Sam Kelly on wed 9 jul 08
hi to all, first posting so i hope I have it right.
I made up some clay from raw materials to use on the wheel.
BallClay 65
China Clay 20
Silica 15
it worked fine on the wheel however there is a problem with wedging,
it wants to break up
when using the rams head method, push down, roll and it breaks into 2
pieces. Any ideas
on modification?
Ivor and Olive Lewis on thu 10 jul 08
Dear Sam Kelly.
Two points, one which you may have overlooked.
Your clay is short. This can be corrected by slaking your ingredients
in an excess volume of water then thoroughly mixing before dewatering
.
You need to allow time for the plastic structure to develop before
dewatering. Do not dewater by spreading the slop over Plaster (Calcium
sulphate) bats. Instead, put it in some sort of cloth sack (I use
Hessian) and allow it to drip dry until is firm but deformable.
The second point is the absence of a fluxing agent in your mixture.
Usually Potash Felspar. This is needed to give a vitreous phase which
binds the other ingredients to give a strong finished product.
Best regards.
Ivor Lewis.
Redhill,
South Australia.
Michael Wendt on thu 10 jul 08
Sam,
What cone do you fire? Your recipe
would be good for cone 20-28 since
it contains no fluxes.
It is very high in ball clay and should be
very cohesive and plastic. Do you age it?
For comparison:
The cone 10 Alfred recipe is:
25 Kaolin
25 Ball Clay
25 Feldspar
25 fine Silica
After firing to cone 10 it produces a tight steely
bell-like ring when tapped.
An easier method of wedging is stack and slam.
Each stack and slam cycle doubles the number
of layers if you are careful to maintain the
laminated structure that occurs during the
repeated cutting in half and stacking.
10 doublings produces over 1000 layers
and in this way, makes the clay very uniform.
Regards,
Michael Wendt
Wendt Pottery
2729 Clearwater Ave.
Lewiston, Id 83501
U.S.A.
208-746-3724
wendtpot@lewiston.com
http://www.wendtpottery.com
http://UniquePorcelainDesigns.com
Des & Jan Howard on fri 11 jul 08
Sam
I seem to remember that you work in porcelain.
I have a feeling the recipe you show was intended to
have different materials. I'll give some recipes
with materials easily available in NSW.
White stoneware
Clay Ceram (white firing plastic secondary kaolin) 65
Potash feldspar 20
Silica (350# or 200#) 15
Quite plastic, Cone 10-11)
White porcelaneous stoneware (this is our standard white body)
Clay Ceram 55
Potash feldspar 25
Silica 350# 20
Quite plastic, we use this for throwing, extruding,
jiggering & pressing.
Des
Sam Kelly wrote:
> hi to all, first posting so i hope I have it right.
>
> I made up some clay from raw materials to use on the wheel.
>
> BallClay 65
> China Clay 20
> Silica 15
>
> it worked fine on the wheel however there is a problem with wedging,
> it wants to break up
> when using the rams head method, push down, roll and it breaks into 2
> pieces. Any ideas
> on modification?
>
--
Des & Jan Howard
Lue Pottery
Lue NSW
Australia
2850
02 6373 6419
Des & Jan Howard on sat 12 jul 08
Sam
Walkers have really dumped their clients in it. David is a very nice
chap, if his minders could be evaded. A 100+ year old establishment
sitting on a multimillion dollar site really brings out the 'let's grab
the money & run' mentality.
As far as I know David will make white bodies at Bendigo, Vic, & the
darker bodies at Feeney's in Brisbane, Qld. A small retail outlet will
be in Melbourne.
Max Campbell of Clayworks must be handing out the champers by the bucket.
Funny thing about freight, the white clay sold as 'Clay Ceram' is dug
56 km from us near Gulgong, bulk shipped 400+ km SE to Sydney, milled &
bagged, shipped 700+ km SW to Walkers in Melbourne, shipped 700+ km N to
a Walker's reseller in Oberon, they bring it 160+ km NW to us.
The price is less than I can buy it bulk in Sydney.
NB All of the previous compass points have an 'ish' suffix.
The clay pit owner invited us to come & take what we want. Sweet!
Last trip post rain was a bit sticky.
If you would like to try out a potentially very vitreous body, no
guarantee as to translucency, should be quite plastic, try this recipe.
