hello,

I'm a new potter who plans to make my own glazes following recipes I find online.  I'm firing them in my home studio at cone 6 in my electric kiln.

I love the Wright's Water Base Blue glaze I found in one of the Ceramics Art issues, but have trouble making this glaze adhere to the bisque piece before firing.  I have not had this problem with any of the other glazes I have made.  Here is the recipe I followed:

Copper carbonate 5%

Lithium carbonate 3%

Strontium carbonate 9%

Frit 3110 59%

Edgar Plastic Kaolin  12%

Flint 17%

Add: Bentonite 2%

Is there anything you can suggest I add to this already mixed glaze (I made up a large batch!).

Someone suggested coating my pieces with karo syrup to help it adhere, but didn't work.  I've tried the brushing medium, but again no success.  Would appreciate any advise on salvaging this glaze, and in addition, what is wrong with this recipe.

thank you,

Rita

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A little more info please:  Are you dipping or brushing?  How many coats?  How thick is the glaze on the pot?  The width of a fingernail?  A dime?  More?

My first thought is to add water.  I always try thinning the glaze when this happens.  I would suggest removing some from your big batch and thin significantly (so you don't mess up the whole thing if this isn't the problem.)  Does even a very thin, watery coat pop off?

I have three glazes that must be applied thin in 3+ coats with a full dry in between or they turn into a disaster area.  I won't be making more of them.

Two other ideas just crossed my mind.  Are you dusting the pots before glazing?  (Wiping with a barely wet sponge and then allowing them to dry?)  Dusty pots can cause issues with some glazes.  And are you bisquing to ^06?  Some people bisque hotter which makes the clay less absorbent.  Nothing wrong with other temps, but it is another possible explanation for this problem.

Even with 12% Kaolin and 2% Bentonite, some glazes with a very high percentage of frit will have a tendency to powder-off.  You may also want to try less water. 

This is a similar glaze formulated with less frit:

114.2%  Water Color Green ^6
  49.1%  Feldspar Custer
  17.5%  Silica
  16.4%  Whiting
   7.7%   Strontium Carbonate
   5.1%   Ferro Frit 3124
   4.1%   Lithium Carbonate
   3.0%   Magnesium Carbonate
   3.1%   Bentonite
   8.2%   Copper Carbonate

This glaze has no suspension apart from the 3.1% Bentonite.  Yet this glaze has to be made with far less water than I typically add, otherwise it simply can't be applied.

*Chuckling*  Ask a question online and you are sure to get every answer humanly possible.  : ) 

thank you Dawn for your suggestions.  I'm brushing the glaze on and have made sure there is no dust/debris on the pots.  I have bisqued them at ^06 too.  this is the only glaze I'm having problems with -- hmmm.  It is quite thin but I'll try thinning it more and apply multiple layers.  I'll try it this weekend...

thanks,

Rita



Rita Mattson said:



Norm Stuart said:

Even with 12% Kaolin and 2% Bentonite, some glazes with a very high percentage of frit will have a tendency to powder-off.  You may also want to try less water. 

This is a similar glaze formulated with less frit:

114.2%  Water Color Green ^6
  49.1%  Feldspar Custer
  17.5%  Silica
  16.4%  Whiting
   7.7%   Strontium Carbonate
   5.1%   Ferro Frit 3124
   4.1%   Lithium Carbonate
   3.0%   Magnesium Carbonate
   3.1%   Bentonite
   8.2%   Copper Carbonate

This glaze has no suspension apart from the 3.1% Bentonite.  Yet this glaze has to be made with far less water than I typically add, otherwise it simply can't be applied.

thanks for your suggestions and the recipe.   I'll give this a try if I can't fix my current batch.

thanks again,

Rita

Glazes with low clay content can have some adherence problems. Glazes that also shrink a lot in drying can flake off. One solution you can try is instead of mixing your dry batch with water, use a gum solution like CMC.

I have a similar problem with two glazes that were given to me when the potter suddenly left town.  One is called Bronze Blue and the other Bronze Green.  I do not have the recipes for them.  Her test tiles looked great - a kind of satiny matte with great layering possibilities.  Each time I try to put them on the pot they dry up like mud flats in a drought and then flake off the pot.  I tried thinning the glaze a lot, brushing multiple coats, but the same thing happens. Dipping - the same thing happens.  Putting them on first and another really stable and sticking glaze over it - that one just follows the lead of the Bronze glaze.  I took out a batch and added some Liquid gum.  This made the glaze which was thicker, very, very thin and the firing results were poor.

Is it possible that glazes can go 'off' over time?

Dry glazes should be stable over time, but once water is added glazes can change as they age. 

1.) Chemical reactions can occur between glaze ingredients once water is added.  Jon Britt explores one example in this article about a particular copper red glaze.

http://www.ceramicstoday.com/articles/flambe_magic.htm

These processes don't involve any magical alchemical transmutation, so exactly the same elements are there, but recombination like the formation of the crystals Jon Britt experienced does change how the glaze fires.

2.) Bacterial action can break down "insoluble" glaze ingredients allowing soluble elements to leech, which are often sodium and potassium salts which cause the glaze to deflocculate requiring the addition of more calcium or magnesium ions.

