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Earthenware Or Stoneware ?


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#1 dolly

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Posted 07 March 2014 - 03:21 AM

Hi All 

I'm new to Earthenware slip form, Although I'm back from a 13 year gap, after making dolls , The kilns been dusted down and all in good working order, have done a couple of fires , with earthenware but want to know whether I'm making the right decision. I've sculpted a humpty dumpty made molds and so forth all came out successful, barring the underglaze which is another matter lol. but what I would like to do is make decorative plant pots about orchid size perhaps bigger. is earthenware going to be strong enough after glazing, also id like a go at mugs, am i using the right clay for these project , can anyone help thanks dolly 



#2 justanassembler

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Posted 07 March 2014 - 04:52 AM

earthenware can be fine for any of these applications--its all about the body, how you use it, glaze it, fire it, etc...  As with everything in ceramics, if you ask a broad question, the answer is almost always: "sure--but it depends."



#3 dolly

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Posted 07 March 2014 - 10:22 AM

thanks for replying I'll keep experimenting, which is all part of the fun lol



#4 Chantay

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Posted 07 March 2014 - 10:37 AM

Earthen ware can be a problem for plants.  When I started in pottery it was with earthen ware.  Low fire clays don't fully vitrify and are able so absorb liquids.  If the pot is kept indoors this may not be a problem.  The problems I saw were mold growing on the bottoms of pots where there was no glaze. This was indoors in a humid area.  If you have a $50 or more orchid, you don't want  the roots to be in a pot that you can't control the moisture and get moldy roots.  The same with a $$ bonsai tree (what I was making pots for).  Also, earthen ware clays will crack during a freeze.  Maybe not the first time but eventually.  If the pot cracks, the roots will dry out too quickly and your $$ bonsai tree can die.  (experience speaks.) Also, some bonsai have to be watered every day, if the pot is sucking in the water, it is not available to the plant.


- chantay

#5 High Bridge Pottery

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Posted 07 March 2014 - 01:35 PM

I love stoneware but I would go with what your kiln can cope with first, not sure what temps yours works with. Once you know that you can start looking at clay bodies and how they can work for you and be changed to suit your needs.

 

I have never had exposure to earthenware so just avoid it, and I like to go as hot as possible. Something about hitting cone 10 makes me happy. Maybe not as happy when it breaks and I sulk off to cone 6.


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#6 AnnaM

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Posted 07 March 2014 - 05:58 PM

For tableware, you definitely need a clay body that vitrifies. Commercial earthenware clays don't. I believe some terracottas are better, and lots of people make mugs out of red earthenware bodies, but I don't know enough about these as I don't throw with them). If the body is absorbent (as commercial earthenware is) liquids will soak in if there is even a tiny compromise in the glaze and mould can start growing under the glaze. Also earthenware is not as good as stoneware at resisting chips and cracks. Be aware too that if you use earthenware for plant pots, you risk water seeping through, so if they are inside you may get water damage on whatever surface they are sitting on.

#7 High Bridge Pottery

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Posted 07 March 2014 - 07:01 PM

I was under the opinion that stoneware doesn't exactly vitrify but just gets dense enough so that it's not really a problem. Vitrification is a term to do with glass and porcelain does turn into glass. I don't know if you fire earthenware till it just becomes a glass makes it waterproof. Sounds possible but never tried it.


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#8 dolly

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Posted 07 March 2014 - 08:51 PM

Thanks for all your replies, yes I was worried about the porosity of the earthenware, but I wanted to use bright underglazes on the pots, and I think some colours don't withstand such high temperatures, will have to compromise somewhere along the line,but that's the fun aspect of playing with clays, you never know what you can achieve til you try it .....



#9 AnnaM

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Posted 07 March 2014 - 09:02 PM

I was taught that stoneware vitrifies? Perhaps I was misinformed. Dolly, my kiln only goes up to cone 02, so I mix approximatelt 30% Ferro 4131 frit in with earthenware clay to make a glassy body that vitrifies at cone 04. It means that you have the water resistance of a stoneware or porcelain with the benefit of the full range of colours. Just don't overfire or you'll get this tragedy:

#10 AnnaM

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Posted 07 March 2014 - 09:04 PM

Attached File  tmp_2014-02-21 21.20.20226883987.jpg   145.12KB   3 downloads


Just short of completely slumping!!

#11 AnnaM

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Posted 07 March 2014 - 09:13 PM

If you mix 4:10 frit to clay mix, it is approx 28.5%.

#12 Babs

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Posted 07 March 2014 - 09:55 PM

If you mix 4:10 frit to clay mix, it is approx 28.5%.

WOw pretty expensive body!

Noticed you were from Australia A friend used to use Walkers white earthenware and did mugs etc. Have you tried the Walkers clays, though since moving location there have been a few changes to their clay bodies.



#13 High Bridge Pottery

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Posted 07 March 2014 - 10:08 PM

I was also taught that about stoneware. It really depends on how you are defining clay.

 

I have seen articles about defining clay by their water absorption. Cant find the exact one but here are a few links talking about similar things.

http://www.claytimes...ay-basics.html 

 

http://books.google....densify&f=false

 

If you scroll up a little on the google books link it talks through what a clay body is and such and such. Couldn't get it to link to the right page... but go from page 139. It is worth a read as it goes on to talk about lots of different clays.


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#14 AnnaM

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Posted 07 March 2014 - 10:59 PM

Babs I haven't tried the Walkers! Adding the frit does make it expensive, Im looking to start using recycled glass powder from Potters industries. They have one which is the equivalent of 325 mesh (or thereabouts) called A1, which I tried a sample of a couple of weeks ago, but haven't gone down to buy a bag yet a they are a bit of a long way ;).

Yes I do remember reading that section of Petersons book actually! I have tried her low fire porcelain recipe. I guess by her definition my clay is closer to a glassy earthenware. For some projects it's actually more of a clay-glass hybrid. It is a hassle to make it this way, especially as I manually fire because I don't have a controller on my kiln (and the risk of loss through overfiring is increased), but the benefit is the colour I can get (which I think may also be attributable to a high level of boron in that frit, but Im not sure)

ANYWAY Dolly for your purposes, it you are wanting to start out making vessels to hold liquid and/or foods best and easiest to start out with stoneware!

#15 dolly

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Posted 08 March 2014 - 08:11 PM

thank you so much , i'm not into the science of all these different mixes, and would take

me forever to get all the info in my unsponge like brain lol, I think your right going onto stoneware, the better option for me. but i was thinking if i fire the stoneware to maturity could i under glaze the items then fire them on a lower temp so not to loose the colours , means i would have to fire 3 times tho. I am very new to this type of clays, as i was used to porcelain.in the past. my love of ceramics is purely sculpting making moulds painting them , the clay and the firing thing is just a necessity. does that make me a bad person lol. 



#16 AnnaM

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Posted 08 March 2014 - 10:22 PM

Do you mean putting an earthenware type glaze over the stoneware glaze?

#17 Marcia Selsor

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Posted 08 March 2014 - 10:33 PM

Earthenware a need to be fired to maturity to vitrify. A good example is Lisa Naples earthenware fired to cone 1 or 2.Most commercial earthenware say fire to. Cone04 which is not hot enough.
Marcia

#18 dolly

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Posted 10 March 2014 - 11:22 AM

No AnnaM I was thinking of using stoneware firing to maturity then velvet under glazing on a low temp , oh I don't know really think I'll wait til i go to Stoke on Trent and see what's on offer there lol, thanks for you advice just keep on experimenting ...






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