Lesson 4 - Add a Native Material to Desktop INSIGHT MDT, Build a Glaze

Lesson 4 - Add a Native Material to Desktop INSIGHT MDT, Build a Glaze

Learn to add a native volcanic ash to the INSIGHT materials database (MDT) and then create a glaze from it maximizing its percentage. Learn to impose an LOI on a material and why this method is better than line blending.

D. Desktop Insight

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A case study of adding the chemistry of a native volcanic ash (having an LOI) to the INSIGHT materials database (MDT). To maximize the percentage of the ash in a glaze, its analysis is entered into Insight as a recipe and it's chemistry is rationalized and compared with a target to see how it is different than an average middle temperature glaze and a strategy is developed to create the glaze. This example also shows how to impose an LOI on a material and it demonstrates the value of this method of formulation compared to trial and error blending.


Lesson 4: Building a Glaze From a Chemically Analyzed Native Material
Having a native material analyzed, LOI measurement and imposition, lab analysis issues, assessing a materials chemistry to maximize its percentage in a glaze, entering an analysis as a recipe and transferring it to an MDT, employing an override MDT, building a glaze from a native material, the advantages of using chemistry to formulate native material glazes.

Building a glaze from a native material
Welcome. In this lesson we will have a native material analyzed to get its chemistry, add it to an MDT in a special way, then formulate a glaze from it.
I will cover LOI measurement and imposition, lab analysis issues, assessing a materials chemistry to maximize its percentage in a glaze, entering an analysis as a recipe and transferring it to an MDT, employing an override MDT, building a glaze from a native material and I will editorialize a little about the advantages of using chemistry to formulate native material glazes.

A Digitalfire and private MDT: how?
We advocate customizing and downloading your INSIGHT materials database from the Digitalfire website via this menu item. But you might be wondering:
How will I be able to add my own native or proprietary materials to the INSIGHT MDT and still be able to download one from the website?
The answer is simple: INSIGHT can open a second MDT to add to and override materials in the first one. We will see more about this later.

Best method to develop a glaze from a volcanic ash?
I am familiar with a volcanic ash layer in a quarry in southern Saskatchewan, Canada. Without a chemical analysis the only way to employ it in glazes is experimental line blending techniques, but that is a lot of work. Would the resultant glazes be adjustable to fit bodies? Would they be hard, resistant to leaching, work with coloring oxides? How would I maximize the percentage of this material in a recipe?
We need chemistry to deal with these issues. So I got a whole earth analysis done for about $50.

Entering an analysis as a recipe
To start I will close all the recipes and key in the first line of the analysis by entering Ca in the Lookup and 8.7 for the amount and updating. That gives me a recipe like this.
How can this work? This is where recipes are supposed to go! But isn't an analysis actually just a percentage recipe of oxides by weight?
INSIGHT can view oxides as if they were available in pure powdered materials and in searching the MDT it looks at them first. Thus Ca is all it needs to find CaO.
The first couple of letters is all INSIGHT needs to identify most of the oxides.

Comparing it with a target formula
I have entered the rest of the analysis.
I have copied recipe 1 to recipe 2 and set recipe 1 to Analysis calculation and recipe 2 to RO Unity.
And then I opened the Roy-Hesselberth target formula and adjusted the column widths to display the other squeezed columns in the formula list.
Finally I clicked the Save button for recipe 1.

Analyses and weight different: Why?
Notice the calculated analysis is not the same as the one entered into the recipe. Why? Because the numbers that the lab returned had an incorrect LOI, we will deal with this in a moment.
Notice that INSIGHT does not calculate the weight for the analysis but it does for the formula. This is because an analysis, by definition, does not have a molecular weight, it expresses relative amounts, it does not enumerate a list of molecules for which a weight can be calculated.

Rationalizing the chemistry
We can tell many things about this material by looking at the formula numbers INSIGHT calculates.
• The alumina is very low (compared to the target). It needs to be increased substantially to turn this ash into a glaze that will fire hard and not run off the ware. Since it has no plasticity, adding kaolin will supply the needed alumina and plasticity to suspend and harden glazes containing it.
• The Si:Al ratio is 60:1, a glaze should be about 10:1.
• The thermal expansion is very low (because this ash has almost no sodium or potassium). This will contribute to non-crazing glazes.
• CaO content is high, it will likely make a hard stoneware glaze, however excessive CaO can spell leaching problems.
• The iron content Fe2O3 looks low in the formula but look at the analysis. 1.2% is significant enough that transparent glazes containing 50% or more of this will likely be a light amber color.

Measuring and imposing an LOI
I need to tell INSIGHT how much weight this material loses on firing. Although labs usually supply a figure, I think it is best to measure the LOI yourself. This is because labs prepare samples for analysis testing by drying them thoroughly first. You need to base the analysis on the powder you have, not what they dried.
To get this make a thin tile from soft stoneware clay and form it into a shallow bowl (about a size that a tennis ball would fit into), fire to cone 6 and weigh it to the nearest 1/10 gram. Put about 30 g of the material powder and weigh again. Fire it at cone 06 and weight again. Derive the LOI using this formula.
I did this and got an LOI of 14.4. So I have selected recipe 1 and chosen Override Calculated LOI in the Calc menu and entered this.

Formula now totals 100-LOI
Notice the analysis numbers in column 1 of the formula list have changed. I added them up, they now total 85.6, that is 100 minus 14.4.
The Imposed LOI is showing, however the recipe total still shows the old number. That is because the imposed LOI only affects the formula.
Now I am going to insert this analysis into the MDT.

