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Self Glazing Cone 04 Porcelain


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#1 AnnaM

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Posted 20 January 2014 - 11:05 PM

Hi all,
I'm new to the forum so hoping someone has some knowledge on this!
After seeing Justin Rothshank's recent work I started looking into finding a similar clay body and I've found a published paper which has a recipe and firing schedule for self glazing porcelain that vitrifies at 1050°C.
This seems to me to be just too good to be true (fingers crossed that it is true!) Does anyone know anything about this? If the recipe is out there why would clay manufacturers not be making and selling this self glazing low fire porcelain?



#2 AnnaM

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Posted 20 January 2014 - 11:07 PM

The recipe is in this paper:

https://www.google.c...kebIwDm8YPqA0NQ

#3 Norm Stuart

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Posted 21 January 2014 - 12:26 AM

Bone china fires to a gloss surface.  It's not that unusual.  But it's not a glaze or a color, just fully vitrified.

 

Anorthite is a calcium rich silicate, a feldspar in other words. 

 

It looks like this - at least this Anorthite sample from the Moon brought back by Apollo does.

 

anorthosite_1.jpg

 

It could be a beautiful glaze to some.

 

Hi all,
I'm new to the forum so hoping someone has some knowledge on this!
Are seeing Justin Rothshank's recent work I started looking into finding a similar clay body and I've found a published paper which has a recipe and firing schedule for self glazing porcelain that vitrifies at 1050°C.
This seems to me to be just too good to be true (fingers crossed that it is true!) Does anyone know anything about this? If the recipe is out there why would clay manufacturers not be making and selling this self glazing low fire porcelain?



#4 AnnaM

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Posted 21 January 2014 - 12:30 AM

https://m.facebook.c...hshankceramics#!/photo.php?fbid=10152183274975421&id=113505525420&set=pb.113505525420.-2207520000.1390282146.&__user=642942404

#5 AnnaM

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Posted 21 January 2014 - 12:32 AM

It apparently looks like the cups in the link I just posted. It is apparently also used in dentistry.

#6 Biglou13

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Posted 21 January 2014 - 09:04 AM

Is that frit in recipe close to any commercially available frit?

Making clay is ez. Why depend on mfgr.
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#7 Norm Stuart

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Posted 21 January 2014 - 09:34 AM

The frit appears to be high in levels of low-temperature flux potassium along phosphorous and silica which are ingredients in a bone china.

 

By themselves the Wollastonite (Calcium Silicate) and Kaolin (aluminum silicate) have melting temperatures which are too high.

 

Unfortunately all of the commercial frits I'm aware of with high levels of Potassium, also have high levels of Sodium which gives the procelain body too much expansion - like Laguna New Zealand Frost.

 

Perhaps someone else knows of a frit with just calcium and potassium flux.

 

Is that frit in recipe close to any commercially available frit?

Making clay is ez. Why depend on mfgr.



#8 neilestrick

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Posted 21 January 2014 - 01:14 PM

Saw a post on ClayArt that said: There is a description of a high potash frit made from pearl ash, feldspar and kaolin in Michael Cardew's "Pioneer Pottery", page 144 to 148. He writes that it "breaks all the rules of frit making" and uses it to make a bright iron red glaze. 


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#9 Norm Stuart

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Posted 21 January 2014 - 02:33 PM

There's no way to come close to K2O:B2O3:SiO2 in a ratio of 1-2-3 or 17% K2O,  33% B2O3, and 50% SiO2. - except to use Pearl Ash, Boric Acid, and Silica to make your own frit.

 

G200-HP Feldspar is a mere 13.2% K2O.  Yet the materials they describe using to make the frit, in the abstract, contain no Boron - just Pearl Ash, Silica and Phosphoric Acid. But in the paper itself they use a different formula which includes Boric Acid and excludes Phosphoric Acid - a mistranslation from Turkish?

 

 

Potassium sure brings out colors.  And using isoelectric Aluminum Phosphate in equal molar amounts, in place of Silca, brings out reds in iron red.

 

Interesting but I know of no commercial frit matching this make-up. 

