Jump to content


PeterH

Member Since 28 Apr 2013
Offline Last Active Today, 03:42 PM
-----

#72164 Trying To Find A Square Plate Mould

Posted by PeterH on 20 December 2014 - 07:43 AM

... and there are always drop moulds

http://lapellaart.bl...d-platters.html




#71688 Adding Subtle Interest To Surface In Electric Kiln To Enhance Visual Qualities

Posted by PeterH on 11 December 2014 - 02:36 PM

I've zero practical experience, but as I understand it you only need to slow the cooling over part firing schedule.

 

See for example

http://ceramicartsda...-up-and-down-2/

... and the freebies it offers.

 

Two examples, each shows a glaze with different firing cycles

http://ceramicartsda...xieTeal_675.jpg

http://ceramicartsda...Tenmoku_675.jpg




#70099 What Type Of Glaze Is This?

Posted by PeterH on 17 November 2014 - 05:07 PM

Marcia, here's another.

 

Cuerda Seca - esp. applying glaze from about 3:20 and the brush used

http://www.spainwebt...-LA-CUERDA-SECA




#69988 For Christmas.

Posted by PeterH on 16 November 2014 - 04:05 AM

From http://en.wikipedia....ki/Caster_sugar

Caster (or castor[31]) (0.35 mm),[30] a very fine sugar in Britain, so-named because the grains are small enough to fit through a castor, a form of sieve. Commonly used in baking and mixed drinks, it is sold as "superfine" sugar in the United States. Because of its fineness it dissolves more quickly than regular white sugar and is thus especially useful in meringues and cold liquids. Castor sugar can be prepared at home by grinding granulated sugar for a couple of minutes in a food processor.

 

[31] The Oxford English Dictionary classifies both spellings as correct, but "castor" used to prevail.

 

 

 




#69832 Stuck In The Mold

Posted by PeterH on 13 November 2014 - 09:38 AM

Years ago I saw an article about casting something really difficult, pure alumina I think.

It had practically zero green strength, which made it difficult to extract from the mould.

So they first cast a very thin layer of paper onto the mould, then the slip. I cannot imagine

that this is too good for the mould, and it may reduce mould life by blocking the pores.

 

If you have a mould you are willing to sacrifice, might be worth a try. From my paperclay

making efforts I would recommend cheap white toilet-paper for making the paper-slip.

It disperses quite readily in water, espicially hot water. [Expensive zeta-potential controlled

paper pulp would presumably be better.] Perhaps you could arange only to cast paper onto

the interior part of your mould.


  • Mug likes this


#69807 Stuck In The Mold

Posted by PeterH on 12 November 2014 - 06:14 PM

Just to clarify,  I put about an eggcup full of the powder in the toe of an old pair of tights and tied it

off to give a full bag.  I then patted this onto the mould surface. [Actually very similar to the bags

of charcoal traditionally used for pouncing.] I then poured as usual. Actually with my mould I couldn't

avoid pouring straight onto the treated part of the mould.

 

I found that this definitely helped separation, but wasn't a panacea.

 

BTW the choice of talc or Neph Sye is to minimise any visible effects on the fired pot. So by all means

test with neph sye, but if you low-fire you may want to switch to talc later.

 

Actually the first time I emptied an unused tea-bag, filled it with powder, then sellotaped it closed. You just

need something porous enough.




#69789 Store Bought Clay Slip Is Way Too Thick...

Posted by PeterH on 12 November 2014 - 01:41 PM

If you stir ithe slip hard and for some time (e.g. with a paint mixer) does thin down. If so it

sounds like the problem might be excessive thixotropy.

 

If it remains thick ... duh! Perhaps start by measuring its density.


  • Ben likes this


#64778 How To Get Started With Old Stains, Etc

Posted by PeterH on 20 August 2014 - 10:30 AM

Basic evening-class stuff, but a test tile with a stripe of each on N glazes one way,

overlain with a stripe of all the colours at right angles shows you the effects of all

N glazes under/over all the others. I wouldn't try with N=40 though!

...  a blank line in one direction [so an Nx(N-1) grid] shows single and double 

coverage of each glaze as well.

 

http://ceramicartsda...alette-part-ii/




#59174 Old Potters Wheel. I'm Fascinated!

Posted by PeterH on 24 May 2014 - 04:30 PM

>Is that the underside of a wheel seen behind him leaning against the wall? It kind of looks like the same circumference so maybe that is what the bottom looks like and might help in figuring all those questions out.

 

... and could the bottom pivot be standing in-front of the that wheel (like an upside down thumb-tack).

 

Could be a very nifty way of getting the centre of gravity of the wheel below a single pivot point,

and most of the mass at the circumference.




#56620 Sugar/candy Raku

Posted by PeterH on 14 April 2014 - 03:14 PM

Thanks, but the sugar raku I'm interested in is a variant of the 2-part naked raku process, in
which the refractory 1st coat contains sugar. Normally 2-part naked raku leaves black "crackle"
lines. On the other hand sugar raku -- from the few photos I've seen -- leaves black patches,
often with some sort of halo effect.

 

Overall effect is something like the left-hand pot in

http://tinyurl.com/pzubofy

 

Every few years I'd try again using the normal 2-part naked raku process, and got a really ugly

pot in a mixture of black and charcoal greys.

