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Hello!

I got all the ingredients today to mix my first batch of glaze - Kitten’s Clear - from John Britt’s book on mid-fire glazes. 

 

Trouble is, the recipe calls for an added 2% of bentonite and the girl who helped me gather all the ingredients either missed/skipped or forgot it. 

 

How essential is the bentonite? Can I proceed without it? I plan to add some whiting and stain. If it’s essential, can someone link a good place to buy some online? I actually have a 100% bentonite clay powder I use for a face mask - would that work as a replacement?

 

thanks!

Edited by Pinkfish
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probably can do it without the bentonite which is used to keep the ingredients in suspension in the main, or the glaze flocculated. need to stir.

It also makes your glaze as it dries on your pots less powdery and so can handle being handled more!!

If indeed the powder you have is bentonite clay powder then I think this is what you are looking for in the first place.

Tip:

Mix the bentonite well with other dry ingredients before adding to water as bentonite forms horrible clumps when added to water on its own.

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4 minutes ago, Babs said:

probably can do it without the bentonite which is used to keep the ingredients in suspension in the main, or the glaze flocculated. need to stir.

It also makes your glaze as it dries on your pots less powdery and so can handle being handled more!!

If indeed the powder you have is bentonite clay powder then I think this is what you are looking for in the first place.

Tip:

Mix the bentonite well with other dry ingredients before adding to water as bentonite forms horrible clumps when added to water on its own.

Yes Babs advice is spot on.

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just a question about adding whiting.    do you mean that you are going to add to the final recipe which probably equals 100 the chemical called whiting which is calcium?   or do you mean that you intend to make the glaze white by adding some opacifier like tin oxide or zircopax?

i ask because the ingredient whiting is usually included in the base recipe to reach the 100 percent so it is already in the glaze mix.

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2 hours ago, oldlady said:

just a question about adding whiting.    do you mean that you are going to add to the final recipe which probably equals 100 the chemical called whiting which is calcium?   or do you mean that you intend to make the glaze white by adding some opacifier like tin oxide or zircopax?

i ask because the ingredient whiting is usually included in the base recipe to reach the 100 percent so it is already in the glaze mix.

This recipe doesn’t have whiting as an ingredient. I planned on adding whiting on top of the 100% ingredients of Kitten’s Clear as well as some mason stain. I am hoping it works as an opacifier. 

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47 minutes ago, Pinkfish said:

This recipe doesn’t have whiting as an ingredient. I planned on adding whiting on top of the 100% ingredients of Kitten’s Clear as well as some mason stain. I am hoping it works as an opacifier. 

Whiting is calcium carbonate which acts as a flux. To opacify, zircopax, tin or sometimes titanium dioxide is used.  

edit: Pres linked a glossary to the top of the Studio Operations and Making Work section, it's a good place to look up materials etc.  

Edited by Min
added glossary link
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The recipe contains 8% kaolin and 17% gerstley, so it should stay suspended reasonably well without the bentonite.  There are various types of bentonite. Some used in cosmetics and soap might not be appropriate for ceramic glaze . I would be careful without knowing exactly what type of bentonite was used in the facial mask.

Whiting is sometimes used in the paint industry as a white pigment, but in a ceramic glaze it melts into calcium oxide, a flux, and would change the glaze. If you are seeking to opacify it, use one of the materials suggested by Min.

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1 hour ago, Dick White said:

The recipe contains 8% kaolin and 17% gerstley, so it should stay suspended reasonably well without the bentonite.  There are various types of bentonite. Some used in cosmetics and soap might not be appropriate for ceramic glaze . I would be careful without knowing exactly what type of bentonite was used in the facial mask.

Whiting is sometimes used in the paint industry as a white pigment, but in a ceramic glaze it melts into calcium oxide, a flux, and would change the glaze. If you are seeking to opacify it, use one of the materials suggested by Min.

Thanks for the info! I guess I learned not to trust the clerks at the local pottery store :(

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12 hours ago, Dick White said:

 

 

 

12 hours ago, Dick White said:

The recipe contains 8% kaolin and 17% gerstley, so it should stay suspended reasonably well without the bentonite.  There are various types of bentonite. Some used in cosmetics and soap might not be appropriate for ceramic glaze . I would be careful without knowing exactly what type of bentonite was used in the facial mask.

Whiting is sometimes used in the paint industry as a white pigment, but in a ceramic glaze it melts into calcium oxide, a flux, and would change the glaze. If you are seeking to opacify it, use one of the materials suggested by Min.

dick, sodium based or calcium based?

is calcium bentonite ever used for pottery?

if in case of using merely for suspension would it make a difference?

Pinkfish, don't put it on face, sucks the moisture out of the desert!

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4 hours ago, Babs said:

is calcium bentonite ever used for pottery?

Yes. 

And we have recently been discussing it a bit here.  Search this very forum for “calcium bentonite”.  

