Can one predict the appearance of a glaze? (part II: tri-axial graphs of the Flux, Glass-formers and Amfoteres)

[Daniel Spruyt]

In a previous post, I discussed briefly a method to predict -with some approximation - the possibility to predict the appearance of a glaze using the Si/Al ratio (and to some extend the SiB/Al ratio). The graphic approach by Michael Bailey in his book 'Cone 6 glazes' is interesting and helps also to document my work.

Thinking about the major elements in the Unity formula, I was thinking to go a step further and use the elements in a tri-axial graph. Some more academic papers have used this approach as well but in a different form and scope.

To avoid misunderstanding:

Flux = Basic Oxides (e.g. Na₂O, CaO, ZnO ...)

Amfoteres = Stabilizers (e.g. Al₂O₃ ...)

Glass-formers = Acidic Oxides (e.g. SiO₂ ...)

After a quite intense search on the Internet I found a way to create tri-axial graphs in Excel. I transformed it such way that I could make graphs showing the Molar percentage out of the Unity formula for the Fluxes, Glass-formers and the Amfoteres. Then I 'calibrated' the background of the graphs using some well known and tested glazes in order to delimit the areas for:

Alkaline Earth Matt

Alkaline Earth - Alumina Matt

Alumina Matt

Alumina - Silica Matt

High Silica Matt

'Best Melt'  - glossy area

Adding up the Fluxes, Glass-formers and Amfoteres from the Unity formula and calculate the Mol % for each group I got a clear view for any new glaze I tested or developed. In some way, it may replace a glaze calculation software for developing glazes - although I use it as a complement to my glaze development tools (INSIGHT and my own software Glazeval).

I show here an example for the same glazes used in the previous post .

Legend:

C6 ABOM 1: (C6 Glazes) - Alumina Boric Oxide Matt

C6 AM1: (C6 Glazes) - Alumina Matt

C6 BG1: (C6 Glazes) - Base Glaze -glossy

C6 HSM5: (C6 Glazes) - High Silica Matt

MC6G 1: (Mastering C6 Glazes) - High Calcium Semimatte 1

MC6G 2: (Mastering C6 Glazes) - High Calcium Semimatte 2

 

Can you work with glazes and possibly develop some without all the above?

Yes, of course. I consider this as valuable addendum to the learning and the better understanding of glazes and by this to help to master the glazes.

In a following post, I will briefly discuss how to predict if glazes show a risk for glaze faults.

[Chantay Poulsen]

Another use is to use it as a teaching tool. It clearly explains the effects of increasing and decreasing ingredients. Couple that with visuals of actual glaze pics and for us visual learners it will be a hit.

[Daniel Spruyt]

Thanks!

Finally a visual oriented peer.

Chantay Poulsen said:

Another use is to use it as a teaching tool. It clearly explains the effects of increasing and decreasing ingredients. Couple that with visuals of actual glaze pics and for us visual learners it will be a hit.

[Nadine Mercader]

I think Chantay's comment was right on and Daniel I think almost all of us is very visual and we understand complex subjects like glaze chemistry far more easily with pictures and graphs as you have so kindly posted.

[Norm Stuart]

I've found it more predictable to create a matte glaze by adding enough titanium, zinc or calcium to cause enough crystallization on the surface to eliminate the shine. 

Increasing the ratio of alumina to silica can also create a matte glaze surface but it has seemed to be greatly affected by the rate at which I cool the kiln.

"Mastering Cone 6 Glazes" has a two High Calcium Semi-Matte glazes as a learning exercise (both in the Insight-Live database under MC6G). The first version is very dry and frankly unattractive looking with a Si:Al ratio of 6.7 to 1, with the second having more silica with a ratio of 6.9 to 1.

Both have a lot of calcium, with 28% and 29% Wollastonite along with some calcium in the frit, and 6% rutile added, so both versions of the high calcium semi-matte are quite matte . . .  I think the better description for the higher alumina version is more opaque, to the point that the glaze has lost any sense of depth.

[Daniel Spruyt]

This is a good example of how difficult glaze recipes travel between potters; it is often mentioned in literature as well.

My experience with MC6G is that I hardly can achieve matte glazes using European raw materials, they all tend to be nearly glossy. (I do use a slow cooling of the kiln).

Another remark: the essential purpose of the triaxial graphs (and the Si/Al ) is to have a quick view on what kind of glaze you are dealing with before doing any practical work!

Norm Stuart said:

I've found it more predictable to create a matte glaze by adding enough titanium, zinc or calcium to cause enough crystallization on the surface to eliminate the shine. 

Increasing the ratio of alumina to silica can also create a matte glaze surface but it has seemed to be greatly affected by the rate at which I cool the kiln.

"Mastering Cone 6 Glazes" has a two High Calcium Semi-Matte glazes as a learning exercise (both in the Insight-Live database under MC6G). The first version is very dry and frankly unattractive looking with a Si:Al ratio of 6.7 to 1, with the second having more silica with a ratio of 6.9 to 1.

Both have a lot of calcium, with 28% and 29% Wollastonite along with some calcium in the frit, and 6% rutile added, so both versions of the high calcium semi-matte are quite matte . . .  I think the better description for the higher alumina version is more opaque, to the point that the glaze has lost any sense of depth.