Questions about Iron Oxide & Nepheline Syenite

[ThisIsMelissa]

Hello all,

This is my first post here on this forum and I'm hoping I can tap into your experience, as my journey with clay only began earlier this year.

 

For some background, I'm taking classes at a community art house.

Stoneware clay... brown, if it matters

Bisque at cone 06

Glaze firings at cone 6

 

I've been in this class a whoppin' 4 weeks and I'm almost as lost as when I started. My only other class was a low-fire class at a different place and we used all commercially prepared glazes from Mayco, Amaco & Duncan.

 

The art house has a lot of its own glazes, slips, stains, etc.

 

Last week, I discovered how lovely an oxide stain looks on our clay.

I really like the look of the clay we use when it has no gloss to it, but most of our glazes are glossy.

 

But in studio last week, a lady had some pieces that she created with stains. They were the look I want to create with my pieces. Kind of a worn leather look.

She said she does the first coat with an iron oxide.... applied with a brush and wiped off.

The next coat is where I get lost.

She grabbed a container that said:

50% Iron Oxide

50% Nepheline Syenite

 

So, being that I'm a complete newbie to raw materials, I asked, "what does the Neph Sy do for you that the Iron Oxide doesn't. She couldn't really answer.

 

Do you think you all might be able to enlighten me?

 

Thanks so much!

Melissa

[Benhim]

The iron itself is just iron oxide and is being used here as a wash. Where as a mixture of iron and Nepheline Syenite is a form of stain that will melt out and adhere to the pot. So it sounds like she is applying a rich iron oxide wash, and wiping off to get a dark iron color contrast, then coming back over with a stain of 50/50 iron/neph sy to complete the worn leathery look. It's a two step process to give highlights and contrast in the surface of the work I assume.

[bciskepottery]

Iron oxides have a high melting point -- somewhere around 2849 F, which is higher than ^6 or ^10. Nepheline Syenite is a member of the feldspar family and a flux -- it helps lower the melting temperature of the iron oxide. So, the addition of the Neph Sy to iron oxide allows it to bond to the clay during firing -- especially important if there is no other glaze being applied.

 

For what its worth, I use a mixture of 50% red iron oxide to 50% Gerstley Borate as a wash. Same principles apply.

[Evelyne]

The iron itself is just iron oxide and is being used here as a wash. Where as a mixture of iron and Nepheline Syenite is a form of stain that will melt out and adhere to the pot. So it sounds like she is applying a rich iron oxide wash, and wiping off to get a dark iron color contrast, then coming back over with a stain of 50/50 iron/neph sy to complete the worn leathery look. It's a two step process to give highlights and contrast in the surface of the work I assume.

 

Any photos to illustrate what it's about ?...I mean final result !

[ThisIsMelissa]

Iron oxides have a high melting point -- somewhere around 2849 F, which is higher than ^6 or ^10. Nepheline Syenite is a member of the feldspar family and a flux -- it helps lower the melting temperature of the iron oxide. So, the addition of the Neph Sy to iron oxide allows it to bond to the clay during firing -- especially important if there is no other glaze being applied.

 

For what its worth, I use a mixture of 50% red iron oxide to 50% Gerstley Borate as a wash. Same principles apply.

 

 

Ok, this makes COMPLETE sense to me! Thank you!

I was kind of wondering how the iron would "melt" into the piece.

 

And it also looks like I should be able to use the Neph Sy/Iron Oxide mix on my remaining low-fire pieces too (cone 05/04). Correct me if I'm wrong?

[bciskepottery]

Evelyne:

 

Google Paul Dresang

 

http://www.siue.edu/artsandsciences/art/galleries/dresang/index.shtml

[bciskepottery]

Iron oxides have a high melting point -- somewhere around 2849 F, which is higher than ^6 or ^10. Nepheline Syenite is a member of the feldspar family and a flux -- it helps lower the melting temperature of the iron oxide. So, the addition of the Neph Sy to iron oxide allows it to bond to the clay during firing -- especially important if there is no other glaze being applied.

 

For what its worth, I use a mixture of 50% red iron oxide to 50% Gerstley Borate as a wash. Same principles apply.

 

 

Ok, this makes COMPLETE sense to me! Thank you!

I was kind of wondering how the iron would "melt" into the piece.

 

And it also looks like I should be able to use the Neph Sy/Iron Oxide mix on my remaining low-fire pieces too (cone 05/04). Correct me if I'm wrong?

 

 

 

Always best to try a test tile first.

[pixie1035]

i toss in ferro frit 3124... same effect.

 

 

 

 

Iron oxides have a high melting point -- somewhere around 2849 F, which is higher than ^6 or ^10. Nepheline Syenite is a member of the feldspar family and a flux -- it helps lower the melting temperature of the iron oxide. So, the addition of the Neph Sy to iron oxide allows it to bond to the clay during firing -- especially important if there is no other glaze being applied.

