Red Clay

[BlackDogPottery]

Through researching many recipes, old and new. Occasionally I come across recipes that have "Red Clay" usually at half the recipe and the like. However I'm not sure what red clay is? I think its considered terra cotta but is something like Redart specifically? Thanks.

[glazenerd]

Red Art and Banta are the two commonly known red clays. (Red color comes from high iron content/carbons). Low fire 04 to 2, if you are trying to retain iron red color. 

[Tyler Miller]

Any bagged red clay will work although Redart is usually what's meant/used--it's also the most widely available.

It isn't true that when in clay bodies it must be between 04-2 to stay red.  The red to brown transition is a function of flux content and degree of vitrification.  There are red stoneware bodies.

[Min]

I used Imco's Navajo Wheel for a while, it's a brick red at ^6 electric fired. Really nice clay but soooo messy to work with. Dundee Red^6 from Georgie's is darker but really quite red also. (it's darker and redder than the image on their website) 

Dundee Red test tile

 

[BlackDogPottery]

Thanks everyone. I have a kiln test with some ground up terra cotta in the glaze. Wish me luck

 

[glazenerd]

Just now, BlackDogPottery said:

Through researching many recipes, old and new. Occasionally I come across recipes that have "Red Clay" usually at half the recipe and the like. However I'm not sure what red clay is? I think its considered terra cotta but is something like Redart specifically? Thanks.

Assuming from your post, you were looking at clay recipes.  Recipes with 50% "red clay" are typically low fire. To clear up the confusion from successive posts: Red Art and Banta Red are earthen ware clay which are used in low fire recipes. As you noted, also used in Terra Cotta formulas. Due to their low fire nature, begin slumping at cone 5-6: which is not their intended range. 

Yes they do make cone 6 red stoneware bodies; but made from Newman Red stoneware clay, and often blended with Lizella clay. This topic however illustrates the problems with internet recipes. As done here, the assertion that earthen ware clays can be substituted  for red burning stoneware clays are  often confused. Both Red Art and Banta have  much higher levels of naturally occurring fluxes that are molecularly bonded to the iron through isomorphic substitution. This molecular bond will darken the iron particles, not through the addition of other KnaO additions.

yes, you can use red clays in glaze recipes, but testing will be required.

[GEP]

 

42 minutes ago, glazenerd said:

Assuming from your post, you were looking at clay recipes.  Recipes with 50% "red clay" are typically low fire.

I don't think this can be assumed. I immediatedly thought BlackDog meant glaze recipes. One of the first glazes I made for a wood firing (cone 10+) was 50% redart and 50% ash. 

[Min]

1 hour ago, BlackDogPottery said:

Thanks everyone. I have a kiln test with some ground up terra cotta in the glaze. Wish me luck

 

Can you post results? Successful or not it's interesting to see how things turn out.

[Joseph Fireborn]

15 minutes ago, GEP said:

 

I don't think this can be assumed. I immediatedly thought BlackDog meant glaze recipes. One of the first glazes I made for a wood firing (cone 10+) was 50% redart and 50% ash. 

I agree here. I use redart a lot as well.

I currently use a fake ash glaze that is 50% redart and some fluxes. It is a beautiful color. It is on the right side of this bud vase the green hued area on the shoulder. One of my favorite glazes, and like Min said please do post your results. Even if they go south. Still a lot to be learned in the world of ceramics.

[Tyler Miller]

Success tends to be rather un-educational.  Negative results are where progress happens.

[Joseph Fireborn]

16 minutes ago, Tyler Miller said:

Success tends to be rather un-educational.  Negative results are where progress happens.

So much this. All my major improvements we're mostly mistakes and aha moments thinking back later about what happened with a failure. One of the reasons I keep failed pots that look interesting around for several months on a shelf in my studio. Gotta think about interesting interactions.

[BlackDogPottery]

1 hour ago, glazenerd said:

Assuming from your post, you were looking at clay recipes.  Recipes with 50% "red clay" are typically low fire. To clear up the confusion from successive posts: Red Art and Banta Red are earthen ware clay which are used in low fire recipes. As you noted, also used in Terra Cotta formulas. Due to their low fire nature, begin slumping at cone 5-6: which is not their intended range. 

Yes they do make cone 6 red stoneware bodies; but made from Newman Red stoneware clay, and often blended with Lizella clay. This topic however illustrates the problems with internet recipes. As done here, the assertion that earthen ware clays can be substituted  for red burning stoneware clays are  often confused. Both Red Art and Banta have  much higher levels of naturally occurring fluxes that are molecularly bonded to the iron through isomorphic substitution. This molecular bond will darken the iron particles, not through the addition of other KnaO additions.

yes, you can use red clays in glaze recipes, but testing will be required.

The recipe (if you can call it that is ) is more of a slip with portions of 3:2    Manganese and Red Clay intended to fire at ^8  but I'm trying to make it work for ^6.  So far the conclusions are replacing the red clay with China Clay makes a dark brown with soft sheen and replacing with Yellow Ochre creates a cold black that buffs into a graphite sheen. 

[BlackDogPottery]

47 minutes ago, Tyler Miller said:

Success tends to be rather un-educational.  Negative results are where progress happens.

Definitely. Success is for when you want to feel comfortable with reputable recipes and hope your kiln load is salvageable. 

[glazenerd]

What color are you trying to achieve in your slip/ clay?