 

I might try putting the raw materials into the next firing in an alumina crucible to see what happens, as I have no other heating source.

 

Saw a post on ClayArt that said: There is a description of a high potash frit made from pearl ash, feldspar and kaolin in Michael Cardew's "Pioneer Pottery", page 144 to 148. He writes that it "breaks all the rules of frit making" and uses it to make a bright iron red glaze. 



#10 AnnaM

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Posted 21 January 2014 - 09:58 PM

Has anyone had any experience with a similar recipe?

#11 PeterH

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Posted 22 January 2014 - 09:14 AM

Norm posted .. using isoelectric Aluminum Phosphate in equal molar amounts, in place of Silca, brings out reds in iron red.

 

Very intriguing result Norm.

 

- Is there any additional information available, apart from your own web page

  http://cone6pots.nin...phate-no-silica

 

- ... including the use of aluminium phosphate in types types of glaze, as suggested at the end of the

  page on Magruder Red.

 

- Could you achieve similar effects supplying the aluminium and phosphate from different sources?

  I ask because I believe that crystalline potassium [or sodium] metaphosphate is highly insoluble.

  http://pubs.acs.org/...021/ie50362a020

  Which sound like an interesting way of making hi-potassium glazes (if the phosphate ion doesn't

  cause trouble). 

 

Regards, Peter

 

PS The solubility of the phosphate may be more like that of hi-alkali frits, as it can be used as a slow-release fertilizer.

 

PPS Another of Norm's pages on aluminium phosphate

http://cone6pots.nin...source=activity



#12 AnnaM

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Posted 23 January 2014 - 07:42 AM

Sorry this all Greek to me! What I was wanting to know specifically is:

1) is this likely to be a foodsafe clay body?
2) does it sound plausible that it would truly be vitrified at cone 04?

I'd like to try it but don't have the faintest idea whether it sounds plausible, and if (to someone more experienced than I) there is something glaringly odd about it, I'd rather wait till I have more money to potentially waste if there's a fairly big chance the exercise would be in vain :)

#13 Norm Stuart

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Posted 23 January 2014 - 12:47 PM

I simply mixed 85% phosphoric acid with "Alumina Hydrate" to get the starting base of hydrated alumina phosphate.

 

You have to keep track of how much you started with to know how much Aluminum Phosphate there is in the hydrate. Because if you try to dry it out it becomes a cement which adheres to glass or ceramic, so I just added it to the glaze as the hydrate.

 

At the time I was trying to add phosphorous to glaze without adding calcium (ie bone ash) for red iron glazes.  The end result for red iron glazes was starting with pure red iron oxide instead the witches brew of iron, barium and other recycled metals I had obtained from Laguna Clay as red iron oxide.

 

It's cheap to buy aluminum phosphate as the powdered sodium aluminum phosphate, which is a food additive - but you're stuck with the extra sodium which raises the COE.  It's tougher to get potassium aluminum phosphate, but for that use I didn't want the potassium wither.

 

Starting with potassium metaphosphate seems like an ideal source ingredient for what AnnaM is trying to do.

 

That's a great idea Peter.  A lot of glazes you wouldn't expect benefit from both potassium and phosphorous.

 

Norm posted .. using isoelectric Aluminum Phosphate in equal molar amounts, in place of Silca, brings out reds in iron red.

 

Very intriguing result Norm.

 

- Is there any additional information available, apart from your own web page

  http://cone6pots.nin...phate-no-silica

 

- ... including the use of aluminium phosphate in types types of glaze, as suggested at the end of the

  page on Magruder Red.

 

- Could you achieve similar effects supplying the aluminium and phosphate from different sources?

  I ask because I believe that crystalline potassium [or sodium] metaphosphate is highly insoluble.

  http://pubs.acs.org/...021/ie50362a020

  Which sound like an interesting way of making hi-potassium glazes (if the phosphate ion doesn't

  cause trouble). 

 

Regards, Peter

 

PS The solubility of the phosphate may be more like that of hi-alkali frits, as it can be used as a slow-release fertilizer.

 

PPS Another of Norm's pages on aluminium phosphate

http://cone6pots.nin...source=activity



#14 Norm Stuart

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Posted 23 January 2014 - 12:57 PM

Anna  - The answer to food safe ceramic body or glaze is always, do a leeching test.

