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Wedging/kneading & Bisque Firing Newbie Questions


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#1 oly

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Posted 04 January 2014 - 05:15 AM

Really grateful for advice on the following four basic points...

 

Wedging/kneading:

 

  • I have been mostly using 'ram's head kneading', should the clay go down on the wheel so that it continues to tighten with the wheel motion?
  • A Valentine's clay I bought comes in lovely cylinder straight out of the bag – should it also be wedged or is it ok to just cut off a length and start centering it straightaway?
  • When making very small items (like egg cups) how do you deal with wedging, or must these be thrown 'off the hump'?

 

Bisque:

 

  • I need to make some tiles for glaze tests, can they go straight in kiln for bisque once they've been cut (ie no drying time first)?

 

Thanks for any help!



#2 RuthB

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Posted 04 January 2014 - 09:16 AM

Wedging and Kneading accomplish a number of things.

The Ram's Head is particularly effective for drying out really wet clay. It can be arched 

to air dry for a while before continuing. The Ram's Head is also good for blending clays

of different moistures. 

The Oriental Shell begins to align clay particles, removes air pockets and allows one to

knead large amounts because only the clay under the hands is worked... the mass rotates

and moves through the hands.

After kneading the clay is closed up into a ball or cylinder, ideal shapes for putting on the wheel.

Slices can be cut off for smaller work and the edges can be patted into a ball.

 

Clay particles do not stay aligned forever. So clay fresh from the bag should also be kneaded. 

How long should the clay be kneaded? With experience, you will note a change in the clay as you 

work it. You also want to watch the moisture content if you are working on plaster. 

 

Centering by coning and throwing continue the process of aligning the particles. Coning will

align the clay particles with clay fresh from the bag. But aligning the particles is a process that will

take longer on the wheel if you skip kneading. Why don't you try both and see what you think.Clay that

has been properly prepared is much more responsive on the wheel.

 

You can throw egg cups or other small items either off the hump or directly on the wheel head. If throwing off 

the hump, measure the amount of each cup in some way, either by what is cupped under

your hands, or more specifically with a gauge or ruler. Throwing on the wheel head may

require a more delicate touch in centering so that the clay stays attached to the wheel. 

 

Your test tiles can go directly in the kiln, but you still want all moisture to be removed before you close the

lid to the kiln, for the kiln's sake. If you stack them, it will take longer for the moisture to go. Stand them on

edge, leaning against each other,with a bit of space between each one. Check for moisture with a

small mirror held to the opening of the kiln.

 

Ruth

Charleston, SC



#3 oly

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Posted 04 January 2014 - 02:11 PM

I haven't used the Valentine's clay yet  – will post when I have, many thanks!

 

By the way I don't understand the terms: 'chamotted', 'when salted', 'flashing slips', 'in a puddle'!  

 

: (

 

 

 

Hi Oly - I used Valentines clay when I was in the UK. I never bothered to wedge or knead it at all, just used it straight out of the bag. It's pretty obvious that it's a highly processed material as it is - anything I could have done to it would have been merely fanciful on my part, I think!

Unless I was reclaiming it from the bin, of course, or if I wanted to introduce some grog into it.

Other than that, just straight out of the bag, coned up and down on the wheel a couple of times ( <-- important), and away.

I must admit I found Valentines a bit 'soapy', even the mildly chamotted one (is that a word?) - how is it now?

I stuck with it simply because it was great when salted - all my flashing slips worked well with it, and it withstood cone 10 'in a puddle' without too much trauma. Happy days!

 

Mr Feeble.



#4 Babs

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Posted 04 January 2014 - 06:34 PM

Really grateful for advice on the following four basic points...

 

Wedging/kneading:

 

  • I have been mostly using 'ram's head kneading', should the clay go down on the wheel so that it continues to tighten with the wheel motion?
  • A Valentine's clay I bought comes in lovely cylinder straight out of the bag – should it also be wedged or is it ok to just cut off a length and start centering it straightaway?
  • When making very small items (like egg cups) how do you deal with wedging, or must these be thrown 'off the hump'?

 

Bisque:

 

  • I need to make some tiles for glaze tests, can they go straight in kiln for bisque once they've been cut (ie no drying time first)?

 

Thanks for any help!

Hi I don't wedge the clay when I make tiles as it seems to induce warping of the tile when fired. This is from observation, not scientific knowledge.



#5 oly

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Posted 05 January 2014 - 07:50 AM

Thanks for all that I understand now! Yes, I have the Valentines original earthstone ES5 clay – ungrogged, haven't tried it yet but have high hopes.

 

The clay i'm using at moment (a different brand) is rather variable in terms of moisture content. Sometimes very soft out of bag, sometimes rather too hard, so I either wedge it to get rid of moisture or add some water to the bag and wait.

 

I guess that is normal, I cant think of any other way of dealing with it.

 

Hoping the Valentine's clay may be more consistent perhaps.

 

 

 

 

 

 

By the way I don't understand the terms: 'chamotted', 'when salted', 'flashing slips', 'in a puddle'!  

 

: (

 

 

 

Apologies, my fault for replying when in a hurry!

 

'Chamotte' = grog

 

'Salted' - I used to salt-glaze in the UK, requiring the addition of handfuls of salt into the kiln at high temperature. Hence, 'when salted'.

 

'Flashing slips' = thin (almost watery) slips applied to unfired pots, to give various effects when in a fuel-burning kiln, typically orange 'flashes' reminiscent of wood-fired pots. Hence 'flashing slips'. The exact chemical composition of the slip (particularly the alumina/silica ratio) determines the effect.

 

'in a puddle' - an apt description of an Orton cone, which instead of gracefully bending over to indicate a certain point in a firing, is reduced to a melted puddle on the kiln shelf, 'cos I over-fired the kiln load! (Actually, the act of salting a kiln does rather put the cones out anyway, but still...)

 

Anyway, I looked at the Valentines range just now, and it seems they have vastly expanded what they do! Which clay is it that you have? I (generally) used to use Earthstone Original (ES5), or the same but with 20% added grog. It was certainly absolutely fine straight out of the bag, and I suspect that others in the Valentines range will be similarly easy.

 

Let us know how you get on!

 

Mr F.

 






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