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Glaze Not Uniformly Glossy On Cone 04 Body

soft paste porcelain cone 04 porcelain gloss glaze problem

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#21 neilestrick

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Posted 12 April 2014 - 08:47 AM

Could be Nancy!

 

Babs, you are a legend thankyou!

 

John,  its used in glass manufacture, containers, electrical glass, construction and automotive glass apparently, stuff like that. I think she said its the stuff they mixed with paint for road marking to make it reflective as well. The powder is actually tiny glass beads, it's typical soda-lime glass.

 

When I spoke to her she said even though the proportions given are a range, that the actual proportions generally don't change - but she couldn't give me a specific composition for the batch I have.

 

I'm going to see if I can get one done I think.

 

You'll have to take them at their word that the batches don't change. You see this a lot on MSDS forms- the exact percentages are not given in order to protect proprietary information. 'Typical soda-lime glass' can still vary greatly from manufacturer to manufacturer.

 

The big down side here is that any formulation you do is going to be totally trial and error since you don't have real numbers to work with. It could take a really long time to get it worked out, and then if there is a change in the cullet you're back at square one. I'd have a backup plan in case that happens.

 

Any idea what mesh size the tiny beads are?


Neil Estrick
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#22 JBaymore

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Posted 12 April 2014 - 01:15 PM

Is that cullet information you gave from a MSDS or from a "typical analysis"?  (If that was supposedly from a "typical analysis" that was useless data also.)  Those are quite different documents.  And a MSDS is useless for technical glaze chemistry work.

 

What "works" for control for one industtry for a material is not necessarily going to work for anotehr.  "Typical" soda-lime glass is a VERY broad generic term. 

 

Many MSDSs are usless for even MEDICAL kind of work... as the companies try to hide proprietary formulas... or try to minimize the real dangers present.

 

Why are you trying to get translucency at such a low firing range?  Rais the firing... and cut the need for frit.

 

best,

 

...................john


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#23 AnnaM

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Posted 13 April 2014 - 11:02 PM

Neil - I think the beads are between 53 & 75 microns, its very fine powder.

 

John, it's not from an MSDS sheet, it's just their table that has the typical composition, that was all they had. 

 

I'm not necessarily going for translucency at low temperature, but I do want a strong and vitreous body, and I would like it to be as white/light as possible.   My kiln doesn't quite get to 1100C (and thats a struggle for it, I can't really push it past cone 03) which is why I got interested in this project initially.

 

Unfortunately, none of the commercial earthenware clays available to us here in Melbourne are vitreous and they are fairly weak (they chip really easily) so I normally add frit to my earthenware bodies to lower the MP and produce a much stronger, vitreous body. The only problem with that is that the frits here are quite expensive, which is why I was interested in developing a recipe with the glass powder.

 

There are a few research papers where people have trialled cullet with good results (in industry rather than for artistic purposes), and I figure once I know what sorts of issues I'm going to encounter if the composition varies (eg, if the alumina decreases or increases, if the soda decreases or increases, etc - how will I tell, what will give me an idea of what's changed and I think thats only going to come from understanding the chemistry really well), then I can adjust the recipe. This is why I asked for title of good textbooks to chase up, so I can have an understanding of what the various components will do in a clay body, so if something goes wrong I have at least an idea where to start to adjust.

 

As it stands now the body is good, except for the fact that it seems to be absorbing the glaze.  The translucency is the added bonus.

 

I'm aware that for those who have access to kilns that can reach stoneware temps it must seem like such a waste of time and effort, but I've had a few emails from people in the same situation as me that are watching with keen interest.  And if I CAN work this out, in the long run it will mean that I'll save money on firing, plus I will have the added benefit of the expanded colour palette. 

 

It may prove to be fruitless eventually, but for now I keep making steps forward so I'll continue on. It would just be easier if there were others that had tried this and succeeded on a large scale that I could get guidance from, and without a ceramics chemistry training I feel like I'm walking forwards blindfolded.   If I can succeed, I think the benefits will be very well worth the effort.



#24 Babs

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Posted 14 April 2014 - 04:13 AM

Anna,

Here's another book that may be of interest to you.

I have it here, found it whilst looking for something else.

"Ceramic science for the potter" W G Lawrence.

Very detailed and covers many aspects of clay bodies: firing; Glaze fit; Thermal Shock;Thermal shock Bodies; and much more.

Hopefully another forum member knows this book, American, and can advise you on it.

If you continue down the path you're on , it may be worth investing in, not a quick read.

I'm hanging onto this one because I hope my chemistry minded daughter sees sense and stops playing with chemistry and starts working with claY..And making glazes for moi

Would consider lending it to you but you may need it for a year or 20!

Keep in touch!



#25 AnnaM

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Posted 14 April 2014 - 07:36 AM

Thanks Babs, there are a couple of secondhand copies on amazon!



#26 JBaymore

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Posted 14 April 2014 - 07:58 AM

Anna,

 

The point here is that without a decent chemical analysis... and also the knowledge of how the analysis changes with each batch of cullet....... even with my extensive background in ceramic chemistry..... I myself can't work with the information you have in any "technical" way.  So learning ceramic chemistry is not going to help you with THIS problem (good to understand overall though).

 

best,

 

.......................john


John Baymore
Immediate Past President; Potters Council
Professor of Ceramics; New Hampshire Insitute of Art

http://www.JohnBaymore.com

#27 Babs

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Posted 14 April 2014 - 06:18 PM

Anna,

 

The point here is that without a decent chemical analysis... and also the knowledge of how the analysis changes with each batch of cullet....... even with my extensive background in ceramic chemistry..... I myself can't work with the information you have in any "technical" way.  So learning ceramic chemistry is not going to help you with THIS problem (good to understand overall though).

 

best,

 

.......................john

John is the book mentioned above a good text for Anna  , not for her present prob. but as a source book?



#28 JBaymore

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Posted 14 April 2014 - 09:21 PM

"Ceramic Science for the Potter" is an absolutely GREAT book.... but not a "starter" book.  Too much information in the wrong format.  It assumes some decent knowledge.  As I remember ,... it is also expensive on the used market (not sure).

 

The best 'starter stuff' is getting Insight Level II and the nice little "Magic of Fire" book that comes with it and the access to the secure info on Digitalfire.com.  Then work thru the tutorials in order... and follow the other stuff in Magic of Fire.  I now use that as the "text" for my Ceramic Materials I course at the college...and have for a few years.

 

"Clay and Glazes for the Potter" (Robin Hoppoer revised edition is best now) is a good first book .... but the price is crazy now.

 

best,

 

...................john


John Baymore
Immediate Past President; Potters Council
Professor of Ceramics; New Hampshire Insitute of Art

http://www.JohnBaymore.com




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