 

If I were to guess, this appears to end up as vitrified glass (aka self-glazing ceramic and the ceramic is glassy) so should be perfectly food safe - but always test.

 

But you have to figure out what this translated Turkish article is calling for, because the body of the paper calls for different ingredients from what the abstract mentions.

 

There's no ceramic frit I know of which contains this particular mix of material.  So if there isn't already a frit for dental use with this make-up Peter's suggestion of potassium metaphosphate is an alternative starting ingredient to what I've suggested. 

 

Sorry this all Greek to me! What I was wanting to know specifically is:

1) is this likely to be a foodsafe clay body?
2) does it sound plausible that it would truly be vitrified at cone 04?

I'd like to try it but don't have the faintest idea whether it sounds plausible, and if (to someone more experienced than I) there is something glaringly odd about it, I'd rather wait till I have more money to potentially waste if there's a fairly big chance the exercise would be in vain :)



#15 PeterH

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Posted 23 January 2014 - 02:38 PM

Hey up! Norm is right that there seems to be an inconsistency.

 

The paper's abstract mentions 43.8% H3PO4

... and then goes on to mention the K2O:B2O3:SiO2 ration (Boron not Phosphorous).

 

The ingredients used (1st para section 2) mentions Boric acid (H3BO3), but not phosphoric acid (H3PO4).

 

The preparation of the frit (1st sentence 2nd para section 2) gives 43.8% H3BO3.

 

Table 1 has a column for  B2O3, but not one for P2O5.

 

... so my guess would be that the initial mention of H3PO4 is some sort of spell-checker assisted typo.

 

IMHO there is no phosphorous, just boron.

 

Back to you Norm for advice on a suitable boron frit.

 

Regards, Peter
 



#16 Norm Stuart

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Posted 23 January 2014 - 02:42 PM

Since Anna says they use this in dental work there may be a frit sold for dental labs, but there's no frit with this make-up being sold through art ceramic channels.  So it would be a matter of melting the soluble ingredients to make your own frit.

 

Hey up! Norm is right that there seems to be an inconsistency.

 

The paper's abstract mentions 43.8% H3PO4

... and then goes on to mention the K2O:B2O3:SiO2 ration (Boron not Phosphorous).

 

The ingredients used (1st para section 2) mentions Boric acid (H3BO3), but not phosphoric acid (H3PO4).

 

The preparation of the frit (1st sentence 2nd para section 2) gives 43.8% H3BO3.

 

Table 1 has a column for  B2O3, but not one for P2O5.

 

... so my guess would be that the initial mention of H3PO4 is some sort of spell-checker assisted typo.

 

IMHO there is no phosphorous, just boron.

 

Back to you Norm for advice on a suitable boron frit.

 

Regards, Peter
 



#17 AnnaM

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Posted 23 January 2014 - 07:04 PM

Ok, so it basically will be a more glassy clay body? Sounds promising? Which would make sense as far as dental porcelain goes as lower porosity would mean less leaching wouldn't it?

What would that be likely to do to plasticity and workability?

#18 AnnaM

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Posted 23 January 2014 - 07:07 PM

Also, (bear in mind I am a complete newbie to this stuff :) ) is there a list somewhere of what all those abbreviations mean?!

#19 AnnaM

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Posted 23 January 2014 - 07:09 PM

Really appreciate all your thoughts on this guys

#20 Mudslinger Ceramics

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Posted 23 January 2014 - 08:01 PM

Hi Anna

 

Was experimenting with this during my undergrad about 12 years ago......

 

Pick up a copy of Sue Peterson's 'The Craft & Art of Clay'', page 381 gives a recipe for ^04 low fired porcelain and page 152 has a recipe for a ^04 Irish 'Belleek' style porcelain.......both came out as a warm white, glassy body with a soft satin sheen. 

 

Being a 2nd year student and not that interested in formulas I used the frits I had on hand, in my case lead bisilicate, but the recipe can also use ground glass which I got from a bottle recycler.

 

Hope this helps.

 

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