Lesson 5B - Difficult Formula to Batch Calcuations in Insight

Learn to do difficult formula to batch conversions. Learn mole%, finding frits by chemistry, Na2O sourcing, oxide oversupply, recipe line added status, overriding in the Supply dialog, when to compromise an exact match.

D. Desktop Insight

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Mole%, formula to batch calculations, finding frits by chemistry, using material XML, Na2O sourcing, handling oxide oversupply, added status in recipe lines, overriding in the Supply dialog, rationalizing when to compromise an exact match and thinking on the mineral level

Difficult Formula-to-Batch Conversions
Welcome. In this lesson we are going to talk about Mole%, formula to batch calculations, finding frits by chemistry, using material XML, Na2O sourcing, handling oxide oversupply, added status in recipe lines, overriding in the Supply dialog, rationalizing when to compromise an exact match and thinking on the mineral level.

Dealing with textbook Mole%
Special purpose glazes can present interesting challenges in formula-to-batch calculations as you can run into dead-ends where it is impossible to match a formula using materials at hand. Often their oxide proportions are contrary to what is normally found in natural materials (and even frits).
On page 41 of Richard Eppler's book Glazes and Glass Coatings there is a chart of special purpose glazes like this.

What is Mole%
Richard 'speaks the language' of mole percent (Mole%) formulas. INSIGHT can do this also, notice it in the Calculation Type menu.
Here is an example of the same glaze shown as a unity formula on the left and mole% on the right. A formula adjusted to Mole% simply recalculates the formula to total 100. Note that Richard also prefers to express each number as a part of 1 (thus 0.5795 instead of 57.95%).
I will work with glaze B69.

Mole% and the formula dialog
I have closed both recipes in INSIGHT and selected Mole% for recipe 1 and RO Unity for recipe 2. Then I selected recipe 1 and chose Enter Formula in the Calc menu to display this dialog, and I have filled in the numbers.
You might object saying that this dialog is intended for unity formulas. But actually it will accept any formula, it does not care if it has been retotaled or unified. I will click Done. INSIGHT is asking if I want to save the existing recipe before pasting this in, I'll click no.

Converting to analysis
INSIGHT converts the formula into an analysis and inserts it into the Recipe List like this.
This looks good but there is a problem. I entered CaO as BaO. I will fix it. Notice that when I open the formula dialog again INSIGHT has remembered all the numbers. It will remember these even between sessions. Here is the problem, I have fixed it and will click Done.

Compare this formula with original
It is important to note what is now in the recipe list: an analysis of the fired glaze with no LOI.
Notice that the numbers in the Formula List match those we entered into the formula dialog (although the decimal is moved two places).
I will set recipe 1 Calculation Type to RO Unity and recipe 2 to No Unity. Remember, we are building a batch from a formula using No Unity as in the last lesson.
This will change the Formula List to this.

Supply Na2O from nepheline syenite
Feldspar or Nepheline Syenite are good sources of Na2O and I will use the latter.
I have selected recipe 2, selected the first blank line after the analysis and entered “neph” in the Materials Lookup. Now I will click Update and then the Supply button. Why did I click the Update button first this time? Because I want to make sure INSIGHT chooses the right material for the line before bringing up the Supply dialog.
Remember, the Supply dialog enables you to specify an amount of material based on how much of an oxide you want it to supply.

Al2O3 oversupplied; we need a frit.
In the Supply dialog I have clicked the Na2O option button and will then click Done.
INSIGHT calculates the right amount of nepheline syenite to supply 0.33 molecules of Na2O.
Notice I have the KNaO box unchecked to be able to see the Na2O and K2O separately.
However notice that Al2O3 has been greatly oversupplied. If you use soda feldspar the same thing will happen. What do we do?
A boron-free, high-sodium, low-alumina material is the answer. But what? A frit. These do exist and you can find them and I will show you where.

Digitalfire Reference Database materials area
You can search at the Digitalfire Reference Database to find this type of material.
Notice I have level 2 access, I got here by logging in at the digitalfire.com home page and clicking the Reference Database link.
I will click the material link, and then click “Search”.

Searching for a frit by chemistry
I have specified that I want a material with less than 5% boron and alumina, and more than 15% sodium and then clicked the Search button.
This is a very powerful search to find a material of the chemistry you need, especially frits.
Notice the first hit, Frit 3110. I will click it.

View the XML for this material
Here is detailed information about it. Now I will scroll to the bottom of the page. Notice this section.
If INSIGHT did not know about this material I could use the XML interpretation feature in the materials dialog and paste this in.

Downloading an MDT with this material
I could also add this material to my MDT by choosing 'Update Materials File' in the INSIGHT help menu to download an MDT to which I have added this.
Notice I have chosen North America as my starter table, then searched for Frit 3110.
However notice that it already is in MDT #1, that is North America. If it where not, I would check it and click the Add button.
Finally I would click the Generate button, it would be built, and a download link would appear.
Perhaps you are wondering what this tab is about.

Other critical downloads
We are learning Spanish and living in Mexico right now, of course, music is a great way to do it.