There are quite a few calcium bentonites on the market (have a browse over at digitalfire), although they are often not well labelled and it appears that some consumers - and possibly some vendors! - do not really know whether they are using/selling sodium bentonite or calcium bentonite.    

 

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8 hours ago, curt said:

Yes. 

And we have recently been discussing it a bit here.  Search this very forum for “calcium bentonite”.  

There are quite a few calcium bentonites on the market (have a browse over at digitalfire), although they are often not well labelled and it appears that some consumers - and possibly some vendors! - do not really know whether they are using/selling sodium bentonite or calcium bentonite.    

 

thanks curt, will search this very forum!

thought you might give it un a nutshell, some dissertations posted here, she types smiling, in case the humour is lost by some...

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pinkfish, it appears you are somewhere in florida, so am i.  not many places to buy ingredients near me.  can you say approximately where you are located?  

it occurred to me that the clerk at the store might have thought you wanted to add a "whitener" and not whiting and you misheard the word.

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Lol, yes Babs.  Know what you mean.   The short answer is that I am afraid there is not really a short answer. But first let me get my dissertation notes out... :lol:

The calcium bentonite will work fine.  That said....

It does swell, but not nearly as much as a sodium bentonite, so you will not get the same extent of suspension if that’s what you are after.

The chemistry would be important, except that if you are only adding 2% it is almost irrelevant.

Bottom line: I agree with everyone else that in this case the bentonite is probably not essential.

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I am interested because I used a recipe which was top heavy in Bentonite, 7% from memory, first time I mixed and used, bit tricky but glaze ended up ok.

new bentonite,well to me, from old potter, glaze cracked fell off pot etc so readily made it unuseable

got advice here on how to alt er recipe, consensus was the guy who made recipe had a sheetload of bentonite.

just read that Portland cement can be used as glaze ingredient.....just throwing you sthing for your next dissertation ...

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Ah, bentonite, just not what it used to be...  wicked shrinkage, for sure!

Mucked around a bit with Portland Cement.  Like whiting on steroids.  Sounds like a perfect topic for my next opus magnum!  You’re the best, Babs!

 

 

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6 hours ago, curt said:

Mucked around a bit with Portland Cement.  Like whiting on steroids.  Sounds like a perfect topic for my next opus magnum!


Once upon a time, a standard cone 10 whiting based clear glaze was pin holing and blistering routinely.   I was convinced that the gas was from the whiting, so I converted the recipe to use Portland cement instead of whiting for the calcium source.   It worked just fine. 
Getting the oxide analysis from the supplier for the bag of cement required multiple phone numbers but was not difficult. 
The main trick was to find the correct additive to prevent the 'cement' from cementing! 
Made a gallon or so, lasted spring and summer semesters.   (The gassing was from the clay body not the whiting). 
 
There is a CM article from way, way, back on using Portland cement as a glaze ingredient.
 
LT
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23 hours ago, oldlady said:

pinkfish, it appears you are somewhere in florida, so am i.  not many places to buy ingredients near me.  can you say approximately where you are located?  

it occurred to me that the clerk at the store might have thought you wanted to add a "whitener" and not whiting and you misheard the word.

No she didn’t mishear. We talked about it quite a bit. She said it would make Kitten’s Clear opaque. I was at Highwater Clays. She was very nice!

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18 hours ago, Magnolia Mud Research said:

Once upon a time, a standard cone 10 whiting based clear glaze was pin holing and blistering routinely.   I was convinced that the gas was from the whiting, so I converted the recipe to use Portland cement instead of whiting for the calcium source.   It worked just fine. 
Getting the oxide analysis from the supplier for the bag of cement required multiple phone numbers but was not difficult. 
The main trick was to find the correct additive to prevent the 'cement' from cementing! 
Made a gallon or so, lasted spring and summer semesters.   (The gassing was from the clay body not the whiting). 
 
There is a CM article from way, way, back on using Portland cement as a glaze ingredient.
 
LT

yeh, that was what zi was reading, 1981 I think.

those mags were pretty classy full of great articles, and not even glossy

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On 3/18/2018 at 4:25 PM, Dick White said:

The recipe contains 8% kaolin and 17% gerstley, so it should stay suspended reasonably well without the bentonite.  There are various types of bentonite. Some used in cosmetics and soap might not be appropriate for ceramic glaze . I would be careful without knowing exactly what type of bentonite was used in the facial mask.

Whiting is sometimes used in the paint industry as a white pigment, but in a ceramic glaze it melts into calcium oxide, a flux, and would change the glaze. If you are seeking to opacify it, use one of the materials suggested by Min.

It’s calcuum bentonite. Very fine and greenish gray in color. Still avoid?

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1 hour ago, Pinkfish said:

It’s calcuum bentonite. Very fine and greenish gray in color. Still avoid?

ignore the bentonite this time, see advice above, stir between applications.

next time...

just don't try to add ben. Later, a lumpy gruel will appear in your bucket

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