Cone 10-11
Clay Ceram 50
Potash feldspar 30
Silica 350# 20
+ Dolomite 1%
+ Limestone 0.5%
I did this one from a supplied % analysis. Clay Ceram is almost totally
kaolinitic. I suspect the original was halloysitic, some extra CaO & MgO
& v. low to zip TiO2 & Fe2O3.
Des
clayart@samkellystudio.com wrote:
> Hi des, thanks for the recipes, much appreciated. With walkers moving to
> Bendigo and the ever increasing cost of freight encouraged me to have a
> go at making my own clay. I will still have to aquire the raw material
> but Keans isn't all that far away.
--
Des & Jan Howard
Lue Pottery
Lue NSW
Australia
2850
02 6373 6419
Sam Kelly on sat 12 jul 08
Thanks for the help, I did dry it out on plaster not realising the mistake.
Sam
Quoting Ivor and Olive Lewis :
> Dear Sam Kelly.
> Two points, one which you may have overlooked.
> Your clay is short. This can be corrected by slaking your ingredients
> in an excess volume of water then thoroughly mixing before dewatering
> .
> You need to allow time for the plastic structure to develop before
> dewatering. Do not dewater by spreading the slop over Plaster (Calcium
> sulphate) bats. Instead, put it in some sort of cloth sack (I use
> Hessian) and allow it to drip dry until is firm but deformable.
> The second point is the absence of a fluxing agent in your mixture.
> Usually Potash Felspar. This is needed to give a vitreous phase which
> binds the other ingredients to give a strong finished product.
> Best regards.
> Ivor Lewis.
> Redhill,
> South Australia.
>
Ron Roy on sat 12 jul 08
Hi Sam,
What cone you firing to?
That clay will leak no mater how high you fire.
When you make new clay it will usually be short - give it another try in a
week or so - you will be surprised.
You need to test for shrinkage and absorbency - let me know if you want
instructions on how to do that.
RR
>hi to all, first posting so i hope I have it right.
>
>I made up some clay from raw materials to use on the wheel.
>
>BallClay 65
>China Clay 20
>Silica 15
>
>it worked fine on the wheel however there is a problem with wedging,
>it wants to break up
>when using the rams head method, push down, roll and it breaks into 2
>pieces. Any ideas
>on modification?
Ron Roy
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Ivor and Olive Lewis on sun 13 jul 08
Dear Sam Kelly,
I have clay that has been dewatered on plaster bats which has been in
damp storage for several months. While sitting immobile it has
fractured from its own weight and the broken surfaces are typical of a
brittle fracture. The only thing that might account for this would be
the adsorption of Calcium ions form Calcium sulphate, a sparingly
soluble solid.
Clay is such an amazing material.
Best regards,
Ivor Lewis.
Redhill,
South Australia.
Sam Kelly on mon 14 jul 08
Hi Ron, thanks for the offer of help. 2 years ago I went through a =20
process of checking the locally avaliable clays for shrinkage and =20
porosity which you then gave me the instructions for the process.
One part that still remains a variable is the differenct various =20
published books stating at what % of porosity of a vitreus body you =20
can call the body earthenware, midfire or stoneware.
Some publications are specific, others not so and the old die hard =20
potters, if it's under cone 9 it's not stoneware(Australia). Where I =20
buy my supplies there are no stoneware clays that the owner recommends =20
to fire at less than cone 9
Quoting Ron Roy :
> Hi Sam,
>
> What cone you firing to?
>
> That clay will leak no mater how high you fire.
>
> When you make new clay it will usually be short - give it another try in a
> week or so - you will be surprised.
>
> You need to test for shrinkage and absorbency - let me know if you want
> instructions on how to do that.
>
> RR
>
>> hi to all, first posting so i hope I have it right.
>>
>> I made up some clay from raw materials to use on the wheel.
>>
>> BallClay 65
>> China Clay 20
>> Silica 15
>>
>> it worked fine on the wheel however there is a problem with wedging,
>> it wants to break up
>> when using the rams head method, push down, roll and it breaks into 2
>> pieces. Any ideas
>> on modification?
>
> Ron Roy
> 15084 Little Lake Road
> Brighton, Ontario
> Canada
> K0K 1H0
>
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