing. (?)  Odd that I could see the white clay between feather grooves before firing, though.  Ah well, live and learn.  I do like the metallic look of the wash, but I'll have to do some more experimenting before I subject another sculpture to it.  As a result of the dark wash obscuring the feathers, I have spent all day mixing a paint color that perfectly matches the original fired clay color and then painting with a super fine brush each teeny tiny, itty-bitty high ridge of each feather.  Not quite the way I planned things....!

 

Attached File  too much stoneware wash 2.jpg   148KB   1 downloadsAttached File  too much stoneware wash.jpg   135.53KB   1 downloads

 

Thanks for the input, Oldlady.  I think I have a misunderstanding of the mirror test. I was trying to decide if the pieces were ready to move past that 212 mark without blowing up.  I was testing for steam with a mirror at a temperature under 212.  Duh!!



#14 Benzine

Benzine

    Socratic Potter

  • Members
  • PipPipPip
  • 1,655 posts
  • LocationThe Hawkeye State

Posted 26 June 2014 - 07:40 AM

Jayne, personally I think that looks great!  When you said that it was dark, I was expecting it to be stained REALLY dark.  I can see, what  you are talking about, in the hair/ feather portion.  But overall, I think it has a really nice, aged look.


"Anything worth believing, is worth questioning"

#15 Biglou13

Biglou13

    Advanced beginner pottery, Advanced in other art

  • Members
  • PipPipPip
  • 1,023 posts
  • LocationNorth Florida

Posted 26 June 2014 - 12:14 PM

At 212F. Water just becoming steam, this is the lowest level water becomes steam.
I'm trying to figure out why everyone is suggesting lower temps.

Steam escaping through drier clay which is technically still open, Will cause explosions or deformity?? What damage will happen if semi dried pieces are Pre heated at 212 vs 200f

If held at lower temp 200 why not finish off at 212 to make sure....?
Caution big brother is watching.
The beige is blinding!!!!!!
The middle of the road is boring

The true sign of intelligence is not knowledge but imagination.
-Albert Einstein

#16 Benzine

Benzine

    Socratic Potter

  • Members
  • PipPipPip
  • 1,655 posts
  • LocationThe Hawkeye State

Posted 26 June 2014 - 01:00 PM

At 212F. Water just becoming steam, this is the lowest level water becomes steam.
I'm trying to figure out why everyone is suggesting lower temps.

Steam escaping through drier clay which is technically still open, Will cause explosions or deformity?? What damage will happen if semi dried pieces are Pre heated at 212 vs 200f

If held at lower temp 200 why not finish off at 212 to make sure....?

 

Preheating lower than 212 F will dry the ware, but if there were moisture left and you go to 212, said moisture will turn to steam and make its way out.  This means the ware will either crack, or explode.  

You might be OK preheating at 212, because the ware could dry enough on its way up to 212, that nothing bad would happen.  But on the the other hand, why not preheat at a temperature, where the moisture can't possibly turn to steam, and save yourself a headache?


"Anything worth believing, is worth questioning"

#17 Babs

Babs

    Advanced Member

  • Members
  • PipPipPip
  • 1,080 posts

Posted 26 June 2014 - 06:48 PM

Soooooo beautiful jayne, thank you.



#18 jrgpots

jrgpots

    The hands can express the soul

  • Members
  • PipPipPip
  • 517 posts
  • LocationHurricane, Utah

Posted 26 June 2014 - 08:03 PM

I know this is off the topic a little bit, And I know you needed a rush on this piece, So I'm sorry aread of time for asking a newbie question...BUT..

 

Would packing sodium silicate around a piece of greenware or sculture dry it out more quickly and completely?.  And would packing it around a large sculture draw more water out of the piece than if the piece were left to air dry?

 

Basically could you dry clay sculture out more completely by packing them in sodium silicate?

 

Jed



#19 Benzine

Benzine

    Socratic Potter

  • Members
  • PipPipPip
  • 1,655 posts
  • LocationThe Hawkeye State

Posted 27 June 2014 - 08:17 AM

I'm not sure on that Jed, but the fastest way that I've found to dry wares, is with a good steady airflow (fan, hair dryer, etc).
"Anything worth believing, is worth questioning"

#20 oldlady

oldlady

    single firing an electric kiln to cone 6

  • Members
  • PipPipPip
  • 1,022 posts
  • Locationharpers ferry west va and pinellas park fl

Posted 27 June 2014 - 08:54 AM

Jayne, that is a lovely sculpture.  how tall is it? 

 

is your wash just oxide and water?  or have you purchased something called a wash?


"putting you down does not raise me up."




0 user(s) are reading this topic

0 members, 0 guests, 0 anonymous users