[Clayart] Throughing thinner?

Ken Chase kchase235 at gmail.com
Thu Oct 27 19:46:53 EDT 2016


Robert:
I would love to see photos. And a photo of
The chuck you referenced. I haven't made a large bowl yet but will eventually. My bottle
Forms are nearly 12" and climbing.
Off line is fine.
Thanks much
Ken

Sent from my iPad

> On Oct 27, 2016, at 9:36 AM, Robert Harris <robertgharris at gmail.com> wrote:
> 
> I throw thin and occasionally I get warping especially on bowls the size of
> the ones Randy is talking about.
> 
> If you're having problems with deformation while the pot is plastic I would
> suggest a) throwing with less water (easier said than done!) and 2) zapping
> it with a blow torch/heatgun before you take it off the wheel.
> 3) Don't trim the base by resting such a large bowl on its rim. I throw a
> large chuck which the centre and strongest part of the bowl rests on.
> It is also important to dry these things as evenly as possible. (Slow is
> not necessarily better, just evenly). The easiest way to do this is put it
> in some sort of box with holes in it.
> 
> None of this really helps with true warpage (as opposed to plastic
> deformation) in the glaze kiln. For that there is really only one
> suggestion and one "real" solution. The first suggestion is to make sure
> your kiln shelves are dead flat - and if possible as even as possible. For
> a large bowl I put it on an extra kiln shelf that I know is flat, and level
> it with fibre or wadding (I don't go overboard on getting it level but I do
> spend a couple of extra minutes).
> 
> But the real solution is ENGINEERING! Design a bowl that can be large and
> thin and won't warp.
> 
> Everyone has a different "look" to their bowl so it's a bit difficult for
> me to advise what to do, but the most obvious thing to do is to thicken up
> your rim. Just like Susie's newspaper trick, a thicker rim will go a fair
> way to preventing warpage. You can then run into the problem that Vince
> mentioned where the pot looks lighter than it "should", however. Personally
> I throw a large flange type lip on my large bowls that is about 25 degrees
> above the horizontal. It actually has a slight curve in it that strengthens
> it, and this flange has a very thick rim on it, which is less noticeable as
> it's edge on to the viewer (the flange itself can be reasonable thin).
> 
> Also consider increasing the diameter of your foot a little. Finally make
> sure the wall of the bowl has a true taper. With the exception of the rim
> (which we've discussed and which should be well compressed!), the walls
> must be as evenly tapered to the top as possible (including the flange, if
> you have one). I once threw a bowl (about 20", wet) where the bottom 1/3
> was either the same thickness or marginally thinner than the top 1/3 and
> the whole thing just sat down around the foot! Basically if you get
> everything as even as possible (and of course this includes as little
> wobble as possible in the thrown form!) then you'll minimize the chance of
> warpage.
> 
> Finally ... try to embrace a little bit of warpage! It's a handmade pot
> after all! I have recently mentioned the diamond lap disc I have for
> smoothing off feet. With a bit of work it can flatten the foot of a warped
> bowl, so that at least there's no rocking.
> 
> Hope that helps,
> 
> Robert
> 
> P.S. I'm happy to send pictures directly of the type of large wide bowls I
> make if anyone is interested.
> 
> 
>> On Thu, Oct 27, 2016 at 8:04 AM, Susie Hite <hiteshome at bellsouth.net> wrote:
>> 
>> I don't usually comment, but I understand the desire to throw thinner.  I
>> love a lot of the Japanese pottery and it is usually thin.  I have
>> unfortunately found that when I throw thin it almost always warps.I feel
>> your pain. The few times I've been successful was when I was able to put a
>> piece of news paper over the rim as soon as it was firm enough not deform
>> the bowl, then when it was leather hard finish drying upside down.  Also
>> bisque fire upside down.  There's no guarantee it won't warp in the glaze
>> firing. =0(After all that it's still as Vince said very fragile.It's still
>> fun to try every once in a while.
>> Good Luck!!!Susie
>> 
>>    On Wednesday, October 26, 2016 9:58 PM, ran mcc <ranmcc at msn.com>
>> wrote:
>> 
>> 
>> Guess it was just a thought. Been making pottery for 40 years.  No
>> training.  No mentors.  Pretty isolated from the clay community except for
>> clay art.
>> 
>> 
>> 
>> Sent from my Verizon Wireless 4G LTE smartphone
>> 
>> 
>> -------- Original message --------
>> From: Vince Pitelka
>> Date:10/26/2016 9:06 PM (GMT-05:00)
>> To: 'Clayart international pottery discussion forum'
>> Subject: Re: [Clayart] Throughing thinner?
>> 
>> Hi Randy -
>> I am curious as to why you would want to lighten them up more.  "Too
>> light" is a real problem in functional ceramics.  Unless this is a
>> conceptual project to produce non-functional "bowls," the weight in your
>> bowls serves an important purpose.
>> - Vince
>> 
>> Vince Pitelka
>> Appalachian Center for Craft
>> Tennessee Tech University
>> vpitelka at dtccom.net
>> https://sites.tntech.edu/wpitelka/
>> 
>> 
>> 
>> 
>> -----Original Message-----
>> From: Clayart [mailto:clayart-bounces at lists.clayartworld.com] On Behalf
>> Of ran mcc
>> Sent: Wednesday, October 26, 2016 11:19 AM
>> To: ClayArt <clayart at lists.clayartworld.com>
>> Subject: [Clayart] Throughing thinner?
>> 
>> I like to throw 12lb bowls that usually will reach to 18 to 19 inches.
>> Using Red Stone from Carolina Clay.  12lb bowls will fire out to about 7lbs
>> with glaze.  I would like to get these bowls lighter in final weight.  I
>> know I can make sure the bottom is minimum thickness,  I know I can trim as
>> much as possible.  I just don't want to get warped bowls.  Are there some
>> techniques you can share to get pieces as thin and light as possible
>> without causing warping in the fire?  Suggestions on maybe a better clay
>> that will hold up better to thin throwing without warping?  Any other
>> suggestions?  Thanks for any help.
>> 
>> 
>> Randy
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