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 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.
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.
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
Subsituting Gerstley Borate in Floating Blue
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.
D. Desktop Insight
Click here to watch this at youtube.com or click here to go to our Youtube channel
Details how to substitute Gerstley Borate for another boron source in the popular Floating Blue glaze recipe. The lesson demonstrates that the most practical way to deal with the GB issue is on a glaze-by-glaze basis, formulating an approach that maintains the chemistry of the glaze, evaluates the sources of boron in the light of the chemistry of GB but also its physical properties and their importance to the working properties of the glaze. The boron sourcing frit (Ferro Frit 3134) is tried first and proves to be unsuitable, then ulexite is employed and found to be an ideal substitute.
Lesson 6: Substituting Gerstley Borate in Floating Blue
Gerstleyborate.com, when frits are not suitable, ulexite, using phantom, static and added status with colorants and retotaling and static materials
Substituting Gerstley Borate in Floating Blue
Welcome. I am going to talk about substituting Gerstley Borate for another material in the popular floating blue glaze recipe.
Also Gerstleyborate.com, when frits are not suitable, ulexite, using phantom, static and added status with colorants and retotaling and static materials.
Gerstley Borate has been a popular ingredient in raw glazes for many years. At digitalfire.com we author a website about this at gerstleyborate.com.
Recently it has gone through various perplexing cycles of becoming unavailable, then available again. More frequent changes in its behavior have accompanied this. The artware and pottery worlds have thus been absorbed in the pursuit of a substitute.
There is an better alternative. You can use INSIGHT to remove GB from your glazes and supply the lost oxides from other materials.
Floating blue glaze recipe
I will demonstrate replacement using the popular Floating Blue cone 6 glaze (this recipe has its own detailed page at gerstleyborate.com). I will replace the GB with another boron sourcing material.
I am going to be mentioning some techniques using INSIGHT that might not be totally clear unless you have watched some of the previous lessons.
Enter and duplicate the recipe
I have made sure the Lessons materials table is selected.
And have keyed floating blue into recipe 1 (I have left out the iron, cobalt and rutile, I am going work with the colorless base only).
Now I am going to click here to duplicate it into recipe 2 and make sure I have both recipes set to RO Unity calculation.
Replace Gerstley Borate with frit 3134
I have also removed the Gerstley Borate from recipe 2 by making sure its line was selected and clicking the line delete button.
I have also selected the next blank line in the recipe and added the same amount of Frit 3134.
Now if I click the MDT button to open the materials dialog you will notice that
With this frit is a good choice
This frit contains no alumina, thus I can source alumina from kaolin to suspend the glaze. I need to think about this because it was the natural claylike nature of Gerstley Borate that kept the original glaze in suspension.
But this frit is not working
At first this frit seems like it could work. But it brings a lot of extra sodium so the nepheline, which is currently supplying the bulk of this, has to be dropped to compensate. This will create a balance that makes juggling the materials to match the oxides quite complex.
Notice I have also checked the KNaO box.
Turkish Ulexite is better
A better solution is to choose a material of more similar mineralogy and chemistry to Gerstley Borate. This is the substitutes page at GerstleyBorate.com.
Turkish Ulexite is imported into North America and other continents in large quantities for use the fiber glass industry.
If I click here I will be taken to a detail page at the Digitalfire Reference Database.
Let's try this ulexite.
Replacing GB with ulexite
I am going to replace the frit with 20 units of ulexite. Notice I have cleared the Label and am about to click Update.
Planning a strategy
Notice that the CaO and MgO are now lacking and the KNaO is high.
If I add materials to source the former, the latter should be pushed downward. Why? Because this is a unity formula, INSIGHT recalculates the fluxes to total one, if I increase one the other amounts drop.
Notice also that the SiO2 and Al2O3 are high. Increasing the total amount of flux is going to force their amounts downward for the same reason.
Matching CaO, MgO with whiting, talc
I have added talc to source MgO and Whiting to source CaO. I played with the amount of each (by incrementing and decrementing) to get the closest formula match on a recipe amount multiple of 1.
