A high-nepheline, zero-silica cone 8 silky matte glaze is cutlery marking and crazing. Why?
I will show you how found a recipe on Facebook, assessed it, substituted my own materials, tested it, adjusted it. Now it is like a cone 10 dolomite matte.
How I found a recipe on Facebook, substituted a frit for the Gerstley Borate and added the extra silica it needed to fight crazing. I got a fabulous cone 6 clear.
Using Insight-live I will demonstrate the surprising amount of silica some cone 6 base glazes that appear OK will accept and still melt well.
How to spot out-of-balance indicators in the chemistry of glazes that suggest susceptibility to scratching or cutlery marking.
Raw lithium carbonate can be replaced with a lithium-containing frit if you can do the chemistry. And you can at insight-live.com.
Use Insight-Live.com to do major surgery on a feldspar saturated cone 10R glaze recipe with multiple issues: blistering, pinholing, crazing, settling, dusting and possibly leaching!
We will substitute wollastonite for whiting and a frit for Gerstley borate in G2571A while maintaining the chemistry of the original recipe.
Insight-live shows recipes in tall narrow panels. They open side-by-side right-ward. They remember the type of calculation last requested. So just opening multiple recipes automatically enables comparison.
The test bars will measure fired porosity and shrinkage over a range of temperatures, drying shrinkage, LOI and pugged water content. They follow procedures defined in Insight-live.com.
How to reference a picture from an external website like flickr.com from within a recipe in Insight-live
A short annotated video of how to create an account at insight-live.com
A short annotated video of how to sign-in to a personal account at insight-live.com
How to import the Digitalfire Insight recipe database file (INSIGHTDATA.DB) and the pictures that attach to recipes therein
Using help, your account, renewal and preferences pages, the managers and panels, recipes, materials, entering a recipe, chemistry, downloading desktop Insight.
How to find them, duplicate them and develop them within your account at insight-live.com
If your recipe is on the clipboard, this shows you how to import it into Insight-live and make adjustments after.
Learn how to add a recipe, title it, add lines and change them, set lines to added status, enter notes and pictures and print a mix ticket
An example of how to enter test results from your ceramic testing into recipes in your account at insight-live.com.
How to take a picture using an iPhone, crop and resample it, save it, then upload it to a recipe.
How to import data from desktop Insight, GlazeMaster, Matrix, GlazChem, HyperGlaze, Generic Spreadsheet CSV into your account at insight-live.com.
How to add and override material data and how to do chemistry calculations in your account at insight-live.com.
How to organize your recipes into a worksheet of recipe rows and material columns, save it as a CSV file and import into Insight-Live.com
A tour around the home page. Where to start.
I will show you some secrets of making a base engobe (or slip) apply to leather hard terracotta ware in a thick, perfectly even layer.
I will show you how to glaze a mug with a liner glaze inside and a colored one outside so that they meet in a perfect line at the rim.
To do a drop-and-hold firing you must manually program your kiln controller. It is the secret to surfaces without pinholes and blisters.
I will show you why people love/hate this material and how I substituted it for Ulexite to make a much easier-to-use glaze that fires just as good or better.
Making 10 gram balls of your glaze and firing them on 2in by 2in tiles is a great way to evaluate their flow, surface and susceptibility to defects.
I will show you why thixotropy is so important. Glazes that you have never been able to suspend or apply evenly will work beautifully.
D. Desktop Insight
Part two of a complete tour. It includes using targets, setting calculation types, entering recipe notes and details, SQLite and a review the menus.
Part one of a complete tour. The anatomy of the recipe window, how to open, edit and save recipes; the materials, oxides and supply oxide dialogs, the MDT.
Learn to how to download a recipe library from your account at Insight-live and open and explore it using desktop Insight
Compare calcium carbonate (whiting) with other sources of CaO (dolomite, wollastonite, frit), learn to understand the chemistry differences between materials and then substitute wollastonite for whiting in a specific recipe.
While comparing a real-world and theoretical feldspar learn to enter, edit, save, normalize recipes and the materials dialog. Glaze chemistry concepts.
Learn to compare a target formula with the chemistry of a feldspar. See why it does not make a good glaze by itself and what materials need to be added to make it into a balanced glaze.
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.
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.
Learn to use a non-unity calculation to convert a formula into a batch recipe using theoretical and real-world materials. Retotal, round-off and make a side-by-side report.
Learn to convert a glossy glaze into a matte by comparing its chemistry with a target matte formula. Alter the chemistry in such a way that the thermal expansion does not rise and it maintains good physical application and suspension properties.
