Green Pooling Blue glaze

[Mary Lou Eshelman]

I bought a beautiful glaze called Green Pooling Blue from Glazemixer.com. It had been posted there without a recipe listed. Now Glazemixer is defunct and I'm looking for someone who knows the recipe for this lovely glaze. It is very runny. I use it on the inside of gloss-white glazed pots and it is greenish blue pooling to a blue that looks like the depths of the sea. If you know of it, I would greatly appreciate the information since it's one of my favorite glazes.

[Erik Evans]

Any chance you have a photo of this glaze for reference?

[Norm Stuart]

As Erik asks, a photo would really help. 

From the description alone it could be a copper glaze with the color shifted blue by zinc or lithium.

Supposedly sodium and potassium induce this same color shift, but it doesn't work in the glazes I've tried.

This tile of Anne Currier Water Color Blue is a low-fire Cone 06 glaze, but it give you an idea of the color I'm describing.

104.0%	Anne Currier Water Blue  Cone ^06 low-fire
73.0%	Ferro Frit 3110
10.0%	Silica
7.0%	Gerstley Borate
7.0%	Kaolin
4.0%	Copper Carbonate
3.0%	Zinc Oxide

This is Zam Celadon a similar copper colored Cone 6 glaze without the color change created by lithium or zinc.  It has a huge amount of sodium, but note there's no color shift to blue.

[Mary Lou Eshelman]

I'm posting a picture of it on a gloss white bowl.

[Norm Stuart]

The glaze in your photo might be a color-shift copper with less copper and less cobalt added.

If so, Watercolor Blue might be a good starting point with less cobalt. Others will have different suggestions.

But any cobalt colored blue translucent glaze will become darker and more intense on the bottom of a pot where it is thicker.

Water Color Blue on the right.  Your photo on the left.

[Mary Lou Eshelman]

Thanks! I think I'll try starting with Watercolor Blue, which I have used before and liked. It is the closest thing to Green Pooling Blue that I know of. Can you explain "color shift copper" a little?

[Norm Stuart]

From trial and error for hundreds of years potters have known that some colorants looked different in and "akaline glaze than they did in their usual glaze.

Much of the collected wisdom can be found here.  https://digitalfire.com/4sight/properties/ceramic_property_glaze_co...

I haven't found these terms particularly helpful, nor do I think they relate well to the "pH of glazes in high temperature chemistry" if you look into that.  So I refer to color change ingredients like lithium, zinc, tin, barium and less strongly strontium etc.  I can give you an idea of why that is, but not the specific answer.

In short what we perceive as color are generally the portion of the wavelengths of white light which are reflected back after hitting an object.  Changing the elements and crystalline structure of a glass can significantly change which wavelengths get reflected, and thus what we call color.

Titanium Dioxide creates crystals we can't see on the surface of a glaze and scatters the light so the surface looks matte, that's pretty easy for me to understand.  But take the fact that tin oxide with green chrome oxide create something which reflects pink or red. What is the particular structural change in the glass which makes the green look red? I've read a lot about the topic and I still haven't the slightest idea. And at some point I realized I didn't need to know why, it's just a color change combination.

In a very real way we're making man-made gems on the surface of our ceramic, and gems have all sort of different colors, created sometimes by tiny little changes in structure.

Take white alumina as an example - in one crystal it's sapphire, a different color depending on the impurities. - https://en.wikipedia.org/wiki/Sapphire

Just a chunk of alumina surrounded by some carbon, the same stuff as coal.

[Tileworks]

Glad you like it :-) It is a glaze recipe we developed for our tile studio. I am sorry I cannot share the recipe but I am glad that you liked the color :-)

I miss Glazemixer, it was a good service. is there anything that has come up to replace it?

Here is a shot of Green Pooling Blue as it was originally intended - on a tile.

[Norm Stuart]

Ivy - Do you know why Glazemixer stopped selling glaze?

They were out of business before I had an opportunity to use their services, so I have no idea who he/she/they were or where they were located.

I suppose any of us with 50 pound bags of raw materials could do the same, but it's probably small margins.

[Tileworks]

I have no idea. I ordered from them a few times a year, so I was disappointed when they folded. I do know that they were hacked badly about a year before they closed up shop.