Notice the KNaO is just a little high
Fine-tuning the new recipe
So now I will decrement the nepheline by 2 to match it up and then increase the kaolin by one to bring the Al2O3 back up to match.
Amazingly the silica does not need to be changed to adjust the SiO2.
Next, I am going to put the colorants into the recipe.
Assigning coloring oxides as phantom
Notice what happened here. When I entered this material I just typed cobalt ox assuming INSIGHT would find it in the materials database and expand the name. But this asterisk indicates that it did not find it. How do I know that? I can click here and this dialog explains what the status characters mean.
To get the name to look right I will edit this blank and update the line.
But that is not really a problem, I do not want coloring oxides in the formula anyway. So I am going to click this checkbox for these two lines and update also.
Using static colorants when retotaling a recipe
OK, these materials are not affecting the calculated formula anymore.
One more problem I want to deal with is this total. I would like to have a total of 107 and designate the coloring oxides as added materials.
But if I just recalculate to 107 the coloring oxide amounts are going to change. The solution is to first mark the three lines with static status. Static lines are ignored during retotal. Notice the new status characters.
Defining colorants as Added materials
I have chosen retotal from the Calc menu and specified 100 and then used Round Amounts in the Calc menu.
Here is the new total and the recipe. I should mention that the static status is not remembered with the recipe.
However added status is. I am going to set each of them as added using this checkbox, thus when I print the recipe they will be separated as such.
Fired samples: Improvements still needed
Take another look at the chemistry.
This glaze is very high in sodium and potassium and its calculated thermal expansion is likewise very high, that means crazing. However the high boron content appears to counteract this somewhat in practice. You can use INSIGHT to substitute some of the KNaO for another flux, but that might affect gloss.
Here are the fired samples. The Ulexite version has the same character, it just needs a cobalt/iron change for a little more color and a flow test to see if fluidity needs adjustment. The glaze slurry seems to work well also.
This is yet another example of a problem that can only be effectively dealt with on the chemistry level.
Many people have struggled with this problem but doing it this way was quite simple, dont you agree?
That is the end of this lesson.
Floating Blue at cone 6 using Boraq Gerstley Borate substitute
Floating Blue is a popular cone 6 glaze recipe used by the pottery community. Gerstley Borate is a material commonly used in recipes as a melter. The recipe produces a variegated surface but is difficult to replicate since its fragile mechanism makes it susceptible to variations in thickness, firing schedule, clay body and material supplies.
Something is definitely wrong. What is it?
An example of how a glaze that contains too much plastic clay has been applied too thick. It shrinks and cracks during drying and is guaranteed to crawl. This is raw Alberta Slip. To solve this problem you need to tune a mix of raw and calcine material. Enough raw is needed to suspend the slurry and dry it to a hard surface, but enough calcine is needed to keep the shrinkage low enough that this cracking does not happen. The Alberta Slip website has a page about how to do the calcining.
Closeup of original floating blue recipe at cone 6
A much better Cone 6 Floating Blue
GR6-M Ravenscrag Cone 6 Floating Blue on Plainsman M340 buff stoneware. This glaze also has this variegated visual character on porcelain. Because it has the GR6 base recipe (more information at ravenscrag.com), the slurry has very good working properties in the studio, it is a pleasure to use. This is an excellent showcase for the variegating mechanism of rutile.
Colemanite and what its decrepitation does in glazes
Decrepitation refers to a decomposition accompanied by scaling, delayering, even disintegration of the glaze layer. Moving rightward these glazes have increasing percentages of colemanite. At its worst (far right) the glaze is spattering off the sample and onto the kiln shelf. The others are crawling, first pulling away from the corners (far left) moving toward pulling away on the flat surfaces (center). Gerstley Borate and Ulexite, similar minerals, are far less likely to do this (but they have other serious issues also). A much better solution is to use frits to source the oxide B2O3 (easy to do in your account at Insight-live.com). Photos courtesy of Nigel Hicken.
Out Bound Links
In Bound Links