Learn what crazing is, how it is related to glaze chemistry, how INSIGHT calculates thermal expansion and how to substitute high expansion oxides (e.g. Na2O, K2O) with lower expansion ones (e.g. MgO, Li2O, B2O3).
Shows four different ways to add materials to the desktop Insight materials database (MDT)
Do this completely outside of Insight, it knows how to read it at each startup.
There are five ways to do it. Generate your MDT at digitalfire.com, copy and paste XML, type in the formula, enter an analysis as a recipe, handle the MDT as a CSV file in Excel.
Wollastonite is 50:50 CaO:SiO2. So why not just substitute 40 wollastonite for 20 calcium carbonate and 20 silica?
Learn to substitute Nepheline Syenite for Soda Feldspar (and vice versa) using the KNaO checkbox to. You will see the benefit of in-recipe substitution calculation rather than making substitution rules.
Learn to reformulate a glaze that is settling in the bucket. Al2O3 and KNaO are sourced by the feldspar, we will source them from kaolin and frits instead.
How to use desktop Insight to substitute wollastonite for calcium carbonate (and vice versa) while maintaining the same SiO2 level. Create substitution rules.
Use Desktop Insight to explore ways of calculating substitutes for Gerstley Borate in the popular Floating Blue cone 6 glaze recipe while maintaining or improving the other raw and fired properties of the glaze.
How to fine-tune the thixotropy of a ceramic engobe for pottery
Tony Hansen takes you through all the steps from opening the box and wedging the clay to taking the fired mug from the kiln.
*Youtube Video, +MP4 Video, #ScreenCast, ^URL
Reducing the Firing Temperature of a Glaze From Cone 10 to 6
Learn the chemistry differences between cone 10 and 6 glazes and how to make a glaze melt at a lower temperature without introducing other problems like crazing.
D. Desktop Insight
Click here to watch this at youtube.com or click here to go to our Youtube channel
A key lesson because it explains the difference between cone 10 and 6 glazes, demonstrates how to evaluate frits to choose the best one to source boron to a glaze, how to determine how much frit to add to increase the amount of B2O3 in the formula by a specific amount, then how to juggle other materials to restore the rest of the chemistry (caused by the increase in other oxides introduced by the frit). It also demonstrates how to make a melt fluidity tester and how to find out which materials in a recipe are contributing a particular oxide to the formula.
Melting temperature is directly related to chemistry, learn what the chemistry differences are between a typical cone 10 and 6 glaze and how to use INSIGHT to make the conversion
Reducing the Firing Temperature of a Cone 10 Glaze to Cone 6
Welcome. In this lesson we are going reduce the firing temperature of a glaze from cone 10 to 6 and end up with a surprise.
I will research glaze melting at digitalfire.com, talk about the differences between the two glaze types, boron sourcing and limits, watching thermal expansion when adding flux and unlinking a recipe from the recipe database.
Find an article at Digitalfire Reference Library
Tobegin I will choose Digitalfire Reference library from the INSIGHT Help menu.
On this page I will click Articles.
That takes me here, a long list related to ceramic chemistry, mineralogy and physical properties.
Then I will choose Find from the browsers Edit menu (in this case Firefox) and look for the words firing temperature. Notice Ctrl-f is the shortcut to find a word on a web page, this works in Internet Explorer also).
Increasing boron is the key
This article, Reducing the Firing Temperature of a Glaze From Cone 10 to 6 says that boron is the magic oxide, increasing its proportion is the best way to move glazes down a few cones. It discusses some of the side effects of adjusting melting temperature that I will not cover here, I will just demonstrate the mechanics of increasing boron since this is the most important.
This one, A Low Cost Tester of Melt Fluidity looks interesting. I will click it.
Glaze melt fluidity tester
This is a very interesting article about a melt fluidity tester you can use to compare two glazes. It also has information about adjusting glaze melting temperature.
Notice this picture. This is a comparison showing the same glaze formula, the one on the left sources MgO and CaO from a frit, the one on the right from talc and calcium carbonate. As you can see melting temperature is more than just the chemistry, frits are a good idea for melting glaze better, no question about it.
Open a target formula for cone 6
To start I am going to open a target formula for cone 6 using this button above the formula list. I will select the Roy-Hesselberth one and click open.
Open 1214M cone 6 recipe in area 1
Here it is.
Then I want to open the 1214M cone 6 recipe that comes with INSIGHT in recipe 1. I will click here and enter enough of the name here to limit the long list of glazes I have stored in INSIGHT. I will click the line and click Open.
Open 1947U cone 10 recipe in area 2
Next, I will select recipe 2 and open the 1947U cone 10 recipe that comes with INSIGHT. I will enter enough of the name here to limit the long list, click the line and click Open.