3.) At our studio, unfortunately the most common reason bucket glazes "change" over time is that people using the glaze don't use their hand to check for sediment at the bottom of the bucket of infrequently used glazes.  As cone 6 glazes often use frit as a primary flux, and this ground glass tends to sink to the bottom, people end up with cloudy refractory glazes - making it obvious the glaze was not fully suspended when they applied it.  They applied the clay-like ingredients with very little frit.  Unfortunately this causes a problem for later users as the percentage of frit in the remaining glaze is increased.


Lyn Rapley said:

Is it possible that glazes can go 'off' over time?

Norm,   What do you do with the sediment if you find it at the bottom of the bucket?  I think I have some buckets like this, and yep, the glazes are poor.  I didn't know I was supposed to do something with the sediment.  Please tell.

Juli

Norm said:

3.) At our studio, unfortunately the most common reason bucket glazes "change" over time is that people using the glaze don't use their hand to check for sediment at the bottom of the bucket of infrequently used glazes.  As cone 6 glazes often use frit as a primary flux, and this ground glass tends to sink to the bottom, people end up with cloudy refractory glazes - making it obvious the glaze was not fully suspended when they applied it.  They applied the clay-like ingredients with very little frit.  Unfortunately this causes a problem for later users as the percentage of frit in the remaining glaze is increased.

Juli -- The sediments at the bottom of glaze buckets are an essential part of the glaze.  With Cone 6 glazes this sediment in primarily the frit (the ground glass which makes the other ingredients melt properly).

You stick your hands in the bucket and mix the stuff back into the glaze, often with the assistance of a spatula or putty knife.  Then you have to break it up with your hands until it is all suspended.

If it has hard-panned that badly you need to first add calcium chloride pellets.  They heat-up when mixed with water and quickly dissolve.

http://www.amazon.com/Scotwood-Industries-9-5J-HEAT-Concentrated-9-...

You have to keep calcium chloride sealed in the container, as it absorbs water from the air turning into goo.  But I prefer this to adding epsom salts (magnesium sulfate) as enough magnesium makes a glaze crawl, while I have never found a glaze changed by the small amount of extra calcium.

If your glaze doesn't have enough clay, I definitely recommend Bentone-EW which I bought from Trinity Ceramics in Texas. US Pigment will be stocking this item soon, and may already have it.  If a glaze requires 1.5% bentonite to suspend, you use only 0.1% Bentone-EW and it mixes well just adding it to the glaze or water - quite unlike common bentonite.



juli long said:

Norm,   What do you do with the sediment if you find it at the bottom of the bucket?  I think I have some buckets like this, and yep, the glazes are poor.  I didn't know I was supposed to do something with the sediment.  Please tell.

Juli

Norm said:

3.) At our studio, unfortunately the most common reason bucket glazes "change" over time is that people using the glaze don't use their hand to check for sediment at the bottom of the bucket of infrequently used glazes.  As cone 6 glazes often use frit as a primary flux, and this ground glass tends to sink to the bottom, people end up with cloudy refractory glazes - making it obvious the glaze was not fully suspended when they applied it.  They applied the clay-like ingredients with very little frit.  Unfortunately this causes a problem for later users as the percentage of frit in the remaining glaze is increased.

Norm, How does the Bentone W compare in price to bentonite?


Norm Stuart said:

Juli -- The sediments at the bottom of glaze buckets are an essential part of the glaze.  With Cone 6 glazes this sediment in primarily the frit (the ground glass which makes the other ingredients melt properly).

You stick your hands in the bucket and mix the stuff back into the glaze, often with the assistance of a spatula or putty knife.  Then you have to break it up with your hands until it is all suspended.

If it has hard-panned that badly you need to first add calcium chloride pellets.  They heat-up when mixed with water and quickly dissolve.

http://www.amazon.com/Scotwood-Industries-9-5J-HEAT-Concentrated-9-...

You have to keep calcium chloride sealed in the container, as it absorbs water from the air turning into goo.  But I prefer this to adding epsom salts (magnesium sulfate) as enough magnesium makes a glaze crawl, while I have never found a glaze changed by the small amount of extra calcium.

If your glaze doesn't have enough clay, I definitely recommend Bentone-EW which I bought from Trinity Ceramics in Texas. US Pigment will be stocking this item soon, and may already have it.  If a glaze requires 1.5% bentonite to suspend, you use only 0.1% Bentone-EW and it mixes well just adding it to the glaze or water - quite unlike common bentonite.



juli long said:

Norm,   What do you do with the sediment if you find it at the bottom of the bucket?  I think I have some buckets like this, and yep, the glazes are poor.  I didn't know I was supposed to do something with the sediment.  Please tell.

Juli

Norm said:

3.) At our studio, unfortunately the most common reason bucket glazes "change" over time is that people using the glaze don't use their hand to check for sediment at the bottom of the bucket of infrequently used glazes.  As cone 6 glazes often use frit as a primary flux, and this ground glass tends to sink to the bottom, people end up with cloudy refractory glazes - making it obvious the glaze was not fully suspended when they applied it.  They applied the clay-like ingredients with very little frit.  Unfortunately this causes a problem for later users as the percentage of frit in the remaining glaze is increased.

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