Frit 3110 is cool and it is already in INSIGHT
It happens that Frit 3110 is already in the lessons materials table. Let us look at it. Remember I need a boron-free, high-sodium, low-alumina material.
This frit fits my requirements, well almost. It would be nice to have zero-boron, but I will have to accept very low boron. I am also going to get a little K2O, that is fine since it is so similar to Na2O.
I will get CaO and SiO2, perfect, I need them.
Let's try it.

Trying frit 3110
I used the Supply button to match Na2O using 132 parts of this frit.
Notice that the only overshoot is this little bit of boron. Is that OK? Likely it is. Boron is a pretty nuetral melter and, remember, ceramic chemistry is not always an exact science. Testing will tell anyway.

K2O supply options: We need Pearl Ash.
However now we have one of those tricky situations that you often encounter in specialized glazes, the need for specialized materials.
I could add feldspar to supply the remaining K2O but I'll overshoot the SiO2. Feldspars also source a lot of alumina and I want to supply the alumina from a kaolin to suspend the glaze.
I could also supply the total of combined K2O and Na2O from the frit, but that too will oversupply the SiO2 when I add the kaolin.
I will need to use Pearl Ash.
I will click the next blank recipe line and supply the K2O using it (remember I do that using the Supply button).

Supply the rest of the oxides
Perfect. Now the rest of the job is looking very much like the last lesson.
I will supply CaO from dolomite, the rest of the MgO from talc, ZnO from Zinc oxide, Al2O3 from Kaolin and Fe2O3 from iron oxide.

Retotaling using added status materials
This is the best I can do using this frit. The B2O3 and SiO2 are both slightly oversupplied.
Now I am going to retotal to 100 using Retotal Recipe in the Calc menu.
Now, I would like this recipe to show the iron as an added amount and have the rest of the recipe total 100. So I selected the line, clicked the Added checkbox and updated.

Rounding the material amounts
Notice the status character to show the Added status.
Then I retotaled to 100 at got this. All the materials except the iron total 100.
Before going on I will choose 'Round Amounts' in the Calc menu.

I need to start again and compromise
Actually, let’s try it again. I need to be realistic and willing to compromise, I do not have Pearl Ash, I have never even seen it.
I am going to need to be satisfied matching the total KNaO as in the last lesson or satisfying part of the K2O with feldspar and tolerating an overshoot on the SiO2. How would I do that?
Notice what I have done here. I have clicked each recipe line and used this button to zero the amounts. I clicked twice to remove the Pearl Ash line.
Then I dragged an empty line from below above the frit and set it at Custer feldspar.

Overriding in the Supply dialog
How about supplying some of this K2O from the feldspar? To do that I have clicked the Custer feldspar line I created on the last step and then the Supply button. Then I will select K2O and manually override the amount needed to 0.07. Why this amount? I’ll tell you on the next step.

Supply the rest of the oxides
Next I selected the Frit 3110 line and matched the Na2O.
As you can see the K2O now matches also. How did this happen? I actually experimented in another INSIGHT session with mixtures of feldspar and frit to produce this proportion.
Now I just need to click each material line, use the supply button and specify the correct oxide to supply for each, CaO for Dolomite, MgO for Talc, ZnO for Zinc and Al2O3 for kaolin.

We have a significant SiO2 overshoot
That produces this. The only overshoot is silica and it is significant.
Are there other options? Yes. I could have matched the MgO using the dolomite and no talc would have been necessary. That would have reduced the SiO2 overshoot somewhat and produced a small CaO excess.
There is another better option.

Nepheline syenite reduces the SiO2 overshoot
Nepheline Syenite contains less silica than feldspar. I have replaced the feldspar with it, adjusted the frit until the KNaO is the same (that’s why I have it set to three decimals), resupplied all the others, retotaled to 100.
This is not bad, the overshoot on the silica is less than half of what it was and I still have enough kaolin to suspend the glaze.

Confronting the physical presence of Alumina
You might say: It is possible to match the formula exactly (except the boron) using the frit and calcined alumina, here it is. Why worry about the kaolin for suspending, we could just add a gum to suspend and harden the glaze.
But the problem is you'll turn the glaze slurry into a sticky syrup, it'll have horrible mixing, application and storage properties.
But there is a fundamental lesson here about the need to think on the mineralogical level also. Alumina is not really a mineral, but like a mineral, it has a physical presence that demands attention. Unless you can grind this material for 50 hours in a ball mill, the particles are not going to dissolve into the glaze melt. Alumina is super refractory and any glaze formula that is derived from an alumina-containing recipe is potentially misleading.

The End
I don’t know about you, but I get a real buzz out the juggling act you can do using the supply button. That one button will really help change your view of materials and see them more as oxide-suppliers than white or colored powders.
That is the end of this lesson.

In Bound Links

  • (Glossary) Digitalfire Insight

    A desktop application for Windows, Linux, Macintosh that you download and install. Insight is a classic glaze chemistry calculator. -It interactively converts recipes to formulas and back. The main Insight window shows side-by-side recipes and their formulas, you can make chemistry changes to one...

By Tony Hansen

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