The main difference: Cone 6 has boron
Now we have a cone 6 formula on the left, a cone 10 on the right and a cone 6 target. Let's look closer.
There is nothing really different about the fluxes, except this cone 10 has a little zinc. But zinc is common in glazes at all temperatures.
The alumina and silica in the cone 10 glaze are higher, but notice in the target that cone 6 glazes can have alumina and silica as high as this cone 10 glaze. Of course, in general, cone 6 glazes have more fluxes, and therefore, less silica and alumina.
The big difference is here, B2O3, or boron.
Why is boron better than other fluxes
Amazingly many people use frits and materials like colemanite and gerstley borate without ever knowing about this magic oxide these materials contribute.
It is a low expansion, low melting glass, that is exactly what we need to reduce the firing temperature of a cone 10 glaze.
Without boron we would have to try and do it with zinc, sodium and lithium, the other fluxing oxides do not melt at cone 6. But these three oxides have so many issues. Sodium is high expansion, zinc conflicts with many colors, lithium can only be used in small amounts or it causes glaze defects. Plus they just do not melt the way boron does.
Comparing a popular frit formula: 3124
But look at this typical frit. It sources so many other oxides besides boron. If we add this to a glaze is it not going to throw the chemistry completely out of whack?
That is why there are so many kinds of frits. Look at the oxides our cone 10 glaze has. The frit does not contribute anything that is not already in the glaze.
If I can use the amount of frit needed to give me a specific amount of boron, I should be able to adjust other materials in my recipe to realign the other oxide amounts.
I will use frit 3134: It has no alumina
But I am going to use Frit 3134 instead, it has fewer oxides (so it is simpler), more boron, and it is the one already in the cone 6 recipe I have opened. It also has no alumina, that will enable me to source Al2O3 from kaolin to suspend the glaze better.
In a minute you are going to see why this frit is so popular.
Increase B2O3, reduce KNaO
I have selected recipe 2, selected the Frit line, then clicked the increment button to increase the amount two-at-a-time until the B2O3 matches the cone 6 recipe.
Now I will match the KNaO numbers. The frit is adding this so I need to reduce the feldspars contribution.
Kill the ZnO
Then next thing I have done is zeroed the amount of zinc in our former cone 10 recipe using this button.
Unlinking the recipe from the database
Before going any further we need to do something. I have clicked the Recipe Details tab.
I am editing the G1947U recipe, it is code number 232 in the database. If I click the Save button I am going to wipe out that recipe and replace it with this.
Then I will choose Duplicate Recipe in the File menu. This will remove the link between this recipe and database record 232. Now when I click the Save button INSIGHT will create a new database record and link this to it and save the recipe there.
Fine tuning the rest of the recipe
Next I will update these blanks, including the date. Mostly I removed information from the 1947U recipe. Then I will click Save.
Now back at the formula, notice the oxides. There are only minor differences between our adjusted cone 10 recipe and the cone 6 one.
I will match up the KNaO by reducing the feldspar, the Al2O3 by increasing the kaolin, the SiO2 by reducing the silica.
Now you know why this frit is popular, it has a balance of oxides similar to most glazes, so adding it to supply boron does not disrupt the chemistry too much.
The new recipe is the same as G1214M!
OK, I have done the adjustments. The cone 6 recipe and our adjusted cone 10 one have the same chemistry.
But check this out. The recipe of the adjusted cone 10 glaze has almost equal parts of the same 5 materials also. Isn't that interesting.
That means that chemically, the standard Digitalfire G1214M cone 6 transparent recipe is just our standard 1947U cone 10 transparent plus 0.2 molar parts of boron and no zinc.
The amazing thing is I did not realize this until composing this lesson.
Noticing cost, thermal expansion
But when I open the original 1947U in area 1 to compare, you would never know this, they look quite different.
So the glaze on the left is the original, the one on the right is our adjustment to make it melt at cone 6.
Notice it raises the thermal expansion, but not by much. The more you adjust glaze chemistry to reduce the melting point the more of a challenge it is to keep expansion, and thus crazing, down. The main reason is the lower silica and alumina. But again, the low expansion boron is the secret to keeping the expansion down.
Notice also that the cost is up, that is expected since frits are more expensive. You can tell INSIGHT the costs of your individual materials using the Overrides/Typecodes dialog.
So, the secret to reducing the firing temperature of a cone 6 glaze is to add boron and leave the rest of the oxide amounts unchanged. There is no way you can do that without ceramic chemistry.
The article that we found at the Digitalfire Reference Library a few minutes ago says that sometimes it is better to identify the color, opacification and variegation mechanisms and then transplant these into a cone 6 base glaze of similar properties to the cone 10 one.
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