[Clayart] sawdust instead of straw in primitive kiln

paul gerhold gerholdclay at gmail.com
Mon Apr 4 23:41:58 UTC 2022

Yes I probably should have said that considering weight and strength and heat transfer  clay is a really poor choice as a means of making a mug to retain  heat.  Clay will never match my Yeti mugs at retaining heat and cold.


Sent from my iPad

> On Apr 4, 2022, at 7:12 PM, Robert Harris <robertgharris at gmail.com> wrote:
> Paul, at first I thought I completely agreed with you.
> And then I realized you hadn't really thought through what you were saying.
> If you think about the vacuum flask, it was first made from mirrored glass,
> then more recently steel. And both of those are even worse at reducing heat
> transfer than ceramic. (Especially when we consider earthenware).
> Now whether it's worthwhile for an anachronistic maker of handmade potter
> to do it is another matter. Material is a poor argument however. And since
> we are anachronisms (from an efficiency point of view), why the hell not
> try?
> A friend of mine just sent me a picture of a commercial, slipcast, double
> walled mug that he bought his wife recently. No handle necessary for piping
> hot coffee. So it's obviously neither difficult nor cost prohibitive.
> (Obviously the interior was conical to provide easy release from the mold,
> so there will be limitations to shape).
> Robert
>> On Mon, 4 Apr 2022 at 13:30, paul gerhold <gerholdclay at gmail.com> wrote:
>> Too much effort in an attempt to make clay do something it really isn't
>> ever going to be good at. Clay can make a great coffee or tea mug but it
>> isn't ever going to be the best material for reducing heat transfer.
>> Paul
>> Sent from my iPad
>>>> On Apr 4, 2022, at 7:26 AM, David Woof <woofpots at hotmail.com> wrote:
>>> Hi Ron, Everyone,
>>> Also, with a bit of good clay, manual dexterity and finesse one can
>> learn to throw a double walled pot with insulating "dead air space" between
>> at a single throwing.
>>> Not a new idea, but often forgotten or disregarded as too difficult to
>> master in "precious" time one allows.
>>> Not so!  Sit down..relax and by the second or third attempt "ya gets it"
>>> Misneach,
>>> Woof....who ain't afraid to try.........If at first you don't
>> Fricassee.......fry, fry a hen!!!
>> *****************************************************************************
>>> ________________________________
>>> From: Clayart <clayart-bounces at lists.clayartworld.com> on behalf of
>> ronroy at ca.inter.net <ronroy at ca.inter.net>
>>> Sent: Sunday, April 3, 2022 10:45 AM
>>> To: Clayart international pottery discussion forum <
>> clayart at lists.clayartworld.com>; L TURNER <magnolia.mud.list at gmail.com>
>>> Subject: Re: [Clayart] sawdust instead of straw in primitive kiln
>>> You can also put two pots together with an air space between. I've
>>> seen this done with slip cast forms. I'm thinking, if ones repeatable
>>> throwing skills are good, it could be done.
>>> Certainly would eliminate the need for handles.
>>> RR
>>> Quoting L TURNER <magnolia.mud.list at gmail.com>:
>>>> Robert,
>>>> (I fire at cone 10 gas reduction).
>>>> I have been playing with laminated clay bodies.    using a standard
>> cone 10
>>>> clay body and applying a mixture of kaolins only as a paste for the
>> outer
>>>> layer.  The outler layer fired to cone 10 is still absorbant (aka: has
>> fine
>>>> holes in the kaolin layer).   so far, I have no problem with the
>> interface
>>>> of the two layers.  For thrown ware, I apply the tacky (but not a slip)
>>>> kaolin paste to the form near the final step of throwing.  On handbuilt
>>>> ware the paste is added after the form is completed.
>>>> If you were to use a similar layer between your inside surface clay body
>>>> and your outside clay body, you might get the "insulation for hot
>> drinks"
>>>> you were looking for.
>>>> If you are using a mid temperature clay body, then use a high fire
>> course
>>>> clay body for the middle layer, or just use the sawdust clay as a middle
>>>> layer.
>>>> LT
>>>>> On Sat, Apr 2, 2022 at 6:55 AM Robert Harris <robertgharris at gmail.com>
>>>>> wrote:
>>>>> I've put sawdust in clay. Biggest problem is that it caused serious
>>>>> pinholing in the glazes. Otherwise it fired just fine.
>>>>> Obviously it depends how much you put in! (My aim was to produce a
>> piece
>>>>> with enough air gaps that it would provide insulation for hot drinks,
>>>>> didn't really work).
>>>>> We also wad all of the posts in our kiln, even in a regular reduction
>>>>> firing, and we use sawdust (about 25-30% by weight which is probably
>>> 60%
>>>>> by volume), makes the wadding just crumble right off.
>>>>> Not sure what your aim is, by adding sawdust.
>>>>> The long fibers in paper help stabilise the clay, but sawdust won't
>> provide
>>>>> that.
>>>>>> On Fri, 1 Apr 2022 at 11:29, Carolyn Curran <cncpots2 at gmail.com>
>> wrote:
>>>>>> My inarticulate bad.   Sorry I confused you.  I intended to add
>> sawdust
>>>>>> IN  the clay body along with vermiculite or perlite and grog...sort
>> of a
>>>>>> paper clay situation, since straw and sawdust both  have cellulose.  I
>>>>>> would probably wet it so there won't be particles flying through air.
>>>>>> With my  COPD and chronic bronchitis,  I  don't think I'd play with a
>>>>>> sawdust firing, although we have a trash can with holes here that was
>>>>>> probably used in that way.  (Heck,  I only use   non toxic iiquid
>>>>>> combustibles  for any raku..have a bottle of
>>>>>> high test  Everclear booze for the purpose, use sparingly at bottom of
>>>>>> combustion chamber..  I have had great success with the alcohol with
>>>>> small
>>>>>> scale work in  old Aim test kiln with one vase almost 8" tall which
>> was
>>>>>> super unique in  subtle coloration. It is still a  big favorite.
>>>>> Carolyn)
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>>> Ron Roy
>>> ronroy at ca.inter.net
>>> Web page ronroy.net
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