 

For what its worth, I use a mixture of 50% red iron oxide to 50% Gerstley Borate as a wash. Same principles apply.

 

[Marcia Selsor]

Hello all,

This is my first post here on this forum and I'm hoping I can tap into your experience, as my journey with clay only began earlier this year.

 

For some background, I'm taking classes at a community art house.

Stoneware clay... brown, if it matters

Bisque at cone 06

Glaze firings at cone 6

 

I've been in this class a whoppin' 4 weeks and I'm almost as lost as when I started. My only other class was a low-fire class at a different place and we used all commercially prepared glazes from Mayco, Amaco & Duncan.

 

The art house has a lot of its own glazes, slips, stains, etc.

 

Last week, I discovered how lovely an oxide stain looks on our clay.

I really like the look of the clay we use when it has no gloss to it, but most of our glazes are glossy.

 

But in studio last week, a lady had some pieces that she created with stains. They were the look I want to create with my pieces. Kind of a worn leather look.

She said she does the first coat with an iron oxide.... applied with a brush and wiped off.

The next coat is where I get lost.

She grabbed a container that said:

50% Iron Oxide

50% Nepheline Syenite

 

So, being that I'm a complete newbie to raw materials, I asked, "what does the Neph Sy do for you that the Iron Oxide doesn't. She couldn't really answer.

 

Do you think you all might be able to enlighten me?

 

Thanks so much!

Melissa

 

[Marcia Selsor]

Is this ^6 reduction or oxidation...gas or electric firing?

Marcia

[ThisIsMelissa]

Is this ^6 reduction or oxidation...gas or electric firing?

Marcia

 

 

It's Electric.

 

Not sure on the reduction/oxidation

is there a way I can know (besides asking at class on Saturday?)

 

 

 

[Benhim]

Is this ^6 reduction or oxidation...gas or electric firing?

Marcia

 

 

It's Electric.

 

Not sure on the reduction/oxidation

is there a way I can know (besides asking at class on Saturday?)

 

 

 

 

 

Electric is oxidation firing. Gas or fuel firing can be oxidation as well, but can also be done in reduction. This is a deep topic with many facets so unless you'd like to discuss it further we can end it there for now.

 

Iron acts differently in the two atmospheres which might be why Marcia Selsor asked the question. In oxidation the iron keeps oxidizing turning from Fe2O3 into Fe2H6O6 or what's called yellow iron oxide. In a reduction atmosphere the iron takes on a new character as it's propensity to bond to oxygen in the oxygen starved kiln, pulls oxygen out of the clay body at a lower temperature which is called body reduction. Then the iron becomes a flux at higher temperatures in a glaze reduction firing. In this process some of the Iron can go from Fe2O3 to FeO or black iron. There's a bit more to it including other iron compounds that can be formed depending on glaze chemistry, but for the purposes of making an iron stain to be used in electric firing most of what I've written here is information over kill already.

 

Here's some more detail on iron compounds. http://wwwchem.uwimona.edu.jm/courses/iron.html

[ThisIsMelissa]

Is this ^6 reduction or oxidation...gas or electric firing?

Marcia

 

 

It's Electric.

 

Not sure on the reduction/oxidation

is there a way I can know (besides asking at class on Saturday?)

 

 

 

 

 

Electric is oxidation firing. Gas or fuel firing can be oxidation as well, but can also be done in reduction. This is a deep topic with many facets so unless you'd like to discuss it further we can end it there for now.

 

Iron acts differently in the two atmospheres which might be why Marcia Selsor asked the question. In oxidation the iron keeps oxidizing turning from Fe2O3 into Fe2H6O6 or what's called yellow iron oxide. In a reduction atmosphere the iron takes on a new character as it's propensity to bond to oxygen in the oxygen starved kiln, pulls oxygen out of the clay body at a lower temperature which is called body reduction. Then the iron becomes a flux at higher temperatures in a glaze reduction firing. In this process some of the Iron can go from Fe2O3 to FeO or black iron. There's a bit more to it including other iron compounds that can be formed depending on glaze chemistry, but for the purposes of making an iron stain to be used in electric firing most of what I've written here is information over kill already.

 

Here's some more detail on iron compounds. http://wwwchem.uwimo...urses/iron.html

 

 

Ok, Thanks for the explanation.

But remember Charlie Brown's teacher? The sounds she made? That's what this was for me! LOL. Since I have absolutely NO experience in chemistry, this was basically a new language for me! How is it that I managed to do so well in HS, but avoided taking Chemistry the whole 4 years?

 

 

[Benhim]

Well all you have to know for your purposes is that the iron is going to change it's forms as it heats up. It takes a mixture of feldspar in this case Nepheline Syenite to make a decent melt on the surface. With out this feldspar the pure iron oxide in any form would not melt out completely and would end up being a dusty coating on the surface of your pot.