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Starting recipes for experiment


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I'm preparing some recipes for cone 6-7 glazes with washed wood ash.

It is not very important that these recipes are perfect, it is important that they are enought different (regarding characteristics of the ingredients) for future experiment with oxides and correction with clay, feldspar or other raw materials. I'm thinking also to mix them one with the other.

It is also important that they are not too much problematic, as probably the 4 and 6 recipes that will need to correct spodumene concentration!

Recipes 1 (already prepared should be ok)
29,4  Potash feldspar
29,4. Ball clay
36,2 Washed wood ash
5       Bentonite 

Recipes 2 (already prepared schould be ok)
29,4  Potash feldspar
29,4. China clay
36,2 Washed wood ash
5       Bentonite

 Recipes 3 (probably ok)
39,3  Soda feldspar
6,2    China clay
21,8  Washed wood ash
6,6    Bentonite
20,4. Quartz
5,7.   Zinc ox.

Recipes 4 (needs correction)
44,4  Spodumene
22,2  Ball clay
6,8    Washed wood ash
7,1    Bentonite
4,45  Talc
10,6  Quartz
4,45  Zinc ox.

Recipes 5  (to have red with red iron ox.) (similar to the original recipe)
44,5  Cornish stone (original recipe was 46,7 potash feldspar)
3,8    China clay
14,3  Bone ash
6,6    Bentonite
16,1  Talc
10,7    Quartz
4     Litio carb.

Recipes 6 (hoping to have green with chromium ox.) (needs correction)
46,7 Spodumene
5      China clay
14,4 Washed wood ash
14,9 Colemanite
5      Bentonite
14    Quartz

Edited by Luca Ask
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Recipes 4 (possible correction)
25  Spodumene
30,6 Soda feldspar
10  Ball clay
7    Washed wood ash
7    Bentonite
5  Talc
9,4  Quartz
5  Zinc ox.
1 Lithium carbonate

The original for cone 6 it have a satiny quality (I probably fire more near to cone 7):

70 Soda feldspar
3 bentonite (i need more for single firing)
3 lithium carbonate
7 dolomite
5 zinc oxide
12 quartz

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Generally bentonite adds nothing of value as a glaze component and is mainly a suspending agent. If one has 10% clay or more in their recipe  a suspending agent is usually not needed. The use of bentonite is usually limited to 2% or less BTW. If you have access to the internet you may want to pop those recipes in the free glaze calculator on Glazy.org this way you can begin to learn glaze components and how they affect your glaze outcomes. Incidentally in general there is no precise way to look at a recipe and understand what cone it will fire to. If it is a successful recipe, then in general it has to be tested to determine what is its  practical firing range.

If you put your recipes in the glaze calc on glazy it will show recipes that are chemically similar to yours as well. A nice learning tool.

Edited by Bill Kielb
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7 hours ago, Bill Kielb said:

Generally bentonite adds nothing of value as a glaze component and is mainly a suspending agent. If one has 10% clay or more in their recipe  a suspending agent is usually not needed. The use of bentonite is usually limited to 2% or less BTW. If you have access to the internet you may want to pop those recipes in the free glaze calculator on Glazy.org this way you can begin to learn glaze components and how they affect your glaze outcomes. Incidentally in general there is no precise way to look at a recipe and understand what cone it will fire to. If it is a successful recipe, then in general it has to be tested to determine what is its  practical firing range.

If you put your recipes in the glaze calc on glazy it will show recipes that are chemically similar to yours as well. A nice learning tool.

I will try, I never used it.

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7 hours ago, liambesaw said:

I'd remove the bentonite from the recipes with 15% or more clay, moreso for the ones with ball clay.

I use more bentonite to adapt recipes to single firing. I have a book (only about single firing) that advises to add 5% bentonite to a glaze recipe to adapt it to single firing.

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12 hours ago, Bill Kielb said:

Generally bentonite adds nothing of value as a glaze component and is mainly a suspending agent. If one has 10% clay or more in their recipe  a suspending agent is usually not needed. The use of bentonite is usually limited to 2% or less BTW. If you have access to the internet you may want to pop those recipes in the free glaze calculator on Glazy.org this way you can begin to learn glaze components and how they affect your glaze outcomes. Incidentally in general there is no precise way to look at a recipe and understand what cone it will fire to. If it is a successful recipe, then in general it has to be tested to determine what is its  practical firing range.

If you put your recipes in the glaze calc on glazy it will show recipes that are chemically similar to yours as well. A nice learning tool.

I tried to use the glaze calculator!

It is very interesting but I dont understand how I can know the ideal cone to fire the glaze recipe.

Is it possible?

 

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5 hours ago, Luca Ask said:

It is very interesting but I dont understand how I can know the ideal cone to fire the glaze recipe.

Is it possible?

Bill gave a good answer to this in his post above, "Incidentally in general there is no precise way to look at a recipe and understand what cone it will fire to. If it is a successful recipe, then in general it has to be tested to determine what is its  practical firing range."

Just to expand on what Bill said a little bit. The ideal cone to fire to is what the optimum cone for your claybody is. Glazes soften and mature over a range of temperatures, underfire and they won't have the materials in a fluid glassy matrix, overfire and the glaze can boil, blister, volatilize, run off the pot etc. Ideally you are looking for a good glaze and claybody interface, the layer where the glaze and clay are slightly joined, for lack of a better word. 

There are "Limits Charts" that show the approximate limits for a well melted glaze but these tend to be for a glossy glaze and don't take into account glazes that are high in an oxide on purpose for specific types of high oxide glazes such as calcium mattes etc. Other problem with these limit charts is they don't differentiate between the particle size of the oxides. Example would calcium supplied from either a frit or wollastonite is going to be incorporated into the melt earlier than if it's supplied from calcium carbonate (aka whiting). Another example would be the silica content in the glaze, the finer mesh 325 silica is going to be active in the glaze melt earlier than say 200 mesh silica. 

All that being said to get a really rough ballpark idea of oxide levels for low, med and high fire glazes have a look at the chart below. You can see there are differences between the two sources of data, as you can see there is no agreement on absolute limits. 

496618916_ScreenShot2021-02-28at9_07_58AM.png.799d3da9ee09a59cb5f3e3c7cea5292d.png

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