There are other places that will custom mix your own recipe for you, but not other places where you can also order other artists' glazes.

[Tom Anderson]

Norm:

I have studied amphoretic oxides for years: not a lot of good information out there. The one thing I have studied, and holds a fair about of truth is the crystal habit of each element we use. Crystalline glaze use silica, zinc, and lithium: all of which have hexagonal crystal structures elementally. Sodium and Potassium have cubic crystals structures: and show up in crystalline glazes as course threading, spikes, and needles.

The other issue is band gap: which for ease of understanding would be small, medium and large magnets on a molecular level. Sodium has a band gap of 1.79 and lithium is 0.024: which makes lithium a non evasive flux in a glaze. By non evasive: I mean it does not have enough molecular polarity to attract other elements: sodium however does. In addition, high sodium glazes can alter the final structure of the glass because it's cubic crystal structure is the most powerful influence. Imagine shining a light through a six sided prism (hexagon), and a four sided prism (cubic): how it refracts light changes.

Tom

[Norm Stuart]

Tom - I never studied high temperature chemistry so I simply take the listing below as a given.

Aklaine Fluxing Oxides R2O and RO
AG2O	silver
K2O	potassium
Li2O	lithium
Na2O	sodium
+
BaO	barium
CaO	calcium
CuO	copper
FeO	iron
MgO	magnesium
SrO	strontium
Neutral or Refractory Oxides R2O3
Bi2O3	bismuth
CO	carbon monoxide
NO	nitric oxide
Both Refractory and Amphoteric
Al2O3	alumina
B2O3	boron - also "glass forming"
Cr2O3	chrome
Amphoteric -   RO and R3O4
Basic to acids, Acidic to bases
GeO	germanium monoxide, eutectic only
PbO	lead
Pb3O4	lead
SnO	tin
ZnO	zinc
Acidic Glass Forming Oxides
CoO	cobalt
GeO2	germanium
MnO2	manganese
SiO2	silica
TiO2	titanium
ZrO2	zircon
CO2	carbon
NO2	nitrogen
NO3	nitrogen
SO2	sulfur
SO3	sulfur

I understand the concept of how they're categorized, but the pH of a molten glaze is a conceptualization which while very useful is difficult for me to reconcile with my day to day experience of acids and bases.

Just from experience though when I read a colorant makes a color change in an "alkaline glaze" the sure solution if adding lithium carbonate.  Trying to achieve the same color-shift with sodium can be frustrating.

Tom Anderson said:

Norm:

I have studied amphoretic oxides for years: not a lot of good information out there. The one thing I have studied, and holds a fair about of truth is the crystal habit of each element we use. Crystalline glaze use silica, zinc, and lithium: all of which have hexagonal crystal structures elementally. Sodium and Potassium have cubic crystals structures: and show up in crystalline glazes as course threading, spikes, and needles.

The other issue is band gap: which for ease of understanding would be small, medium and large magnets on a molecular level. Sodium has a band gap of 1.79 and lithium is 0.024: which makes lithium a non evasive flux in a glaze. By non evasive: I mean it does not have enough molecular polarity to attract other elements: sodium however does. In addition, high sodium glazes can alter the final structure of the glass because it's cubic crystal structure is the most powerful influence. Imagine shining a light through a six sided prism (hexagon), and a four sided prism (cubic): how it refracts light changes.

Tom

[Tom Anderson]

Norm:

I think cobalt needs to be added to the acidic column: my cobalt crystalline glazes are much more fluid than the others. In fact, it is not uncommon to see "boiling" marks: Fara Shimbo I believed used the word "felting" to describe the surface effect.

I have long preached about the purity levels of the materials we purchase.It is common to see 8% sodium in the alumina we purchase. Silica can be as low as 80% pure, and the rest being sodium, potassium, selenium, and sulfur. Yellow zinc is also notoriously impure: with high levels of sulfur, cadmium, and selenium. Glaze calculators have a specific analysis for a specific type of these products: which can be much lower than we actually purchase. When I switched to Imsil A-25 and French process zinc, and higher purity Nep Sy: many of the problems went away,

Tom