 

Last time I tried cooling it in oxidation, with more interesting results.

 

Firstly tried quenching as soon as it came out of the kiln.
Attached File  quench_350.JPG   47.33KB   4 downloads

 

Then letting it air cool sitting on a brick

Attached File  air_350.JPG   57.65KB   4 downloads

Different, but nothing like the pictures I'd seen.

 

Finally I tried to repeat the second experiment, but botched it. I put it on short damp grass to cool, and

it had fallen on its side by the time I got back.

Attached File  grass_350.JPG   59.03KB   2 downloads

Obviously it had seen a mixture of oxidation and reduction.

 

So, I'm interested to know how other people cool their sugar raku.

 

Regards, Peter

 

For completeness.

Fired somewhere in the range 1030-1050C.

Slip was china clay 3, flint 2, sugar 2 by volume. I also tried a 3:2:1 mix but it was rather faint.

 




#55779 Formulating An Exceptionally Refractory Clay Body.

Posted by PeterH on 30 March 2014 - 03:23 PM

Tyler,

 

I believe that Hessian crucibles were traditionally used for this sort of thing, although I cannot supply a recipe.

 

IIRC 'Pioneer Pottery' by Michael Cardew has a section on DIY kiln furniture, which might have something helpful

(including advice on multiple firings to develop mullite structures?).

 

How high a temperature do you want to use. What controlled facilities do you have for crucible preparation.

 

Regards, Peter

 

http://www.scienceda...61123120134.htm

http://www.rsc.org/c...er/23110602.asp

http://www.academia....rial_Properties

 

 

PS Silly me, it's wootz steel isn't it.

 

http://www.bladesmit...?showtopic=4541

... contains the recipe

EPK 40
Calcined Kaolin 20
Tennesee Ball Clay 20
Grog 10
Flint 10

Mix with 500 g water per 1000 g mixture.

 

For a flavour of authenticity

http://www.swordforu...or-wootz-poulad
 




#55714 Drawing Through A Glaze

Posted by PeterH on 29 March 2014 - 05:18 PM

Another video, showing hoe Phil combines faceting with finger wiping, good potters are a very ingenious lot.

 

Finally, Phil moves from informative videos into high-pressure telemarketing, but cannot keep a straight face.




#54441 Ceramics Projects As A Means To An End

Posted by PeterH on 11 March 2014 - 07:29 PM

Tyler,

 

I'm even going to play with using them for making crucible steel or wootz, which has a lovely dendritic structure

 

Have you tried Damascus steel blades?

 

I don't know if it's possible with the technology you are using, but I've got a few paper lying around somewhere on

analysis of historic artefacts, and attempts at modern reconstructions if you are interested.

 

Regards, Peter




#50401 Crazing Problem

Posted by PeterH on 16 January 2014 - 09:36 AM

Essentially the same point as Kevin's. If you have any spare "good" tiles - and they have not crazed on

standing - it might be worthwhile trying one of the freeze-heat torture tests to see if they were on the

borderline of crazing. Indian ink is wonderful in making fine crackle visible.

 

Regards, Peter




#50015 What To Do With Old, Dry, Moldy Clay?

Posted by PeterH on 12 January 2014 - 02:30 PM

Marcia,

There may be a grain of truth in the suggestion that the Chinese had a special kaolin,

thanks to that wonder ingredient of many old technologies - stale urine.

 

For those who have access to the scientific journals, its well worth reading:

Weiss, "A Secret of Chinese Porcelain Manufacture"
http://onlinelibrary...306971/abstract

 

To make up from the brevity of the abstract, I quote from the 2nd page of:

Rytwo. "Clay Minerals as an Ancient Nanotechnology"

http://www.ehu.es/se...9/macla9_15.pdf

 

Chinese Porcelain:. Porcelain has been made in China probably since
the 6th or 7th century A. D. Quartz, feldspar, and kaolin were then,
as now, the raw materials employed. The name “kaolin”, for china
clay derived from old deposits on the mountain Kao- ling in China.
Observations had been made since the 9th century about the fact that
“chinese have particularly fine clay which they use to make drinking
vessels with the delicacy of glass; although they are made of clay.”
Such items had great strength, were shaped perfectly by hand, and have
wall thickness of less than 0.4mm! During Mongol domination (1280-1368)
the knowledge was lost.  Ceramics from the following Ming dinasty was
not as thin as before, even they tried to use the most plastic kaolin
deposits they found. Only till the end of the Ming dinasty (1644) thin
ceramics appear again, but in this case those were made from illite,
which has a-priori a considerably higher plasticity than kaolin,
making it easier to handle. The secret of ancient Chinese kaolin-based
porcelain must therefore lie in some technique enabling delicate items
to be formed from kaolin of poor plasticity, which would normally be
expected to require clays of extremely good plasticity. Weiss (1963)
showed that by mixing kaolinite with urea and aging it “The kaolinite
crystals did not dissolve, but the urea-based chemicals penetrated into
the crystal lattice and increased the distance between the kaolinite
layers from 7.2 to 10.7 A.  Rheological behavior of kaolin does indeed
increase strongly with this pretreatment. A kaolin of low thixotropy
subjected to this treatment yields a material surpassing the best ceramic
kaolins and approximating sodium bentonites.

 

Regards, Peter