[BlackDogPottery]

2 minutes ago, glazenerd said:

What color are you trying to achieve in your slip/ clay?

Something dark. Mostly a deep brown.

[glazenerd]

Cut the read art down to 25%, and lose the manganese. Replace the other 25% with EPK; then 25% silica! and 25% spar. Fire a small test piece to see if you like the color. To deepen the brown, add red art in 5% increments! and reduce EPK proportionately. You can also blend Newman red and red art to "redden" the brown....mahogany. Another clay that will do strange colors is Imco burgundy.

have fun.   Remember you have to maintain flux molarity to ensure your slip bonds.

[Tyler Miller]

2 hours ago, glazenerd said:

Assuming from your post, you were looking at clay recipes.  Recipes with 50% "red clay" are typically low fire. To clear up the confusion from successive posts: Red Art and Banta Red are earthen ware clay which are used in low fire recipes. As you noted, also used in Terra Cotta formulas. Due to their low fire nature, begin slumping at cone 5-6: which is not their intended range. 

Yes they do make cone 6 red stoneware bodies; but made from Newman Red stoneware clay, and often blended with Lizella clay. This topic however illustrates the problems with internet recipes. As done here, the assertion that earthen ware clays can be substituted  for red burning stoneware clays are  often confused. Both Red Art and Banta have  much higher levels of naturally occurring fluxes that are molecularly bonded to the iron through isomorphic substitution. This molecular bond will darken the iron particles, not through the addition of other KnaO additions.

yes, you can use red clays in glaze recipes, but testing will be required.

Tom, Dale Neese's cone 5 ox rust red stoneware body, and Linda Arbuckle's Orange cone 7-9 stoneware bodies get their red colour from redart, among other bodies.  I thought I'd mention it as food for thought.

Also, not100% sure that isomorphous substitution is the best way to explain the presence of iron in a secondary clay.  It does occur, but the occurrence better explains the buff colour of fireclays and some ball clays than extensively weathered and impure secondary clays.

Cool to see you learning about this stuff.

Apologies to all for the minor hijack.

[BlackDogPottery]

1 hour ago, glazenerd said:

Cut the read art down to 25%, and lose the manganese. Replace the other 25% with EPK; then 25% silica! and 25% spar. Fire a small test piece to see if you like the color. To deepen the brown, add red art in 5% increments! and reduce EPK proportionately. You can also blend Newman red and red art to "redden" the brown....mahogany. Another clay that will do strange colors is Imco burgundy.

have fun.   Remember you have to maintain flux molarity to ensure your slip bonds.

Will try this! Out of curiousity, have you used fired this before? How was the texture? I'm searching for something thats pretty matte. 

[glazenerd]

Black: short answer- yes. Testing effects and limits of iron  in clay bodies currently. Once you cross  (x/2) % of iron in a clay body! it will leach into the glaze causing micro-crystals: which the eye perceives as matte. Cross (y/2) in iron,  and the glaze will undulate, giving it a textured look. Cross (r/2)% of iron! and you have a useless piece of pottery. X, y,  and r simply represent limits I am currently working on.

Tyler, isomorphic substitution explains how sodium, calcium, potassium, and magnesium cations attached themselves to the iron. Sorry for the confusion. I keep my answers as short and simple as possible, if I answer at all. Yes there are ways to manipulate recipes to produce color, but I try to  keep it simple.

[Tyler Miller]

28 minutes ago, glazenerd said:

 

Tyler, isomorphic substitution explains how sodium, calcium, potassium, and magnesium cations attached themselves to the iron. 

Um, it doesn't.  Iron will swap out for magnesium in olivine minerals, but another reaction occurs when what you're talking about happens.  I'd happily be corrected, but I don't think iron can substitute for sodium or potassium ever.

Maybe leave soil chem stuff out altogether?  i know you're excited to share what you're learning (and it is exciting stuff) but it's tough stuff to make relevant in a clear and non-confusing way.

[glazenerd]

Here are various levels of iron- all clear glazes.

[glazenerd]

The one on the right, attempting to replicate terra cotta in stoneware.

The one on the left is porcelain: using titanium, iron and (ip) to produce color. No stains used.

Tyler, I use to be exited to share; not so much these days.

 

[Min]

12 hours ago, BlackDogPottery said:

Something dark. Mostly a deep brown.

Another approach would be to use Barnard to give you the colour. There is a recipe on this link, I've seen some of Mary Fox's work, the slip is very dark and smooth. (that's one of her pots on the link). If you took out some of the Barnard I think you would have a nice rich dark brown. If you give it a go I would suggest mixing it with 30 Barnard, brush on a test piece, add 5 more Barnard and brush on another test and so forth until you get up to the 45 as called for in the original recipe. The original Barnard is long since discontinued but there are substitutes available. (it does contain Manganese so usual cautions about firing fumes and safety)

[BlackDogPottery]

I will upload an image later. Yes it seems like you can use the terra cotta in this recipe. It melted smoother than the last two ingredients. The finish is a velvet metallic feel thats black with brown specks. Probably a type of crystal growth.

[Joseph Fireborn]

2 minutes ago, BlackDogPottery said:

I will upload an image later. Yes it seems like you can use the terra cotta in this recipe. It melted smoother than the last two ingredients. The finish is a velvet metallic feel thats black with brown specks. Probably a type of crystal growth.

Sounds very appealing. Can't wait to see the pictures.