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Hi all

Is zircopax OK to use in place of white pigment or stain? I want to make a basic white underglaze with it. I am worried about pinholing or peeling though. I want to fire to about 1150 centigrade. Any help appreciated.

 

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someone here can help you if you put more info in your post.   the recipe, what is white pigment,  the clay you use, the type of pot you want to make all help in giving you the right answer.  knowing your intended outcome helps guide you to it.

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Hi oldlady. Thanks for your reply!

My recipe is Ferro frit 20, Ball clay 20, Kaolin 20.

In my country we have something called white pigment- sorry I dont know what it comprises. I dont have any but I have zircopax so I want to use that instead but I have heard that it can cause pinholing and peeling if used in large percentages.

I am trying to make a large jug -( about 40cm. high) with my local red earthenware.

I want to know what % zircopax to use that will give me a satin matt or shiny surface. I dont what a dry matt.

And I want to know if I should add some bentonite to mitigate the drying effects of the zircopax. It is a micropore 6, so quite refined type of zircopax available in my country.

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Yes, zircopax can be used to make white glazes. The problem might be it giving a different kind of white, if the white stain sold where you live uses Titanium or Tin Oxide as an opacifier instead of zirconium silicate.
Some people feel the Zirconium white is too bright/harsh, you can use half Zircopax, half Tin oxide and or add small amounts of Titanium Oxide or light rutile to tone it down. 
I think you are firing to cone 5? Not sure how much you’d need to add, because I use cone 03 terracotta clay. Some recipes call for up to 20% of zircopax. I use about 12-15% (but usually 10% is enough) when looking for a solid white and since my glazes are balanced never get pinholes. But according this old link it seems that my experience holds true at cone 5/6.
http://www.potters.org/subject21453.htm
Pinholes could be caused by different things (zircopax has never given me much trouble). The Recipe, how you mix it, how you bisque and what type of clay can also factor in:
https://digitalfire.com/4sight/glossary/glossary_pinholing.html
https://digitalfire.com/4sight/troubleshooting/ceramic_troubleshooting_glaze_pinholes_pitting.html
Peeling is cause by the clay and glaze having different expansion % .
https://digitalfire.com/4sight/education/understanding_thermal_expansion_in_ceramic_glazes_198.html
https://digitalfire.com/4sight/troubleshooting/ceramic_troubleshooting_glaze_crazing.html
https://digitalfire.com/4sight/education/adjusting_glaze_expansion_by_calculation_to_solve_shivering_199.html
That website also has recipes…
You could try doing a 3 part line blend. Adding Zircopax starting with 5% up to 10%, and then add 2 to  3% of frit and/or subtracting  2 to 3% kaolin at a time if you get pinholes. 
Probably bentonite is not needed, because the recipe you listed is very high in clay content … you could try adding 1% if needed…
https://digitalfire.com/4sight/material/bentonite_106.html
Good Luck!
 

Edited by enbarro

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@vivk, are you looking for an underglaze or a glaze? Your title says underglaze but then I read this so wasn't sure.

On 9/6/2018 at 12:51 AM, vivk said:

satin matt or shiny surface. I dont what a dry matt.

 

If it is an underglaze you are looking for are you planning on using a glaze overtop of it or are you looking for a vitreous slip? 

Also, you are using a clay that fires to 1150C (very approx cone 3)?

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Hi Min

On 9/12/2018 at 5:41 PM, Min said:

@vivk, are you looking for an underglaze or a glaze? Your title says underglaze but then I read this so wasn't sure.

If it is an underglaze you are looking for are you planning on using a glaze overtop of it or are you looking for a vitreous slip? 

Also, you are using a clay that fires to 1150C (very approx cone 3)?

Hi . yes I am looking for a bright white underglaze to use on a red earthenware . I fire to 1100 or cone 03 in an electric kiln. I use a glossy transparent glaze over it . ideally I want an underglaze that works as a slip as well and can be used on both greenware and bisque.

 

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Cone 03 and cone 3, not the same thing...

But if you actually fire cone 03, the link below has several recipes for slips that can be used on greenware and bisque.

www.priscillahollingsworth.com/uploads/4/9/8/3/4983085/lowfire_glaze_list.pdf

Btw, underglazes are usually dry (not glossy), is that what you are looking for? 

Regards

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1 hour ago, enbarro said:

Cone 03 and cone 3, not the same thing...

But if you actually fire cone 03, the link below has several recipes for slips that can be used on greenware and bisque.

www.priscillahollingsworth.com/uploads/4/9/8/3/4983085/lowfire_glaze_list.pdf

Btw, underglazes are usually dry (not glossy), is that what you are looking for? 

Regards

Hi. Ok, so I see there is a bit of confusion. But it has helped me clarify things- initially I was wanting a zircopax underglaze to work under my glossy transparent glaze which fires at around 1100.

I said 1150 which caused the confusion of cone 3 when I actually meant cone03 (1100)

have since tried some test tiles, using 10%zircopax in my recipe and found it works ok at 1100. And does not bubble under the glaze I use, which is a relief. So thanks everyone for your input and useful links, which have been very helpful.

Now I am trying that same recipe as a slip over bisqued ware- hope it works.

That link does not work btw.

Edited by vivk
faulty link

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