Naming and saving the material analysis
To do this the material must have a name.
I have clicked the Recipe Details tab and entered “Elkwater Ash” into the Description.
I am going to click the Recipe 1 half of the Save button to save this analysis in the INSIGHT recipe database.

Set up to store material as RO unity
Next, I will make sure that recipe 1 is selected, choose the RO Unity calculation type for recipe 1. Why? To make sure INSIGHT stores the material in RO unity.
I have also closed the target column.

Open the materials dialog
I have used the Edit Materials item in the Utility menu to display the Materials dialog because double clicking a recipe line or clicking the MDT button would have displayed the oxides dialog since the lines contain oxides.
You can maintain the order of the materials list yourself or have INSIGHT sort the MDT each time you save it using an option in the Preferences dialog. However, the order does not matter, INSIGHT can find materials quickly either way.
First you need to decide whether to replace an existing material or insert a record and extend the table length by one. It is common to replace a material with a more up-to-date version or replace one that will never be used.

Inserting a record and filling it
However in this case I inserted a record.
I scrolled down the list to the materials starting with the letter ‘E’ by pressing ‘e’ while the list was in focus. I clicked on the ‘English Kaolin’ line and clicked the Insert Material menu item and then confirmed. That left this empty record.
Now I need to choose the Get Formula from Recipe Calculation menu item. INSIGHT seeks confirmation like this and I will click OK.

View the results, save the material
Notice the analysis matches the one shown in the Formula List on the recipe window. Also, the LOI and name have been properly set.
I will click the OK button to save this material record for the rest of this session. To save it permanently I would click Save (Keep in mind however INSIGHT will not overwrite the lessons MDT, I have that one open).
Now, lets make a glaze using this material so I will close the materials dialog.

Set both recipes to analysis calculation
Now I will select recipe 2 and click the Close button and decline INSIGHTs offer to save it. Then I will set both recipes to analysis calculation.

Entering the new material into recipe 2
I have selected the first blank line to begin building a glaze and entered ‘Elkwater Ash’ with an amount of ‘75’ and clicked Update. I am optimistic about the percentage I can get into a recipe.
I now have the original lab analysis on one side and the recipe and just this one material we put in the MDT on the other. Lets compare them.

The analysis are different. why?
Notice that the analyses for the two recipes are different. Why? In recipe 2 INSIGHT is showing us what comes out of the kiln, there is no LOI on a fired material, analysis 2 thus totals 100. Notice the Calculated and imposed LOIs. Calculated analyses only adjust to accomodate imposed LOIs and recipe 2 does not have one.
Now I will change both Calculation Types to RO Unity…

Use target to propose additions to create glaze
Now they are the same.
It is a bit of a challenge trying to decide what to add to this material to make it into a glaze so I have opened a target formula for cone 6.
I already know that:
• I cannot use high-silica feldspar because the silica in the ash is already high.
• Kaolin is needed, both to source Al2O3 and suspend the slurry (we'll have to tolerate the SiO2 that it brings).
• I need to add materials that supply only non-CaO fluxing oxides (because the ash is high in CaO).
• I need to add fluxes will push the proportion of SiO2 down. I will employ talc to add magnesia and strontium carbonate to source SrO.

Add the materials, we have a good match
To accomplish all of this I have added 20 parts of kaolin, 10 parts strontium and 10 parts talc.
This matches the target pretty well and the chances of it firing to a good glass are excellent.

Chemistry vs. blending to formulate glazes
You will likely agree that this exercise demonstrates the practicality of this type of approach. There is a direct relationship between the oxide formula of a glaze and fired results. The more you learn about oxides and their contribution to the glass the more you will build your rationalization skills.
It is truly possible to create a technically well rounded glaze from a native material on the first try. Would trial and error blending have isolated a recipe that employs this high a percentage?
However trial and error blending with variegators, opacifiers and colorants to establish visual character is a logical next step.

Creating an override MDT
Now, how do I make this material available to INSIGHT if I want to use an MDT that I download from digitalfire.com?
The secret is an Override MDT and this menu item in the materials dialog: "Save MDT as XML Starter". This saves the current MDT to a new file of my choosing with just one material record in it. That will be the starting point for my own list of materials.
Before continuing I want to mention again that if I click the MDT button INSIGHT will open the Oxides dialog if my cursor is on an oxide in the recipe list. For this reason I will choose Edit Materials in the Utility menu.

The file name is the key
But how do I get INSIGHT to read the materials in my override MDT after it has read the main one? The secret is the file name and location: If I save it as mymaterials.xml into the Insight folder in MyDocuments folder INSIGHT will read it. Not only will it add the materials, but if any have the same names, they will override.
Now I will save this, quit INSIGHT and start it again to get it to show this item in the Materials Table popup.

Adding the ash to the override MDT
Here it is. I will choose it and open the materials dialog. It has one material in it, namely the first one that was in the active MDT when I created it. I will close this, and open the Elkwater Ash recipe that I saved earlier and then open the materials dialog again. Then I will select the Albany Slip material to replace it and choose "Get Formula From Recipe Calculation" in the Utility menu. This confirmation dialog will appear followed by another that warns me to make sure I have set an LOI.

INSIGHT will always know this material
Here is the material and notice the LOI is set, INSIGHT calculated it.
Now I will save it permanently and close this window and then choose the LESSONS MDT in the Materials Table popup.
Then I will open the materials dialog again and go to the bottom on the list. Here it is, it has been added. And it will be added onto the end of any MDT that I activate.

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By Tony Hansen

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